The SMA and pre-SMA are considered part of the externally directed DAN (Vincent et al., 2008), but they are active during meditation along with the salience detecting/executive FPC network (Brefczynski-Lewis et al., 2007; Manna et al., 2010; Hasenkamp et al., 2012). The length of practice time of meditators, interestingly, was negatively correlated with all of these areas during the shifting phase, indicating that more meditation experience is associated with less activity during the shifting phase (Hasenkamp et al., 2012).

## **SPINAL MOTOR NEURONS**

The supplementary eye fields, frontal eye fields, pre-motor and motor cortices all share reciprocal connections with the LC (Shook et al., 1990). The LC projects extensively to the spinal cord depolarizing and enhancing spinal motor neuron excitability (Fung et al., 1991; White et al., 1991), making them receptive to the initiation of movement, while exercise, itself, spontaneously activates the LC (Warren et al., 1984; Haxhiu et al., 2003). These capacities of the LC may play a role in the attentive enhancement of movement during yoga.

## **LC BEHAVIOR PATTERNS TONIC BASELINE FIRING**

Higher baseline (tonic) firing in the LC is associated with enhanced labile attention and modest burst firing to various low salience distracter stimuli. This enhanced receptivity to the stimuli of the present moment is thought to optimize learning in unknown novel environments (Aston-Jones and Cohen, 2005).

During one of the earliest western scientific studies of meditation, the Zen masters reported that during meditation they had "more clearly perceived each stimulus than in their ordinary awakening state" (Kasamatsu and Hirai, 1966). Long-term meditators have repeatedly been found to exhibit an enhanced receptivity to stimuli (Jha et al., 2007; Slagter et al., 2007, 2009; Kerr et al., 2008; MacLean et al.,2010; Naranjo and Schmidt,2012;Cahn et al.,2013; Mirams et al., 2013), including to low salience and habituated standard stimuli (Cahn et al., 2013), suggestive of higher tonic baseline LC activity.

Increased receptivity to stimuli, as initiated by the activation of the FPC orienting system to oddball stimuli, causes a subjective expansion of time (Tse et al., 2004). Such a subjective expansion of time has recently been observed in meditators (Kramer et al., 2013).

## **PHASIC BASELINE FIRING**

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In contrast, lower, intermediate, more synchronous phasic baseline firing in the LC promotes larger, robust bursts to attended significant known stimuli, rapid well-learned dominant, autoassociative responses, enhanced selective attention, and reduced responding to distractor stimuli. This pattern is thought to optimize behavior in known familiar environments (Aston-Jones and Cohen, 2005) with a well-known coping response available.

## **SNS MODULATION OF LC BASELINE FIRING**

In the LC, changes in baseline firing, along with their associated subsequent bursting patterns, differentially modulate the state of the brain, the central nervous system, to optimize behavior in either novel or familiar environments, particularly if they are stressful environments.

Similarly, in the peripheral SNS, epinephrine (P-E) and P-NE are differentially released from the adrenal medulla (Mason et al., 1961; Brady, 1967; Frankenhaeuser, 1971; Stoddard et al., 1987; Morrison and Cao, 2000) under stress. Although they do not cross the blood brain barrier, P-E (Holdefer and Jensen, 1987) and P-NE (Svensson et al., 1980; Elam et al., 1984) inversely modify baseline firing in the LC.

During circumstances of novel stress a substantial amount of P-E is releasedfrom the adrenal medulla along with a small amount of P-NE (Mason et al., 1961; Brady, 1967; Frankenhaeuser et al., 1968; Frankenhaeuser, 1971). P-E elevates the baseline tonic firing in the LC (Holdefer and Jensen, 1987). This increases the release of C-NE, causing increased cortical arousal, decreased selective attention, and increased receptivity to the novel stimuli of the present moment. By the elevating of tonic baseline firing in the LC, P-E also enhances memory (Holdefer and Jensen, 1987) for the novel events through the increase in C-NE (Lemon et al., 2009; Reid and Harley, 2010).

In contrast to novel stress, under conditions of familiar stress (Mason et al., 1961; Brady, 1967; Frankenhaeuser et al., 1968; McCarty and Kopin, 1978; McCarty et al., 1978), especially with a well-known coping response available (Mandler, 1967; Frankenhaeuser et al., 1968), substantial amounts of P-NE are released from the adrenal medulla with virtually no P-E (Brady, 1967; Frankenhaeuser and Rissler, 1970; Frankenhaeuser, 1971). By elevating blood pressure, P-NE dose-dependently inhibits baseline tonic firing in the LC via the vagus and the NTS (Svensson et al., 1980; Elam et al., 1984). This causes rapid well-known dominant, autoassociative coping responses, increased selective attention, decreased responding to low salience distractor stimuli, and increased resistance to extinction (Craigmyle, N. A., unpublished data). Decreased perception of affect has also been observed (McCubbin et al., 2011). This classic stress and arousal behavior pattern (Easterbrook, 1959; Friedman et al., 1960, 1975; Zajonc, 1965; Eysenck, 1976; Geen, 1976; Geen and Gange, 1977) is consistently associated with relatively low, intermediate, phasic baseline LC activity (Aston-Jones and Cohen, 2005).

## **INVERSE RELATIONSHIP OF CORTICAL AND PERIPHERAL SNS AROUSAL**

As mentioned, there is an inverse relationship between cortical arousal and peripheral SNS arousal (Nagai et al., 2004a,b, 2009; Duschek et al., 2007, 2013). The contingent negative variation (CNV) has been used as an index of cortical arousal during orienting and attention, while changes in skin conductance were measured and pharmacological and biofeedback methods were used to elevate blood pressure, a measure of peripheral SNS arousal. Elevated blood pressure was shown to decrease the CNV amplitude in normotensive subjects (Duschek et al., 2007, 2013).

The dose-dependent inhibition of baseline firing in the LC by elevated blood pressure (Svensson et al., 1980; Elam et al., 1984) may contribute to this inverse correlation of peripheral SNS and cortical arousal.

In contrast, enhanced CNV cortical arousal-related activity in the AC, the midcingulate/SMA and the insula is associated with decreases in peripheral SNS arousal (Nagai et al., 2004b), which may be due to the capacity of these areas of the brain to inhibit the rostral VLM (Viltart et al., 2003), causing a reflex fall in SNS nerve activity and blood pressure (Standish et al., 1995). This relationship may also contribute to the inverse relationship of cortical and peripheral SNS arousal seen during meditation.

## **PRINCIPAL AREAS MODULATING THE LC AND SNS – DIRECTLY AND RECIPROCALLY**

A limited number of areas differentially influence activity in the integrated central noradrenergic LC and the peripheral noradrenergic SNS systems.

## **AC, SMA, Pre-SMA**

These areas have been briefly addressed above.

## **ORBITOFRONTAL CORTEX**

The orbitofrontal cortex (OFC) is another prominent descending cortical projection to the LC (Aston-Jones and Cohen, 2005). Activity in the AC and OFC is negatively correlated and they have complementary and reciprocal roles in monitoring the outcome of behavior (Aston-Jones and Cohen, 2005). While the AC is active in relation to self-generated decision-making, the OFC is active when the decisions are guided by the experimenter (Ullsperger and von Cramon, 2004; Walton et al., 2004), when the decisions and the reward characteristics of the stimuli are predictable (Baxter and Croxson, 2013; Rudebeck et al., 2013), are essentially known, and a coping response is available. Whereas the activity in the AC during salience detection and decision-making elevates tonic baseline firing in the LC enhancing receptivity to the various stimuli of the present moment, activity in the OFC may lower baseline firing in the LC potentiating selective attention and the rapid performance of expected well-known, autoassociative responses.

## **ASCENDING AUTONOMIC TRACTS**

The ascending autonomic tracts from the periphery also influence the LC. Cardiorespiratory, visceral and somatosensory autonomic stimuli regulate LC activity through ascending autonomic tracts with putative implications for psychiatry and psychopharmacology (Svensson, 1987). The cardiovascular stimuli from the autonomic environment seem to predominate over external environmental stimuli with respect to the LC's influence on behavior (Svensson, 1987).

The parasympathetic vagus nerve influences activity in the LC, primarily via the NTS, while the ascending sympathetic lamina 1 STT projects directly and reciprocally to the LC (Craig, 1992).

#### **CENTRAL AUTONOMIC NUCLEI**

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The LC projects reciprocally to central autonomic nuclei including the sympatheticVLM, the parasympathetic DM, and regions of the NTS. The LC also projects to the region of the parasympathetic NA (Sakai et al., 1977; Westlund and Coulter, 1980). The LC core has been found to project extensively to regions giving rise to parasympathetic outflow, while the subcoeruleus (peri-coeruleus) region projects to sympathetic regions (Westlund and Coulter, 1980). The LC is a distinct part of the central neuronal circuit innervating various regions of the rat heart (Standish et al., 1995).

As mentioned, the NA contains primary source nuclei for the cardiopulmonary branch of the vagus (Standish et al., 1995), has myelinated axons thought to rapidly modulate the function of the heart and lungs (Standish et al., 1995) and some of its neurons simultaneously innervate both the adrenal gland and the stellate sympathetic ganglion (Jansen et al., 1995) through which it can rapidly modulate the SNS.

There are alpha 1 (Boychuk et al., 2012), alpha 2 (Haxhiu et al., 2003), and beta 1 (Bateman et al., 2012) adrenergic receptors in the NA, each differentially modulating NA function. Alpha 1 receptors facilitate inhibitory neurotransmission (Boychuk et al., 2012), while beta 1 adrenergic receptors decrease both inhibitory and excitatory neurotransmission to cardiac vagal neurons (Bateman et al., 2012).

Locus coeruleus activation dilates the airways via NA alpha 2 adrenergic receptors (Haxhiu et al., 2003), while fear and emotional distress may facilitate bronchoconstrictive attacks (Lehrer et al., 1993; Haxhiu et al., 2003; Rosenkranz et al., 2005, 2012). Exercise spontaneously activates the LC (Haxhiu et al., 2003) and dilates the airways (Warren et al., 1984; Haxhiu et al., 2003). The dilation of the airways by the LC via the NA may contribute to the decreased respiratory rate and HF-HRV, which are associated with meditation (Lazar et al., 2005; Tang et al., 2009; Kodituwakku et al., 2012) and yoga. The AC appears to be a critical component in the circuitry that links the development of peripheral symptoms with emotion and cognition in asthma (Rosenkranz and Davidson, 2009). Activation of the LC by the AC may play a role in the beneficial effects of mind–body influences in asthma.

The NA is also, as previously mentioned, closely linked to the rapid expression and regulation of emotional state (Porges, 1995; Tonhajzerova et al., 2013). A withdrawal of the cardiopulmonary vagal efferent outflow from the NA is seen during both acute and chronic stress, which, in healthy individuals, is accompanied by increased sympathetic tone (Porges, 1995), by increased levels of P-NE.

Following bilateral lesions of the LC, animals fail to show normal cardioaccelerator responses to threatening stimuli (Redmond, 1977; Snyder et al., 1977). The loss of the inhibitory influence of the LC on the NA, through its adrenergic receptors, may contribute to this failure.

## **AMYGDALA**

#### *The AM is of particular importance in influencing the LC, SNS, and the AC*

The AM forms the core of a second, early-activated emotional salience detecting network or orienting system comprised of the superior colliculus, pulvinar, and AM (Liddell et al., 2005; Luo et al., 2007; Tamietto and de Gelder, 2010; Van den Stock et al., 2011; de Gelder et al., 2012). This system acts as a preconsciousness early warning system (Liddell et al., 2005; Luo et al., 2007; Tamietto and de Gelder, 2010; Van den Stock et al., 2011; de Gelder et al., 2012), particularly to threatening emotional stimuli, including threatening subliminal stimuli (Liddell et al., 2005). An early activation of the LC following subliminal stimuli has been observed, indicating this AM system may initially activate the LC (Liddell et al., 2005).

The early AM and the later cortical salience detecting orienting networks are reciprocally interconnected, sequentially activated, and both modulate the activity levels in the LC and in the SNS, each contributing differentially to adapt the state of the whole organism to environmental change.

The AM has reciprocal projections to the LC, the AC, and to the NTS and DM, amongst various other regions including the VLM, insula, and OFC (Price and Amaral, 1981; Amaral and Price, 1984; Volz et al., 1990).

The AM projects reciprocally to both the dorsal AC of the dmPFC and to the ventral AC of the vmPFC. The tract between the AM and the ventral AC is a white matter tract (Kim and Whalen, 2009), allowing for rapid transmission. Increased activity in the vmPFC is correlated with increased parasympathetic vagal activity (Lane et al., 2009; Tang et al., 2009) and the vmPFC is thought to exert a tonic influence on the parasympathetic NA during the resting state (Wong et al.,2007). Both the AM and the AC,independently, are required for the occurrence of conditioned bradycardia, the conditioned heart rate decrease that develops in response to significant stimuli (Powell et al., 1997).

Although the AM was long presumed to project to the NA (Schwaber et al., 1982; Volz et al., 1990) to rapidly activate the SNS (Porges, 1995), more recently, this could not be confirmed (Standish et al., 1995). The AM may, however, rapidly modulate activity in the NA through its white matter tract with the vmPFC.

Following stimuli, the AM directly receives an early relatively "crude" version of the stimuli via the superior colliculus and pulvinar in10–20 ms (Luo et al., 2007;Van den Stock et al., 2011). If the stimulus is significant, the AM responds rapidly within 20–30 ms and activates the LC (Liddell et al., 2005), in another10–20 ms (Bouret et al., 2003). These activations occur before the cortical frontal eye fields are activated at approximately 64 ms, the supplementary eye field at 81 ms, and the AC at100 ms (Pouget et al., 2005). All the above activations appear to commence prior to conscious awareness of the stimuli (Fried et al., 2011; Kreiman, 2012).

When conditions allow for cortical processing, the mPFC, both dorsal and ventral, is believed to regulate and control the AM, either increasing or decreasing AM activity (Ohman, 2005; Kim et al., 2011a,b). During rest, in normal low anxiety humans, activity in the vmPFC is positively correlated with the AM, while dmPFC activity is negatively correlated (Kim et al., 2011b).

Following a familiar, stressful, significant stimulus, with a known coping response available, the AM is thought to "take the PFC "off line" to allow faster, more habitual responses mediated by the posterior and/or subcortical structures to regulate behavior" (Arnsten, 1997).

The cortical mPFC, however, can in turn regulate and control the AM (Ohman, 2005; Kim et al., 2011a,b), to either enhance activity in the AM or to take the AM, itself, "off line."

Meditators exhibit lower activity in the AM (Brefczynski-Lewis et al., 2007; Creswell et al., 2007; Lutz et al., 2008), an inhibition of the AM occurs during meditation (Lutz et al., 2008) and decreased gray matter density in the AM emerges over time (Hölzel et al., 2010).

Arnsten (1997) has suggested the AM may take the PFC "off line" by activating the LC, causing high levels of C-NE and

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dopamine in the cortex to inhibit the PFC – the DLPFC in particular. Interestingly, evidence points to the LC as a common origin for both the C-NE and the dopamine in the cortex (Devoto and Flore, 2006).

The central nucleus of the AM (CeA) projects to the LC. Stimulation of the CeA stimulates the LC, producing a large single or double burst, followed by an extended refractory period (Bouret et al., 2003). In response to a familiar, stressful, significant stimulus, the CeA would be expected to stimulate the LC, eliciting a large burst of C-NE, followed by an extended refractory period, SNS peripheral arousal and elevated blood pressure, resulting in decreased cortical arousal (Duschek et al., 2007, 2013).

## *The LC projects to the basolateral amygdala influencing memory*

Activation of the LC modulates activity in the basolateral amygdala (BLA) by releasing C-NE. The C-NE inhibits spontaneous firing in the majority of the BLA neurons via alpha 2 adrenergic receptors, while exciting others via beta adrenergic receptors (Buffalari and Grace, 2007).

Elevated activity in the LC acts via the BLA beta adrenergic receptors to enhance the consolidation of memory (Roozendaal and McGaugh, 2011) in the hippocampus (McReynolds et al., 2010), and the cortex (Chavez et al., 2013), in both the mPFC (Roozendaal et al., 2009) and in the insula (Bermudez-Rattoni et al., 2005).

Arousal-induced release, or systemic injection of the peripheral adrenal hormones P-E and cortisol (corticosterone in rats) enhances the consolidation of memory via the action of C-NE on BLA beta receptors (Chavez et al., 2013).

Considerable evidence indicates that peripheral action on the vagus nerve stimulates the LC to release this C-NE in the BLA (McIntyre et al., 2012). Systemic administration of P-E has been shown to dose-dependently elevate tonic baseline firing in the LC (Holdefer and Jensen, 1987). In contrast, amphetamines, like P-NE (Svensson et al., 1980; Elam et al., 1984), inhibit LC baseline firing (Holdefer and Jensen, 1987).

Activation of the LC by exercise has also been shown to enhance memory, including in older people and those with the early stages of Alzheimer's disease (Segal et al., 2012).

Following acute stress there is a period of increased connectivity between the AC, LC, and AM, which may contribute to the consolidation of memory for the significant events (van Marle et al., 2010). The LC is active during slow wave sleep contributing to the consolidation and the re-consolidation of memory (Sara, 2010; Eschenko et al., 2012) and is also involved in the successful retrieval of emotional memory (Sterpenich et al., 2006).

## *Long-term stress induces homeostatic changes in the interrelationship between the AM and the LC*

In controls, increased norepinephrine in the BLA inhibited spontaneous firing in the majority of the BLA neurons, with some showing excitation at lower doses but inhibition at higher doses. Norepinephrine also decreased responsiveness of these neurons to electrical stimulation of the entorhinal and sensory association cortices (Buffalari and Grace, 2009). However, following chronic cold stress, norepinephrine led to an increase in the excitatory effects of norepinephrine on BLA neurons and a facilitation of responses to the stimulation of the entorhinal and sensory association cortices (Buffalari and Grace, 2009).

During stress, the CeA is a major source of elevated corticotropin-releasing factor (CRF) in the peri-coerulear LC (Van Bockstaele et al., 2001, 2010), the area of the LC that projects to sympathetic regions (Westlund and Coulter, 1980). CRF activates the LC raising C-NE levels in the posterior parts of the ventral medial (VPm) thalamus (Devilbiss et al., 2012). Although increased levels of LC output can facilitate sensoryevoked responses of VPm thalamic and barrel field cortical neurons in an inverted U dose–response relationship, high levels of peri-coerulear LC infusions of CRF caused a dose-dependent suppression of sensory-evoked discharge in the VPm thalamus and in cortical barrel field neurons resulting in a net decrease in signal-to-noise of sensory-evoked responses (Devilbiss et al., 2012).

## **PAIN AND THE COERULEOSPINAL CENTRIFUGAL PAIN CONTROL SYSTEM**

The Vpm thalamus is the thalamic relay nucleus for the sympathetic STT, which carries the afferent interoceptive information, including pain, to the anterior insula (by way of the dorsal posterior insula) and to the somatosensory BA3a (Craig, 2004, 2009). The branch of the STT that projects to the AC relays in the ventrocaudal portion of the medial dorsal thalamic nucleus (Craig, 2004).

The LC projects reciprocally to the STT (Craig, 1992; Westlund and Craig, 1996). The descending coeruleospinal inhibitory pathway from the LC and subcoeruleus (peri-coeruleus) is one of the centrifugal pain control systems. The function of this LC system is thought to maintain the accuracy of intensity coding in the dorsal horn, while inhibiting nocioceptive signals in order to extract other sensory information that is essential for circumstantial judgment (Tsuruoka et al., 2011).

Activation of the LC can produce profound antinociception (Tsuruoka et al., 2011, 2012; Hayashi et al., 2012) and can inhibit the nociceptive activity of spinal dorsal horn neurons and trigeminal subnucleus caudalis neurons (Hayashi et al., 2012). Nocioceptive signals from visceral organs and cutaneous receptive fields converge on single dorsal horn neurons. Electrical stimulation of the LC inhibited both the visceral (colorectal distention) and the cutaneous pinch responses, with a reduction in the intensity-response magnitude curve without a change in the response threshold (Hayashi et al., 2012).

Fear-induced antinociception also occurs via LC pathways (Biagioni et al., 2013), seizure-induced antinociception involves LC alpha 2 and beta adrenergic receptors (Felippotti et al., 2011) and the LC is thought to play a role in the antinociception caused by stimulation of the motor cortex (Viisanen and Pertovaara, 2010).

Chronic pain stress changes the influence of the AM on the LC from excitation to inhibition (Viisanen and Pertovaara, 2007).

Locus coeruleus responses to noxious stimulation were initially enhanced following experimental neuropathy, however, after 10– 14 days microinjections of glutamate into the CeA produced a dose-related inhibition of the discharge rate of LC neurons. There was no significant effect on discharge rates in control groups. Spinal antinociception due to LC electrical stimulation was also

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weaker in the nerve injured rats. The enhanced inhibition of the LC by the CeA was thought to suppress the noradrenergic pain inhibition and promote neuropathic pain (Viisanen and Pertovaara, 2007).

Long-term pain can increase the likelihood of mood or anxiety disorders by as much as threefold (The Neuroscientist, 2012).

Long-term chronic pain (>28 days) caused an increase in LC bursting activity, tyrosine hydroxylase expression and that of the norepinephrine transporter; and enhanced expression and sensitivity of the inhibitory alpha 2 adrenoceptors in the LC. This was accompanied by an inability to cope with stressful situations, depressive and anxiogenic-like behaviors (Alba-Delgado et al., 2013). As mentioned, increased LC bursting activity is associated with lower, inhibited, LC baseline levels.

Meditation has been repeatedly found to reduce pain (Zeidan et al., 2012).

In a 2012 review of meditation-related pain relief, mindfulness meditation was found to significantly reduce pain through a number of unique brain mechanisms (Zeidan et al.,2012). In meditators during pain, higher activation was seen in the dorsal AC and insula, but was reduced in the medial prefrontal-OFC (vmPFC), DLPFC, and AM. Meditation significantly reduced lower level processing in the primary somatosensory cortex, while the increased activity in the rostral AC and anterior insula was associated with intensity reductions and the decreased orbitofrontal and thalamic activity was associated with reduced unpleasantness (Zeidan et al., 2012).

In meditators, most of the areas of the brain associated with the reduction of pain, including the salience detecting dorsal AC and insula, the primary somatosensory area and the thalamus, receive projections from the ascending STT (Craig, 2004, 2009). The reduced lower level processing in the primary somatosensory area, decreased thalamic activity and the intensity reductions associated with the higher dorsal AC and insula activity could be the result of the LC's profound antinociceptive action on the ascending STT, reducing the response intensity magnitude curve without a change in response threshold (Hayashi et al., 2012). By this route, the AC activation of the LC may contribute to meditation-induced reduction of pain.

## **VAGUS NERVE STIMULATION**

Chemical or electrical stimulation of the vagus nerve alters LC activity and that of its forebrain targets suggesting that the therapeutic effects of vagal nerve stimulation (VNS) may involve the LC-noradrenergic system (George and Aston-Jones, 2010). It has been suggested that the effects of VNS on learning and memory, mood, seizure suppression, and recovery of function following brain damage are mediated, in part, by the release of C-NE in the terminal fields of the LC (Roosevelt et al., 2006). VNS is also being investigated with respect to anxiety (George et al., 2008), inflammation, and the immune response (George and Aston-Jones, 2010).

The initiation of VNS activates the LC (Dorr and Debonnel, 2006), increasing not only the spontaneous (baseline) firing rate, but also the percentage of LC neurons firing in bursts (Manta et al., 2009). The LC has an excitatory influence on the dorsal raphe (Dorr and Debonnel, 2006). Long-term (14 days) VNS increased activity in the serotonin neurons of the dorsal raphe nucleus, as seen with other antidepressant treatments (Manta et al., 2009), through an activation of alpha 1 adrenergic neurons and increased tonic activation of post-synaptic 5-HT1A receptors in the hippocampus (Manta et al., 2013). Long-term VNS, further, significantly increased extracellular C-NE levels in the prefrontal cortex and hippocampus and enhanced the tonic activation of post-synaptic alpha 2 adrenoceptors on pyramidal neurons (Manta et al., 2013).

A recent review discusses some of the beneficial effects of mindfulness-based stress reduction, mindfulness-based cognitive therapy, and Zen meditation to alleviate depression, anxiety, pain, and psychological distress (Marchand, 2012).

The kinds of pain and suffering alleviated by meditative practices, are remarkably similar to those alleviated by stimulation of the vagus. The increased activation of the LC by both practices may contribute to the beneficial similarities.

## **BLOOD VOLUME, OXYGEN DEMAND, CELLULAR ENERGY METABOLISM, AND INFLAMMATION**

The LC–NE network optimizes coupling of cerebral blood volume with oxygen demand through local vasodilation in active brain areas, while constricting volume in other areas (Bekar et al., 2012). Of increasing interest is the modulation by C-NE of glia, astrocytes, oligodendrocytes, and microglia in their critical support functions (Bekar et al., 2008; Chandley and Ordway, 2012; O'Donnell et al., 2012). C-NE, for example, acts on astrocytes to enhance glutamate uptake, while increasing production and breakdown of glycogen (O'Donnell et al., 2012). Microglia, often thought of as the primary immune effector cells of the CNS, represent a major target of C-NE signaling in the cortex (O'Donnell et al., 2012). C-NE modulates microglia disease responses, suppressing inflammatory gene transcription and reducing expression of pro-inflammatory cytokines, while enhancing production of brain-derived neurotrophicfactor (BDNF) to promote neuronal survival (O'Donnell et al., 2012). The mechanism by which C-NE reduces the expression of pro-inflammatory cytokines is still a topic of debate, but may involve the regulation of the NF-kB signaling system by B2 adrenergic receptor driven increases in cAMP (O'Donnell et al., 2012).

Yogic meditation downregulated transcripts of pro-inflammatory cytokines, decreasing expression of NF-kB associated proinflammatory genes (Black et al., 2013). Mindfulness-based stress reduction training also resulted in a significantly smaller poststress inflammatory response (Rosenkranz et al., 2013). The regulation of gene expression by yoga, meditation, and related practices has recently begun to be investigated (Saatcioglu, 2013). The activation of the LC, by the AC and by exercise, may again be a contributing factor.

## **NEUROPLASTICITY**

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In post-mortem studies of depressed humans a loss of glial cells has been demonstrated in the AC, DLPFC, and OFC, amongst other areas (Chandley and Ordway, 2012). It has been hypothesized that given the intimate functional relationship between C-NE and glia, particularly astrocytes, the glial deficits may be secondary to a deficiency of C-NE (Chandley and Ordway, 2012).

Research indicates that LC neuron loss appears with aging (Shibata et al.,2006) and depression (Shibata et al.,2007), and that such loss is prominent in Parkinson's and Alzheimer diseases (Bekar et al., 2012). A diminished ability to couple blood volume to oxygen demand (Bekar et al., 2012), and to support other neuronal and non-neuronal cellular requirements (Bekar et al., 2008; Chandley and Ordway, 2012; O'Donnell et al., 2012) due to a reduction in C-NE from LC neurons, may contribute to their pathogenesis.

 The elevated C-NE due to the activation of the LC by the AC may play a role.

## **DISCUSSION**

In early 2012, when the Hasenkamp paper was published and research for this paper began, some aspects of the AC's activation of the LC and inhibition of the SNS to maximize adaptation in changing environments were already known. Included were the increased receptivity to the stimuli of the present moment caused by activating the LC; the possible reduction of stress through the inhibition of the stress associated SNS; the LC behavior patterns and the potential importance of understanding that the LC is not activated in tandem with the SNS, but that stress associated elevated P-NE inhibits the LC dose-dependently enhancing the phasic behavior pattern; that higher tonic base line firing is not associated only with stress and arousal, but with increased receptivity to the stimuli of the present moment, with increased awareness. These aspects were already understood and seemed of significant importance to understanding the neuroscientific process underlying the changes in state initiated by meditation.

During 2012 and 2013, however, numerous papers have been published that further implicate the integrated norepinephrine systems in the enhancement of cortical executive network functions and in the modulation of the AM, NA, VPm, STT, and pain, as well as in the modulation of astrocytes and glia, blood volume, oxygen supply, cellular energy metabolism, inflammation, and even of neuroplasticity.

These aspects were generally unknown in early 2012, and have vastly expanded the understanding of the role of the AC's activation of the LC and inhibition of the SNS in general, and potentially in the beneficial changes initiated by meditation.

The AC and the anterior insula, together, form the cortical salience detecting network, are usually jointly activated, contain numerous recently evolved von Economo neurons, and undergo

#### **REFERENCES**

Alba-Delgado, C., Llorca-Torralba, M., Horrillo, I., Ortega, J. E., Mico, J. A., Sánchez-Blázquez, P., et al. (2013). Chronic pain leads to concomitant noradrenergic impairment and mood disorders. *Biol. Psychiatry* 73, 54–62. doi: 10.1016/j.biopsych.2012.06.033

Amaral, D. G., and Price, J. L. (1984). Amygdalo-cortical projections in the monkey (*Macaca fascicularis*). *J. Comp. Neurol.* 230, 465–496. doi: 10.1002/cne.902300402

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structural changes in longer term meditators. Reviews of their functions (Craig, 2009; Medford and Critchley, 2010; Menon and Uddin, 2010) implicate them in the capacity for awareness of self and awareness of the moment.

The AC is active during salience detecting and monitoring of the stimuli in the present moment, is naturally activated by novel or significant stimuli and normally ceases activity as the eventencoding cycle ends. During mindfulness meditation the AC is active "at the moment of awareness of mind wandering." This suggests the AC is active "at the moment of awareness" of whatever is occurring now, in the present moment.

During meditation, following the initial "awareness of mind wandering," one "shifts" to "sustained attention," one shifts to sustain the attention of awareness of the present moment.

Without the development of a capacity to intentionally sustain the attention of awareness of the present moment, this quality of attention will normally be lost as the event-encoding cycle ends. The various practices of meditation, however, can develop a capacity to intentionally sustain the attention of awareness of whatever is occurring in the present moment, irrespective of the nature of the stimuli and irrespective of the environment from which they come, whether external, internal, or interoceptive.

As mentioned, the salience detecting/executive FPC cortical orienting network, including both the AC and the insula, shifts between the external DAN and the internal DMN, while the AC and insula receive information from the interoceptive STT. This may allow the AC, in coordination with the insula, to monitor and detect the salience of the stimuli of the present moment from all environments, irrespective of the nature of the stimuli, whether known or Unknown.

Meditation may develop the capacity for an intentional attention of awareness, which activates the AC of the salience detecting/executive FPC cortical orienting network, initiating a variety of physiological cascades through its modulation of the central LC and peripheral SNS norepinephrine systems, via both parasympathetic and sympathetic routes, to maximize receptivity and adaptation in changing environments.

Buddha realized he had found a pathway to the elimination of pain and suffering. The inhibition of the SNS and activation of the LC by the AC during meditation may be a contributing factor worthy of further scientific exploration.

#### **ACKNOWLEDGMENTS**

I would like to thank Dr. Phillip R. Shaver for his insight into the elevated peripheral norepinephrine behavior pattern, Dr. Torgny H. Svensson, Dr. Donald A. Powell, Dr. Gerald Epstein and Dr. Zoran Josipovic for their encouragement, and Carina Paraiso and Diana Boy of Frontiers in Psychology for inviting me.

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**Conflict of Interest Statement:** The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

*Received: 26 June 2013; paper pending published: 10 August 2013; accepted: 22 September 2013; published online: 16 October 2013.*

*Citation: Craigmyle NA (2013) The beneficial effects of meditation: contribution of the anterior cingulate and locus coeruleus. Front. Psychol. 4:731. doi: 10.3389/fpsyg.2013. 00731*

*This article was submitted to Consciousness Research, a section of the journal Frontiers in Psychology.*

*Copyright © 2013 Craigmyle. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.*

## Plasticity of visual attention in Isha yoga meditation practitioners before and after a 3-month retreat

## *Claire Braboszcz 1,2\*, B. Rael Cahn3, Bhavani Balakrishnan4, Raj K. Maturi 5, Romain Grandchamp1,2 and Arnaud Delorme1,2,6*

*<sup>1</sup> Centre de Recherche Cerveau et Cognition, UPS, Université de Toulouse, Toulouse, France*

*<sup>2</sup> CERCO, CNRS UMR5549, Toulouse, France*

*<sup>3</sup> Department of Psychiatry and Human Behaviour, UC Irvine, Orange, CA, USA*

*<sup>4</sup> Isha Yoga Centre, Isha Foundation, Coimbatore, India*

*<sup>5</sup> Department of Ophthalmology, Volunteer, Indiana University School of Medicine Shareholder, Midwest Eye Institute, Indianapolis, IN, USA*

*<sup>6</sup> SCCN, INC, UCSD, La Jolla CA, USA*

#### *Edited by:*

*Zoran Josipovic, New York University, USA*

#### *Reviewed by:*

*Zoran Josipovic, New York University, USA Thilo Hinterberger, Universitätsklinikum Regensburg, Germany*

#### *\*Correspondence:*

*Claire Braboszcz, LABNIC, Département des Neurosciences, Université de Genève,1 rue Michel-Servet, 1211 Genève, Switzerland e-mail<EMAIL_ADDRESS>
Meditation has lately received considerable interest from cognitive neuroscience. Studies suggest that daily meditation leads to long lasting attentional and neuronal plasticity. We present changes related to the attentional systems before and after a 3 month intensive meditation retreat. We used three behavioral psychophysical tests - a Stroop task, an attentional blink task, and a global-local letter task-to assess the effect of Isha yoga meditation on attentional resource allocation. 82 Isha yoga practitioners were tested at the beginning and at the end of the retreat. Our results showed an increase in correct responses specific to incongruent stimuli in the Stroop task. Congruently, a positive correlation between previous meditation experience and accuracy to incongruent Stroop stimuli was also observed at baseline. We also observed a reduction of the attentional blink. Unexpectedly, a negative correlation between previous meditation experience and attentional blink performance at baseline was observed. Regarding spatial attention orientation as assessed using the global-local letter task, participants showed a bias toward local processing. Only slight differences in performance were found pre- vs. post- meditation retreat. Biasing toward the local stimuli in the global-local task and negative correlation of previous meditation experience with attentional blink performance is consistent with Isha practices being focused-attention practices. Given the relatively small effect sizes and the absence of a control group, our results do not allow clear support nor rejection of the hypothesis of meditation-driven neuronal plasticity in the attentional system for Isha yoga practice.

**Keywords: meditation, attention, Stroop task, attentional blink, global-local task**

## **1. INTRODUCTION**

Behavioral results show that meditation practice increases performance in attentional tasks suggesting improved allocation of attentional resources, enhanced sustained attention skills, faster re-allocation of attentional resources, improved cognitive flexibility, and decreases in automatic responding (Valentine and Sweet, 1999; Carter et al., 2005; Cahn and Polich, 2006; Slagter et al., 2007; Hodgins and Adair, 2010). These changes are most likely linked to structural, anatomical and functional changes observed in meditators compared to control populations (Hoelzel et al., 2011; Luders et al., 2011, 2012; Kang et al., 2013). Lutz et al. (2008) have outlined a theoretical framework for the study of meditation according to which meditation practice involve at least three attention regulation subsystems. Meditation may help train selective attention, which pertains to the selection of information from the flow of sensory inputs. Meditation also requires sustained attention for continuous monitoring of the object of meditation. Finally while meditating, one often has to redirect attention from a source of distraction toward the intended object of meditation. These transient attentional shifts involve executive attention, that is the monitoring and resolution of conflict among thoughts, feelings and mental plans. Although useful to define the scope of our study and interpret our results this taxonomy is likely an oversimplification as the different attentional systems are most likely strongly intermingled. Meditation practices are usually classified depending on the attentional engagement they require, along a continuum from focused attention to mindfulness practices (Cahn and Polich, 2006; Lutz et al., 2007, 2008). Focused attention meditation techniques involve sustained attention on a selected internal or external object of awareness, whereas mindfulness meditation, also known as openmonitoring or open-awareness meditation, involves adopting an attentive and non-elaborative cognitive stance toward anything that may occur from moment-to-moment in the mental field of experience. Recently, the "automatic self transcending" category has been proposed to denote practices marked by the absence of individual control or effort during meditation thus leading to a transcending of the sense of self as a separate choosing agent, a characteristic of meditation practice that likely is related to the notion of non-dual awareness and varies from one practice to another in ways not fully characterized as of yet (Travis and Shear, 2010; Josipovic, 2013).

Isha Yoga, the meditation tradition studied in this article, includes many practices and, specifically during the 3 month retreat studied in this article, three primary practices were done daily which may be categorized into each of these three categories. *Lingasanchalana* meditation, in which the practitioner is seated and focused on one point, with eyes either opened or closed, is primarily a focused attention practice. *Samyama* meditation is a seated meditation involving the instruction to pay attention to the breath with eyes fully or partially open and passively observing thoughts in addition to watching the breath. This is a practice with a focused attention basis in which the instruction is to continually attend to the breath, although there is some open-monitoring/mindfulness component to this practice as well. *Shoonya* meditation is typically done after a set of physical postures and breathing exercises and involves sitting with eyes closed and engaging in a process of conscious non-doing that purportedly creates a distance between ones self and ones body and mind. This practice could be considered a form of openawareness practice with self-transcending occurring through a non-doing aspect or alternatively conceived as a focused practice in that the explicit focus is on "non-doing"—as soon as one notices mental content arising in awareness the injunction is to attempt to reinstate a "non-doing"/nothingness experience and to use a mantra if necessary to do so. Alternatively, within the Isha yoga tradition, this practice is spoken of as a self-transcending practice and may be in line with the proposed self-transcending style of practice. The nuances of these practices and the best and most inclusive and accurate classification system for meditative practices is beyond the scope of this article. In addition to these three meditation techniques, Isha Yoga also includes practice of diverse yoga postures, breathing and physical exercise as well as chanting.

To assess the extent to which Isha Yoga meditation affects the processing of visual information, we used three attentional tasks corresponding to three different attentional characteristics: the attentional blink task (temporal attention), the Stroop task (conflict monitoring/executive attention and automated responding), and a global-local task (spatial attention to global vs. local aspects of the visual field). The subjects were tested at the beginning and end of a 3-month full time Isha Yoga meditation retreat.

In the attentional blink task (Raymond et al., 1992), subjects tend to be blind to a visual stimulus presented briefly after another stimulus when the first stimulus is consciously perceived. This phenomenon arises because of the limited availability of attentional resources: the brain has difficulty processing the second of the two images presented in rapid succession since it is processing of the first of the two stimuli. However, openmonitoring/mindfulness type meditation, by disengaging some of the brain resources and leading to a more efficient cognitive processing state, has been shown to decrease the magnitude of the attentional blink effect (Slagter et al., 2007; Van Leeuwen et al., 2009).

The Stroop task (Stroop, 1935) uses color names written in congruent and incongruent ink color. Participants are asked to indicate the color of the ink verbally or by pressing a key. When the ink color and the word name mismatch (incongruent case), reaction time to indicate the ink color is slowed down (and accuracy decreased) due to involuntary automated processing of the conflicting semantic contents of the stimuli, relative to the congruent stimulus. This effect is termed the Stroop interference effect and the paradigm thus mobilizes executive attention and conflict monitoring capacities. It has been previously demonstrated that decreases in Stroop interference are seen in long-term meditators with experience in both focused attention and openmonitoring practice typical of Buddhist training regimens (Chan and Woollacott, 2007; Moore and Malinowski, 2009; Teper and Inzlicht, 2013) as well related to meditation interventions including both mindfulness and Transcendental Meditation (Alexander et al., 1989; Wenk-Sormaz, 2005; Anderson et al., 2007) and these improvements have been conceptualized as improvements in executive attention and cognitive flexibility and decreases in automatic responding patterns. We predicted that subjects would perform better after the 3-month retreat related to enhanced cognitive flexibility and decreased automated interference from semantic processes.

Finally, the global-local task is a measure of the dispositional focus of attention at either a global or more local level and the ability to switch between these levels of visual attention. This test is based on the fact that due to the limited attentional processing capacities of the brain, when attending to the global shape of an object less attention is available to attend to the local details and vice versa. Moreover, information in the non-attended level of processing interferes with the attended level of processing due to involuntary capture of attention. Work by Navon (1977) and replicated by others since has found that most people spontaneously show a bias toward the global level of perception indicated by both (1) faster responses to a task to identify the global letter than to identify the local letters when the two letters are incongruent and, (2) greater global biasing on the local task relative to local biasing on the global task. On the local task (instructing press button corresponding to the local letters) when the global letter is incongruent vs. congruent with the local letters there is an increased reaction time/decreased accuracy related to global-biasing. Conversely, on the global task (instructing press button corresponding to the global letter), when the local letters are incongruent vs. congruent with the global letter there is an increase in reaction time/decreased accuracy related to local biasing. There has been limited previous experimental work with the global-local task in relation to meditation one such study has found improvements in Stroop performance in participants with experience in a variety of Buddhist meditation practices relative to controls but no changes on global-local task performance (Chan and Woollacott, 2007). Another study has found that Zen meditators with a predominance of training in both focused attention and open-monitoring practice demonstrate faster reaction times across all stimuli and a decrease in the magnitude of global attentional bias relative to controls (Van Leeuwen et al., 2012). In contrast a group of practitioners with primary experience in focused attention practice alone tended to show local attentional bias instead of the normal global attentional bias, and a 4 day intensive retreat in open-monitoring practice tended to reduce the magnitude of this local attentional biasing such that the reaction times to the two stimuli were more equivalent. These investigators interpreted this set of findings as indicative of the fact that focused attention practices may tend to lead toward local feature biasing whereas open-monitoring practices may lead toward a reduction in biasing to either the local or global levels (Van Leeuwen et al., 2012).

A recent study showed that increased local attention bias during the global task was correlated with an increased magnitude of the attentional blink and that greater global attention bias overall during this task predicted decreased attentional blink consistent with the notion that diffusion of attention may be indexed by both greater relative global compared to local attentional bias and decreased attentional blink magnitude (Dale and Arnell, 2010).

Our hypothesis was that at the end of the retreat our subjects would be able to better redirect their attention than at the beginning (increased attentional flexibility) and would thus show a decrease specifically in the magnitude of the local biasing effect during the global task and global biasing effect on the local task. This was hypothesized based on the fact that while some aspects of the Isha Yoga meditation practices (*Lingasanchalana*, *Samyama*) have a focused attention quality to them, there is also an openmonitoring aspect to the *Shoonya* practice that might lead to a decrease in attentional biasing.

## **2. METHODS**

#### **2.1. PARTICIPANTS**

Subjects were tested at the beginning and at the end of a 3-month retreat in the Isha center in Nashville, TN, USA. 103 Isha Yoga meditators participated in the study. All participants signed consent forms and the study was approved by the Quorum independent ethical review committee. 89 of the 103 participants tested at the beginning of the study completed the retreat and were recorded again at the end of the retreat. Seven participants did not understand the tasks correctly despite the training session and were removed from analysis. Thus, results presented here comprise 82 participants (mean age: 37.5 years old; max: 63; min: 21, ±9*.*4).

#### **2.2. MEDITATION PRACTICE PRIOR TO THE RETREAT**

Prior to the retreat the participants had practiced *Shoonya* meditation during an average of 4 years (±2*.*8 years), 6.5 days a week (±0*.*5 days). Although we do not have access to data concerning the precise time spent practicing *Shoonya* meditation every day, the Isha Yoga school recommends practicing it at least 15 min twice daily. Only 50 participants practiced *Samyama* meditation prior to the retreat, and they practiced it for an average of 3 years (±2 years), in average 3.2 days per week (±2*.*1 day). No participant practiced *Lingasanchalana* meditation prior to the retreat.

#### **2.3. DESCRIPTION OF THE PRACTICES DURING THE RETREAT**

The 3 month retreat required participants to engage in daily meditative practices. For the first 6 weeks of the retreat all participants practiced *Samyama* meditation for 30-50 min and *Shoonya* meditation for 30 min daily. For the last 6 weeks, they practiced *Lingasanchalana* meditation for 2–3 h every day. Beside pure meditative practices participants also practiced yoga postures (2 h every day) as well as physical exercise (40 min every day) and chanting (1 h every day). Finally during the first 6 weeks of the retreat only they practiced breath watching (1 h a day) and specific body postures called kriyas (2 h a day).

#### **2.4. PROTOCOLE**

#### *2.4.1. Recording schedule*

At the beginning of the retreat, participants were tested on all three tasks and they were again tested on the same three tasks at the end of the retreat. Due to the relatively large number of subjects participating in the study, the pre- and post-tests could not all be done on the same day. Days of recording for pre-test started from the first day and finished up to 12 days after the retreat started. Recording for the post-tests started 16 days before and finished 3 days after the end of the retreat. We used the number of days relative to the beginning and to the end of the retreat as a statistical regressor to assess if this could have influenced our results (see Statistics).

#### *2.4.2. Task presentation*

For all stimulus presentations, we used desktop computers running the Matlab Psychophysics toolbox (v3.0.8) under Windows XP operating systems. Stimuli were presented on a 17" DELL M781 mm CRT computer screen. The computer screen was set to 120 Hz and a resolution of 800 × 600. Two identical computers and screens were used to collect the data. Subjects sat 50 cm from the screen. Before performing the experiment, for training purposes, participants performed a shorter version of each of the tasks (three trials of the attentional blink task, 12 trials of the Stroop task and four trials of the global-local task). During this training phase the participants were allowed to repeat the training tasks again if they had problems understanding them.

#### **2.5. STROOP TASK**

The Stroop task consisted of showing the capitalized words "RED," "BLUE" and "YELLOW," or the control words "LOT" (control word for "RED"), "SHIP" (control word for "BLUE") and "FLOWER" (control word for "YELLOW") on a computer screen (Raz et al., 2007). Three sequences of 60 stimuli each were presented to subjects. Each sequence started with the text "Press the key matching the COLOR OF THE INK as fast as possible - Please use 'Z' for red, 'X' for yellow, and 'C' for blue - Press enter to start." Subjects were able to rest from 1 to 5 min between sequences. Each sequence of 60 stimuli contained 12 unique stimuli repeated 5 times. Three of the 12 stimuli were the color word with matching ink color. Three of the 12 stimuli were the control words and six of the stimuli were the color words with non matching ink color - Stroop condition. The stimulus sequence was pseudorandomized such that no consecutive stimuli had the same color. The 'Z,' 'X,' and 'C' keys had a small sticker indicating the color they corresponded to. The color was indicated with words ("RED," "BLUE," "YELLOW"). This was done to make sure that subjects were not confused during the experiment about which button corresponded to which color. The computer screen background was gray (#808080 - at the midpoint between black and white in the RGB color scale). We used the standard red, blue and yellow inks in the RGB color scale (#FF0000, #0000FF, and #00FFFF respectively) using Arial font and letter size of 9 mm. Stimulus presentation and keystroke latency acquisition were performed using the Matlab psychophysics toolbox (Brainard, 1997). The timing of each trial was as follows: each word was presented until the subject pressed one of the three keys. The word was immediately followed by a feedback word "Correct" or "Incorrect" in black ink and using Arial font and letter size of 4.5 mm based on whether the subject had provided a correct or an incorrect response. The feedback word remained on the screen for 0.5 s. Then a 1-s gray screen was presented until the next trial. Subjects performed 3 runs of 60 stimulus presentations (**Figure 1B**).

## **2.6. ATTENTIONAL BLINK TASK**

In the attentional blink task, series of letters were rapidly presented to subjects (**Figure 1A**). These series of letters contained one or two numbers that subjects were subsequently asked to report. To avoid potential ambiguities between letters and numbers, we used only 21 letters (A, C, D, E, F, G, H, J, K, L, M, N, P, R, T, U, V, W, X, Y, Z) and 8 numbers (2, 3, 4, 5, 6, 7, 8, 9). The sequence length was fixed to 19. Each letter or number was presented in white (gray level 255) on a gray background (gray level 168) for exactly 50 ms followed by 33 ms of a gray screen. The size of the letter was about 2 cm on the screen corresponding to a visual angle of 2.3 degree. A first number T1 was presented at a position chosen randomly between 3 and 11 in the sequence (Slagter et al., 2007). On one third of the trials, no second number was presented (condition T2 absent). On one third of the trials, a second number was presented three letters after the first number (condition T2 short; for example, if the first number was at position 10, the second one was at position 14). At this position (332 ms post T1) the attentional blink effect is expected to be maximal. Finally, on one third of the trials, a second number was presented seven letters after the first number (condition T2 long), 664 ms post T1 which is outside the significant attentional blink time window. After each sequence, participants were asked to enter the first and the second number (0 if they thought there was none) and then confirm their choice before the next trial. Participants were instructed to guess the numbers if they thought a second number was present but were not sure what it was. Subjects were tested on a total of 120 trials. Stimuli presentation latency and screen vertical blanking were carefully monitored using custom Matlab scripts and CRT analog computer monitors were used to ensure that the presentation time on the screen matched the presentation time in the experimental script.

## **2.7. GLOBAL-LOCAL TASK**

In the global-local task, subjects were shown large letters (H and T) on a computer screen. The large letters were made up of an aggregate of small letters that could be congruent (large H made of small Hs or large T made of small Ts) or incongruent (large H made of small Ts or large T made of small Hs) with respect to the large letter. The small letters were 0.8 cm high and the large letters were 8 cm high on the computer screen. A fixation cross was present at all times except when the letters were presented. Letters were shown on the computer screen until the subject responded. After each subjects response, there was a delay of 1 s before the next stimulus was presented. Before each sequence of letters, instruction were shown on a computer screen indicating to subjects whether they should respond to the presence of small (local condition) or large (global condition) letters. We instructed subjects to categorize specifically large letters or small letters and to press the letter H or T on the computer keyboard to indicate their choice. Subject performed a total of 52 trials in 4 sessions of 13 trials each. In sessions 1 and 3, subjects were instructed to focus on large letters and in session 2 and 4 they were instructed to focus on small letters (**Figure 1C**).

## **2.8. STATISTICS**

Since our data did not fit the normal distribution (Kolmogorov– Smirnov test), we used non-parametric statistic Wilcoxon ranksum tests and used Bonferroni correction for multiple comparisons. For all tests, the degree of freedom was 81. For

assessing the effect that meditation experience and age had on results, we used a general linear model and bootstrap statistics. We used Matlab to perform all statistical tests.

## **3. RESULTS**

#### **3.1. STROOP TASK**

#### *3.1.1. Accuracy*

In the Stroop task, subjects tended to commit less errors to incongruent stimuli at the end of the retreat (*p <* 0*.*05, 86.5% correct responses at pre-test vs. 87.4% correct response at post-test) (**Figure 2**). We found no significant difference in accuracy to congruent (*p* = 0*.*9) or neutral (*p* = 0*.*7) stimuli between pre- and post-retreat tests. For each subject, we also calculated the Stroop Interference (SI) by subtracting the accuracy score to incongruent stimuli from accuracy score to congruent stimuli. We found a significant diminution of the Stroop Interference after the retreat compared to before the retreat (*p <* 0*.*05, mean SI at pre-retreat test was 1.8, mean SI at post-retreat test was 0.8).

#### *3.1.2. Reaction time*

We did not observe any significant effects in reaction time for any of the comparisons we tested. Specifically, we did not observe a difference in RT for incongruent, congruent, or neutral stimuli when comparing pre- and post-retreat assessments. Similarly, we did not observe a significant difference in the RT Stroop Interference, computed as the difference of RT for congruent and incongruent stimuli for each subject, between pre- and post-retreat assessments.

#### **3.2. ATTENTIONAL BLINK TASK**

Attentional blink performances were improved at the end of the retreat when compared to performances at the beginning: the rate of detection of the T2 target within the window of the attentional blink (T2 short; target T2 following a short interval after T1) was 59% at pre-test vs. 70% at post-test (*p <* 0*.*0001). Significant increases in performance between pre- and post-tests were also

found for the targets T1, and T2 long (*p <* 0*.*05; mean detection rate of T1 at pre-test 84 vs. 87% at post-test; mean detection rate of T2 long at pre-test is 75 vs. 81% at post-test). No significant difference for detection of the absence of T2 (T2 absent) was found (mean T2 absent detection rate at pre-test 55 vs. 61% at post test). However, as shown in **Figure 3**, comparison of post-test improvement between each type of stimulus revealed that performances increased significantly more for detection of T2 presented in a short interval than for any of the other targets (T2 short performance increase vs. T1 performance increase *p <* 0*.*0002; T2 short performance increase vs. T2 long performance increase *p <* 0*.*001; T2 short performance increase vs. T2 absent performance increase *p <* 0*.*005).

To assess potential short term learning effects, we divided subjects trials into 2 groups of equal sizes: the first half and the second half of the trials. Within each pre and post test session, for each type of target, we did not find any significant differences in performances between the first half and the second half of the trials (ranksum test).

#### **3.3. GLOBAL-LOCAL LETTER TASK**

#### *3.3.1. Accuracy*

At the beginning and at the end of the retreat, participants made significantly less errors on congruent than on incongruent trials during both the global and the local tasks (*p <* 0*.*001) see **Figure 4**. There were no significant differences in performance between pre- and post-retreat tests in either the congruent or incongruent conditions for the local (congruent condition *p* = 0*.*6; incongruent condition *p* = 0*.*2) or global (congruent condition *p* = 0*.*7; incongruent condition *p* = 0*.*6) tasks. We computed

**FIGURE 3 | Mean accuracy improvement for each target type between pre and post test in the attentional blink task.** Standard error of the mean are shown for each condition. ∗∗indicates *p <* 0*.*005 and ∗∗∗indicates *p <* 0*.*0005.

the congruency effect interference score (performance on congruent minus performance on incongruent trials) but did not find significant differences between pre- and post- retreat scores on this measure either (local task: *p* = 0*.*7; global task: *p* = 0*.*1).

#### *3.3.2. Reaction times*

Participants were significantly faster in responding to congruent than incongruent trials during the global task both before and after the retreat (*p <* 0*.*005; see **Figure 5**) but we did not find a significant congruency effect for the local task, although we did observe a trend (*p* = 0*.*057). We found no significant differences between RTs before and RTs after the retreat for any of the specific trial types as a class. However, there was a significant faster mean RT in response to incongruent stimuli in the local versus global task (*p* = 0*.*04) before the retreat, and only a trend difference (*p* = 0*.*1) after the retreat.

#### **3.4. ATTENTIONAL BLINK AND GLOBAL-LOCAL PERFORMANCE**

We tested the hypothesis that performances in the global-local task would be correlated with performance in the attentional blink task. We divided participants into quartiles based on their scores on the local-interference (defined as the difference between RTs to incongruent and congruent conditions when subjects had to respond based on the global stimuli) and global interference (defined as the difference between RTs to incongruent and congruent conditions when subjects had to respond based the local stimuli) measures, for both pre and post retreat assessments. Low local interference participants had scores within the first quartile (pre retreat, *n* = 20; post retreat, *n* = 21) and high local interference participants had score within the last quartile (pre retreat, *n* = 21; post retreat, *n* = 21). We used linear regression to assess any relationship between attentional blink performances and local interference scores and did not find any significant correlations either before or after the retreat. We did the same analysis using the global-interference measure and similarly found no significant correlations.

#### **3.5. INFLUENCE OF AGE AND PRIOR MEDITATION EXPERIENCE ON TASK PERFORMANCES**

We used a general linear model to assess the effect of participants age and prior meditation experience on task performances.

For each task, we computed the correlation between years of *Shoonya* meditation practice (since it was the only meditation practice shared by all participants prior to the retreat, see section 2.2), age of the participants, and performance for each of the tasks for the pre-retreat assessments. In the attentional blink task, age and previous *Shoonya* meditation experience of the participants both had a significant negative influence on T1 response accuracy (age: regression coefficient (reg. coef.) = −0.46, *p <* 0*.*005; previous meditation experience: reg. coef. = −0.04; *p <* 0*.*005) T2 long (age: reg. coef. = −0.22, *p <* 0*.*01; previous meditation experience: reg. coef. = −0.30; *p <* 0*.*01) and T2 short response accuracy (age: reg. coef. = −0.29, *p <* 0*.*01; previous meditation experience: reg. coef. = −0.14; *p <* 0*.*01 ) but not T2 absent (*p <* 0*.*1) response accuracy. In the Stroop task, the age and meditation experience of participants did not affect reaction time. However, we observed a significant positive influence of these factors on accuracy to both incongruent (age: reg. coef. = 0.11, *p <* 0*.*005; previous meditation experience: reg. coef. = 0.16; *p <* 0*.*005) and neutral stimuli (age: reg. coef. = 0.03, *p <* 0*.*05; previous meditation experience:reg. coef. = 0.05; *p <* 0*.*05). Both increased age and prior meditation experience significantly correlated with decreases of Stroop interference (age: reg. coef. = −0.10, *p <* 0*.*01; previous meditation experience: reg. coef. = −0.07; *p <* 0*.*01) Finally, there was no significant influence of either age or meditation experience on performance to congruent stimuli. In the global-local task, we did not observe any significant effect of age or meditation experience on accuracy or RT to either type of stimuli.

## **4. DISCUSSION**

We tested 82 meditation practitioners at the beginning and at the end of a 3 month full time meditation retreat using three attentional tasks: an attentional blink task, a Stroop task and a globallocal task . Our results show a modest decrease in the magnitude of the attentional blink at the end of the retreat compared to the beginning. Unexpectedly, we also found that previous meditation experience correlated with decreased performance in accurately recognizing both the T1 and T2 stimuli of the attentional blink paradigm. Comparing the magnitude of improved performance on the attentional blink paradigm to previous studies indicated a similar magnitude of improvement in a control cohort of novices with minimal meditation experience and no significant intervention. This is thus casting doubt on the interpretation that this effect was a specific result of meditation during the retreat and more in support of this being related to improved performance secondary to simple learning mechanisms. Comparing pre- and post-retreat assessment of conflict monitoring and automated responding as assessed by the Stroop paradigm we observed decreased Stroop interference related to improved accuracy on the incongruent trials of the Stroop task. Congruent with this, previous meditation experience in our cohort also correlated with increased accuracy on incongruent trials and decreased Stroop interference at the baseline pre-retreat assessment. We found no significant main effects of the retreat on accuracy or reaction time in the incongruent trials of the global-local task although a pattern of relatively faster reaction times on the local task relative to the global task both pre and post retreat indicated that this cohort

showed an unusual local attentional biasing, possibly related to the practices in this tradition being more in the focused attention domain.

#### **4.1. EFFECT OF RECORDING SCHEDULE**

Because of the large number of subjects and our limited data collection capabilities, some subjects were recorded after the beginning of the retreat and some subjects were recorded before the end of the retreat. We thus checked for correlation of pre- and post test performances with pre- and post- test date expressed as the day the test occurred relative to the beginning and the end of the retreat. Overall, we computed 18 regressions scores that did not lead to significant correlation with pre- or post-retreat test date after applying the Bonferroni correction for multiple comparisons.

#### **4.2. ISHA YOGA MEDITATION AND REDUCTION OF STROOP INTERFERENCE**

Our results show increased accuracy scores on incongruent Stroop stimuli at the end of the retreat compared to the beginning. In addition, previous meditation experience correlated with more accurate performance at the baseline assessment. These results are in accordance with a previous reports demonstrating less Stroop interference in experienced Buddhist meditators compared to controls (Moore and Malinowski, 2009; Teper and Inzlicht, 2013) as well as in a cohort of diverse long term meditators of different traditions (Chan and Woollacott, 2007). Moreover, decreased Stroop interference after training in mindfulness meditation in college-age students (Wenk-Sormaz, 2005), as well as after training in Transcendental Meditation in older adults (Alexander et al., 1989) have been previously reported, although one report found no changes in Stroop task performance after a mindfulness-based stress reduction (MBSR) intervention (Anderson et al., 2007). The decrease in Stroop interference we report here is consistent with the notion that the flexible executive attention and reduction in automatic responding measured through the Stroop color-word interference task is one of the domains of attention positively affected through this meditative practice.

It is of note that a recent study utilizing EEG concomitantly with Stroop performance (Teper and Inzlicht, 2013) found that, in addition to decreased Stroop interference, experienced meditators showed increased amplitude of the ERN event-related potential known to be related to the engagement of anterior cingulate cortex in conflict monitoring, thus providing some indirect evidence that these Stroop findings may be related to enhanced anterior cingulate functioning related to the long hours of practice during meditation retreat.

#### **4.3. MEDITATION AND REDUCTION OF THE ATTENTIONAL BLINK**

We observed an increased detection rate (70%) of the target T2 presented in the short interval after T1 (window of the attentional blink) relative to the pre-retreat test (59%). One previous study assessed the effect of meditation and the attentional blink effect.

Slagter et al. (2007) did a pre/post testing before and after a 3 month intensive Vipassana (open-monitoring/mindfulness) meditation retreat with 17 expert meditation practitioners of diverse meditation traditions compared to a group of novice meditators.

Our study found an improvement in the meditation retreat participants equal to the control group participants in the Slagter study (from about 60 to 70% T2-short correct) and not as robust as the meditator group participants in that study (who showed an average of about 60 to 80% T2-short correct). As we did not have a control group to compare the meditator cohort data in this study, we cannot assume that the rather modest improvement in performance was specifically related to the intensive meditation practice during the Isha Yoga retreat. Of note, during the Isha Yoga meditation retreat considered here, participants spent about 1.5–4 h daily sitting in silent meditation whereas in Slagter et al. (2007)'s study open-monitoring Vipassana meditation during the retreat was practiced intensively 10–12 h a day. It is possible that with more intensive practice of sitting meditation the observed effects of Isha Yoga meditation practice would have been more robusts.

The contrast in findings between this study of the effects of the Isha Yoga 3-month retreat and the earlier report before and after a 3-month Vipassana retreat seems to indicate that intensive open-monitoring/mindfulness training may more specifically modulate the attentional capacities underlying the performance of the attentional blink paradigm. This is possibly related to Vipassana practice engaging the attentional mechanisms on present moment awareness with a greater focus on sensitively attending to internal and external experience with concomitant purposeful cognitive non-elaboration on experience. In contrast, the *Shoonya*, *Samyama*, and *Lingasanchalana* practices done in the Isha Yoga retreat have a less explicit focus on open-monitoring and are instead favorising the focused attention spectrum of practice. Consistent with this interpretation, in contrast to the negative correlation we obtained between previous Isha Yoga meditation practice and attentional blink performance at baseline, Van Leeuwen et al. (2009) showed that older adult expert meditation practitioners with extensive experience in both focused attention and open-monitoring practice did not show the same decrease in attentional blink performance relative to young adults as older non-meditators, seeming to implicate more pure openmonitoring practice as important to improving attentional blink performance.

Although our modest improvement in performance and lack of a control cohort precludes our attributing the improvements that we did observe in the attentional blink paradigm to the meditation practiced in retreat, it is also possible that some of this improvement may have been due to the "open monitoring" aspect of the diverse Isha Yoga meditation practices. Indeed, Olivers and Nieuwenhuis (2005, 2006) demonstrated that the attentional blink can be attenuated if instead of concentrating hard on the task, the subject is asked to simultaneously perform an additional task or even simply instructed to concentrate less on the task. It is possible that at the end of the retreat our subjects might have engaged a more diffuse attentional deployment, preventing them from allocating too much attentional resource to the initial T1 stimulus in the stream of stimuli.

Overall we take the smaller improvement in attentional blink performance in this Isha Yoga retreat cohort relative to the previous Vipassana retreat cohort assessed by Slagter et al. (2007) using a very similar attentional blink paradigm as likely related to the difference in attentional deployment in more pure openmonitoring practice resulting in greater diffusion of attention and resultant optimization of attentional resources on this task assessing temporal attention capacities. Indeed, the fact that meditation experience in the Isha Yoga cohort actually correlated with worse attentional blink performance at the pre-retreat assessment tends to argue that this form of meditation practice did not specifically lead to improved attentional blink performance.

#### **4.4. GLOBAL-LOCAL TASK**

Both at the beginning and at the end of the retreat, participants were faster to respond in the local task than in the global task to stimuli with incongruent global and local features. Moreover, participants were faster to respond at the global level when stimuli were congruent than when stimuli were incongruent and the speed of responding was thus biased by local features. However, there was only a trend difference in reaction time between congruent and incongruent stimuli when responding to the local level at both the beginning and end of the retreat, indicating a decreased magnitude of global biasing relative to local biasing. These results suggest that overall this global-local paradigm tended to evoke in this cohort a non-standard tendency for local processing to predominate over global processing. Previous literature (Navon, 1977) has demonstrated that most individuals show a global precedence effect and thus respond more quickly on a global compared to a local task when shown stimuli with conflicting local and global features. Thus it seems likely that this cohort of Isha Yoga meditation practitioners shows a greater tendency toward local processing, which may be related to their meditation practice. In particular, given previous reports of focused attention practices leading to greater local processing precedence (Van Leeuwen et al., 2012) this finding seems to further support that Isha Yoga meditation practices are primarily concentrative in nature.

The only pre-/post- differences in performance on the globallocal task found was related to slight decrease in the magnitude of the faster reaction time to incongruent stimuli in the local relative to global task condition. This finding indicates a possible slight relative increase in global attentional processing after the retreat, somewhat in line with the hypothesized increase in global attentional biasing that we predicted might accompany improvements in attentional blink performance. However this metric is not as specific and robust a metric of global processing as the globallocal interference effects which were not found to be affected by the retreat so reading much into this finding is unwarranted.

It is of note that the one previous study assessed the globallocal task as well as Stroop performance in experienced meditators vs. controls also found improvements in Stroop task performance but no effect of meditation in performance on the global-local task (Chan and Woollacott, 2007). Although we did not replicate the results of Dale and Arnell (2010) showing a correlation between greater attention to the local level in the global-local Navon task and greater magnitude of the attentional blink, we did demonstrate the complementary finding that meditators in this tradition of more focused attention practices show biasing toward the local processing on the Navon task and those with greater pre-retreat practice also tended to display greater attentional blink amplitude.

Another explanation pertains to the type of meditation we studied. Other types of meditation involving visualization such as those practiced in Tibetan Buddhism might be expected to engage a more robust effect compared to Isha Yoga meditation which does not involve any visualization. For example, Carter et al. (2005) have found higher performance in the maintenance of bistable visual stimuli in Tibetan Buddhist meditators practicing meditation requiring to focus on one point (real or imagined), compared to the same meditators practicing compassion meditation, consistent with the now well established notion that different meditation practices engage attentional processes in very different ways and thus have different effects on many aspects of the attentional system.

## **5. CONCLUSION**

Our study reinforces that increased cognitive flexibility and decreases in automatic responding as indexed by the Stroop task is one likely concomitant to diverse forms of meditative practice including Isha Yoga practices which involve more focused attentional mechanisms as well as some explicit focus on selftranscending. The results point toward a negligible effect of this form of more focused meditation on the efficiency of temporal attentional resource allocation indexed by the performance on the attentional blink task in contrast to the improvements previously observed with open-monitoring practices. Lastly, there is some indication that this form of practice may predispose individuals toward greater local precedence in spatial visual attention instead of the more typical global precedence seen in the population through performance on the Local-Global task. The Stroop task result is the most robust since increases in accuracy in the task seen between pre- and post- recording is reinforced in the observed correlation between previous meditation experience and improved performance on this task. All of these effects would be much more reliably interpreted in the presence of a control group, which is the primary limitation of this study.

## **ACKNOWLEDGMENTS**

The Isha Institute of Inner Sciences provided subjects and the place to conduct the study. This project was supported by a generous donator interested in Isha Yoga. Data analysis was supported by a thesis fellowship from the CNRS research organization. The authors also wish to express their appreciation to Heleen Slagter for her assistance in designing the attentional blink experiment.

## **REFERENCES**

**Conflict of Interest Statement:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

*Received: 01 October 2013; accepted: 17 November 2013; published online: 12 December 2013.*

*Citation: Braboszcz C, Cahn BR, Balakrishnan B, Maturi RK, Grandchamp R and Delorme A (2013) Plasticity of visual attention in Isha yoga meditation practitioners before and after a 3-month retreat. Front. Psychol. 4:914. doi: 10.3389/fpsyg. 2013.00914*

*This article was submitted to Consciousness Research, a section of the journal Frontiers in Psychology.*

*Copyright © 2013 Braboszcz, Cahn, Balakrishnan, Maturi, Grandchamp and Delorme. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.*

## A suspended act: increased reflectivity and gender-dependent electrophysiological change following Quadrato Motor Training

## *Tal Dotan Ben-Soussan1,2\*, Aviva Berkovich-Ohana3, Joseph Glicksohn1,4 and Abraham Goldstein1,5*

*<sup>1</sup> The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, Israel*

*<sup>2</sup> Research Institute for Neuroscience, Education and Didactics, Patrizio Paoletti Foundation, Italy*

*<sup>3</sup> Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel*

*<sup>4</sup> Department of Criminology, Bar-Ilan University, Ramat Gan, Israel*

*<sup>5</sup> Department of Psychology, Bar-Ilan University, Ramat Gan, Israel*

#### *Edited by:*

*Zoran Josipovic, New York University, USA*

#### *Reviewed by:*

*Zoran Josipovic, New York University, USA Fred Travis, Maharishi University of Management, USA*

#### *\*Correspondence:*

*Tal Dotan Ben-Soussan, Research Institute for Neuroscience, Education and Didactics, Patrizio Paoletti Foundation, Via Cristoforo Cecci 2., Santa Maria degli Angeli, 06081 Assisi, Italy e-mail: research@ fondazionepatriziopaoletti.org*

Quadrato Motor Training (QMT) is a specifically-structured walking meditation, aimed at improving reflectivity and lowering habitual thought and movement. Here we set out to examine the possible effect of QMT on reflectivity, employing the Hidden Figures Test (HFT), which assesses both spatial performance (measured by correct answers) as well as reflectivity (interpolated from correct answers and reaction time). In the first study (*n* = 24, only females), we showed that QMT significantly improves HFT performance, compared to two groups, controlling for cognitive or motor aspects of the QMT: *Verbal Training* (identical cognitive training with verbal response) and *Simple Motor Training* (similar motor training with reduced choice requirements). These results show that QMT improves HFT performance above the pre-post expected learning. In the second study, building on previous literature showing gender-dependent effects on cognitive performance, we conducted a preliminary pilot examining gender-dependent effect of training on reflectivity and its electrophysiological counterparts. EEG analyses focused on theta, alpha and gamma coherence. HFT performance and resting-state EEG were measured in 37 participants (20 males), using a within-subject pre-post design. Following training, HFT performance improved in both genders. However, we found a gender-dependent difference in functional connectivity: while theta and alpha intra-hemispheric coherence was enhanced in females, the opposite pattern was found in males. These results are discussed in relation to neuronal efficiency theory. Together, the results demonstrate that QMT improves spatial performance, and may involve a gender-dependent electrophysiological effect. This study emphasizes both the importance of studying gender-related training effects within the contemplative neuroscience endeavor, as well as the need to widen its scope toward including "contemplation in action."

#### **Keywords: motor training, reflectivity, spatial cognition, EEG coherence, gender**

## **INTRODUCTION**

Reflectivity is the capacity of humans to exercise introspection, by examining one's conscious thoughts and feelings, resulting in the inhibition of habitual thought or behavior. Quadrato Motor Training (QMT) is a specifically-structured walking meditation, aimed at improving reflectivity. The QMT requires a state of enhanced attention, as it combines dividing attention to the motor response and cognitive processing for producing the correct direction of movement to the next point in the Quadrato space (Paoletti and Salvagio, 2011; Dotan Ben-Soussan et al., 2013). Due to the increased awareness to the body and its location in space, in response to very specific instructions, QMT can be conceived of as "Mindful movement." Mindful movement is a general term for practices that involve bringing awareness to the detailed experience of movement, such as when practicing walking meditation or yoga (Kabat-Zinn, 2009). Yet, in comparison to other Mindful movement practices, the QMT has the advantage of being a relatively short training (possibly several minutes), and can be relatively easily practiced in limited spaces. These unique aspects render the QMT a technique warranted of scientific exploration, with the future aim of implementing this technique in various health promoting and educational setups.

Reflectivity can be directly measured by a spatial task assessing Field Dependence-Independence (FDI) (Glicksohn and Kinberg, 2009), named the Hidden Figures Test (HFT). Here, we set out to investigate a possible QMT-induced increase in reflectivity using the HFT. We additionally utilized electroencephalography (EEG), in the attempt to relate changes in reflectivity with functional connectivity, measured by coherence, while taking into consideration gender effects for both measures (Jausovec and Jausovec, 2005; Aliakbari and Tazik, 2011). This study is referred to as Study 2, subsequently. However, as HFT performance is considered to improve following learning (Witkin et al., 1971a,b; Stericker and LeVesconte, 1982; Woodfield, 1984; Ludwig and Lachnit, 2004), it is hard to disentangle the QMT-induced improvement in HFT performance from the regular learning curve. To this end, we report the results of a study, referred to hereafter as Study 1, where HFT performance was tested in a pre-post design in a QMT group compared to two control groups, showing that QMT significantly enhanced HFT performance, well above the other groups which showed no significant change.

The construct of reflectivity has been conceptualized as a tendency to gather more information, more carefully and systematically, compared to impulsive performers (Messer, 1976). Reflective individuals are suggested to implement an analytic process and are considered more cognitively mature compared to impulsive individuals (Rozencwajg and Corroyer, 2005). Importantly, reflectivity has been found to be modifiable by training (Messer, 1976). One way to measure reflectivity is by means of a spatial task of embedded figures, originally designed to assess FDI (Glicksohn and Kinberg, 2009). FDI describes two contrasting ways of processing information, Field Dependence (FD) and Field Independence (FI), this being the most studied cognitive style (Witkin et al., 1977), and is the mode by which learners approach, acquire and process information (Witkin and Goodenough, 1981). Individuals located toward the FD end have difficulty in separating incoming information from its contextual surroundings, and are more likely to be influenced by external cues and to be non-selective in their information uptake. In contrast, FI individuals have less difficulty in separating the essential information from its context, and are more likely to be influenced by internal than external cues, and to be more selective in their information input (Riding and Cheema, 1991; Zhang, 2004). Glicksohn and Kinberg (2009) examined individual performance on embedded figures tests. Using reaction time (RT) and the number of correct detections, they postulated four templates of performance, indicative of: (1) FI—participants detect more embedded figures, and do so quite quickly; (2) FD—participants detect fewer embedded figures, and do so quite slowly; (3) impulsiveness (Imp)—individuals detect fewer embedded figures, and do so quite quickly; and (4) reflectiveness (Ref)—individuals detect more embedded figures, and do so quite slowly. It should be noted here that reflective individuals are significantly more FI than impulsive ones (Messer, 1976), and that both of these groups (FI and Ref) are thought to exhibit better performance in learning and memory tasks (Blackman and Goldstein, 1982). Here, we intend to adopt such a finely-tuned approach to the study of possible QMT-induced reflectivity, profiling individual differences. It should be considered, however, that participants tend to generally perform better on embedded figures tests after practice (Witkin et al., 1971a,b; Stericker and LeVesconte, 1982; Woodfield, 1984; Ludwig and Lachnit, 2004), hence such an improvement does not necessarily indicate an increase in reflectivity. However, within such improvement, four patterns may be discerned (Kepner and Neimark, 1984): (1) stable FI, namely high scores (number of figures detected) at both test and retest; (2) stable FD, namely low scores at both times; (3) improvement from test to retest, including (but not necessarily) a move from FD to FI; and (4) a decline in performance. Hereafter, we consider pattern 3 to operationalize an increase in reflectivity.

Depraz et al. (2000) have described the subtle dynamic of becoming more reflective in three interdependent phases: first, *suspension* from the habitual act of mind and body, then redirection of *attention* inwardly, and finally *receptivity* toward the experience. Contemplative practices can be expected to increase reflectivity, based on two arguments. First, various contemplative practices entail an improvement in attention (Brefczynski-Lewis et al., 2007; Chambers et al., 2008; Lutz et al., 2008, 2009). Second, contemplative practice, through the three phases of reflectivity (suspension, a shift of attention inwards and receptivity), enables one to disrupt normal cognitive and perceptual functioning, and hence to become more FI or reflective (Depraz et al., 2000; So and Orme-Johnson, 2001). However, there is surprisingly little research on contemplation-improved reflectivity, most of it measuring directly only the related measure of FI, and reporting conflicting results. While some studies have not found significant changes (Kurie and Mordkoff, 1970; Goldman et al., 1979), others report FI to increase following meditation (Linden, 1973; So and Orme-Johnson, 2001). Here, we study directly both reflectivity and FI. As voluntary control and planning require reflective consciousness (Legrand, 2007), we hypothesize that the QMT will induce an on-going suspension of the habitual act of moving, resulting in increased reflectivity and FI.

Meditation practices have been consistently related in EEG studies to increased power and coherence within the theta (4–7 Hz) and alpha (8–13 Hz) frequencies (Alexander et al., 1987; Aftanas and Golocheikine, 2001; Travis, 2001; Travis et al., 2002, 2009; Baijal and Srinivasan, 2010). Alpha activity increases were suggested to reflect increased relaxation; while theta increased activity has been related to heightened attention, decreased anxiety and low thought content (reviewed by Cahn and Polich, 2006). In contrast, the results relating to gamma activity (>25 Hz) have been scarce and much less consistent, some reporting increased gamma activity (Lutz et al., 2004) while others reporting decreased activity (Faber et al., 2004; Berkovich-Ohana et al., 2012, 2013; Lehmann et al., 2012). While meditation research examined both power and functional connectivity, research examining whole-body contemplative movement practices, such as Tai Chi and Qigong, has mostly focused on power, reporting increased frontal theta and alpha activity (reviewed by Cahn and Polich, 2006). As EEG coherence changes in the context of contemplative practices are usually confined within the theta, alpha, and gamma bands, our study focuses on these bands in the analyses.

Results regarding the connection between FDI and EEG coherence are confusing. While some studies found that FI participants display less inter-hemisphere alpha coherence, suggesting more hemispheric specialization (O'Connor and Shaw, 1978; Oltman et al., 1979; Zoccolotti, 1982), others have found that FI participants had higher alpha coherence compared to those who were FD (Colter and Shaw, 1982). Nevertheless, we hypothesized that our participants should exhibit more reflectivity and FI, hence an increase in inter-and intra-hemispheric EEG coherence, especially within the alpha and theta bands (Colter and Shaw, 1982). Gender may, however, moderate this, given that: (1) baseline EEG coherence is higher in females than in males (van Beijsterveldt et al., 1998), though this might be reversed in the gamma band (Jausovec and Jausovec, 2010); (2) an increase in both alpha and theta coherence from baseline to task is more prominent in females than in males (Beaumont et al., 1978; Volf and Razumnikova, 1999).

It is important to consider that gender-dependent differences have been frequently observed in both the motor and the cognitive realms (e.g., Kimura, 1992; for review, see Diamond et al., 1983; Baron-Cohen and Hammer, 1997). The different genderdependent functional connectivity effects have been related to gender differences in brain structures, especially within the corpus callosum (Corsi-Cabrera et al., 1997; Jausovec and Jausovec, 2005). Hence, in the first study we studied only females to reduce intra-group variability. In the first study, we set out to study the effect of QMT on HFT performance by comparing the QMT to two control groups: *Verbal Training* (VT, identical cognitive training with verbal response) and *Simple Motor Training* (SMT, similar motor training with reduced choice requirements). As will be shown, results indicated that only the QMT group, and not the control groups, showed better HFT performance. In the second study we set out to examine gender-dependent differences, comparing the effects of QMT for male and female participants on reflectivity, as well as studying the possible EEG counterparts. As will be shown, both genders exhibited better HFT performance and reflectivity following the QMT, albeit showing an opposite EEG pattern. These results are discussed in light of neuronal efficiency theory.

## **STUDY 1**

#### **METHODS**

#### *Participants and design*

A total of 24 female (28 ± 3 years in age) students participated in the study, none of whom practiced QMT before (for the detailed procedure, see Dotan Ben-Soussan et al., 2013). In order to avoid gender-dependent differences in performance (Terlecki et al., 2008) and reduce intra-group variability we focused on female participants. Data were collected both before and after a single training session lasting 7 min in each of three training groups (the participants having been randomly allocated to these): (1) Quadrato Motor training (QMT—3 choices and whole-body response, *n* = 9); (2) Simple motor training (SMT—1 choice and whole-body response, *n* = 7); and (3) Verbal training (VT—3 choices and verbal response, *n* = 8). The collected data included the HFT, reported here. Other measures included EEG and an Alternative Uses task, reported elsewhere (Dotan Ben-Soussan et al., 2013).

## *Training groups*

*Quadrato Motor Training (QMT).* Briefly, the participant stood at one corner of a 0.5 m × 0.5 m square and made movements in response to verbal instructions given by an audio tape recording. There were three optional directions of movement. The instructions directed participants to keep the eyes focused straight ahead, hands loose at the side of the body. They were also told to immediately continue with the next instruction and not to stop due to mistakes. At each corner, there were three possible directions to move. The training thus consisted of 12 possible movements (**Figure 1**). Training consisted of a sequence of 69 commands, lasting 7 min.

Two variables that were addressed in other studies of motor learning are limb velocity and the decision regarding the responding limb (Criscimagna-Hemminger et al., 2002; Donchin et al., 2003). In order to control these parameters, we used a movement sequence paced at a rate of an average of 0.5 Hz (similar to a slow walking rate), and we instructed the participants to begin all movements with the leg closest to the center of the square (a detailed description can be found in Dotan Ben-Soussan et al., 2013).

*Simple Motor Training (SMT).* The SMT group provided similar motor performance as the QMT group but with reduced cognitive demands. This group moved from corner to corner on the square in exactly the same manner as the QMT group (pace, duration, auditory cue), but their movement was consistently 1-2-3-4-1 etc. The participants heard the same recordings as the QMT group. However, while the QMT group was told that each number represented a different corner of the square, the SMT group was told to simply begin at a certain corner and to continue to the next corner clockwise in response to the instructions. That is, regardless of the number specified on the tape, they always moved in the same sequence. This reduced the uncertainty and the cognitive demand, compared to the QMT group.

*Verbal Training (VT).* The VT group was designed to reduce motor load while keeping the same cognitive load and uncertainty. The participants, who were instructed to only make verbal responses, stood 1 m in front of the square, but did not move to the corners. Instead, they responded to the taped commands verbally by stating what direction of movement would be required in order to reach the corner specified by the command. For example, for a movement from corner 1 to corner 2, they were required to say "straight." All other training parameters were kept identical to the QMT (pace, duration, auditory cue).

#### *Hidden figures test*

We employed a computerized version of the Hidden Figures Test (HFT, detailed in Glicksohn and Kinberg, 2009), generated using E-Prime 1.1 (Psychology Software Tools). The participants were required to locate a simple figure embedded within a complex figure, both of them appearing on the screen, side by side (**Figure 2**). The figures ranged in size between 10.5 × 4 cm and 12 × 6.5 cm, and were viewed from a comfortable viewing distance. The participants were allocated 30 s for each of 16 trials. Based on the data collected by Glicksohn and Kinberg (2009), we split the test into two even sets of 8 tasks, matched for degree of difficulty, defined as number of hits for item/(number of hits + number of false alarms for item) in that study (*n* = 80). The two sets were presented in a counterbalanced order across participants. Before the test, one practice trial was given. The participant attempted to locate the simple figure as quickly as possible, within the time allocated. On detecting the figure, the participant pressed a button, and the complex figure was presented again, so that the participant could

**FIGURE 1 | The Quadrato Motor Training (QMT). (A)** A graphical illustration of the QMT. **(B)** A participant during the QMT while waiting for the next instruction (left) and following the instruction (right).

indicate the embedded figure for the experimenter. Two scores were obtained for each trial: correct/incorrect detection, and reaction time (RT). All RTs were subsequently log-transformed to normalize the data, and mean log(RT) was computed for each participant.

#### *Statistical analyses*

To answer the question regarding the effects of QMT on HFT performance, we ran a Group (QMT, SMT, VT) × Training (pre, post) analysis of variance (ANOVA) for correct HFT responses, adopting the Greenhouse-Geisser criterion. Whenever needed, we added *post-hoc t*-tests.

#### **RESULTS**

We report a significant Group × Training interaction [*F*(2, <sup>21</sup>) = 5.95, *MSE* = 0.63, *p* < 0.01] for the number of correct detections in the HFT. For QMT, correct detections significantly increased [*t*(8) = −2.86, *p* < 0.05] in contrast to SMT and VT which showed no change following training (see **Figure 3**).

To summarize Study 1, the QMT-induced improved performance on the HFT was significantly higher compared to the two control groups, which emphasized either the cognitive or the motor training of QMT, but not both. The two control groups showed no improvement, indicating that in this setup there is no significant improvement due to the pre-post HFT learning itself. Subsequently, in Study 2, as a continuation of Study 1, we wanted to examine whether similar effects could be observed in male participants following QMT.

## **STUDY 2 METHODS** *Participants and design*

A total of 37 volunteers (29 ± 4 years in age) participated in the study, which was conducted both in Israel (10 females—out of which nine participated in Study 1 in the QMT group, and 8 males) in the MEG unit at the Gonda Brain Research Center, and in Italy (7 females, and 12 males) in the cognitive neurophysiology laboratory of the Research Institute for Neuroscience Education and Didactics. All participants were right-handed with no medical history that might affect their EEG. The study was approved by the ethics committee of Bar-Ilan University. Upon entering the lab, the participant signed a written informed consent. Then, we recorded baseline EEG for 5 min (2.5 min eyes open and fixed and then 2.5 min eyes closed). Subsequently, the HFT Task (see section Hidden Figures Test) was presented. All data were collected both before and after a single QMT session lasting 7 min. In order to pool the female participants together and all male participants together, we conducted two *t*-tests (the first for comparing the participants who took part in Study 1 to the additional 8 females; and the second for comparing the Israeli and Italian male participants). The two independent *t*-tests revealed no differences in performance in the HFT within the female and male groups, allowing us to pool our participants.

#### *Hidden figures test*

The task was the same as in Study 1. In addition to the analysis conducted as in section Hidden Figures Test, based on Glicksohn and Kinberg (2009), four profiles were defined: (1) Field Dependent (FD) = low success + long RT; (2) Field Independent (FI) = high success + short RT; (3) Reflective (Ref) = high success + long RT; (4) Impulsive (Imp) = low success + short RT. High success was defined as an above-median number of correct detections at baseline (median = 4); long RT was defined as an above-median Log(RT) at baseline (median = 4.21).

## *Electrophysiological measurements*

EEG data were recorded using a 65-channel geodesic sensor net (Electrical Geodesics Inc., Eugene, USA), sampled at 500 Hz and referenced to the vertex (Cz) with analog 0.1–200 Hz band-pass filtering. Impedance was usually kept under 40 k-, lower than the customary 50 k with this system (Ferree et al., 2001). EEG signals showing eye movements or muscular artifacts were manually excluded, and bad channels were replaced using spatial interpolation (Perrin et al., 1989). The data were referenced offline to average reference. The first 32 non-overlapping, artifact-free epochs of 2.048 s duration were extracted from each electrode for further analysis from the eyes-closed resting state period, as previously reported (Dotan Ben-Soussan et al., 2013). Coherence values were calculated from the multitapered pair-wise cross-spectra. The coherence values were normalized using Fisher's *z* transformation. We calculated coherence within the theta, alpha, and gamma frequencies (4–7, 8–13, 25–45 Hz, respectively). Notably, gamma effects are at risk of contamination by muscle activity from scalp and neck (Whitham et al., 2007) and saccade-related spike potentials (SP) due to eye movements (Yuval-Greenberg and Deouell, 2009). In order to minimize this risk, and as SP is elicited at the onset of small saccades, which occur during eyesopen fixation (Martinez-Conde et al., 2004), our report focuses on eyes-closed conditions. Furthermore, to eliminate muscle artifacts, we used three additional steps for caution. First, we carefully visually inspected the raw data, manually extracting artifact-free epochs. Second, as the EMG peaks at 70–80 Hz (Cacioppo et al., 1990), we used much lower frequencies of 25–45 Hz. And third, we excluded from statistical analyses all the circumference electrodes, closest to eyes, neck and face muscles (Berkovich-Ohana et al., 2012).

For the sake of data reduction and statistical comparisons, we chose one central electrode site in each region of interest. Since frontal, central, temporal and parietal areas are important for cognition and action, we chose to focus on bilateral frontal, central, temporal, and parietal electrode sites (F3, F4, C3, C4, T7, T8, P5, P6) (**Figure 4**). We defined electrode "pairs of interest" (POI), on the basis of prior knowledge concerning movement and meditation (Andres et al., 1999; Lutz et al., 2004, 2007).

## *Statistical analyses*

In order to answer the question of gender-difference in HFT performance, we ran a Gender × Training (pre, post) analysis of variance (ANOVA) for the two measures of HFT: (1) number of correct detections; (2) mean log(RT). Whenever needed, we added *post-hoc* one-tailed *t*-tests. Change in number of correct

detections was calculated by subtracting the number of correct figures detected before QMT from the number of correct detections following QMT. Change in log(RT) was calculated by subtracting pre from post QMT log(RT).

Then, in order to study the possible gender-dependent electrophysiological counterparts of the QMT effects, we ran six ANOVAs for the *z*-transformed theta, alpha and gamma coherences, for intra- and inter-hemispheric connections separately. For intra-hemispheric coherence, we ran a 4-way ANOVA: Gender × Training × Hemisphere × Electrode Pair (F-T, F-P, T-P). For inter-hemispheric coherence, we ran a Three-Way ANOVA: Gender × Training × Bilateral Electrode Pair (F-F, C-C, T-T, P-P). For all the ANOVAs we adopted the Greenhouse-Geisser criterion.

## **RESULTS**

## *HFT*

We found a significant Training effect [*F*(1, <sup>35</sup>) = 9.57, *MSE* = 1.66, *p* <.005] for the number of correct detections (**Figure 5A**), which extend the results of Study 1 to males; but not for mean log(RT). The Gender × Training interaction was not significant for either measure. No difference in performance between the male and female participants was found either at baseline, or following training, for either measure (**Figures 5B,C**). As can be seen from **Figure 5**, on average there is an increase in the detection of one more figure following QMT, and the test-retest correlation found here of 0.57 (*n* = 37, *p* < 0.0001) is relatively high, though is lower than the .78-.92 range found for the GEFT (Kepner and Neimark, 1984). This correlation is comparable to the correlation that we have computed between the two sets derived from the HFT of a previous study (Glicksohn and Kinberg, 2009),

**FIGURE 5 | Pre-post difference in performance on the HFT task (mean ± SEM). (A)** Main effect for pre-post difference in number of correct detections; **(B)** Pre-post difference in number of correct detections as a function of Gender; **(C)** Pre-post difference in mean log(RT) as a function of Gender; (∗*p* < 0.05; ∗∗*p* < 0.005).

which is.67 (*n* = 80, *p* < 0.0001). An overall view of the relationship between HFT performance (see section Results) and RT is presented as a scatter plot (**Figure 6**). Of the 37 participants, 12 (6 females) exhibited a trend toward reflectivity or FI following QMT. The results show increased reflectivity in both genders.

A positive correlation was found between the change in score for the two change in number of correct detections and change in log(RT) measures (*r* = 0.36, *p* < 0.05, *n* = 37), indicating that better performance on the HFT following QMT is related to longer latency of correct response. Again, we can compare this to the respective difference scores computed for two sets derived from the HFT of the previous study, which is 0.22 (*n* = 76, *p* = 0.053). Thus, it is not simply the case that QMT leads to *faster* RT, as reported elsewhere for a simple reaction time task (Dotan Ben-Soussan et al., 2013), rather that performance on the HFT is indicative of reflectiveness (more correct detections coupled with longer RT; Glicksohn and Kinberg, 2009).

#### *Electrophysiological data*

Of importance to the question related to training-induced gender-dependent effects, the first set of three ANOVAs yielded within the theta band a significant Gender × Training interaction [*F*(1, <sup>35</sup>) = 11.32, *MSE* = 0.03, *p* < 0.005]. As seen in **Figure 7A**, while the female group demonstrated significantly increased intra-hemispheric theta coherence [*t*(16) = −2.56, *p* < 0.05], this was significantly decreased in the male group [*t*(19) = 2.57, *p* < 0.05]. A similar pattern was found within the alpha band, the Gender × Training interaction being significant [*F*(1, <sup>35</sup>) = 7.22, *MSE* = 0.05, *p* < 0.05]. As seen in **Figure 7B**, while the female group demonstrated significantly increased intra-hemispheric alpha coherence [*t*(16) = −2.02, *p* < 0.05], this was significantly decreased in the male group [*t*(19) = 1.76, *p* < 0.05]. No such interaction was found for intra-hemispheric gamma coherence.

The second set of three ANOVAs yielded a significant Gender × Training interaction for both theta [*F*(1, <sup>35</sup>) = 11.05, *MSE* = 0.02, *p* < 0.005] and alpha coherence [*F*(1,35) = 5.92, *MSE* = 0.06, *p* < 0.05]. As seen in **Figures 7C,D**, while the female group demonstrated significantly increased inter-hemispheric theta coherence [*t*(16) = −2.46, *p* < 0.05], theta and alpha coherence significantly decreased in the male group [*t*(19) = 2.74, 1.81, respectively, *p* < 0.05]. *Post-hoc* analysis revealed a significant increase in temporal alpha coherence in the females who did not improve having low HFT performance at baseline [*t*(4) = −4.87, *p* < 0.01], while an opposite pattern was observed in males. More specifically, frontal alpha coherence significantly decreased in the males who improved [*t*(6) = 2.84, *p* < 0.05]. Although not significant, a similar trend occurred for intrahemispheric alpha. In addition, a significant positive correlation was found between change in theta and alpha coherence, both for intra- and inter-hemispheric connections (*r* = 0.75, and 0.79, respectively, *p* < 0.0001, *n* = 37), in accordance with previous reports (Sauseng et al., 2002; van Albada and Robinson, 2013).

In addition, a significant Gender × Training × Electrode Pair interaction was found for inter-hemispheric gamma coherence [*F*(3, <sup>105</sup>) = 3.01, *MSE* = 0.01, *p* < 0.05]. As seen in **Figure 8**, only the female group demonstrated post-training increased inter-hemispheric bilateral temporal gamma coherence [*t*(16) = −2.16, *p* < 0.05].

Marginally significant differences were found between the female and male groups at baseline for inter- and intra- hemispheric gamma coherence [*t*(35) = 1.97, 1.96, *p* = 0.06], but not for theta or alpha. Following QMT, a significant difference was found for intra-hemispheric theta and alpha [*t*(35) = 2.80, 2.79, *p* = 0.008]. A similar difference was found for inter-hemispheric theta and alpha [*t*(35) = 2.36, 3.38, *p* < 0.05] but not for gamma coherence.

To summarize Study 2, following training, reflectivity improved for 32% of the participants. Importantly, while a similar trend of improved reflectivity was observed in both genders, there was a differential effect in EEG coherence for males and females. More specifically, temporal alpha increased in the females, while an opposite pattern was observed in males. In addition, the female group demonstrated post-training increased inter-hemispheric bilateral temporal gamma coherence

## **DISCUSSION**

#### **QMT IMPROVES REFLECTIVITY**

The behavioral result of Study 1 has demonstrated that a session of QMT improved performance in the HFT task. This was in contrast to SMT and VT, representing the motor and cognitive aspects of the training, respectively. In addition, Study 2 indicates that training enabled our participants to become more reflective, as well as more FI. The current results suggest that a short practice (7 min) of QMT can be advantageous for improving reflectivity. This supports the claim raised by Depraz et al. (2000) that although reflectivity can sometimes be thought to require a long duration of time to manifest itself, it might be triggered faster, especially in situations we are not accustomed to in our daily life. The current results strengthen previous claims that simple cognitive tests measuring solely reaction time are not sufficiently sensitive to evaluate changes in higher cognitive functions (Dietrich and Sparling, 2004; Dotan Ben-Soussan et al., 2013) such as reflectivity.

What could be the cause of the QMT-improved reflectivity? The three inter-dependent phases described for the dynamics of a reflective act include suspension, redirection of attention inwardly and receptivity, with suspension of habitual activity being the most important to initiate the reflective act (Depraz et al., 2000). In relation to that, it could be argued that given the continual state of attending and waiting for the next instruction during the QMT, the participants were obliged to enter this state of *suspending* the tendency for habitual movement, that of moving where and when you want. In fact, the QMT requires re-instantaneous suspended acts. The suspended movement that begins the process of reflectivity is "forced" here by a different instruction at each step of the QMT. That is, the relatively long inter stimulus intervals (1200 ms) between current location and next location, as well as waiting within the position until the next instruction in the QMT can be regarded as empty time, a time of silence. However, even when it is very brief, a silence of a few seconds can appear exponentially longer (Depraz et al., 2000). Pockett (2003, p. 63) has suggested that when one is "actively engaged in the external world" (as these participants had to be) then "time slows down." We thus suggest that it is this bodily awareness required in the QMT combined with attending that reduce reactivity and increase reflectivity (Depraz et al., 2000; Bishop et al., 2004; Kirk et al., 2011; Greenberg et al., 2012). Furthermore, the QMT requires dividing *attention* inwardly and outwardly, simultaneously listening to the instruction as well as attending to the position of the body in space. In line with that, Depraz et al. (2000) have related to the inner/outer distinction, claiming that the time of relative emptiness (represented here as the time with no specific instructions except the attending, waiting for the next instruction) enables the transition from "looking for" to "letting come," which in turn leads to and further requires a state of receptiveness, which in turn removes the inside/outside distinction (Depraz et al., 2000), and creates a "space for silence" related to increased reflectivity and expansion of time (Dawson, 2003; Paoletti and Salvagio, 2011).

In support of this claim, it was previously shown that another form of contemplative practice, Mindfulness meditation, dilates the subjective time experienced, in comparison to control participants (Berkovich-Ohana et al., 2012). Indeed, accumulating findings show that Mindfulness brings one back to greater awareness to the present moment (Farb et al., 2007; Kabat-Zinn, 2009; Brewer et al., 2011; Berkovich-Ohana et al., 2012; Vago and Silbersweig, 2012) and to the body (Farb et al., 2007, 2012; Price and Thompson, 2007; Kerr et al., 2013). Possibly, similar to Mindfulness, QMT increases attention to the body and to the present moment by requiring attendance to the coming instruction and consequently responding to it. This in turn enables a state of increased reflectivity.

It could be suggested that increased reflectivity was only for one third of the participants that we report due to the short training. Possibly, a longer session, or a longer-term training with similar short sessions might result in increased percentages of enhanced reflectivity. However, these hypotheses can only be studied in a follow-up study.

#### **GENDER-DEPENDENT ELECTROPHYSIOLOGICAL CHANGES**

We hypothesized that better performance on the HFT would be related to increased alpha coherence, and that QMT would increase coherence, and more so in females. As it turned out, both hypotheses were supported by the results for the female group, and were opposite for the male group, hence underscoring the importance of studying gender differences.

As a starting point, we observed overall gender differences in pre-QMT resting state coherence, indicative of trait effects, with males exhibiting lower coherence (both intra- and interhemisphere) in the theta, alpha and gamma bands compared to females. These results are consistent with a previous study of highly intelligent individuals, reporting that males displayed greater decoupling (mostly of frontal brain areas), whereas females showed the opposite pattern, namely of more coupling (mostly between frontal and parietal areas) (Jausovec and Jausovec, 2005). This is further in line with the idea of differential brain organization in males and females (Volf and Razumnikova, 1999; Amunts et al., 2000; Mohr et al., 2005), whereby females consistently display higher inter-hemispheric coherence at rest and during cognitive task performance compared to males (Beaumont et al., 1978; Corsi-Cabrera et al., 1997; Volf and Razumnikova, 1999). The higher female coherence was previously interpreted as reflecting higher collaboration between the hemispheres or less hemispheric specialization for females (Amunts et al., 2000; Mohr et al., 2005; Ramos-Loyo and Sanchez-Loyo, 2011), suggesting that the left hemispheric is more dominant for different abilities, such as language and navigation in males, in comparison to females (Volf and Razumnikova, 1999; Ramos-Loyo and Sanchez-Loyo, 2011). The decreased trait coherence observed in the male group in the current study may thus be related to increased hemispheric specialization in males in general.

#### *Training-related gender differences*

Showing a similar pattern as the differential gender trait differences, QMT-induced electrophysiological changes included significantly increased theta and alpha coherence in females, in support of our hypothesis, while the opposite was found for males. The increased theta and alpha coherence observed in the female group is consistent with studies examining electrophysiological changes following meditation. Meditative practices, irrespective of gender, have consistently been related to increased coherence, especially inter- and intra-hemispheric theta and alpha coherence (Alexander et al., 1987; Aftanas and Golocheikine, 2001; Travis, 2001; Travis et al., 2002, 2009; Cahn and Polich, 2006; Baijal and Srinivasan, 2010). Unfortunately, gender-related analyses within meditation reports are scarce, as either gender is not reported at all (e.g., Lutz et al., 2004), or there are no gender-specific baseline differences, hence these are not subsequently considered (Travis et al., 2009), or not mentioned (e.g., Aftanas and Golocheikine, 2001; Travis et al., 2002; Baijal and Srinivasan, 2010). Although gender differences have not yet been systematically investigated in previous electrophysiologically-based meditation studies, some gender differences in behavioral measures were found following meditation. For example, while Qigong meditation was found to contribute positively to addiction treatment outcomes in both genders, female participants reported significantly more reduction in anxiety and withdrawal symptoms than did the male group (Chen et al., 2010). An opposite pattern was observed for TM, for which reduced drinking rates was reported among male university students but not in female students (Haaga et al., 2011). Our finding of QMT-induced gender-related differences in coherence is in accord with another study reporting gender-related electrophysiological differences. In this study (Duregger et al., 2007), a motor related evoked potential (contingent negative variation—CNV) was shown to manifest differently in females, showing higher frontal activation, compared to males, showing higher temporoparietal activation.  Related to this, it is important to keep in mind the gender-dependent differences frequently observed in motor and cognitive realms (Baron-Cohen and Hammer, 1997). More specifically, while women are better in fine-motor coordination (e.g., placing pegs in pegboard holes) men are better in target-directed motor skills, such as guiding or intercepting projectiles (Kimura, 1992). Finally, there are gender differences in brain morphology in relation to spatial cognition and mental rotation performance: while females have more gray matter in the parietal lobe than males, males have greater parietal surface area (Koscik et al., 2009). Koscik et al. (2009) further concluded that the structural gender difference could be a neurobiological substrate for the gender difference in mental rotation performance. In light of the above studies, showing genderdependent strategies and neural structure, the current results of gender-dependent electrophysiological change following training could be interpreted as reflecting different strategies to achieve the same cognitive and motor goal.