insular cortex insular cortex the insular cortex (also insula and insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes) within each hemisphere of the mammalian brain. insular cortexthe insula of the right side, exposed byremoving the opercula.coronal section of brain immediately infront of pons. (insula labeled at upper right.)detailspart ofcerebral cortex of brainarterymiddle cerebralidentifierslatincortex insularismeshd000087623neuronames111neurolex idbirnlex_1117ta98a14.1.09.149 a12.2.07.053ta25502fma67329anatomical terms of neuroanatomy the insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body's homeostasis. these functions include compassion, empathy, taste, perception, motor control, self-awareness, cognitive functioning, interpersonal experience, and awareness of homeostatic emotions such as hunger, pain and fatigue. in relation to these, it is involved in psychopathology. the insular cortex is divided into two parts: the anterior insula and the posterior insula in which more than a dozen field areas have been identified. the cortical area overlying the insula toward the lateral surface of the brain is the operculum (meaning lid). the opercula are formed from parts of the enclosing frontal, temporal, and parietal lobes. structure connections the anterior part of the insula is subdivided by shallow sulci into three or four short gyri. the anterior insula receives a direct projection from the basal part of the ventral medial nucleus of the thalamus and a particularly large input from the central nucleus of the amygdala. in addition, the anterior insula itself projects to the amygdala. one study on rhesus monkeys revealed widespread reciprocal connections between the insular cortex and almost all subnuclei of the amygdaloid complex. the posterior insula projects predominantly to the dorsal aspect of the lateral and to the central amygdaloid nuclei. in contrast, the anterior insula projects to the anterior amygdaloid area as well as the medial, the cortical, the accessory basal magnocellular, the medial basal, and the lateral amygdaloid nuclei. the posterior part of the insula is formed by a long gyrus. the posterior insula connects reciprocally with the secondary somatosensory cortex and receives input from spinothalamically activated ventral posterior inferior thalamic nuclei. it has also been shown that this region receives inputs from the ventromedial nucleus (posterior part) of the thalamus that are highly specialized to convey homeostatic information such as pain, temperature, itch, local oxygen status, and sensual touch. a human neuroimaging study using diffusion tensor imaging revealed that the anterior insula is interconnected to regions in the temporal and occipital lobe, opercular and orbitofrontal cortex, triangular and opercular parts of the inferior frontal gyrus. the same study revealed differences in the anatomical connection patterns between the left and right hemisphere. the 'circular sulcus of insula' (or sulcus of reil) is a semi-circular sulcus or fissure that separates the insula from the neighboring gyri of the operculum in the front, above, and behind. cytoarchitecture the insular cortex has regions of variable cell structure or cytoarchitecture, changing from granular in the posterior portion to agranular in the anterior portion. the insula also receives differential cortical and thalamic input along its length. the anterior insular cortex contains a population of spindle neurons (also called von economo neurons), identified as characterising a distinctive subregion as the agranular frontal insula. development the insular cortex is considered a separate lobe of the telencephalon by some authorities. other sources see the insula as a part of the temporal lobe. it is also sometimes grouped with limbic structures deep in the brain into a limbic lobe. as a paralimbic cortex, the insular cortex is considered to be a relatively old structure. function multimodal sensory processing, sensory binding functional imaging studies show activation of the insula during audio-visual integration tasks. taste the anterior insula is part of the primary gustatory cortex. interoceptive awareness further information: interoception there is evidence that, in addition to its base functions, the insula may play a role in certain higher-level functions that operate only in humans and other great apes. the spindle neurons found at a higher density in the right frontal insular cortex are also found in the anterior cingulate cortex, which is another region that has reached a high level of specialization in great apes. it has been speculated that these neurons are involved in cognitive-emotional processes that are specific to primates including great apes, such as empathy and metacognitive emotional feelings. this is supported by functional imaging results showing that the structure and function of the right frontal insula is correlated with the ability to feel one's own heartbeat, or to empathize with the pain of others. it is thought that these functions are not distinct from the lower-level functions of the insula but rather arise as a consequence of the role of the insula in conveying homeostatic information to consciousness. the right anterior insula is engaged in interoceptive awareness of homeostatic emotions such as thirst, pain and fatigue, and the ability to time one's own heartbeat. moreover, greater right anterior insular gray matter volume correlates with increased accuracy in this subjective sense of the inner body, and with negative emotional experience. it is also involved in the control of blood pressure, in particular during and after exercise, and its activity varies with the amount of effort a person believes he/she is exerting. the insular cortex also is where the sensation of pain is judged as to its degree. further, the insula is where a person imagines pain when looking at images of painful events while thinking about their happening to one's own body. those with irritable bowel syndrome have abnormal processing of visceral pain in the insular cortex related to dysfunctional inhibition of pain within the brain. another perception of the right anterior insula is the degree of nonpainful warmth or nonpainful coldness of a skin sensation. other internal sensations processed by the insula include stomach or abdominal distension. a full bladder also activates the insular cortex. one brain imaging study suggests that the unpleasantness of subjectively perceived dyspnea is processed in the right human anterior insula and amygdala. the cerebral cortex processing vestibular sensations extends into the insula, with small lesions in the anterior insular cortex being able to cause loss of balance and vertigo. other noninteroceptive perceptions include passive listening to music, laughter and crying, empathy and compassion, and language. motor control in motor control, it contributes to hand-and-eye motor movement, swallowing, gastric motility, and speech articulation. it has been identified as a "central command” centre that ensures that heart rate and blood pressure increase at the onset of exercise. research upon conversation links it to the capacity for long and complex spoken sentences. it is also involved in motor learning and has been identified as playing a role in the motor recovery from stroke. homeostasis it plays a role in a variety of homeostatic functions related to basic survival needs, such as taste, visceral sensation, and autonomic control. the insula controls autonomic functions through the regulation of the sympathetic and parasympathetic systems. it has a role in regulating the immune system. self the insula has been identified as playing a role in the experience of bodily self-awareness, sense of agency, and sense of body ownership. social emotions the anterior insula processes a person's sense of disgust both to smells and to the sight of contamination and mutilation — even when just imagining the experience. this associates with a mirror neuron-like link between external and internal experiences. in social experience, it is involved in the processing of norm violations, emotional processing, empathy, and orgasms. the insula is active during social decision making. tiziana quarto et al. measured emotional intelligence (ei) (the ability to identify, regulate, and process emotions of themselves and of others) of sixty-three healthy subjects. using fmri ei was measured in correlation with left insular activity. the subjects were shown various pictures of facial expressions and tasked with deciding to approach or avoid the person in the picture. the results of the social decision task yielded that individuals with high ei scores had left insular activation when processing fearful faces. individuals with low ei scores had left insular activation when processing angry faces. emotions the insular cortex, in particular its most anterior portion, is considered a limbic-related cortex. the insula has increasingly become the focus of attention for its role in body representation and subjective emotional experience. in particular, antonio damasio has proposed that this region plays a role in mapping visceral states that are associated with emotional experience, giving rise to conscious feelings. this is in essence a neurobiological formulation of the ideas of william james, who first proposed that subjective emotional experience (i.e., feelings) arise from our brain's interpretation of bodily states that are elicited by emotional events. this is an example of embodied cognition. in terms of function, the insula is believed to process convergent information to produce an emotionally relevant context for sensory experience. to be specific, the anterior insula is related more to olfactory, gustatory, viscero-autonomic, and limbic function, whereas the posterior insula is related more to auditory-somesthetic-skeletomotor function. functional imaging experiments have revealed that the insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness, and sadness. the anterior insular cortex (aic) is believed to be responsible for emotional feelings, including maternal and romantic love, anger, fear, sadness, happiness, sexual arousal, disgust, aversion, unfairness, inequity, indignation, uncertainty, disbelief, social exclusion, trust, empathy, sculptural beauty, a ‘state of union with god’, and hallucinogenic states. functional imaging studies have also implicated the insula in conscious desires, such as food craving and drug craving. what is common to all of these emotional states is that they each change the body in some way and are associated with highly salient subjective qualities. the insula is well-situated for the integration of information relating to bodily states into higher-order cognitive and emotional processes. the insula receives information from "homeostatic afferent" sensory pathways via the thalamus and sends output to a number of other limbic-related structures, such as the amygdala, the ventral striatum, and the orbitofrontal cortex, as well as to motor cortices. a study using magnetic resonance imaging found that the right anterior insula is significantly thicker in people that meditate. other research into brain activity and meditation has shown an increase in grey matter in areas of the brain including the insular cortex. another study using voxel-based morphometry and mri on experienced vipassana meditators was done to extend the findings of lazar et al., which found increased grey matter concentrations in this and other areas of the brain in experienced meditators. the strongest evidence against a causative role for the insula cortex in emotion comes from damasio et al. (2012) which showed that a patient who suffered bilateral lesions of the insula cortex expressed the full complement of human emotions, and was fully capable of emotional learning. salience functional neuroimaging research suggests the insula is involved in two types of salience. interoceptive information processing that links interoception with emotional salience to generate a subjective representation of the body. this involves, first, the anterior insular cortex with the pregenual anterior cingulate cortex (brodmann area 33) and the anterior and posterior mid-cingulate cortices, and, second, a general salience network concerned with environmental monitoring, response selection, and skeletomotor body orientation that involves all of the insular cortex and the mid-cingulate cortex. a related idea is that the anterior insula, as part of the salience network, interacts with the mid-posterior insula to combine salient stimuli with autonomic information, leading to a high state of physiological awareness of salient stimuli. an alternative or perhaps complementary proposal is that the right anterior insular regulates the interaction between the salience of the selective attention created to achieve a task (the dorsal attention system) and the salience of arousal created to keep focused upon the relevant part of the environment (ventral attention system). this regulation of salience might be particularly important during challenging tasks where attention might fatigue and so cause careless mistakes but if there is too much arousal it risks creating poor performance by turning into anxiety. auditory perception recent research indicates that the insular cortex is involved in auditory perception. responses to sound stimuli were obtained using intracranial eeg recordings acquired from patients with epilepsy. the posterior