group had increased brain activity in the pSTS and ventral striatum when viewing biological motion, and decreased ventral striatum activity in response to scrambled motion. Children in the hyperactive group evidenced decreased brain activity in the pSTS, amygdala, thalamus, and hippocampus when viewing biological motion. The authors' hypothesized that participation in PRT differentially affected brain activity of children depending on their baseline characteristics (e.g. children who displayed too little brain activity in response to social stimuli evidenced increased brain activity after intervention, whereas children who displayed too much brain activity in response to social stimuli evidenced decreased activity after intervention).

Van Hecke and colleagues [83] used electrophysiology (EEG) to measure brain activity before and after participation in a randomized control trial of the Program for the Education and Enrichment of Relational Skills (PEERS; [84, 85]) versus a waitlist control (WLC) condition. PEERS is an empirically validated, manualized program which focuses on making and keeping friends for adolescents with ASD [86].

**71**

brain circuitry in ASD.

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

Venkataraman and colleagues [88] used a Bayesian probabilistic model to characterize fMRI activity in 19 children with ASD (mean age 5.87 years) before and after 16 weeks of PRT. Similar to Ventola et al. [82], the fMRI paradigm involved watching two types of light displays: biological motion and scrambled motion. The probabilistic model allowed the authors to measure PRT-induced changes in neural connectivity between neural regions of interest. Results indicated both reduced connectivity between the posterior cingulate cortex (PCC) and orbitofrontal cortex and increased connectivity between the PCC and areas of the ventral occipital temporal extrastriate cortex. These results are interesting given that the PCC is known for its role in social cognitive processes, the orbitofrontal cortex has been implicated in reward processes, and the ventral occipital and temporal cortices play a role in processing socially meaningful stimuli (including biological motion). These findings suggest that PRT causes a shift, in which connectivity between the PCC and orbitofrontal cortex is decreased while PCC and the ventral occipital-temporal

Yang and colleagues [89] utilized fMRI as a pre-intervention predictor of intervention response in 20 children with ASD (mean age 5.90 years). The authors measured brain activity during a biological motion paradigm prior to 16 weeks of PRT. Results demonstrated that pre-intervention brain activity in areas implicated in: (1) social perception (fusiform gyrus, inferior temporal gyrus, middle temporal gyrus), (2) social attention (inferior parietal gyrus, superior parietal lobule), (3) emotion regulation and reward (orbitofrontal cortex, ventrolateral prefrontal cortex, anterior insula), and (4) social reward (putamen, pallidum, amygdala, hippocampus, ventral striatum) while viewing biological motion predicted behavioral improvements on the SRS from pre- to post-intervention. For all 4 regions, greater levels of pre-intervention brain activity were associated with increased behavioral improvements from pre- to post- intervention. Results from this study suggest that neuroscience methods may be able to predict which children are most likely to benefit from a specific intervention, as well as underscoring the importance of brain regions associated with social perception, emotion regulation, and reward for understanding how interventions may affect

Baker and colleagues [90] used event-related potentials (ERP) to measure brain response to reward in ASD adolescents before and after participation in the PEERS

35 adolescents (13-14 years old) with ASD were randomly assigned to receive PEERS, 31 were randomly assigned to WLC, and 30 neurotypical (TD) adolescents were assessed prior to the intervention for comparison purposes. The authors measured brain activity patterns during "resting state" during which adolescents were instructed to focus on a fixation point for three minutes. Of particular interest was patterns of brain activity in the right versus left hemispheres as previous research suggests that individuals who have left-hemisphere dominance have higher approach motivation and positive affect compared to those with right-hemisphere dominance who are often characterized as withdrawn [87]. Prior to intervention, the two groups of teens with ASD evidenced less left-dominant asymmetry compared to the TD group. When comparing post-intervention brain activity of teens who received PEERS to brain activity in the TD group, differences in left-hemispheric dominance were no longer observed. Differences between the WLC group and the TD group were still observed after the 14-week intervention period (during which the WLC group did not receive intervention). These findings suggest that participation in PEERS (compared to a waitlist condition) significantly changed patterns of brain activity to be increasingly left-hemisphere dominant, which is more similar to patterns observed

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

in neurotypical teens.

cortex connection is strengthened.

#### *Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

35 adolescents (13-14 years old) with ASD were randomly assigned to receive PEERS, 31 were randomly assigned to WLC, and 30 neurotypical (TD) adolescents were assessed prior to the intervention for comparison purposes. The authors measured brain activity patterns during "resting state" during which adolescents were instructed to focus on a fixation point for three minutes. Of particular interest was patterns of brain activity in the right versus left hemispheres as previous research suggests that individuals who have left-hemisphere dominance have higher approach motivation and positive affect compared to those with right-hemisphere dominance who are often characterized as withdrawn [87]. Prior to intervention, the two groups of teens with ASD evidenced less left-dominant asymmetry compared to the TD group. When comparing post-intervention brain activity of teens who received PEERS to brain activity in the TD group, differences in left-hemispheric dominance were no longer observed. Differences between the WLC group and the TD group were still observed after the 14-week intervention period (during which the WLC group did not receive intervention). These findings suggest that participation in PEERS (compared to a waitlist condition) significantly changed patterns of brain activity to be increasingly left-hemisphere dominant, which is more similar to patterns observed in neurotypical teens.

Venkataraman and colleagues [88] used a Bayesian probabilistic model to characterize fMRI activity in 19 children with ASD (mean age 5.87 years) before and after 16 weeks of PRT. Similar to Ventola et al. [82], the fMRI paradigm involved watching two types of light displays: biological motion and scrambled motion. The probabilistic model allowed the authors to measure PRT-induced changes in neural connectivity between neural regions of interest. Results indicated both reduced connectivity between the posterior cingulate cortex (PCC) and orbitofrontal cortex and increased connectivity between the PCC and areas of the ventral occipital temporal extrastriate cortex. These results are interesting given that the PCC is known for its role in social cognitive processes, the orbitofrontal cortex has been implicated in reward processes, and the ventral occipital and temporal cortices play a role in processing socially meaningful stimuli (including biological motion). These findings suggest that PRT causes a shift, in which connectivity between the PCC and orbitofrontal cortex is decreased while PCC and the ventral occipital-temporal cortex connection is strengthened.

Yang and colleagues [89] utilized fMRI as a pre-intervention predictor of intervention response in 20 children with ASD (mean age 5.90 years). The authors measured brain activity during a biological motion paradigm prior to 16 weeks of PRT. Results demonstrated that pre-intervention brain activity in areas implicated in: (1) social perception (fusiform gyrus, inferior temporal gyrus, middle temporal gyrus), (2) social attention (inferior parietal gyrus, superior parietal lobule), (3) emotion regulation and reward (orbitofrontal cortex, ventrolateral prefrontal cortex, anterior insula), and (4) social reward (putamen, pallidum, amygdala, hippocampus, ventral striatum) while viewing biological motion predicted behavioral improvements on the SRS from pre- to post-intervention. For all 4 regions, greater levels of pre-intervention brain activity were associated with increased behavioral improvements from pre- to post- intervention. Results from this study suggest that neuroscience methods may be able to predict which children are most likely to benefit from a specific intervention, as well as underscoring the importance of brain regions associated with social perception, emotion regulation, and reward for understanding how interventions may affect brain circuitry in ASD.

Baker and colleagues [90] used event-related potentials (ERP) to measure brain response to reward in ASD adolescents before and after participation in the PEERS

*Oxytocin and Health*

**Authors Participants Intervention,**

• Mage = 5.90 yrs., SDage = 1.07 yrs.

• Mage = 13.88 yrs., SDage = 2.21 yrs. 7 TD (6 male, 1 female) • Mage = 13.46 yrs., SDage = 2.29 yrs.

*Neuroscience outcome measures of behavioral interventions in children with ASD.*

Yang et al. [89] 20 ASD (13 male, 7

female)

Baker et al., [90] 7 ASD (6 male, 1 female)

**Neuroscience Methodology, & Task**

PRT; 16 weeks; 7 hours/week fMRI Participants viewed biological motion clips and scrambled motion clips.

PEERS; 16 weeks; 1.5 hours/week ERP Participants completed a reward task with feedback that was social (face) or nonsocial (arrow) with correct or incorrect feedback (face: smile vs frown; arrow: upward vs downward).

**Neuroscientific Findings**

striatum)

Increased neural sensitivity to both social and nonsocial rewards (RewP amplitude) after versus

before intervention.

Pre-intervention brain activity in the following areas while viewing biological motion predicted behavioral improvements on the SRS from pre- to postintervention. (1) social perception (fusiform gyrus, inferior temporal gyrus, middle temporal gyrus), (2) social attention (inferior parietal gyrus, superior parietal lobule), (3) emotion regulation and reward (orbitofrontal cortex, ventrolateral prefrontal cortex, anterior insula), and (4) social reward (putamen, pallidum, amygdala, hippocampus, ventral

**70**

**Table 3.**

activity after intervention).

group had increased brain activity in the pSTS and ventral striatum when viewing biological motion, and decreased ventral striatum activity in response to scrambled motion. Children in the hyperactive group evidenced decreased brain activity in the pSTS, amygdala, thalamus, and hippocampus when viewing biological motion. The authors' hypothesized that participation in PRT differentially affected brain activity of children depending on their baseline characteristics (e.g. children who displayed too little brain activity in response to social stimuli evidenced increased brain activity after intervention, whereas children who displayed too much brain activity in response to social stimuli evidenced decreased

Van Hecke and colleagues [83] used electrophysiology (EEG) to measure brain activity before and after participation in a randomized control trial of the Program for the Education and Enrichment of Relational Skills (PEERS; [84, 85]) versus a waitlist control (WLC) condition. PEERS is an empirically validated, manualized program which focuses on making and keeping friends for adolescents with ASD [86].

program compared to a typically developing sample. Response to social and nonsocial rewards were measured using the reward-related positive component (RewP) in seven adolescents with ASD and seven TD adolescents, aged 10 to 17 years. Prior to intervention, patterns of reward-related brain activity (RewP mean amplitude) did not differ between groups. However, after intervention the ASD group demonstrated an enhanced sensitivity to rewards, regardless of social or nonsocial condition, compared to the TD group. Additionally, ASD participants with less robust responses to social rewards prior to the start of the PEERS intervention demonstrated the most gains in social behaviors (as measured via SRS-2 [91]; Social Skills Improvement System, [92]. Findings from this study suggest an enhancement of the neural response to rewards after teens with ASD receive training in social skills and additionally that teens with attenuated responses to social rewards may gain the most benefit from intervention.

Taken together, these seven studies provide evidence for two critical concepts: (1) *Behavioral Intervention* can significantly change patterns and/or magnitude of brain activity in response to social stimuli for children with ASD, and (2) *Neuroscience* may be able to predict individual levels of behavioral intervention response and could eventually be used to advance "precision medicine" (e.g. to predict who is most likely to benefit from a specific intervention). The first concept is central to our theoretical framework, as it suggests that participation in empirically based interventions changes brain activity in children with ASD- -particularly in response to social stimuli and in brain areas/patterns of activity related to social perception and reward. Neural changes in the reward system and other areas of the "social brain" after interventions provides an empirical basis for our hypothesis that the addition of pharmacological compounds that enhance brain activity/responses in those same regions might lead to increased benefits for children with ASD.

#### **7. Current research combining oxytocin and behavioral interventions in ASD**

Although there are no published studies (to our knowledge) that have conducted double-blind, placebo-controlled trials combining oxytocin administration with an empirically validated behavioral intervention in ASD, two trials are currently underway and recorded on ClinicalTrials.Gov (identifiers NCT02918864 and NCT03370510). We also note that a large-scale multi-site trial of the behavioral effects of oxytocin versus placebo is underway by the Study of Oxytocin in Autism to Improve Reciprocal Social Behaviors (SOARS-B; clinical trial identifier NCT01944046). One paper describing the rationale and methods for the trial has been published [93].

#### **8. Does timing matter?**

As noted above, we hypothesize that empirically based behavioral interventions designed to increase social-communication skills such as social initiation/motivation are more likely to be enhanced by oxytocin administration than interventions focused on other aspects of ASD (e.g. disruptive behaviors, anxiety). Such interventions are typically aimed towards young children (i.e. ESDM was developed for children ages 1-4) due to the targeted skills. We hypothesize that age is likely to play an important role in the efficacy of combining oxytocin with behavioral interventions

**73**

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

such that younger children are more likely to benefit due to: (a) Early interventions in ASD often focus on improving social motivation and initiation, whereas interventions for older children are less likely to have such an emphasis. As oxytocin has been shown to affect the reward system, behavioral interventions designed to increase the reward value of social stimuli are likely to be the best candidates for this framework. (b) Increased neural plasticity in younger ages and the negative neuro-developmental sequelae described in the social motivation hypothesis. That is, young children have been hypothesized to benefit more from early intervention for ASD compared to older children due to neural plasticity, and the social motivation hypothesis posits that decreased reward value of social stimuli early in life leads to a negative cascade of developmental consequences [5, 94]. It therefore seems likely that younger children are best positioned to benefit from combining behavioral intervention with oxytocin because early interventions may disrupt this negative developmental cascade and help children move back towards a typical trajectory. (c) Accumulating evidence that interventions for ASD are likely to be more effective if started earlier in life [94–96]. It is unclear, however, exactly how age will affect our theoretical model. Future research should pay close attention to how and if age is a predictor when measuring outcomes of combining oxytocin and

Taken together, considering extant research findings from behavioral and neural effects of oxytocin administration along with those on brain activity in response to behavioral interventions in children with ASD suggests that both oxytocin and behavioral interventions lead to measurable changes in regions of the "social brain" and reward network. These findings, combined with those suggesting that oxytocin administration may improve social-communication in children with ASD, provide the empirical basis of our hypothesis [57] that combining oxytocin administration with behavioral interventions may improve outcomes related to social-communication. We hypothesize that the administration of oxytocin prior to each session of an intervention may "prime" the neural reward system to be maximally responsive to the behavioral skills taught during the intervention session. Due to the central role of the reward system in our theoretical model we hypothesize that this combined approach may be most effective for social-communicative skills requiring social motivation (e.g. social initiation/approach) and be maximally beneficial for young children. See **Figure 1** for hypothesized neural mechanisms underlying the efficacy of combining interventions with oxytocin to

It is important to note, however, that this approach is unlikely to be equally effective in all children with ASD. As with all interventions, there does not appear to be any "one size fits all" approach to help children with ASD. It will be critical to measure and characterize individual differences that may explain variability in treatment efficacy from *biological* (e.g. levels of oxytocin concentration in plasma/ saliva before and after oxytocin administration, genetic expression of candidate genes relevant for oxytocin; OXTR, VAP1, brain activity in response to social stimuli prior to oxytocin administration, age), *behavioral* (e.g. social communicative symptom profile prior to oxytocin administration), and *psychological* (e.g. co-occurring diagnoses such as ADHD, anxiety, etc.) standpoints. Such individual differences will likely be central to our understanding of how, why, and for whom

this combined approach will be maximally effective.

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

behavioral intervention in ASD.

**9. Conclusions**

improve outcomes.

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

such that younger children are more likely to benefit due to: (a) Early interventions in ASD often focus on improving social motivation and initiation, whereas interventions for older children are less likely to have such an emphasis. As oxytocin has been shown to affect the reward system, behavioral interventions designed to increase the reward value of social stimuli are likely to be the best candidates for this framework. (b) Increased neural plasticity in younger ages and the negative neuro-developmental sequelae described in the social motivation hypothesis. That is, young children have been hypothesized to benefit more from early intervention for ASD compared to older children due to neural plasticity, and the social motivation hypothesis posits that decreased reward value of social stimuli early in life leads to a negative cascade of developmental consequences [5, 94]. It therefore seems likely that younger children are best positioned to benefit from combining behavioral intervention with oxytocin because early interventions may disrupt this negative developmental cascade and help children move back towards a typical trajectory. (c) Accumulating evidence that interventions for ASD are likely to be more effective if started earlier in life [94–96]. It is unclear, however, exactly how age will affect our theoretical model. Future research should pay close attention to how and if age is a predictor when measuring outcomes of combining oxytocin and behavioral intervention in ASD.

#### **9. Conclusions**

*Oxytocin and Health*

most benefit from intervention.

children with ASD.

been published [93].

**8. Does timing matter?**

**in ASD**

program compared to a typically developing sample. Response to social and nonsocial rewards were measured using the reward-related positive component (RewP) in seven adolescents with ASD and seven TD adolescents, aged 10 to 17 years. Prior to intervention, patterns of reward-related brain activity (RewP mean amplitude) did not differ between groups. However, after intervention the ASD group demonstrated an enhanced sensitivity to rewards, regardless of social or nonsocial condition, compared to the TD group. Additionally, ASD participants with less robust responses to social rewards prior to the start of the PEERS intervention demonstrated the most gains in social behaviors (as measured via SRS-2 [91]; Social Skills Improvement System, [92]. Findings from this study suggest an enhancement of the neural response to rewards after teens with ASD receive training in social skills and additionally that teens with attenuated responses to social rewards may gain the

Taken together, these seven studies provide evidence for two critical concepts: (1) *Behavioral Intervention* can significantly change patterns and/or magnitude of brain activity in response to social stimuli for children with ASD, and (2) *Neuroscience* may be able to predict individual levels of behavioral intervention response and could eventually be used to advance "precision medicine" (e.g. to predict who is most likely to benefit from a specific intervention). The first concept is central to our theoretical framework, as it suggests that participation in empirically based interventions changes brain activity in children with ASD- -particularly in response to social stimuli and in brain areas/patterns of activity related to social perception and reward. Neural changes in the reward system and other areas of the "social brain" after interventions provides an empirical basis for our hypothesis that the addition of pharmacological compounds that enhance brain activity/responses in those same regions might lead to increased benefits for

**7. Current research combining oxytocin and behavioral interventions**

Although there are no published studies (to our knowledge) that have conducted double-blind, placebo-controlled trials combining oxytocin administration with an empirically validated behavioral intervention in ASD, two trials are currently underway and recorded on ClinicalTrials.Gov (identifiers NCT02918864 and NCT03370510). We also note that a large-scale multi-site trial of the behavioral effects of oxytocin versus placebo is underway by the Study of Oxytocin in Autism to Improve Reciprocal Social Behaviors (SOARS-B; clinical trial identifier NCT01944046). One paper describing the rationale and methods for the trial has

As noted above, we hypothesize that empirically based behavioral interventions designed to increase social-communication skills such as social initiation/motivation are more likely to be enhanced by oxytocin administration than interventions focused on other aspects of ASD (e.g. disruptive behaviors, anxiety). Such interventions are typically aimed towards young children (i.e. ESDM was developed for children ages 1-4) due to the targeted skills. We hypothesize that age is likely to play an important role in the efficacy of combining oxytocin with behavioral interventions

**72**

Taken together, considering extant research findings from behavioral and neural effects of oxytocin administration along with those on brain activity in response to behavioral interventions in children with ASD suggests that both oxytocin and behavioral interventions lead to measurable changes in regions of the "social brain" and reward network. These findings, combined with those suggesting that oxytocin administration may improve social-communication in children with ASD, provide the empirical basis of our hypothesis [57] that combining oxytocin administration with behavioral interventions may improve outcomes related to social-communication. We hypothesize that the administration of oxytocin prior to each session of an intervention may "prime" the neural reward system to be maximally responsive to the behavioral skills taught during the intervention session. Due to the central role of the reward system in our theoretical model we hypothesize that this combined approach may be most effective for social-communicative skills requiring social motivation (e.g. social initiation/approach) and be maximally beneficial for young children. See **Figure 1** for hypothesized neural mechanisms underlying the efficacy of combining interventions with oxytocin to improve outcomes.

It is important to note, however, that this approach is unlikely to be equally effective in all children with ASD. As with all interventions, there does not appear to be any "one size fits all" approach to help children with ASD. It will be critical to measure and characterize individual differences that may explain variability in treatment efficacy from *biological* (e.g. levels of oxytocin concentration in plasma/ saliva before and after oxytocin administration, genetic expression of candidate genes relevant for oxytocin; OXTR, VAP1, brain activity in response to social stimuli prior to oxytocin administration, age), *behavioral* (e.g. social communicative symptom profile prior to oxytocin administration), and *psychological* (e.g. co-occurring diagnoses such as ADHD, anxiety, etc.) standpoints. Such individual differences will likely be central to our understanding of how, why, and for whom this combined approach will be maximally effective.

#### **Figure 1**

*(1.1) Neuroscience Outcomes after Behavioral Intervention for Children with ASD. This figure depicts results from studies which measured brain activity before and after behavioral intervention. The brain areas highlighted in red indicate increased brain activity after behavioral intervention, whereas regions shown in blue indicate decreased brain activity after behavioral intervention. Results related to neural connectivity are shown with a dotted line. A. Dawson et al. [79], proposed neural generators of the Nc component (Reynolds & Richards, 2005) are highlighted (medial frontal gyrus, inferior frontal gyrus, anterior cingulate cortex); B. Voos et al. [80] (fusiform gyrus, dorsolateral prefrontal cortex, posterior superior temporal sulcus (pSTS), ventrolateral prefrontal cortex (vlPFC)); C. Ventola et al. [82], ventral striatum (VS), pSTS, amygdala, thalamus, and hippocampus; D. Venkataraman et al. [88], reduction in connectivity between the posterior cingulate cortex (PCC) and orbital frontal cortex (OFC) and an increase in connectivity between the PCC and regions of ventral occipital temporal extrastriate cortex; E. Baker et al. [90], proposed neural generators of the RewP component (Carlson et al., 2011 & Proudfit, 2015) are highlighted (ventral striatum, dorsal striatum, OFC, medial frontal cortex); F\*. Yang et al. [89], activity in the following pre-intervention brain areas were used to predict behavioral improvements: fusiform gyrus, inferior temporal gyrus, middle temporal gyrus, inferior parietal gyrus, superior parietal lobule, OFC, ventrolateral prefrontal cortex, anterior insula, putamen, pallidum, amygdala, hippocampus, ventral striatum. \*This study used neuroscience measures prior to intervention as a predictor of intervention success, whereas the other studies used neuroscience measures pre- and post-intervention. (1.2) Neuroscience Results after Oxytocin Administration in Children with ASD. This figure depicts results from studies that have measured brain activity after oxytocin administration. Results related to neural connectivity are shown with a dotted line (red dotted line indicates increased connectivity, blue dotted line indicates decreased connectivity). G. Gordon et al., [55] (dorsal and ventral striatum, premotor cortex, posterior cingulate, pSTS); H. Gordon et al. [56] (pSTS, right amygdala, right brain stem); I. Greene et al., [56] (right nucleus accumbens (NAcc), right frontal pole (FP), left anterior cingulate cortex (ACC), left superior frontal cortex, bilateral OFC, functional connectivity during nonsocial reward anticipation (between the right NAcc and the right FP); frontostriatal functional connectivity between left ACC, bilateral postcentral gyrus, left inferior front gyrus, left precentral gyrus, and left medial frontal gyrus). (1.3) Neural Mechanisms Underlying the Proposed Additive Benefit of Combining Oxytocin with Behavioral Intervention. This figure depicts the proposed additive benefits of combining oxytocin administration with behavioral interventions for children with ASD. Brain regions that have been implicated in both behavioral intervention and oxytocin administration are labeled. We propose that oxytocin administration will "prime" neural structures related to reward and/or social information processing, which will make behavioral intervention sessions more effective.*

**75**

**Author details**

Katherine Kuhl Meltzoff Stavropoulos\* and Elizabeth Baker University of California, Riverside, Riverside, California, USA

provided the original work is properly cited.

\*Address all correspondence to<EMAIL_ADDRESS>
© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

#### **Author details**

*Oxytocin and Health*

**Figure 1**

*(1.1) Neuroscience Outcomes after Behavioral Intervention for Children with ASD. This figure depicts results from studies which measured brain activity before and after behavioral intervention. The brain areas highlighted in red indicate increased brain activity after behavioral intervention, whereas regions shown in blue indicate decreased brain activity after behavioral intervention. Results related to neural connectivity are shown with a dotted line. A. Dawson et al. [79], proposed neural generators of the Nc component (Reynolds & Richards, 2005) are highlighted (medial frontal gyrus, inferior frontal gyrus, anterior cingulate cortex); B. Voos et al. [80] (fusiform gyrus, dorsolateral prefrontal cortex, posterior superior temporal sulcus (pSTS), ventrolateral prefrontal cortex (vlPFC)); C. Ventola et al. [82], ventral striatum (VS), pSTS, amygdala, thalamus, and hippocampus; D. Venkataraman et al. [88], reduction in connectivity between the posterior cingulate cortex (PCC) and orbital frontal cortex (OFC) and an increase in connectivity between the PCC and regions of ventral occipital temporal extrastriate cortex; E. Baker et al. [90], proposed neural generators of the RewP component (Carlson et al., 2011 & Proudfit, 2015) are highlighted (ventral striatum, dorsal striatum, OFC, medial frontal cortex); F\*. Yang et al. [89], activity in the following pre-intervention brain areas were used to predict behavioral improvements: fusiform gyrus, inferior temporal gyrus, middle temporal gyrus, inferior parietal gyrus, superior parietal lobule, OFC, ventrolateral prefrontal cortex, anterior insula, putamen, pallidum, amygdala, hippocampus, ventral striatum. \*This study used neuroscience measures prior to intervention as a predictor of intervention success, whereas the other studies used neuroscience measures pre- and post-intervention. (1.2) Neuroscience Results after Oxytocin Administration in Children with ASD. This figure depicts results from studies that have measured brain activity after oxytocin administration. Results related to neural connectivity are shown with a dotted line (red dotted line indicates increased connectivity, blue dotted line indicates decreased connectivity). G. Gordon et al., [55] (dorsal and ventral striatum, premotor cortex, posterior cingulate, pSTS); H. Gordon et al. [56] (pSTS, right amygdala, right brain stem); I. Greene et al., [56] (right nucleus accumbens (NAcc), right frontal pole (FP), left anterior cingulate cortex (ACC), left superior frontal cortex, bilateral OFC, functional connectivity during nonsocial reward anticipation (between the right NAcc and the right FP); frontostriatal functional connectivity between left ACC, bilateral postcentral gyrus, left inferior front gyrus, left precentral gyrus, and left medial frontal gyrus). (1.3) Neural Mechanisms Underlying the Proposed Additive Benefit of Combining Oxytocin with Behavioral Intervention. This figure depicts the proposed additive benefits of combining oxytocin administration with behavioral interventions for children with ASD. Brain regions that have been implicated in both behavioral intervention and oxytocin administration are labeled. We propose that oxytocin administration will "prime" neural structures related to reward and/or*

*social information processing, which will make behavioral intervention sessions more effective.*

**74**

Katherine Kuhl Meltzoff Stavropoulos\* and Elizabeth Baker University of California, Riverside, Riverside, California, USA

\*Address all correspondence to<EMAIL_ADDRESS>
© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Maenner M J 2020 Prevalence of autism spectrum disorder among children aged 8 years — autism and developmental disabilities monitoring network, 11 sites, United States, 2016 *MMWR Surveill Summ* **69**

[2] American Psychiatric Association 2013 *Diagnostic and statistical manual of mental disorders* (Washington, DC: American Psychiatric Publishing)

[3] Dawson G, Webb S J and McPartland J 2005 Understanding the nature of face processing impairment in autism: insights from behavioral and electrophysiological studies *Dev Neuropsychol* **27** 403-24

[4] Chevallier C, Kohls G, Troiani V, Brodkin E S and Schultz R T 2012 The social motivation theory of autism *Trends Cogn Sci* **16** 231-9

[5] Dawson G 2008 Early behavioral intervention, brain plasticity, and the prevention of autism spectrum disorder *Dev Psychopathol* **20** 775-803

[6] Stavropoulos K K M and Carver L J 2013 Research Review: Social motivation and oxytocin in autism – implications for joint attention development and intervention *Journal of Child Psychology and Psychiatry* **54** 603-18

[7] Gainer H, Altstein M and Whitnall M H 1987 The cell biology and development of vasopressinergic and oxytocinergic neurons *Prog. Brain Res.* **72** 153-61

[8] Magon N and Kalra S 2011 The orgasmic history of oxytocin: Love, lust, and labor *Indian J Endocrinol Metab* **15** S156-61

[9] Carter C S and Porges S W 2013 The biochemistry of love: An oxytocin hypothesis *EMBO reports* **14** 12-6

[10] Modi M E and Young L J 2012 The oxytocin system in drug discovery for

autism: Animal models and novel therapeutic strategies *Horm Behav* **61** 340-50

[11] Domes G, Heinrichs M, Michel A, Berger C and Herpertz S C 2007 Oxytocin improves "mind-reading" in humans *Biological Psychiatry* **61** 731-3

[12] Hurlemann R, Patin A, Onur O A, Cohen M X, Baumgartner T, Metzler S, Dziobek I, Gallinat J, Wagner M, Maier W and Kendrick K M 2010 Oxytocin enhances amygdala-dependent, socially reinforced learning and emotional empathy in humans *J. Neurosci.* **30** 4999-5007

[13] Kosfeld M, Heinrichs M, Zak P J, Fischbacher U and Fehr E 2005 Oxytocin increases trust in humans *Nature* **435** 673-6

[14] Gordon I, Martin C, Feldman R and Leckman J F 2011 Oxytocin and social motivation *Dev Cogn Neurosci* **1** 471-93

[15] Baskerville T A and Douglas A J 2010 Dopamine and oxytocin interactions underlying behaviors: Potential contributions to behavioral disorders *CNS Neuroscience & Therapeutics* **16** e92-123

[16] Baskerville T A, Allard J, Wayman C and Douglas A J 2009 Dopamine– oxytocin interactions in penile erection *European Journal of Neuroscience* **30** 2151-64

[17] Shapiro L E and Insel T R 1989 Ontogeny of oxytocin receptors in rat forebrain: A quantitative study *Synapse* **4** 259-66

[18] Krol K M, Moulder R G, Lillard T S, Grossmann T and Connelly J J 2019 Epigenetic dynamics in infancy and the impact of maternal engagement *Science Advances* **5** eaay0680

**77**

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

**1580** 188-98

**44** 521-31

**56** 444-52

[27] Anagnostou E, Soorya L, Brian J, Dupuis A, Mankad D, Smile S and Jacob S 2014 Intranasal oxytocin in the

treatment of autism spectrum disorders: A review of literature and early safety and efficacy data in youth *Brain Research*

[28] Dadds M R, MacDonald E, Cauchi A, Williams K, Levy F and Brennan J 2014 Nasal oxytocin for social deficits in childhood autism: A randomized controlled trial *J Autism Dev Disord*

[29] Guastella A J, Gray K M, Rinehart N J, Alvares G A, Tonge B J, Hickie I B, Keating C M, Cacciotti-Saija C and Einfeld S L 2015 The effects of a course of intranasal oxytocin on social behaviors in youth diagnosed with autism spectrum disorders: A randomized controlled trial *Journal of Child Psychology and Psychiatry*

[30] Yatawara C J, Einfeld S L, Hickie I B, Davenport T A and Guastella A J 2016 The effect of oxytocin nasal spray on social interaction deficits observed in young children with autism: A randomized clinical crossover trial *Molecular Psychiatry* **21** 1225-31

[31] Strathearn L, Kim S, Bastian D A, Jung J, Iyengar U, Martinez S, Goin-Kochel R P and Fonagy P 2018 Visual systemizing preference in children with autism: A randomized controlled trial of intranasal oxytocin *Development and*

[32] Ooi Y P, Weng S-J, Kossowsky J, Gerger H and Sung M 2017 Oxytocin and autism spectrum disorders: A systematic review and meta-analysis of

[33] Baron-Cohen S, Wheelwright S, Hill J, Raste Y and Plumb I 2001 The "Reading the Mind in the Eyes" Test revised version: A study with normal adults, and adults with asperger

*Psychopathology* **30** 511-21

randomized controlled trials *Pharmacopsychiatry* **50** 5-13

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

[19] LeClerc S and Easley D 2015 Pharmacological therapies for autism spectrum disorder: A review *P T*

[20] Modahl C, Fein D, Waterhouse L and Newton N 1992 Does oxytocin deficiency mediate social deficits in autism? *J Autism Dev Disord* **22** 449-51

[21] Modahl C, Green L A, Fein D, Morris M, Waterhouse L, Feinstein C and Levin H 1998 Plasma oxytocin levels in autistic children *Biological Psychiatry*

[22] Parker K J, Oztan O, Libove R A, Sumiyoshi R D, Jackson L P, Karhson D S, Summers J E, Hinman K E, Motonaga K S, Phillips J M, Carson D S, Garner J P and Hardan A Y 2017 Intranasal oxytocin

treatment for social deficits and

autism *Proc Natl Acad Sci USA*

[23] Green L, Fein D, Modahl C, Feinstein C, Waterhouse L and Morris M 2001 Oxytocin and autistic disorder: Alterations in peptide forms *Biological*

[24] Andari E, Duhamel J-R, Zalla T, Herbrecht E, Leboyer M and Sirigu A 2010 Promoting social behavior with oxytocin in high-functioning autism spectrum disorders *PNAS* **107** 4389-94

[25] Guastella A J, Einfeld S L, Gray K M, Rinehart N J, Tonge B J, Lambert T J and Hickie I B 2010 Intranasal oxytocin improves emotion recognition for youth

[26] Tachibana M, Kagitani-Shimono K, Mohri I, Yamamoto T, Sanefuji W, Nakamura A, Oishi M, Kimura T, Onaka T, Ozono K and Taniike M 2013 Long-term administration of intranasal oxytocin is a safe and promising therapy for early adolescent boys with autism spectrum disorders *Journal of Child and Adolescent Psychopharmacology* **23** 123-7

with autism spectrum disorders *Biological Psychiatry* **67** 692-4

biomarkers of response in children with

**40** 389-97

**43** 270-7

**114** 8119-24

*Psychiatry* **50** 609-13

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

[19] LeClerc S and Easley D 2015 Pharmacological therapies for autism spectrum disorder: A review *P T* **40** 389-97

[20] Modahl C, Fein D, Waterhouse L and Newton N 1992 Does oxytocin deficiency mediate social deficits in autism? *J Autism Dev Disord* **22** 449-51

[21] Modahl C, Green L A, Fein D, Morris M, Waterhouse L, Feinstein C and Levin H 1998 Plasma oxytocin levels in autistic children *Biological Psychiatry* **43** 270-7

[22] Parker K J, Oztan O, Libove R A, Sumiyoshi R D, Jackson L P, Karhson D S, Summers J E, Hinman K E, Motonaga K S, Phillips J M, Carson D S, Garner J P and Hardan A Y 2017 Intranasal oxytocin treatment for social deficits and biomarkers of response in children with autism *Proc Natl Acad Sci USA* **114** 8119-24

[23] Green L, Fein D, Modahl C, Feinstein C, Waterhouse L and Morris M 2001 Oxytocin and autistic disorder: Alterations in peptide forms *Biological Psychiatry* **50** 609-13

[24] Andari E, Duhamel J-R, Zalla T, Herbrecht E, Leboyer M and Sirigu A 2010 Promoting social behavior with oxytocin in high-functioning autism spectrum disorders *PNAS* **107** 4389-94

[25] Guastella A J, Einfeld S L, Gray K M, Rinehart N J, Tonge B J, Lambert T J and Hickie I B 2010 Intranasal oxytocin improves emotion recognition for youth with autism spectrum disorders *Biological Psychiatry* **67** 692-4

[26] Tachibana M, Kagitani-Shimono K, Mohri I, Yamamoto T, Sanefuji W, Nakamura A, Oishi M, Kimura T, Onaka T, Ozono K and Taniike M 2013 Long-term administration of intranasal oxytocin is a safe and promising therapy for early adolescent boys with autism spectrum disorders *Journal of Child and Adolescent Psychopharmacology* **23** 123-7

[27] Anagnostou E, Soorya L, Brian J, Dupuis A, Mankad D, Smile S and Jacob S 2014 Intranasal oxytocin in the treatment of autism spectrum disorders: A review of literature and early safety and efficacy data in youth *Brain Research* **1580** 188-98

[28] Dadds M R, MacDonald E, Cauchi A, Williams K, Levy F and Brennan J 2014 Nasal oxytocin for social deficits in childhood autism: A randomized controlled trial *J Autism Dev Disord* **44** 521-31

[29] Guastella A J, Gray K M, Rinehart N J, Alvares G A, Tonge B J, Hickie I B, Keating C M, Cacciotti-Saija C and Einfeld S L 2015 The effects of a course of intranasal oxytocin on social behaviors in youth diagnosed with autism spectrum disorders: A randomized controlled trial *Journal of Child Psychology and Psychiatry* **56** 444-52

[30] Yatawara C J, Einfeld S L, Hickie I B, Davenport T A and Guastella A J 2016 The effect of oxytocin nasal spray on social interaction deficits observed in young children with autism: A randomized clinical crossover trial *Molecular Psychiatry* **21** 1225-31

[31] Strathearn L, Kim S, Bastian D A, Jung J, Iyengar U, Martinez S, Goin-Kochel R P and Fonagy P 2018 Visual systemizing preference in children with autism: A randomized controlled trial of intranasal oxytocin *Development and Psychopathology* **30** 511-21

[32] Ooi Y P, Weng S-J, Kossowsky J, Gerger H and Sung M 2017 Oxytocin and autism spectrum disorders: A systematic review and meta-analysis of randomized controlled trials *Pharmacopsychiatry* **50** 5-13

[33] Baron-Cohen S, Wheelwright S, Hill J, Raste Y and Plumb I 2001 The "Reading the Mind in the Eyes" Test revised version: A study with normal adults, and adults with asperger

**76**

**15** S156-61

*Oxytocin and Health*

**References**

[1] Maenner M J 2020 Prevalence of autism spectrum disorder among children aged 8 years — autism and developmental disabilities monitoring network, 11 sites, United States, 2016

autism: Animal models and novel therapeutic strategies *Horm Behav*

[11] Domes G, Heinrichs M, Michel A, Berger C and Herpertz S C 2007 Oxytocin improves "mind-reading" in humans *Biological Psychiatry* **61** 731-3

[12] Hurlemann R, Patin A, Onur O A, Cohen M X, Baumgartner T, Metzler S, Dziobek I, Gallinat J, Wagner M, Maier W and Kendrick K M 2010 Oxytocin enhances amygdala-dependent, socially reinforced learning and emotional empathy in humans *J. Neurosci.* **30**

[13] Kosfeld M, Heinrichs M, Zak P J, Fischbacher U and Fehr E 2005 Oxytocin increases trust in humans

[14] Gordon I, Martin C, Feldman R and Leckman J F 2011 Oxytocin and social motivation *Dev Cogn Neurosci* **1** 471-93

[15] Baskerville T A and Douglas A J 2010 Dopamine and oxytocin interactions underlying behaviors: Potential contributions to behavioral disorders *CNS Neuroscience & Thera-*

[16] Baskerville T A, Allard J, Wayman C and Douglas A J 2009 Dopamine– oxytocin interactions in penile erection *European Journal of Neuroscience* **30**

[17] Shapiro L E and Insel T R 1989 Ontogeny of oxytocin receptors in rat forebrain: A quantitative study *Synapse*

[18] Krol K M, Moulder R G, Lillard T S, Grossmann T and Connelly J J 2019 Epigenetic dynamics in infancy and the impact of maternal engagement *Science*

**61** 340-50

4999-5007

*Nature* **435** 673-6

*peutics* **16** e92-123

2151-64

**4** 259-66

*Advances* **5** eaay0680

[2] American Psychiatric Association 2013 *Diagnostic and statistical manual of mental disorders* (Washington, DC: American Psychiatric Publishing)

[3] Dawson G, Webb S J and McPartland J 2005 Understanding the nature of face processing impairment in autism: insights from behavioral and electrophysiological studies *Dev Neuropsychol* **27** 403-24

[4] Chevallier C, Kohls G, Troiani V, Brodkin E S and Schultz R T 2012 The social motivation theory of autism

[5] Dawson G 2008 Early behavioral intervention, brain plasticity, and the prevention of autism spectrum disorder

[6] Stavropoulos K K M and Carver L J 2013 Research Review: Social motivation and oxytocin in autism – implications for joint attention development and intervention *Journal of Child Psychology*

[7] Gainer H, Altstein M and Whitnall M H 1987 The cell biology and development of vasopressinergic and oxytocinergic neurons *Prog. Brain Res.* **72** 153-61

[8] Magon N and Kalra S 2011 The orgasmic history of oxytocin: Love, lust, and labor *Indian J Endocrinol Metab*

[9] Carter C S and Porges S W 2013 The biochemistry of love: An oxytocin hypothesis *EMBO reports* **14** 12-6

[10] Modi M E and Young L J 2012 The oxytocin system in drug discovery for

*Trends Cogn Sci* **16** 231-9

*Dev Psychopathol* **20** 775-803

*and Psychiatry* **54** 603-18

*MMWR Surveill Summ* **69**

syndrome or high-functioning autism *Journal of Child Psychology and Psychiatry* **42** 241-51

[34] Lord C, Risi S, Lambrecht L, Cook E H, Leventhal B L, DiLavore P C, Pickles A and Rutter M 2000 The Autism Diagnostic Observation Schedule-Generic: A standard measure of social and communication deficits associated with the spectrum of autism *J Autism Dev Disord* **30** 205-23

[35] Aman M G, Singh N N, Stewart A W and Field C J 1985 The aberrant behavior checklist: A behavior rating scale for the assessment of treatment effects *Am J Ment Defic* **89** 485-91

[36] Achenbach T M and Edelbrock C 1991 Child behavior checklist *Burlington (Vt)* **7** 371-92

[37] Constantino J N and Gruber C P 2005 *Social Responsiveness Scale* (WPS)

[38] Reynolds C R and Kamphaus R W 1992 *Behavior Assessment System for Children* (Circle Pines, MN: American Guidance Service)

[39] Wolf J M, Tanaka J W, Klaiman C, Cockburn J, Herlihy L, Brown C, South M, McPartland J, Kaiser M D, Phillips R and Schultz R T 2008 Specific impairment of face processing abilities in children with autism spectrum disorder using the Let's Face It! Skills Battery *Autism Res* **1** 329-40

[40] Dennis M, Purvis K, Barnes M A, Wilkinson M and Winner E 2001 Understanding of literal truth, ironic criticism, and deceptive praise following childhood head injury *Brain and Language* **78** 1-16

[41] Happé F G E 1994 An advanced test of theory of mind: Understanding of story characters' thoughts and feelings by able autistic, mentally handicapped, and normal children and adults *J Autism Dev Disord* **24** 129-54

[42] Gadow K and Sprafkin J 2009 *The symptom inventories: An annotated bibliography*

[43] Bodfish J W, Symons F J, Parker D E and Lewis M H 2000 Varieties of repetitive behavior in autism: Comparisons to mental retardation *J Autism Dev Disord* **30** 237-43

[44] Scahill L, Riddle M A, McSwiggin-Hardin M, Ort S I, King R A, Goodman W K, Cicchetti D and Leckman J F 1997 Children's Yale-Brown obsessive compulsive scale: Reliability and validity *Journal of the American Academy of Child & Adolescent Psychiatry* **36** 9

[45] Baron-Cohen S 2007 *Mind reading: The interactive guide to emotions* (Jessica Kingsley Publishers)

[46] Gresham F M and Elliott S N 1990 *The Social Skills Rating System* (American Guidance Service)

[47] Tonge B J, Brereton A V, Gray K M and Einfeld S L 1999 Behavioural and emotional disturbance in highfunctioning autism and asperger syndrome *Autism* **3** 117-30

[48] Nowicki S and Duke M P 2001 Nonverbal receptivity: The Diagnostic Analysis of Nonverbal Accuracy (DANVA) *Interpersonal sensitivity: Theory and measurement* The LEA series in personality and clinical psychology (Mahwah, NJ, US: Lawrence Erlbaum Associates Publishers) pp 183-98

[49] Moore D G, Hobson R P and Lee A 1997 Components of person perception: An investigation with autistic, nonautistic retarded and typically developing children and adolescents *British Journal of Developmental Psychology* **15** 401-23

[50] Einfeld S L and Tonge B J 1995 The Developmental Behavior Checklist: The development and validation of an instrument to assess behavioral and emotional disturbance in children and

**79**

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

individuals with ASD: Neuroimaging and behavioral evidence *Progress in Molecular Biology and Translational Science* Autism vol 173, ed M Ilieva and W K W Lau

[58] Eldevik S, Hastings R P, Hughes J C, Jahr E, Eikeseth S and Cross S 2009 Meta-analysis of early intensive behavioral intervention for children with autism *Journal of Clinical Child &*

*Adolescent Psychology* **38** 439-50

[59] Kasari C and Lawton K 2010 New directions in behavioral treatment of autism spectrum disorders *Curr Opin*

[60] Dawson G, Rogers S, Munson J, Smith M, Winter J, Greenson J, Donaldson A and Varley J 2010 Randomized, controlled trial of an intervention for toddlers with autism: The Early Start Denver Model *Pediatrics*

[61] Reichow B, Barton E E, Boyd B A and Hume K 2012 Early intensive behavioral intervention (EIBI) for young children with autism spectrum disorders (ASD) *Cochrane Database Syst*

[62] Howlin P, Magiati I, Charman T and MacLean J 2009 Systematic review of early intensive behavioral interventions for children with autism *Am J Intellect*

[63] Dawson G and Burner K 2011 Behavioral interventions in children and adolescents with autism spectrum disorder: A review of recent findings

[64] Schreibman L, Dawson G, Stahmer A C, Landa R, Rogers S J, McGee G G, Kasari C, Ingersoll B, Kaiser A P, Bruinsma Y, McNerney E, Wetherby A and Halladay A 2015 Naturalistic

developmental behavioral interventions: Empirically validated treatments for autism spectrum disorder *J Autism Dev*

*Curr Opin Pediatr* **23** 616-20

(Elsevier) pp 209-38

*Neurol* **23** 137-43

**125** e17-23

*Rev* **10** CD009260

*Dev Disabil* **114** 23-41

*Disord* **45** 2411-28

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

adolescents with mental retardation *J*

[51] Guy W 1976 *ECDEU assessment manual for psychopharmacology* (Rockville, Md: U.S. Dept. of Health, Education, and Welfare, Public Health Service, Alcohol, Drug Abuse, and Mental Health Administration, National Institute of Mental Health, Psychopharmacology Research Branch, Division of Extramural Research

[52] Brannan A M, Heflinger C A and Bickman L 1997 The caregiver strain questionnaire: Measuring the impact on the family of living with a child with serious emotional disturbance *Journal of Emotional and Behavioral Disorders*

[53] Spence S H, Barrett P M and Turner C M 2003 Psychometric properties of the Spence Children's Anxiety Scale with young adolescents *Journal of Anxiety*

[54] Gordon I, Wyk B C V, Bennett R H, Cordeaux C, Lucas M V, Eilbott J A, Zagoory-Sharon O, Leckman J F, Feldman R and Pelphrey K A 2013 Oxytocin enhances brain function in children with autism *PNAS* **110** 20953-8

[55] Gordon I, Jack A, Pretzsch C M, Vander Wyk B, Leckman J F, Feldman R and Pelphrey K A 2016 Intranasal oxytocin enhances connectivity in the neural circuitry supporting social motivation and social perception in children with autism *Sci Rep* **6** 35054

[56] Greene R K, Spanos M, Alderman C, Walsh E, Bizzell J, Mosner M G, Kinard J L, Stuber G D, Chandrasekhar T, Politte L C, Sikich L and Dichter G S 2018 The effects of intranasal oxytocin on reward circuitry responses in children with autism spectrum disorder *Journal of Neurodevelopmental Disorders* **10** 12

[57] Baker E and Stavropoulos K K M 2020 The effects of oxytocin administration on

*Autism Dev Disord* **25** 81-104

Programs)

**5** 212-22

*Disorders* **17** 605-25

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

adolescents with mental retardation *J Autism Dev Disord* **25** 81-104

*Oxytocin and Health*

*Psychiatry* **42** 241-51

*Dev Disord* **30** 205-23

*(Vt)* **7** 371-92

Guidance Service)

syndrome or high-functioning autism

[42] Gadow K and Sprafkin J 2009 *The symptom inventories: An annotated*

[43] Bodfish J W, Symons F J, Parker D E and Lewis M H 2000 Varieties of repetitive behavior in autism: Comparisons to mental retardation *J*

McSwiggin-Hardin M, Ort S I, King R A, Goodman W K, Cicchetti D and Leckman J F 1997 Children's Yale-Brown obsessive compulsive scale: Reliability and validity *Journal of the American Academy of Child*

[45] Baron-Cohen S 2007 *Mind reading: The interactive guide to emotions* (Jessica

[46] Gresham F M and Elliott S N 1990

[47] Tonge B J, Brereton A V, Gray K M and Einfeld S L 1999 Behavioural and emotional disturbance in highfunctioning autism and asperger syndrome *Autism* **3** 117-30

[48] Nowicki S and Duke M P 2001 Nonverbal receptivity: The Diagnostic Analysis of Nonverbal Accuracy (DANVA) *Interpersonal sensitivity: Theory and measurement* The LEA series in personality and clinical psychology (Mahwah, NJ, US: Lawrence Erlbaum Associates Publishers) pp 183-98

[49] Moore D G, Hobson R P and Lee A 1997 Components of person perception: An investigation with autistic, nonautistic retarded and typically developing children and adolescents *British Journal of Developmental Psychology* **15** 401-23

[50] Einfeld S L and Tonge B J 1995 The Developmental Behavior Checklist: The development and validation of an instrument to assess behavioral and emotional disturbance in children and

*Autism Dev Disord* **30** 237-43

[44] Scahill L, Riddle M A,

*& Adolescent Psychiatry* **36** 9

*The Social Skills Rating System* (American Guidance Service)

Kingsley Publishers)

*bibliography*

[34] Lord C, Risi S, Lambrecht L, Cook E H, Leventhal B L, DiLavore P C, Pickles A and Rutter M 2000 The Autism Diagnostic Observation Schedule-Generic: A standard measure of social and communication deficits associated with the spectrum of autism *J Autism*

[35] Aman M G, Singh N N, Stewart A W and Field C J 1985 The aberrant behavior checklist: A behavior rating scale for the assessment of treatment effects *Am J Ment Defic* **89** 485-91

[36] Achenbach T M and Edelbrock C 1991 Child behavior checklist *Burlington*

[37] Constantino J N and Gruber C P 2005 *Social Responsiveness Scale* (WPS)

[38] Reynolds C R and Kamphaus R W 1992 *Behavior Assessment System for Children* (Circle Pines, MN: American

[39] Wolf J M, Tanaka J W, Klaiman C, Cockburn J, Herlihy L, Brown C, South M, McPartland J, Kaiser M D, Phillips R and Schultz R T 2008 Specific impairment of face processing abilities in children with autism spectrum disorder using the Let's Face It! Skills

[40] Dennis M, Purvis K, Barnes M A, Wilkinson M and Winner E 2001 Understanding of literal truth, ironic criticism, and deceptive praise following

[41] Happé F G E 1994 An advanced test of theory of mind: Understanding of story characters' thoughts and feelings by able autistic, mentally handicapped, and normal children and adults *J Autism*

childhood head injury *Brain and*

*Language* **78** 1-16

*Dev Disord* **24** 129-54

Battery *Autism Res* **1** 329-40

*Journal of Child Psychology and*

**78**

[51] Guy W 1976 *ECDEU assessment manual for psychopharmacology* (Rockville, Md: U.S. Dept. of Health, Education, and Welfare, Public Health Service, Alcohol, Drug Abuse, and Mental Health Administration, National Institute of Mental Health, Psychopharmacology Research Branch, Division of Extramural Research Programs)

[52] Brannan A M, Heflinger C A and Bickman L 1997 The caregiver strain questionnaire: Measuring the impact on the family of living with a child with serious emotional disturbance *Journal of Emotional and Behavioral Disorders* **5** 212-22

[53] Spence S H, Barrett P M and Turner C M 2003 Psychometric properties of the Spence Children's Anxiety Scale with young adolescents *Journal of Anxiety Disorders* **17** 605-25

[54] Gordon I, Wyk B C V, Bennett R H, Cordeaux C, Lucas M V, Eilbott J A, Zagoory-Sharon O, Leckman J F, Feldman R and Pelphrey K A 2013 Oxytocin enhances brain function in children with autism *PNAS* **110** 20953-8

[55] Gordon I, Jack A, Pretzsch C M, Vander Wyk B, Leckman J F, Feldman R and Pelphrey K A 2016 Intranasal oxytocin enhances connectivity in the neural circuitry supporting social motivation and social perception in children with autism *Sci Rep* **6** 35054

[56] Greene R K, Spanos M, Alderman C, Walsh E, Bizzell J, Mosner M G, Kinard J L, Stuber G D, Chandrasekhar T, Politte L C, Sikich L and Dichter G S 2018 The effects of intranasal oxytocin on reward circuitry responses in children with autism spectrum disorder *Journal of Neurodevelopmental Disorders* **10** 12

[57] Baker E and Stavropoulos K K M 2020 The effects of oxytocin administration on

individuals with ASD: Neuroimaging and behavioral evidence *Progress in Molecular Biology and Translational Science* Autism vol 173, ed M Ilieva and W K W Lau (Elsevier) pp 209-38

[58] Eldevik S, Hastings R P, Hughes J C, Jahr E, Eikeseth S and Cross S 2009 Meta-analysis of early intensive behavioral intervention for children with autism *Journal of Clinical Child & Adolescent Psychology* **38** 439-50

[59] Kasari C and Lawton K 2010 New directions in behavioral treatment of autism spectrum disorders *Curr Opin Neurol* **23** 137-43

[60] Dawson G, Rogers S, Munson J, Smith M, Winter J, Greenson J, Donaldson A and Varley J 2010 Randomized, controlled trial of an intervention for toddlers with autism: The Early Start Denver Model *Pediatrics* **125** e17-23

[61] Reichow B, Barton E E, Boyd B A and Hume K 2012 Early intensive behavioral intervention (EIBI) for young children with autism spectrum disorders (ASD) *Cochrane Database Syst Rev* **10** CD009260

[62] Howlin P, Magiati I, Charman T and MacLean J 2009 Systematic review of early intensive behavioral interventions for children with autism *Am J Intellect Dev Disabil* **114** 23-41

[63] Dawson G and Burner K 2011 Behavioral interventions in children and adolescents with autism spectrum disorder: A review of recent findings *Curr Opin Pediatr* **23** 616-20

[64] Schreibman L, Dawson G, Stahmer A C, Landa R, Rogers S J, McGee G G, Kasari C, Ingersoll B, Kaiser A P, Bruinsma Y, McNerney E, Wetherby A and Halladay A 2015 Naturalistic developmental behavioral interventions: Empirically validated treatments for autism spectrum disorder *J Autism Dev Disord* **45** 2411-28

[65] Hart B M and Risley T R 1968 Establishing use of descriptive adjectives in the spontaneous speech of disadvantaged preschool children *J Appl Behav Anal* **1** 109-20

[66] Ingersoll B 2010 Brief report: Pilot randomized controlled trial of reciprocal imitation training for teaching elicited and spontaneous imitation to children with autism *J Autism Dev Disord* **40** 1154-60

[67] Ingersoll B and Schreibman L 2006 Teaching reciprocal imitation skills to young children with autism using a naturalistic behavioral approach: Effects on language, pretend play, and joint attention *J Autism Dev Disord* **36** 487-505

[68] Ingersoll B and Wainer A 2013 Initial efficacy of Project ImPACT: A parent-mediated social communication intervention for young children with asd *J Autism Dev Disord* **43** 2943-52

[69] Kasari C, Freeman S and Paparella T 2006 Joint attention and symbolic play in young children with autism: a randomized controlled intervention study *J Child Psychol Psychiatry* **47** 611-20

[70] Kasari C, Paparella T, Freeman S and Jahromi L B 2008 Language outcome in autism: Randomized comparison of joint attention and play interventions *Journal of Consulting and Clinical Psychology* **76** 125

[71] Rogers S J and Dawson G 2009 *Early start denver model curriculum checklist for young children with autism* (Guilford Press)

[72] Fuller E A, Oliver K, Vejnoska S F and Rogers S J 2020 The effects of the Early Start Denver Model for children with autism spectrum disorder: A meta-analysis *Brain Sciences* **10** 368

[73] Koegel R L and Koegel L K 2006 *Pivotal response treatments for autism: Communication, social, & academic*

*development* (Baltimore, MD, US: Paul H Brookes Publishing)

[74] Koegel R L, Koegel L K and Carter C M 1999 Pivotal teaching interactions for children with autism *School Psychology Review* **28** 576-94

[75] Koegel R L, Koegel L K and McNerney E K 2001 Pivotal areas in intervention for autism *Journal of Clinical Child & Adolescent Psychology* **30** 19-32

[76] Verschuur R, Didden R, Lang R, Sigafoos J and Huskens B 2014 Pivotal response treatment for children with autism spectrum disorders: A systematic review *Rev J Autism Dev Disord* **1** 34-61

[77] Bozkus-Genc G and Yucesoy-Ozkan S 2016 Meta-analysis of pivotal response training for children with autism spectrum disorder *Education and Training in Autism and Developmental Disabilities* **51** 13-26

[78] Stavropoulos K K M 2017 Using neuroscience as an outcome measure for behavioral interventions in autism spectrum disorders (ASD): A review *Research in Autism Spectrum Disorders* **35** 62-73

[79] Dawson G, Jones E J H, Merkle K, Venema K, Lowy R, Faja S, Kamara D, Murias M, Greenson J, Winter J, Smith M, Rogers S J and Webb S J 2012 Early behavioral intervention is associated with normalized brain activity in young children with autism *J Am Acad Child Adolesc Psychiatry* **51** 1150-9

[80] Voos A C, Pelphrey K A, Tirrell J, Bolling D Z, Vander Wyk B, Kaiser M D, McPartland J C, Volkmar F R and Ventola P 2013 Neural mechanisms of improvements in social motivation after pivotal response treatment: two case studies *J Autism Dev Disord* **43** 1-10

[81] Kaiser M D, Hudac C M, Shultz S, Lee S M, Cheung C, Berken A M, Deen B, Pitskel N B, Sugrue D R, Voos A

**81**

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes…*

[89] Yang D, Pelphrey K A, Sukhodolsky D G, Crowley M J, Dayan E, Dvornek N C, Venkataraman A, Duncan J, Staib L and Ventola P 2016 Brain responses to biological motion predict treatment outcome in young children with autism

[90] Baker E, Veytsman E, Martin A M, Blacher J and Stavropoulos K K M 2020 Increased neural reward responsivity in adolescents with ASD after social skills intervention *Brain Sciences* **10** 402

[91] Constantino J N 2012 *Social Responsiveness Scale* (WPS)

*Scales* (Pearson)

**98** 106103

*Pathology* **16** 36-42

*Dev Disord* **42** 210-20

[92] Gresham F M and Elliott S N 2008 *Social Skills Improvement System Rating*

[93] Spanos M, Chandrasekhar T, Kim S-J, Hamer R M, King B H, McDougle C J, Sanders K B, Gregory S G, Kolevzon A, Veenstra-VanderWeele J and Sikich L 2020 Rationale, design, and methods of the Autism Centers of Excellence (ACE) network Study of Oxytocin in Autism to improve Reciprocal Social Behaviors (SOARS-B) *Contemp Clin Trials*

[94] Webb S J, Jones E J H, Kelly J and Dawson G 2014 The motivation for very early intervention for infants at high risk for autism spectrum disorders *International Journal of Speech-Language*

[95] Zachor D and Ben-Itzchak E 2017 Variables affecting outcome of early intervention in autism spectrum disorder *J Pediatr Neurol* **15** 129-33

[96] Eldevik S, Hastings R P, Jahr E and Hughes J C 2012 Outcomes of behavioral intervention for children with autism in mainstream pre-school settings *J Autism*

*Transl Psychiatry* **6** e948

*DOI: http://dx.doi.org/10.5772/intechopen.96859*

[82] Ventola P, Yang D Y J, Friedman H E, Oosting D, Wolf J, Sukhodolsky D G and Pelphrey K A 2015 Heterogeneity of neural mechanisms of response to pivotal response treatment *Brain Imaging*

[83] Van Hecke A V, Stevens S, Carson A

McKindles R J, Remmel R and Brockman S 2015 Measuring the plasticity of social approach: A randomized controlled trial of the effects of the PEERS intervention on EEG asymmetry in adolescents with autism spectrum disorders *Journal of Autism and Developmental Disorders*

[84] Laugeson E A and Frankel F 2011

[86] Laugeson E A, Frankel F, Mogil C and Dillon A R 2009 Parent-assisted social skills training to improve friendships in teens with autism spectrum disorders *J*

*Social skills for teenagers with developmental and autism spectrum disorders: The PEERS treatment manual*

[85] Laugeson E A, Frankel F, Gantman A, Dillon A R and Mogil C 2012 Evidence-based social skills training for adolescents with autism spectrum disorders: The UCLA PEERS program *J Autism Dev Disord* **42** 1025-36

*Autism Dev Disord* **39** 596-606

*Psychology* **89** 525-7

[87] Mitchell A M and Pössel P 2012 Frontal brain activity pattern predicts depression in adolescent boys *Biological*

[88] Venkataraman A, Yang D Y J, Dvornek N, Staib L H, Duncan J S, Pelphrey K A and Ventola P 2016 Pivotal

functional rewiring of the brain among individuals with autism spectrum disorder *Neuroreport* **27** 1081-5

response treatment prompts a

M, Karst J S, Dolan B, Schohl K,

C, Saulnier C A, Ventola P, Wolf J M, Klin A, Vander Wyk B C and Pelphrey K A 2010 Neural signatures of autism *Proc*

*Natl Acad Sci U S A* **107** 21223-8

*Behav* **9** 74-88

**45** 316-35

(Routledge)

*Priming the Pathway: Combining Oxytocin and Behavioral Intervention to Improve Outcomes… DOI: http://dx.doi.org/10.5772/intechopen.96859*

C, Saulnier C A, Ventola P, Wolf J M, Klin A, Vander Wyk B C and Pelphrey K A 2010 Neural signatures of autism *Proc Natl Acad Sci U S A* **107** 21223-8

*Oxytocin and Health*

*Behav Anal* **1** 109-20

[65] Hart B M and Risley T R 1968 Establishing use of descriptive

adjectives in the spontaneous speech of disadvantaged preschool children *J Appl*  *development* (Baltimore, MD, US: Paul H

[74] Koegel R L, Koegel L K and Carter C M 1999 Pivotal teaching interactions for children with autism *School Psychology*

[75] Koegel R L, Koegel L K and McNerney E K 2001 Pivotal areas in intervention for autism *Journal of Clinical Child & Adolescent Psychology* **30** 19-32

[76] Verschuur R, Didden R, Lang R, Sigafoos J and Huskens B 2014 Pivotal response treatment for children with autism spectrum disorders: A systematic review *Rev J Autism Dev Disord* **1** 34-61

[77] Bozkus-Genc G and Yucesoy-Ozkan S 2016 Meta-analysis of pivotal response

training for children with autism spectrum disorder *Education and Training in Autism and Developmental*

[78] Stavropoulos K K M 2017 Using neuroscience as an outcome measure for behavioral interventions in autism spectrum disorders (ASD): A review *Research in Autism Spectrum Disorders*

[79] Dawson G, Jones E J H, Merkle K, Venema K, Lowy R, Faja S, Kamara D, Murias M, Greenson J, Winter J, Smith M, Rogers S J and Webb S J 2012 Early behavioral intervention is

associated with normalized brain activity in young children with autism *J Am Acad*

*Child Adolesc Psychiatry* **51** 1150-9

[80] Voos A C, Pelphrey K A, Tirrell J, Bolling D Z, Vander Wyk B, Kaiser M D, McPartland J C, Volkmar F R and Ventola P 2013 Neural mechanisms of improvements in social motivation after pivotal response treatment: two case studies *J Autism Dev Disord* **43** 1-10

[81] Kaiser M D, Hudac C M, Shultz S, Lee S M, Cheung C, Berken A M, Deen B, Pitskel N B, Sugrue D R, Voos A

*Disabilities* **51** 13-26

**35** 62-73

Brookes Publishing)

*Review* **28** 576-94

[66] Ingersoll B 2010 Brief report: Pilot

[67] Ingersoll B and Schreibman L 2006 Teaching reciprocal imitation skills to young children with autism using a naturalistic behavioral approach: Effects on language, pretend play, and joint attention *J Autism Dev Disord* **36** 487-505

[68] Ingersoll B and Wainer A 2013 Initial efficacy of Project ImPACT: A parent-mediated social communication intervention for young children with asd *J Autism Dev Disord* **43** 2943-52

[69] Kasari C, Freeman S and Paparella T 2006 Joint attention and symbolic play in

[70] Kasari C, Paparella T, Freeman S and Jahromi L B 2008 Language outcome in autism: Randomized comparison of joint attention and play interventions *Journal of Consulting and*

[71] Rogers S J and Dawson G 2009 *Early start denver model curriculum checklist for young children with autism*

[72] Fuller E A, Oliver K, Vejnoska S F and Rogers S J 2020 The effects of the Early Start Denver Model for children with autism spectrum disorder: A meta-analysis *Brain Sciences* **10** 368

[73] Koegel R L and Koegel L K 2006 *Pivotal response treatments for autism: Communication, social, & academic*

young children with autism: a randomized controlled intervention study *J Child Psychol Psychiatry* **47** 611-20

*Clinical Psychology* **76** 125

(Guilford Press)

randomized controlled trial of reciprocal imitation training for teaching elicited and spontaneous imitation to children with autism *J Autism Dev Disord* **40** 1154-60

**80**

[82] Ventola P, Yang D Y J, Friedman H E, Oosting D, Wolf J, Sukhodolsky D G and Pelphrey K A 2015 Heterogeneity of neural mechanisms of response to pivotal response treatment *Brain Imaging Behav* **9** 74-88

[83] Van Hecke A V, Stevens S, Carson A M, Karst J S, Dolan B, Schohl K, McKindles R J, Remmel R and Brockman S 2015 Measuring the plasticity of social approach: A randomized controlled trial of the effects of the PEERS intervention on EEG asymmetry in adolescents with autism spectrum disorders *Journal of Autism and Developmental Disorders* **45** 316-35

[84] Laugeson E A and Frankel F 2011 *Social skills for teenagers with developmental and autism spectrum disorders: The PEERS treatment manual* (Routledge)

[85] Laugeson E A, Frankel F, Gantman A, Dillon A R and Mogil C 2012 Evidence-based social skills training for adolescents with autism spectrum disorders: The UCLA PEERS program *J Autism Dev Disord* **42** 1025-36

[86] Laugeson E A, Frankel F, Mogil C and Dillon A R 2009 Parent-assisted social skills training to improve friendships in teens with autism spectrum disorders *J Autism Dev Disord* **39** 596-606

[87] Mitchell A M and Pössel P 2012 Frontal brain activity pattern predicts depression in adolescent boys *Biological Psychology* **89** 525-7

[88] Venkataraman A, Yang D Y J, Dvornek N, Staib L H, Duncan J S, Pelphrey K A and Ventola P 2016 Pivotal response treatment prompts a functional rewiring of the brain among individuals with autism spectrum disorder *Neuroreport* **27** 1081-5

[89] Yang D, Pelphrey K A, Sukhodolsky D G, Crowley M J, Dayan E, Dvornek N C, Venkataraman A, Duncan J, Staib L and Ventola P 2016 Brain responses to biological motion predict treatment outcome in young children with autism *Transl Psychiatry* **6** e948

[90] Baker E, Veytsman E, Martin A M, Blacher J and Stavropoulos K K M 2020 Increased neural reward responsivity in adolescents with ASD after social skills intervention *Brain Sciences* **10** 402

[91] Constantino J N 2012 *Social Responsiveness Scale* (WPS)

[92] Gresham F M and Elliott S N 2008 *Social Skills Improvement System Rating Scales* (Pearson)

[93] Spanos M, Chandrasekhar T, Kim S-J, Hamer R M, King B H, McDougle C J, Sanders K B, Gregory S G, Kolevzon A, Veenstra-VanderWeele J and Sikich L 2020 Rationale, design, and methods of the Autism Centers of Excellence (ACE) network Study of Oxytocin in Autism to improve Reciprocal Social Behaviors (SOARS-B) *Contemp Clin Trials* **98** 106103

[94] Webb S J, Jones E J H, Kelly J and Dawson G 2014 The motivation for very early intervention for infants at high risk for autism spectrum disorders *International Journal of Speech-Language Pathology* **16** 36-42

[95] Zachor D and Ben-Itzchak E 2017 Variables affecting outcome of early intervention in autism spectrum disorder *J Pediatr Neurol* **15** 129-33

[96] Eldevik S, Hastings R P, Jahr E and Hughes J C 2012 Outcomes of behavioral intervention for children with autism in mainstream pre-school settings *J Autism Dev Disord* **42** 210-20

**83**

**Chapter 6**

*Chitose Orikasa*

and sexual dimorphism are discussed.

cated in brain sexual dimorphism [2].

**Abstract**

**1. Introduction**

Regulation of Morphological and

Sexual dimorphism of the adult brain regulates sex-dependent functions including reproductive and neuroendocrine activities in rodents. It is determined by sex steroid hormones during a critical perinatal period in female and male rodents. Sex steroids act on each nuclear receptor in the brain and control different physiological and neuroendocrine functions and behaviors.  This review addresses and focuses largely on the role of sexdependent differences in the brain, and their crucial functions in animal models. Particularly, recent intriguing data concerning the diversity of neuronal functions

**Keywords:** Sexual dimorphism, Sex steroid: Estrogen, ERα, ERβ, Neuronal plasticity

Sexual dimorphism is characterized by morphological and physiological changes driven by sex steroids. In the rodent brain, it occurs during a critical period characterized by higher plasticity of neurons allowing changes in neuronal circuits and connectivity. For instance, hormonal manipulation during this time window, such as castration in males or replacement therapy in females (injections of androgen or estrogen), resulted in the conversion of intrinsic features and alteration of structures and functions of neural circuits in the brain. In rodents, critical time span for brain sex differentiation extends from embryonic day (ED) 18 to the postnatal day 10 [1], while in human it is exclusively embryonic day (ED12–22). Post this critical period, neuronal plasticity is lost and the effects of sex steroids can be diverted to activational effects in the brain. The mechanisms involved in defining the timing and duration of the neonatal critical period for the brain sexual differentiation remains to be determined. It is proposed that epigenetic modifications such as DNA methylation and histone acetylation might control the expression of genes impli-

The neuroendocrine systems, which control the action of sex steroids, including that on neural circuits, are differentiated in a sex-dependent manner, resulting in the regulation of reproductive and sex-specific behaviors. The actions of sex steroids in masculinization and feminization of the brain are mediated by steroid hormone receptors. In both human and nonhuman primates, young male and females show sex differences in toy preferences [3, 4]. Girls with congenital adrenal hyperplasia (CAH)

Functional Aspects of Sexual

Dimorphism in the Brain

#### **Chapter 6**

## Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain

*Chitose Orikasa*

#### **Abstract**

Sexual dimorphism of the adult brain regulates sex-dependent functions including reproductive and neuroendocrine activities in rodents. It is determined by sex steroid hormones during a critical perinatal period in female and male rodents. Sex steroids act on each nuclear receptor in the brain and control different physiological and neuroendocrine functions and behaviors.  This review addresses and focuses largely on the role of sexdependent differences in the brain, and their crucial functions in animal models. Particularly, recent intriguing data concerning the diversity of neuronal functions and sexual dimorphism are discussed.

**Keywords:** Sexual dimorphism, Sex steroid: Estrogen, ERα, ERβ, Neuronal plasticity

#### **1. Introduction**

Sexual dimorphism is characterized by morphological and physiological changes driven by sex steroids. In the rodent brain, it occurs during a critical period characterized by higher plasticity of neurons allowing changes in neuronal circuits and connectivity. For instance, hormonal manipulation during this time window, such as castration in males or replacement therapy in females (injections of androgen or estrogen), resulted in the conversion of intrinsic features and alteration of structures and functions of neural circuits in the brain. In rodents, critical time span for brain sex differentiation extends from embryonic day (ED) 18 to the postnatal day 10 [1], while in human it is exclusively embryonic day (ED12–22). Post this critical period, neuronal plasticity is lost and the effects of sex steroids can be diverted to activational effects in the brain. The mechanisms involved in defining the timing and duration of the neonatal critical period for the brain sexual differentiation remains to be determined. It is proposed that epigenetic modifications such as DNA methylation and histone acetylation might control the expression of genes implicated in brain sexual dimorphism [2].

The neuroendocrine systems, which control the action of sex steroids, including that on neural circuits, are differentiated in a sex-dependent manner, resulting in the regulation of reproductive and sex-specific behaviors. The actions of sex steroids in masculinization and feminization of the brain are mediated by steroid hormone receptors. In both human and nonhuman primates, young male and females show sex differences in toy preferences [3, 4]. Girls with congenital adrenal hyperplasia (CAH)

show to preference toward toys of males and to have decreased female-typical behavior [5]. These results argue that behavioral sex differences are caused by sex steroids. Estrogen is produced locally in the brain from testosterone by the aromatase cytochrome P450 enzyme [6, 7] and affects sexual differentiation by biding to estrogen receptor (ER) in rodents. Maternal and fetal estrogen can be bound by the α-fetoprotein produced by fetal liver cells and yolk-sac cells, thereby preventing their passage through the blood–brain barrier [8]. This mechanism results in female brain being free from estrogen.  The effects of testosterone and its enzymatic derivative, estradiol, on their receptors are therefore critical for the sexual differentiation of the brain.

#### **2. Region-specific regulation of the ER**

#### **2.1 Sex-specific differences in the anteroventral periventricular nucleus**

The crucial role of estrogens in the sexual differentiation of the brain is mediated by estrogen receptors subtypes ERα [10, 11] and ERβ [12]. The amount of steroid hormone receptors differentiated and available development differs between sexes. The anteroventral periventricular nucleus (AVPV) is greater in size and cell number in females than in males [13, 14]. In the AVPV, the distribution of ERα is similar in both sexes, but its expression levels are higher in females than in males in prepubertal and adult rats [15]. In contrast, the distribution pattern for ERβ detected by nonisotopic *in situ* hybridization and immunohistochemistry is different between sexes [16]. Specifically, in females, a vast majority of ERβ-positive cells is located in the most medial portion of the AVPV, whereas the ERβ-containing cells in males are dispersed more laterally in the AVPV (**Figure 1**). The distribution of ERβ is reversed by neonatal hormonal manipulations [16]. Therefore, sex-specific physiological functions are predictable for sexual dimorphism in the AVPV.

#### **2.2 ER**β **sexual dimorphism in the AVPV**

Steroid-mediated organization of the brain might involve cell apoptosis, cell migration, neurogenesis, cell differentiation and synaptogenesis. Estrogen and androgen induce programmed cell death [17] by the sequential activation of cysteine-dependent asparate-specific proteases (caspase) during the development of the hypothalamus [18] in the dimorphism of dopaminergic neurons in the AVPV [19–21]. The total number of ERβ-positive cells within the AVPV is not different between intact females and males [15, 22]. This is assumed to be caused by mechanisms other than apoptosis namely the sexual dimorphic expression of ERβ in the AVPV.  Indeed, a region-specific ERβ gene expression is observed in the AVPV [22]. Moreover, the steroids might act on specific regions in the brain [22]. In brain slices from developing mouse brain, estradiol but not dihydrotestosterone induces and modulates neuronal migration [23, 24]. These results suggest that sexual dimorphism of ERβ in the AVPV might contribute to migration rather than apoptosis or neurogenesis.

#### **2.3 Functional implications in ERα and ERβ localization in the AVPV**

In the AVPV of female rats, a majority of ERβ-positive cells also express ERα [16]. It has been shown that ERα together with kisspeptin regulates ovulation, while ERβ is

**85**

**Figure 1.**

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain*

rather modified by these events [25]. At the molecular level, ERs bind to an estrogen responsive element (ERE) [26] after heterodimer formation [27], which allows the integration and collaboration of various signaling pathways for the completion of ovulation. The experimental infusion of antisense oligonucleotides in females results in decreased ERβ expression in the AVPV and consequently a persistent estrous [16]. Moreover, ERβ-positive cells and dopaminergic neurons have comparable distribution patterns in the AVPV [16]. Both ERα and ERβ have a role in the sexual dimorphism of dopaminergic neurons in the AVPV in both sexes [16, 28]. The secretion of luteinizing hormone (LH) is controlled by dopaminergic projections to neurons producing the gonadotropin-releasing hormone (GnRH) [29]. The cycle of female rats stalls ovulation state by small lesions of the AVPV [30]. Altogether, these data suggest that ERα and ERβ are colocalized with GnRH and are involved in LH secretion [31, 32]. In particular, ERα exerts a positive role for GnRH neurons, while ERβ exerts a negative control of those neurons [25]. Nonclassical ERE-independent ERα effects are involved in negative regulation on pulsatile GnRH secretion, while ERβ effects are involved in positive regulation on that secretion [31, 33]. It is still controversial to

*Sexual dimorphism in the AVPV. ER*β *positive cells aggregated densely in females (A-C), whereas the ER*β*containing cells in males (D-F) dispersed more laterally in the AVPV in the AVPV. Scale, 100* μ*m. From [16].*

*DOI: http://dx.doi.org/10.5772/intechopen.97470*

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain DOI: http://dx.doi.org/10.5772/intechopen.97470*

#### **Figure 1.**

*Oxytocin and Health*

show to preference toward toys of males and to have decreased female-typical behavior [5]. These results argue that behavioral sex differences are caused by sex steroids. Estrogen is produced locally in the brain from testosterone by the aromatase cytochrome P450 enzyme [6, 7] and affects sexual differentiation by biding to estrogen receptor (ER) in rodents. Maternal and fetal estrogen can be bound by the α-fetoprotein produced by fetal liver cells and yolk-sac cells, thereby preventing their passage through the blood–brain barrier [8]. This mechanism results in female brain being free from estrogen.  The effects of testosterone and its enzymatic derivative, estradiol, on their

receptors are therefore critical for the sexual differentiation of the brain.

**2.1 Sex-specific differences in the anteroventral periventricular nucleus**

The crucial role of estrogens in the sexual differentiation of the brain is mediated by estrogen receptors subtypes ERα [10, 11] and ERβ [12]. The amount of steroid hormone receptors differentiated and available development differs between sexes. The anteroventral periventricular nucleus (AVPV) is greater in size and cell number in females than in males [13, 14]. In the AVPV, the distribution of ERα is similar in both sexes, but its expression levels are higher in females than in males in prepubertal and adult rats [15]. In contrast, the distribution pattern for ERβ detected by nonisotopic *in situ* hybridization and immunohistochemistry is different between sexes [16]. Specifically, in females, a vast majority of ERβ-positive cells is located in the most medial portion of the AVPV, whereas the ERβ-containing cells in males are dispersed more laterally in the AVPV (**Figure 1**). The distribution of ERβ is reversed by neonatal hormonal manipulations [16]. Therefore, sex-specific physiological functions are predictable for sexual dimorphism in the AVPV.

Steroid-mediated organization of the brain might involve cell apoptosis, cell migration, neurogenesis, cell differentiation and synaptogenesis. Estrogen and androgen induce programmed cell death [17] by the sequential activation of cysteine-dependent asparate-specific proteases (caspase) during the development of the hypothalamus [18] in the dimorphism of dopaminergic neurons in the AVPV [19–21]. The total number of ERβ-positive cells within the AVPV is not different between intact females and males [15, 22]. This is assumed to be caused by mechanisms other than apoptosis namely the sexual dimorphic expression of ERβ in the AVPV.  Indeed, a region-specific ERβ gene expression is observed in the AVPV [22]. Moreover, the steroids might act on specific regions in the brain [22]. In brain slices from developing mouse brain, estradiol but not dihydrotestosterone induces and modulates neuronal migration [23, 24]. These results suggest that sexual dimorphism of ERβ in the AVPV might

contribute to migration rather than apoptosis or neurogenesis.

**2.3 Functional implications in ERα and ERβ localization in the AVPV**

In the AVPV of female rats, a majority of ERβ-positive cells also express ERα [16]. It has been shown that ERα together with kisspeptin regulates ovulation, while ERβ is

**2. Region-specific regulation of the ER**

**2.2 ER**β **sexual dimorphism in the AVPV**

**84**

*Sexual dimorphism in the AVPV. ER*β *positive cells aggregated densely in females (A-C), whereas the ER*β*containing cells in males (D-F) dispersed more laterally in the AVPV in the AVPV. Scale, 100* μ*m. From [16].*

rather modified by these events [25]. At the molecular level, ERs bind to an estrogen responsive element (ERE) [26] after heterodimer formation [27], which allows the integration and collaboration of various signaling pathways for the completion of ovulation. The experimental infusion of antisense oligonucleotides in females results in decreased ERβ expression in the AVPV and consequently a persistent estrous [16]. Moreover, ERβ-positive cells and dopaminergic neurons have comparable distribution patterns in the AVPV [16]. Both ERα and ERβ have a role in the sexual dimorphism of dopaminergic neurons in the AVPV in both sexes [16, 28]. The secretion of luteinizing hormone (LH) is controlled by dopaminergic projections to neurons producing the gonadotropin-releasing hormone (GnRH) [29]. The cycle of female rats stalls ovulation state by small lesions of the AVPV [30]. Altogether, these data suggest that ERα and ERβ are colocalized with GnRH and are involved in LH secretion [31, 32]. In particular, ERα exerts a positive role for GnRH neurons, while ERβ exerts a negative control of those neurons [25]. Nonclassical ERE-independent ERα effects are involved in negative regulation on pulsatile GnRH secretion, while ERβ effects are involved in positive regulation on that secretion [31, 33]. It is still controversial to

regulate GnRH neurons by ERs. Considering the inherent male distribution pattern of ERβ, a peculiar characteristic of the dopaminergic innervation in the AVPV [28] might be responsible for the GnRH secretion in the brain of males.

#### **2.4 Formation of the sexually dimorphic nucleus in the preoptic area**

The sexually dimorphic nucleus in the preoptic area (SDN-POA) was first characterized by Nissl staining, revealing in a larger volume in the brain of male rats than that in the brain of female rats [1, 34]. The volume of this nucleus is altered by gonadal steroids during the perinatal critical period [1]. Somatostatin might also be involved in sexual dimorphism in the SDN-POA. Indeed, during development, cells positive for somatostatin are expressed in a sex-dependent manner in the SDN-POA. Sex reversal of the dimorphism of somatostatin expression is observed in orchidectomized males and estrogen treated female pups [35]. The somatostatin mRNA-positive cells are significantly more in males than in females, but eventually the difference recedes. Somatostatin expression in females is steady during the postnatal development. The transcription of somatostatin is transient and seems to contribute to the development of the SDN-POA. Somatostatin might prompt neuronal differentiation and survival via the somatostatin receptor.

Immunostaining against calbindin D28k, a major cytoplasmic calcium-binding and buffering protein, has been successfully used to identify the rat hypothalamus [36], SDN-POA [35, 37] and provides an alternative to Nissl staining [37]. Distribution of calbindin-labeled cells in the SDN-POA is similar to somatostatin in both sexes. It has been suggested that apoptosis has a role in sexual differentiation of the SDN-POA [38]. However, no difference in the total numbers of calbindin positive cells was observed in the SDN-POA after perinatal administration of bromodeoxyuridine in both sexes [39]. On the contrary, in the postnatal SDN-POA, these neurons still show an aggregated distribution in females, while they are dispersed laterally in males [39]. Altogether, these data suggest that, besides apoptosis, cell proliferation and migration might contribute to the morphological difference in the rat SDN-POA. Moreover, ERα are reported to be expressed in the SDN-POA [40], suggesting the presence of estrogenic action in the SDN-POA sexual dimorphism.

Moreover, Nissl stained SDN-POA had not been reported in mouse until recently identified by calbindin immunohistochemistry [41] (**Figure 2**). The morphological sexdependent differences of the mouse SDN-POA were first demonstrated and established in terms of morphology and linked to gonadal steroid hormones during the prenatal critical period. Male mice have a greater number of calbindin-positive cells than females [41]. Similar differences within medial POA/anterior hypothalamic area (AHA) are observed in sheep, which are smaller in females than in males [42]. The volume of this nucleus in males is smaller in male-oriented than in female-oriented individuals. In humans, interstitial nuclei of the anterior hypothalamus (INAH) are considered comparable to those of rodent and sheep. The INAH is smaller in females than in males and smaller in homosexual men than in heterosexual men [43].  The male mice copulatory behavior and the preference for females is attributed to this difference in the SDN-POA [44–47]*.* Further functional analysis is required to completely understand the mechanisms involved in the sexual dimorphism of the SDN-POA.

#### **2.5 Sexual dimorphic expression and function of ERs in the preoptic area**

In the preoptic area (POA), ERα expression is much higher in females than in males [48]. This sex difference occurs during the perinatal period. After birth, the

**87**

**Figure 2.**

*CB-positive cells is prominent. Sale, 400* μ*m. From [41].*

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain*

expression of ERs is down regulated in the POA by estrogen [49]. The decreased ERα expression occurs in both sexes but the differential expression in the POA between females and males persists throughout life. Although the ERα levels

*Sexual dimorphism in the SDN-POA. Calbindin (CB)-immunoreactive cells in the mouse SDN-POA in males (A-E) and in females (F-J) in the rostral-caudal direction. In males (B-D), but not females, a cell aggregate of*

*DOI: http://dx.doi.org/10.5772/intechopen.97470*

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain DOI: http://dx.doi.org/10.5772/intechopen.97470*

#### **Figure 2.**

*Oxytocin and Health*

tostatin receptor.

regulate GnRH neurons by ERs. Considering the inherent male distribution pattern of ERβ, a peculiar characteristic of the dopaminergic innervation in the AVPV [28]

The sexually dimorphic nucleus in the preoptic area (SDN-POA) was first characterized by Nissl staining, revealing in a larger volume in the brain of male rats than that in the brain of female rats [1, 34]. The volume of this nucleus is altered by gonadal steroids during the perinatal critical period [1]. Somatostatin might also be involved in sexual dimorphism in the SDN-POA. Indeed, during development, cells positive for somatostatin are expressed in a sex-dependent manner in the SDN-POA. Sex reversal of the dimorphism of somatostatin expression is observed in orchidectomized males and estrogen treated female pups [35]. The somatostatin mRNA-positive cells are significantly more in males than in females, but eventually the difference recedes. Somatostatin expression in females is steady during the postnatal development. The transcription of somatostatin is transient and seems to contribute to the development of the SDN-POA. Somatostatin might prompt neuronal differentiation and survival via the soma-

Immunostaining against calbindin D28k, a major cytoplasmic calcium-binding and buffering protein, has been successfully used to identify the rat hypothalamus [36], SDN-POA [35, 37] and provides an alternative to Nissl staining [37]. Distribution of calbindin-labeled cells in the SDN-POA is similar to somatostatin in both sexes. It has been suggested that apoptosis has a role in sexual differentiation of the SDN-POA [38]. However, no difference in the total numbers of calbindin positive cells was observed in the SDN-POA after perinatal administration of bromodeoxyuridine in both sexes [39]. On the contrary, in the postnatal SDN-POA, these neurons still show an aggregated distribution in females, while they are dispersed laterally in males [39]. Altogether, these data suggest that, besides apoptosis, cell proliferation and migration might contribute to the morphological difference in the rat SDN-POA. Moreover, ERα are reported to be expressed in the SDN-POA [40], suggesting the presence of estrogenic action in the SDN-POA sexual dimorphism. Moreover, Nissl stained SDN-POA had not been reported in mouse until recently identified by calbindin immunohistochemistry [41] (**Figure 2**). The morphological sexdependent differences of the mouse SDN-POA were first demonstrated and established in terms of morphology and linked to gonadal steroid hormones during the prenatal critical period. Male mice have a greater number of calbindin-positive cells than females [41]. Similar differences within medial POA/anterior hypothalamic area (AHA) are observed in sheep, which are smaller in females than in males [42]. The volume of this nucleus in males is smaller in male-oriented than in female-oriented individuals. In humans, interstitial nuclei of the anterior hypothalamus (INAH) are considered comparable to those of rodent and sheep. The INAH is smaller in females than in males and smaller in homosexual men than in heterosexual men [43].  The male mice copulatory behavior and the preference for females is attributed to this difference in the SDN-POA [44–47]*.* Further functional analysis is required to completely understand the mechanisms involved in the sexual dimorphism of the SDN-POA.

**2.5 Sexual dimorphic expression and function of ERs in the preoptic area**

In the preoptic area (POA), ERα expression is much higher in females than in males [48]. This sex difference occurs during the perinatal period. After birth, the

might be responsible for the GnRH secretion in the brain of males.

**2.4 Formation of the sexually dimorphic nucleus in the preoptic area**

**86**

*Sexual dimorphism in the SDN-POA. Calbindin (CB)-immunoreactive cells in the mouse SDN-POA in males (A-E) and in females (F-J) in the rostral-caudal direction. In males (B-D), but not females, a cell aggregate of CB-positive cells is prominent. Sale, 400* μ*m. From [41].*

expression of ERs is down regulated in the POA by estrogen [49]. The decreased ERα expression occurs in both sexes but the differential expression in the POA between females and males persists throughout life. Although the ERα levels

are higher in females than in males, a comparable distribution pattern of ERα is observed [16, 48]. The POA has been implicated to be involved in steroid activation of the male copulatory behavior [50].  ERα and oxytocin containing neurons in the mPOA participate to control copulatory behavior in male rats [52–54]*.* In females, the POA and the adjacent bed nucleus of the stria terminalis (BNST) is considered essential for controlling maternal [55–58] and mating behaviors [59]. ERα in the mPOA is involved in the regulation of maternal care, maternal aggression and sexual behavior [56]. ERβ is detected by *in situ* hybridization and immunohistochemistry in the medial preoptic nucleus (mPOA) and more caudally in the BNST [16] (**Figure 3**). In males, ERβ in the mPOA is involved in aggressive behavior [60]. Overall in rodents, identical brain regions control specific behaviors depending on the sex. Recently, it is shown that the male-typical mounting behavior and female-typical pup retrieval behavior are induced by ERα located in the same region of the POA [61]. These data suggest that the sex specific neural circuits are able to control opposite behaviors. Therefore, sex-typical behaviors are likely induced by the harmonic expression of sex specific receptors together with sex steroid. Besides the neural circuit with a high degree of plasticity in the sexual dimorphic nervous system assuring precise sex-specific behavior events, there may be a possible the involvement of circumstances in ensuring responsiveness of the sex steroids.

#### **2.6 Functional diversity of the ventromedial hypothalamus**

The volume of the ventromedial hypothalamus (VMH) is larger in males than in females [62, 63]. ERα and ERβ are expressed in the VMH of rodents [22, 48].

#### **Figure 3.**

*Schematic representation of the distribution of ER*β *mRNA-positive cells in the forebrain of rats through rostrocaudal axis. Scale, 100 μm. AC, anterior commissure; AVPV, anteroventral periventricular nucleus; BST, bed nucleus of the stria terminals; Fx, fornix; MPN, medial preoptic nucleus; OC, optic chiasm; SCN, suprachiasmatic nucleus; V3, third ventricle. From [16].*

**89**

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain*

However, ERα expression is abundant in the ventrolateral portion of the VMH and is higher in female rats than in male rats [48]. The sex difference is most likely due to the conversion of testosterone into estrogen, which downregulates ERα expression. Moreover, the aromatase signal in males is more robust than in females [64].  ERβ expression in the adult VMH is downregulated by estrogen or testosterone administration. The difference in expression is reversed by administration of estrogen in female rats or orchidectomy male rats.  Estrogen, converted from circulating androgen in males, downregulates ERα and ERβ expression in the VMH [22, 48] and consequently physiological functions. Estrogen together with progesterone in the VMH induces female sexual reproductive behavior such as lordosis,

In adult males, the expression of ERα is lower than that in females. Cells in the male VMH are activated during fighting [66]. In these processes, ERα is involved in sexual [67] and aggressive behaviors in mice [68, 69], whereas ERβ is assume to be inhibitory to the aggressive behavior [68]. Other studies have demonstrated that male sexual behavior is not affected by ERβ in the VMH [70], but is profoundly regulated by ERα and the androgen receptor (AR), suggesting a possible distinct role for ERβ and ERα on each behavior. Opposing social behaviors, such as mounting and attack, are regulated by ERα [67] or progesterone receptor [71] cells located in discrete regions of the VMH. Sex steroid receptor expression in the VMH is induced by environmental hormonal milieu during the critical period and in turn controls the dynamic action of the sex hormones on sex-specific behavior in adults [66, 72]. These data suggest that males and females seem to exhibit identical neural circuits in the VMH, but the activated receptors might contribute to inducing the sex-typical behavior. The sex-specific neural circuit dictated by sex steroids could

**3. Alternative mechanism for sexual dimorphism in the medial amygdala**

The medial amygdala (MeA) is larger volume in males than in females [73] and this difference is abolished after castration in males and androgen treatment in females [74]. In adults, the size and volume of neurons is modified by circulating androgen. After castration of adult male rats, the cell soma size in the posterodorsal MeA (MePD) is similar to the one observed in females [74]. However, the number of MeA neurons in both sexes is not affected by adult androgens [75]. Steroid hormones also influence the organization of the MePD during the neonatal period [76, 77] and its metabolite, estrogen, results in masculinization of the MePD. ERα and ERβ are abundantly expressed in the MePD [22, 48, 78, 79] where the aromatase enzyme is also detected [80, 81]. ERs mediate estrogen-induced modifications in the MePD associated with masculinization and male-specific behaviors [82]. However, the masculinization in the MePD in the adult brain is mostly driven by circulating androgen [82]. Both the action of ER [82] and AR [83] in the MePD on the size of neuronal somas and in the sexual behavior mostly occurs in the adults [82]. In adults, there is no sex-dependent difference in ER subtype and expression in the MePD, but there is a sexual dimorphic expression of ERβ but not ERα in newborns [84]. Neonatal hormonal manipulations could not reverse the sex differences in ERβ in both sexes, suggesting that ERβ-mediated estrogen actions are not involved in the sexual dimorphism in the MePD. Furthermore, ERβ is highly expressed in the

*DOI: http://dx.doi.org/10.5772/intechopen.97470*

sexual receptivity and odor preference [65].

work in conjunction with estrogen-mediated ERs.

#### *Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain DOI: http://dx.doi.org/10.5772/intechopen.97470*

However, ERα expression is abundant in the ventrolateral portion of the VMH and is higher in female rats than in male rats [48]. The sex difference is most likely due to the conversion of testosterone into estrogen, which downregulates ERα expression. Moreover, the aromatase signal in males is more robust than in females [64].  ERβ expression in the adult VMH is downregulated by estrogen or testosterone administration. The difference in expression is reversed by administration of estrogen in female rats or orchidectomy male rats.  Estrogen, converted from circulating androgen in males, downregulates ERα and ERβ expression in the VMH [22, 48] and consequently physiological functions.

In adult males, the expression of ERα is lower than that in females. Cells in the male VMH are activated during fighting [66]. In these processes, ERα is involved in sexual [67] and aggressive behaviors in mice [68, 69], whereas ERβ is assume to be inhibitory to the aggressive behavior [68]. Other studies have demonstrated that male sexual behavior is not affected by ERβ in the VMH [70], but is profoundly regulated by ERα and the androgen receptor (AR), suggesting a possible distinct role for ERβ and ERα on each behavior. Opposing social behaviors, such as mounting and attack, are regulated by ERα [67] or progesterone receptor [71] cells located in discrete regions of the VMH. Sex steroid receptor expression in the VMH is induced by environmental hormonal milieu during the critical period and in turn controls the dynamic action of the sex hormones on sex-specific behavior in adults [66, 72]. These data suggest that males and females seem to exhibit identical neural circuits in the VMH, but the activated receptors might contribute to inducing the sex-typical behavior. The sex-specific neural circuit dictated by sex steroids could work in conjunction with estrogen-mediated ERs.

#### **3. Alternative mechanism for sexual dimorphism in the medial amygdala**

The medial amygdala (MeA) is larger volume in males than in females [73] and this difference is abolished after castration in males and androgen treatment in females [74]. In adults, the size and volume of neurons is modified by circulating androgen. After castration of adult male rats, the cell soma size in the posterodorsal MeA (MePD) is similar to the one observed in females [74]. However, the number of MeA neurons in both sexes is not affected by adult androgens [75]. Steroid hormones also influence the organization of the MePD during the neonatal period [76, 77] and its metabolite, estrogen, results in masculinization of the MePD. ERα and ERβ are abundantly expressed in the MePD [22, 48, 78, 79] where the aromatase enzyme is also detected [80, 81]. ERs mediate estrogen-induced modifications in the MePD associated with masculinization and male-specific behaviors [82]. However, the masculinization in the MePD in the adult brain is mostly driven by circulating androgen [82]. Both the action of ER [82] and AR [83] in the MePD on the size of neuronal somas and in the sexual behavior mostly occurs in the adults [82]. In adults, there is no sex-dependent difference in ER subtype and expression in the MePD, but there is a sexual dimorphic expression of ERβ but not ERα in newborns [84]. Neonatal hormonal manipulations could not reverse the sex differences in ERβ in both sexes, suggesting that ERβ-mediated estrogen actions are not involved in the sexual dimorphism in the MePD. Furthermore, ERβ is highly expressed in the

*Oxytocin and Health*

sex steroids.

are higher in females than in males, a comparable distribution pattern of ERα is observed [16, 48]. The POA has been implicated to be involved in steroid activation of the male copulatory behavior [50].  ERα and oxytocin containing neurons in the mPOA participate to control copulatory behavior in male rats [52–54]*.* In females, the POA and the adjacent bed nucleus of the stria terminalis (BNST) is considered essential for controlling maternal [55–58] and mating behaviors [59]. ERα in the mPOA is involved in the regulation of maternal care, maternal aggression and sexual behavior [56]. ERβ is detected by *in situ* hybridization and immunohistochemistry in the medial preoptic nucleus (mPOA) and more caudally in the BNST [16] (**Figure 3**). In males, ERβ in the mPOA is involved in aggressive behavior [60]. Overall in rodents, identical brain regions control specific behaviors depending on the sex. Recently, it is shown that the male-typical mounting behavior and female-typical pup retrieval behavior are induced by ERα located in the same region of the POA [61]. These data suggest that the sex specific neural circuits are able to control opposite behaviors. Therefore, sex-typical behaviors are likely induced by the harmonic expression of sex specific receptors together with sex steroid. Besides the neural circuit with a high degree of plasticity in the sexual dimorphic nervous system assuring precise sex-specific behavior events, there may be a possible the involvement of circumstances in ensuring responsiveness of the

**2.6 Functional diversity of the ventromedial hypothalamus**

The volume of the ventromedial hypothalamus (VMH) is larger in males than in females [62, 63]. ERα and ERβ are expressed in the VMH of rodents [22, 48].

*Schematic representation of the distribution of ER*β *mRNA-positive cells in the forebrain of rats through rostrocaudal axis. Scale, 100 μm. AC, anterior commissure; AVPV, anteroventral periventricular nucleus; BST, bed nucleus of the stria terminals; Fx, fornix; MPN, medial preoptic nucleus; OC, optic chiasm; SCN,*

**88**

**Figure 3.**

*suprachiasmatic nucleus; V3, third ventricle. From [16].*

MePD of adult female and male rats and is not affected by gonadectomy or estrogen treatment in both sexes [22]. Therefore, the ERβ expression also acts independent of activity in this structure.

In the MePD, sexual dimorphism involves mechanisms distinct from other regions of the brain. The MePD receives inputs from the olfactory and pheromonal systems, suggesting a functional role of this structure in sex arousal and regulation of adult social behaviors, including mating, aggressive [85, 86], and territorial behavior [87]. Acquisition of mating stimuli induces Fos in the ERs in the MeA [88]. Finally, the mechanisms induced by the ERs in the MeA and those involved in sexual stimuli [89], gonadotropin secretion [90], ovulation [91] sex and courtship behaviors [87], onset of puberty [92], parenting, and reproduction [85, 89, 93] still remain to be identified.

#### **4. Conclusion**

Sexual dimorphism is characterized by morphological differences in several regions of the brain.    Consequently, CAH results in masculinized female brain, thereby leading to male-typical preferences, which are the congenital characteristics inherently caused by steroid and not acquired by learning.

ER expression levels contribute substantially to the physiological and behavioral differences. However, the extent to which the amounts of ER control the development of sexual dimorphism remains to be clarified. Sex-specific neural circuits activated by sex steroids might contribute to the functional role of ERs activated by estrogens. Recently it was evidenced that a high neuronal plasticity rate in neural circuits is necessary to ensure precise sex-specific responsiveness to sex steroids. The mechanism involved in the regulating the local action of sex steroids remains to be elucidated. Particularly, the expression and regulation of genes implicated in sexual dimorphism must be investigated.

#### **Acknowledgements**

This work was supported, in part, by grants-in-aid for scientific research from the Japanese Ministry of Education, Science, Sports and Culture [19 K12738 (2019-2021)] (C.O.).

**91**

**Author details**

Chitose Orikasa

Nippon Medical School, Kawasaki, Japan

provided the original work is properly cited.

\*Address all correspondence to<EMAIL_ADDRESS>
*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain*

Department of Bioregulation, Institute for Advanced Medical Science,

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*DOI: http://dx.doi.org/10.5772/intechopen.97470*

#### **Declarations interest**

None.

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain DOI: http://dx.doi.org/10.5772/intechopen.97470*

### **Author details**

*Oxytocin and Health*

activity in this structure.

remain to be identified.

**4. Conclusion**

MePD of adult female and male rats and is not affected by gonadectomy or estrogen treatment in both sexes [22]. Therefore, the ERβ expression also acts independent of

In the MePD, sexual dimorphism involves mechanisms distinct from other regions of the brain. The MePD receives inputs from the olfactory and pheromonal systems, suggesting a functional role of this structure in sex arousal and regulation of adult social behaviors, including mating, aggressive [85, 86], and territorial behavior [87]. Acquisition of mating stimuli induces Fos in the ERs in the MeA [88].     Consequently, CAH results in masculinized female brain, thereby leading to male-typical preferences, which are the congenital characteristics inherently caused by steroid and not acquired by learning.  However, the extent to which the amounts of ER control the development of sexual dimorphism remains to be clarified. Sex-specific neural circuits activated by sex steroids might contribute to the functional role of ERs activated by estrogens. Recently it was evidenced that a high neuronal plasticity rate in neural circuits is necessary to ensure precise sex-specific responsiveness to sex steroids. The mechanism involved in the regulating the local action of sex steroids remains to be elucidated. Particularly, the expression and regulation of genes implicated in

This work was supported, in part, by grants-in-aid for scientific research from the Japanese Ministry of Education, Science, Sports and Culture [19 K12738

sexual dimorphism in the brain of all living beings.

sexual dimorphism must be investigated.

**Acknowledgements**

(2019-2021)] (C.O.).

**Declarations interest**

None.

**90**

Chitose Orikasa Department of Bioregulation, Institute for Advanced Medical Science, Nippon Medical School, Kawasaki, Japan

\*Address all correspondence to<EMAIL_ADDRESS>
© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Gorski, R.A., 1968. Influence of age on the response to paranatal administration of a low dose of androgen. Endocrinology. 82, 1001-1004.

[2] Forger, *Philos Trans R Soc Lond B Biol Sci.* 2016;371(1688):20150114.

[3] Berenbaum, S.A., 1999. Effects of early androgens on sex-typed activities and interests in adolescents with congenital adrenal hyperplasia. Horm. Behav. 35, 102-110.

[4] Grabowska, A., 2017. Sex on the brain: Are gender-dependent structural and functional differences associated with behavior? J Neurosci Res. 95, 200-212.

[5] Spencer, D., Pasterski, V., A S Neufeld, S.A.N., Glover, V., Thomas G O'Connor, T.G., Hindmarsh, P.C., Ieuan A Hughes, I.A., Acerini,C.L., Melissa Hines, M., 2021. Prenatal androgen exposure and children's gender-typed behavior and toy and playmate preferences Horm Behav. 127, 104889.

[6] MacLusky, N.J., Philip, A., Hurlburt C, Naftolin F. Estrogen formation in the developing rat brain: sex differences in aromatase activity during early post-natal life. Psychoneuroendocrinology. 1985, 10, 355-361.

[7] McEwen, B.S., Lieberburg, I., Chapta,l C., Krey, L., 1977. Aromatization: important for sexual differentiation of the neonatal rat brain. Horrn. Behav. 9, 249-263.

[8] MacLusky, N.J., Lieberburg, I., McEwen, B.S., 1979. The development of estrogen receptor systems in the rat brain: perinatal development. Brain Res. 178, 129-142.

[9] MacLusky, N.J., Naftolin, F., 1981. Sexual differentiation of the central

nervous system. Science. 211, 1294-1303.

[10] Green, S., Walter, P., Kumar, V., Krust, A., Bornert, J.M., Argos, P., Chambon, P., 1986. Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A. Nature. 320, 134-139.

[11] Koike, S., Sakai, M., Muramatsu, M., 1987. Molecular cloning and characterization of rat estrogen receptor cDNA. Nucleic Acids Res. 15, 2499-2513.

[12] Kuiper, G.G.J.M., Enmark, E. Pelto-Huikko, M. Nilsson, S., Gustaffsson J.-A. 1996. Cloning of a novel estrogen receptor expressed in rat prostate and ovary. Proc. Natl. Acad. Sci. USA. 93, 5925-5930.

[13] Davis, E.C., Shryne, J.E., Gorski, R.A., 1996. Structural sexual dimorphisms in the anteroventral periventricular nucleus of the rat hypothalamus are sensitive to gonadal steroids perinatally, but develop peripubertally. Neuroendocrinology. 63, 142-148.

[14] Simerly, R.B., 1998. Organization and regulation of sexually dimorphic neuroendocrine pathways. Behav. Brain Res. 92, 195-203.

[15] Kanaya, M., Morishita, M., Tsukahara S., 2018. Temporal Expression Patterns of Genes Related to Sex Steroid Action in Sexually Dimorphic Nuclei During Puberty. Front Endocrinol (Lausanne). 9, 213.

[16] Orikasa, C., Kondo, Y., Hayash,i S., McEwen, B.S., Sakuma, Y., 2002. Sexually dimorphic expression of estrogen receptor beta in the anteroventral periventricular nucleus of the rat preoptic area: implication in luteinizing hormone surge. Proc Natl Acad. Sci. U.S.A. 99, 3306-3311.

**93**

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain*

1627-1637.

7681-7694.

14077-14082.

**54,** 339-344.

102, 1645-1648.

2250-2259.

modulation of luteinizing hormone responses to kisspeptin in the female rat: implications for the generation of the preovulatory surge. Endocrinology 149,

[26] Li, X., Huang, J., Yi, P., Bambara, R.A., Hilf, R., Muyan, M., 2004. Single-chain estrogen receptors (ERs)

heterodimer emulates functions of the ERalpha dimer in genomic estrogen signaling pathways. Mol. Cell. Biol. 24,

[27] Powell, E., Shanle, E., Brinkman, A., Li, J., Keles, S., Wisinski, K.B., Wei Huang, W., Xu W., 2012. Identification of estrogen receptor dimer selective ligands reveals growth-inhibitory effects on cells that co-express ERα and

[28] Simerly, R.B., Zee, M.C., Pendleton, J.W., Lubahn, D.B., Korach, K.S., 1997. Estrogen receptor-dependent sexual differentiation of dopaminergic neurons in the preoptic region of the mouse. Proc. Natl. Acad. Sci. U.S.A. 94,

reveal that the ERalpha/beta

ERβ. PLoS One 7, e30993.

[29] Cruz, M. E., Villegas, G.,

Dominguez-Gonzalez, A., Chavira, R. & Dominguez,R. (2001) *Brain Res. Bull.*

[30] Wiegand, S. J., Terasawa, E. & Bridson, W. E. (1978) Endocrinology

[31] Hu, L., Gustofson, R.L., Feng, H., Leung, P.K., Mores, N., Krsmanovic, L.Z., Catt, K.J., 2008. Converse regulatory functions of estrogen receptor-alpha and -beta subtypes expressed in hypothalamic gonadotropin-releasing hormone neurons. Mol. Endocrinol. 22,

[32] Skynner, M.J., Sim, J.A., Herbison, A.E., 1999. Detection of estrogen receptor a and b messenger ribonucleic

*DOI: http://dx.doi.org/10.5772/intechopen.97470*

[17] Arai, Y., Murakami, S., Nishizuka, M., 1994. Androgen enhances neuronal degeneration in the developing preoptic area: apoptosis in the anteroventral periventricular nucleus (AVPvN-POA).

[18] Thompson, C.K., Brenowitz, E.A., 2008. Caspase inhibitor infusion protects an avian song control circuit from seasonal-like neurodegeneration. J.

[19] Forger, N.G., 2006. Cell death and sexual differentiation of the nervous system. Neuroscience. 138, 929-938.

[20] Tsukahara, S., 2009. Sex differences and the roles of sex steroids in apoptosis of sexually dimorphic nuclei of the preoptic area in postnatal rats. J. Neuroendocrinol. 21, 370-376.

[21] Waters, E.M., Richard B Simerly, R.B., 2009. Estrogen induces caspase-

hypothalamic development. J. Neurosci.

[22] Orikasa, C., Sakuma, Y., 2004. Sex and region-specific regulation of oestrogen receptor beta in the rat hypothalamus. J. Neuroendocrinol. 16,

[23] Henderson, R.G., Brown, A.E., Tobet, S.A., 1999. Sex differences in cell migration in the preoptic area / anterior hypothalamus of mice. J. Neurobiol. 41,

[24] Knoll, J.G., Wolfe, C.A., Tobet, S.A., 2007. Estrogen modulates neuronal movements within the developing preoptic area-anterior hypothalamus. Eur. J. Neurosci. 26, 1091-1099.

[25] Roa, J., Vigo, E., Castellano, J.M., Gaytan, F., Navarro, V.M., Aguilar, E., Dijcks, F.A. Ederveen, A.G.H., Pinilla, L., van Noort, P.I., Tena-Semper, M., 2008. Opposite roles of estrogen receptor (ER)-alpha and ERbeta in the

dependent cell death during

29, 9714-9718.

964-969.

252-266.

Horm. Behav. 28, 313-319.

Neurosci. 28,7130-7136.

*Regulation of Morphological and Functional Aspects of Sexual Dimorphism in the Brain DOI: http://dx.doi.org/10.5772/intechopen.97470*

[17] Arai, Y., Murakami, S., Nishizuka, M., 1994. Androgen enhances neuronal degeneration in the developing preoptic area: apoptosis in the anteroventral periventricular nucleus (AVPvN-POA). Horm. Behav. 28, 313-319.

[18] Thompson, C.K., Brenowitz, E.A., 2008. Caspase inhibitor infusion protects an avian song control circuit from seasonal-like neurodegeneration. J. Neurosci. 28,7130-7136.

[19] Forger, N.G., 2006. Cell death and sexual differentiation of the nervous system. Neuroscience. 138, 929-938.

[20] Tsukahara, S., 2009. Sex differences and the roles of sex steroids in apoptosis of sexually dimorphic nuclei of the preoptic area in postnatal rats. J. Neuroendocrinol. 21, 370-376.

[21] Waters, E.M., Richard B Simerly, R.B., 2009. Estrogen induces caspasedependent cell death during hypothalamic development. J. Neurosci. 29, 9714-9718.

[22] Orikasa, C., Sakuma, Y., 2004. Sex and region-specific regulation of oestrogen receptor beta in the rat hypothalamus. J. Neuroendocrinol. 16, 964-969.

[23] Henderson, R.G., Brown, A.E., Tobet, S.A., 1999. Sex differences in cell migration in the preoptic area / anterior hypothalamus of mice. J. Neurobiol. 41, 252-266.

[24] Knoll, J.G., Wolfe, C.A., Tobet, S.A., 2007. Estrogen modulates neuronal movements within the developing preoptic area-anterior hypothalamus. Eur. J. Neurosci. 26, 1091-1099.

[25] Roa, J., Vigo, E., Castellano, J.M., Gaytan, F., Navarro, V.M., Aguilar, E., Dijcks, F.A. Ederveen, A.G.H., Pinilla, L., van Noort, P.I., Tena-Semper, M., 2008. Opposite roles of estrogen receptor (ER)-alpha and ERbeta in the modulation of luteinizing hormone responses to kisspeptin in the female rat: implications for the generation of the preovulatory surge. Endocrinology 149, 1627-1637.

[26] Li, X., Huang, J., Yi, P., Bambara, R.A., Hilf, R., Muyan, M., 2004. Single-chain estrogen receptors (ERs) reveal that the ERalpha/beta heterodimer emulates functions of the ERalpha dimer in genomic estrogen signaling pathways. Mol. Cell. Biol. 24, 7681-7694.

[27] Powell, E., Shanle, E., Brinkman, A., Li, J., Keles, S., Wisinski, K.B., Wei Huang, W., Xu W., 2012. Identification of estrogen receptor dimer selective ligands reveals growth-inhibitory effects on cells that co-express ERα and ERβ. PLoS One 7, e30993.

[28] Simerly, R.B., Zee, M.C., Pendleton, J.W., Lubahn, D.B., Korach, K.S., 1997. Estrogen receptor-dependent sexual differentiation of dopaminergic neurons in the preoptic region of the mouse. Proc. Natl. Acad. Sci. U.S.A. 94, 14077-14082.

[29] Cruz, M. E., Villegas, G., Dominguez-Gonzalez, A., Chavira, R. & Dominguez,R. (2001) *Brain Res. Bull.* **54,** 339-344.

[30] Wiegand, S. J., Terasawa, E. & Bridson, W. E. (1978) Endocrinology 102, 1645-1648.

[31] Hu, L., Gustofson, R.L., Feng, H., Leung, P.K., Mores, N., Krsmanovic, L.Z., Catt, K.J., 2008. Converse regulatory functions of estrogen receptor-alpha and -beta subtypes expressed in hypothalamic gonadotropin-releasing hormone neurons. Mol. Endocrinol. 22, 2250-2259.

[32] Skynner, M.J., Sim, J.A., Herbison, A.E., 1999. Detection of estrogen receptor a and b messenger ribonucleic

**92**

178, 129-142.

*Oxytocin and Health*

**References**

1001-1004.

Behav. 35, 102-110.

200-212.

355-361.

[1] Gorski, R.A., 1968. Influence of age

nervous system. Science. 211,

[10] Green, S., Walter, P., Kumar, V., Krust, A., Bornert, J.M., Argos, P., Chambon, P., 1986. Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A. Nature. 320,

[11] Koike, S., Sakai, M., Muramatsu, M., 1987. Molecular cloning and

[12] Kuiper, G.G.J.M., Enmark, E. Pelto-Huikko, M. Nilsson, S., Gustaffsson J.-A. 1996. Cloning of a novel estrogen receptor expressed in rat prostate and ovary. Proc. Natl. Acad.

[13] Davis, E.C., Shryne, J.E., Gorski,

peripubertally. Neuroendocrinology. 63,

[14] Simerly, R.B., 1998. Organization and regulation of sexually dimorphic neuroendocrine pathways. Behav. Brain

Expression Patterns of Genes Related to

[16] Orikasa, C., Kondo, Y., Hayash,i S., McEwen, B.S., Sakuma, Y., 2002. Sexually dimorphic expression of estrogen receptor beta in the

anteroventral periventricular nucleus of the rat preoptic area: implication in luteinizing hormone surge. Proc Natl Acad. Sci. U.S.A. 99, 3306-3311.

[15] Kanaya, M., Morishita, M., Tsukahara S., 2018. Temporal

Sex Steroid Action in Sexually Dimorphic Nuclei During Puberty. Front Endocrinol (Lausanne). 9, 213.

Sci. USA. 93, 5925-5930.

R.A., 1996. Structural sexual dimorphisms in the anteroventral periventricular nucleus of the rat hypothalamus are sensitive to gonadal steroids perinatally, but develop

characterization of rat estrogen receptor cDNA. Nucleic Acids Res. 15, 2499-2513.

1294-1303.

134-139.

142-148.

Res. 92, 195-203.

[2] Forger, *Philos Trans R Soc Lond B Biol*

[3] Berenbaum, S.A., 1999. Effects of early androgens on sex-typed activities and interests in adolescents with congenital adrenal hyperplasia. Horm.

[4] Grabowska, A., 2017. Sex on the brain: Are gender-dependent structural and functional differences associated with behavior? J Neurosci Res. 95,