Wednesday, March 7, 2018

The Neuro- Physio -Biology of Meditation

Dr Ruwan M Jayatunge 
In general terms meditation is the non-judgmental observation of the ongoing stream of internal experiences as they arise. However meditation is a complex mental process involving changes in cognition, sensory perception, affect, hormones, and autonomic activity (Newberg & Iversen, 2003). Grabovac and team (2011) indicate that focused attention, decentering, and emotion regulation as mechanisms of mindfulness. Nonetheless meditation has a huge impact on body and brain physiology, besides meditation has enhanced neuroplastic potential. Jevning and colleagues (1992) view meditation as an integrated response with peripheral circulatory and metabolic changes subserving increased central nervous activity. 
Neuroimaging studies with positron emission tomography and functional magnetic resonance imaging have been used to study the neurological effects of meditationNeuroimaging studies demonstrate the functional up-regulation of brain regions of affect regulation and attention control (Rubia, 2009). Neuroimaging studies showed that mindfulness meditation practice activates the prefrontal cortex (PFC) and the anterior cingulate cortex (ACC) (Chiesa & Serretti, 2010). 
The prefrontal cortex is the cerebral cortex that covers the front part of the frontal lobe (Murray et al., 2016). The prefrontal cortex is essential for attentional control, manipulation of stored knowledge and modulation of complex actions, cognition, emotion and behavior (Allegri & Harris,   2001).  The prefrontal cortex has the ability to represent information not currently in the environment and intelligently guide thought, action, and emotion, including the inhibition of inappropriate thoughts, distractions, actions, and feelings (Goldman-Rakic ,1996).
Activation of the prefrontal cortex improves working memory. Working memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving (Cohen et al, 1997). Prefrontal neuropsychology emphasizes conscious, goal-directed behavior guided by past experience (Weinberger, 1993). Mindfulnessmeditation activates prefrontal cortex and enhances cognitive functioning (Stillman et al., 2016).
The anterior cingulate cortex involves in attention, decision-making, ethics and morality.  Anterior cingulate cortex has an important role in emotional self-control as well as focused problem-solving, error recognition, and adaptive response to changing conditions (Allman et al., 2006).  The anterior cingulate cortex activation signifies better emotional awareness. Therefore Gu and colleagues (2013) defined the anterior cingulate cortex as the conscious experience of emotions
Allman and group (2006) proposed that the anterior cingulate cortex is a specialization of neocortex. (The neocortex, also called the neopallium and isocortex, is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition, and generation of motor commands, spatial reasoning and language-Wikipedia). The British neuroscientist, Francis Crick identifies anterior cingulate cortex as the center of free will in humans. Chiesa and Serretti (2010) state that mindfulness meditation practice activates the prefrontal cortex.  
Young and team (2018) found increased insular cortex (insula) activity following mindfulness-based interventions.  Insular cortex is involved in consciousness mainly compassion, empathy, perception, self-awareness, cognitive functioning, and interpersonal experience. Laneri and team (2017) hypothesized that   mindfulness meditation regulates anterior insula activity. The insular cortex dysfunctions are associated with anxiety disorders (Paulus & Stein, 2006).
A Brodmann area is a region of the cerebral cortex that has unique structure and functions. Brodmann's maps of the cerebral cortex are universally used to locate neuropsychological functions (Strotzer , 2009). Meditation experts have highly activated brain areas especially Brodmann area 39, 40, 44 and 45 (Gundel et al., 2018).
The Electroencephalography (EEG) studies of the meditating brain have been done in the past few decades. Electroencephalographic studies have revealed a significant increase in alpha and theta activity during meditation (Chiesa & Serretti, 2010; Lomas et al., 2015).  The alpha state is an intensely pleasurable and relaxed state of consciousness essential to stress reduction and high levels of creativity. The alpha brain waves are associated with meditative states.
Lomas, Ivtzan and Fu (2015) indicated that mindfulness is associated with increased theta power.  Theta brain waves are commonly linked to enhanced levels of creativity, emotions, and spontaneity. Theta brain waves occur most often in sleep but are also dominant in the deepmeditation. Lagopoulos and team (2009) state that nondirective meditation techniques alter theta and alpha EEG patterns significantly more than regular relaxation..  
Meditation can produce measurable changes in the brain regions that involved in memory, learning, and emotion. There is a positive correlation between meditation practice and brain gray matter density. Hölzel and team (2008) indicate that greater gray matter concentration for meditators in the right anterior insula, which is involved in interoceptive awareness. In addition meditation practice could increase gray matter concentration in left hippocampus, posterior cingulate cortex,temporo-parietal junction and cerebellum. (Hölzel et al., 2011)
Esch (2014) points out that Meditation can cause structural alterations in grey and white matter, particularly in areas related to attention and memory.  Meanwhile Leung and team (2013) found greater gray matter volume in the left temporal lobe in the loving-kindness meditationexperts. Meditation-related neuroplasticity is crucially associated to a functional reorganization of activity patterns in prefrontal cortex and in the insula (Manna et al., 2010).
Luders and team (2013) found structural changes in the corpus callosum (the corpus callosum is important in communication between brain hemispheres) among long term meditators and they surmise greater connectivity, possibly reflecting increased hemispheric integration during cerebral processes involving (pre) frontal regions.  
Evidence suggests that mindfulness practice is associated with neuroplastic changes in the anterior cingulate cortex, insula, temporo-parietal junction, fronto-limbic network, and default mode network structures (Hölzel et al., 2011). The cingulate cortex involved with emotion formation and processing, learning and memory (Kozlovskiy et al, 2012). Insula plays a complex role in emotion, homeostasis (including error detection), autonomic function, sensation, salience, and awareness (Nieuwenhuys, 2012). The temporoparietal junction is an area of the brain where the temporal and parietal lobes meet, at the posterior end of the Sylvian fissure and mainly involved in information processing and perception. Frontostriatal circuits are neural pathways that connect frontal lobe regions with the basal ganglia (striatum) that mediate motor, cognitive, and behavioural functions within the brain (Alexanderet al., 1986).The fronto-limbic network is important in emotion processing. The brain’s “default mode network plays a role in internally focused processes as autobiographical memory, imagining the future, and social cognition (Spreng et al. 2009).

Some experts believe that mindfulness meditation enhances cognitive control or cognitive flexibility. According to Scott (1962) cognitive flexibility is the mental ability to switch between thinking about two different concepts and to think about multiple concepts simultaneously. Moore and Malinowski (2009) state that mindfulness is intimately linked to improvements of attentional functions and cognitive flexibility.  Mindfulness meditation can increase the function of control networks (Tang et al., 2015). Wimmer and team (2016) found that mindfulness training improved cognitive inhibition and data-driven information processing. As described by MacLeod (2007) cognitive inhibition is the mind's ability to tune out stimuli that are irrelevant to the task/process at hand or to the mind's current state.

According to Tomasino and  Fabbro (2016) meditation increase  activation in the right dorsolateral prefrontal cortex and in the left caudate/anterior insula and decreased activation in the rostral prefrontal cortex and right parietal area 3b. The dorsolateral prefrontal cortex is one of the most recently evolved parts of the human brain and it is important in cognitive processes (Elliott, 2003). The head of the caudate nucleus is concerned with multi-modal information processing and inhibition. The anterior insular cortex is defined as the conscious experience of emotions (Gu et al’, 2013) and important in emotional awareness. The rostral prefrontal cortex is important in executive functions. 
Ngô  (2013) identifies following brain structures are associated with meditation;  attention regulation (anterior cingulate cortex), body awareness (insula, temporoparietal junction), emotion regulation (modulation of the amygdala by the lateral prefrontal cortex), cognitive re-evaluation (activation of the dorsal medial prefrontal cortex or diminished activity in prefrontal regions), exposure/extinction/reconsolidation (ventromedial prefrontal cortex, hippocampus, amygdala) and flexible self-concept (prefrontal median cortex, posterior cingulated cortex, insula, temporoparietal junction). 
Mindfulness has been associated with enhanced performance monitoring (Saunders et al., 2016). According to Teper and Inzlicht (2013) meditators showed greater executive control. (Executive controls are   set of cognitive processes that are necessary for the cognitive control of behavior: selecting and successfully monitoring behaviors that facilitate the attainment of chosen goals) Meditation experience has been linked to increased functional coupling between the posterior cingulate, dorsal anterior cingulate, and dorsolateral prefrontal cortex, which are regions that have been consistently implicated in processes of attention and executive control (Brewer et al., 2011; Zanesco et al., 2013). Meditation   can improve executive attention (Elliott et al., 2014). In addition mindfulness practice facilitates critical thinking (Noone & Hogan, 2016).
In neuroscience, the default mode network (DMN), also default network, or default state network, is a large scale brain network of interacting brain regions known to have activity highly correlated with each other and distinct from other networks in the brain (Buckner et al., 2008). The default mode network is active in mind-wandering.

Meditation has been associated with relatively reduced activity in the default mode network, a brain network implicated in self-related thinking and mind wandering (Garrison et al., 2016). Following mediation the deactivation of the default mode network that generates spontaneous thoughts can be observed with the activation of the temporoparietal junction which assumes a central role in empathy and compassion (Ngô, 2013). Taylor and team (2013) suggest that meditation training leads to functional connectivity changes between core default mode network regions possibly reflecting strengthened present-moment awareness.

Studies suggest that meditation can increase empathy. Empathy is the ability to experience and understand what others feel without confusion between oneself and others (Decety & Lamm , 2006). According to Dr. Nassir Ghaemi – Psychiatrist and the author of the famous book “A First-Rate Madness: Uncovering the Links Between Leadership and Mental Illness” empathy is not a mere concept but a neurobiological fact.

Empathy involves not only the affective experience of the other person's actual or inferred emotional state but also some minimal recognition and understanding of another's emotional state (Decety &, Jackson, 2004) The social neuroscientific investigation of empathy has revealed that the same neural networks engaged during first-hand experience of affect subserve empathic responses (Engen &  Singer , 2013). Bruneau and colleagues (2012) studied the networks in processing others’ emotional suffering and found dorsomedial prefrontal cortex responds selectively to emotional pain. Bruneau and colleagues (2015) showed the amygdala activity to the control of other-focused empathy.  Bird and colleagues (2010) state that empathic brain responses to the suffering of others are associated with increased activation in left anterior insula.

Mindfulness meditation increase compassionate behavior toward others (Laneri et al., 2017). Meditation has observable changes in brain structure related to empathy (Sorrell, 2015). Compassion meditation is accompanied by activation in brain areas involved with empathy i.e., the left medial prefrontal cortex and the anterior cingulate gyrus (Engström & Söderfeldt, 2010).

Meditation is commonly thought to induce physiologically quiescent states (Khalsa et al., 2015). Meditation has efficient relaxation response(Buttle, 2015). According to Professor Herbert Benson, the relaxation response is a physical state of deep rest that changes the physical and emotional responses to stress and the opposite of the fight or flight response. In other words the relaxation response is the mind-body intervention that offsets the physiological effects caused by stress (Benson, 1974).  Krygier and team (2013) explicate that Vipassana meditationshows some evidence of altered sympatho-vagal balance.
Meditation is a positive emotional experience. It is a Focused internalized attention. Focused internalized attention gives rise to emotionally positive "blissful" experience which is accompanied by increased anterior frontal and midline theta synchronization (Aftanas & Golocheikine , 2001).  Meditation state can decrease the amplitude of neurophysiologic processes that subserve  attentional engagement elicited by unexpected and distracting stimuli (Cahn & , Polich  2009). Emotional regulation appears to be accompanied by increased activation in prefrontal cortex (PFC) and/or decreased activation in regions such as the amygdala and insula (Stein, 2008).Mindfulness meditation improves emotion regulation (Tang, 2016). Hanley et al (2014) identify meditation as a positive emotion regulatory strategy. 

Zeidan and team (2014) hypothesized that mindfulness meditation attenuates anxiety through mechanisms involved in the regulation of self-referential thought processes. They tend to state that meditation-related anxiety relief was associated with activation of the anterior cingulate cortex, ventromedial prefrontal cortex and anterior insula. Mindfulness training may improve well-being via changes in emotional information processing (Roberts-Wolfe et al., 2012). In addition meditation practices have possible long-term changes in the brain and their positive effects on empathy, meta cognitive skills and health (Gundel et al., 2018).

Saunders and team (2016) highlight that mindfulness meditation boosts early neural performance monitoring through meditation's influence on affective processing. Long-term practice of mindfulness leads to emotional stability by promoting acceptance of emotional states and enhanced present-moment awareness, rather than by eliciting control over low-level affective cerebral systems from higher-order cortical brain regions(Taylor et al, 2011). Mindfulness meditation has been shown to promote emotional stability (Taylor et al, 2013). Crosswell  and team (2017) state that mindfulness training may lead to an enhanced emotional experience coupled with the ability to recovery quickly from negative emotional states.

Mindfulness meditation reduces pain in experimental and clinical settings and mindfulness meditation-induced pain relief activated higher-order brain regions, including the orbitofrontal and cingulate cortices. (Zeidan et al., 2015). According to Brown and Jones (2010) meditation reduces the anticipation and negative appraisal of pain. Mindfulness meditation-related pain relief may share a common final pathway with other cognitive techniques in the modulation of pain (Zeidan et al., 2012). Zeidan and team (2011) state that reductions in pain and unpleasantness associate with thalamic deactivation. They further explain that meditation engages multiple brain mechanisms that alter the construction of the subjectively available pain experience from afferent information. Mindfulness meditation has most prominent effect on psychological aspects on living with chronic pain, improving associated depression and quality of life (Ball et al., 2017).

Using functional magnetic resonance imaging Ives-Deliperi and team (2011) observed significant signal decreases during mindfulnessmeditation in midline cortical structures associated with interoception, including bilateral anterior insula, left ventral anterior cingulate cortex, right medial prefrontal cortex, and bilateral precuneus.  In contrast they observed significant signal increase in the right posterior cingulate cortex. Hence Ives-Deliperi and team (2011) concluded that mindfulness achieves its positive outcomes through a process of dis-identification.

Mindfulness, as a metacognitive form of awareness, involves the process of decentering, a shifting of cognitive sets that enables alternate appraisals of life events (Garland  et al.,2009). Mindfulness meditation facilitates present moment awareness and emotional acceptance. Teper and Inzlicht (2013) state that meditators show greater executive control. Mindfulness is associated with brain regions involved in executive attention, emotion regulation, and self-referential processing (Lu et al ., 2014).

Mindfulness is associated with enhanced prefrontal cortical regulation of affect through labeling of negative affective stimuli (Creswell, 2007). Vipassana meditation evokes a brain state of enhanced perceptual clarity and decreased automated reactivity (Cahn et al., 2013). Long-term Vipassana meditation contributes to increased occipital gamma power related to long-term meditational expertise and enhanced sensory awareness (Cahn et al., 2010). However different meditation styles and traditions are characterized by different patterns of neural activation (Tomasino et al., 2014).

Meditation has positive impact on neuronal and molecular bases of the changes in the brain. On the molecular level, during meditation dopamine and melatonin are found to increase, serotonin activity is modulated, and cortisol as well as norepinephrine have been proven to decrease (Esch, 2014).  Advanced meditators have higher melatonin levels than non-meditators (Solberg et al., 2004). Kruis and team (2016) indicate that short-term meditation practice induces stable changes in baseline striatal dopaminergic functioning. Brand and colleagues (2012) found decreased cortisol levels among the experienced meditators.

In the brain, dopamine functions as a neurotransmitter. Dopamine is produced in the substantia nigra and the ventral tegmental area in the brain. Dopamine acts as a powerful regulator of different aspects of cognitive brain functions (Nieoullon, 2002).  Low levels of dopamine activity in the brain can cause depression. A substantial body of evidence accrued from animal and human studies indicate that dopamine play an important role in the pathophysiology of depression (Robinson, 2007). Meditation increase in endogenous dopamine release (Kjaer et al., 2002).

Serotonin is a monoamine neurotransmitter works as a mood regulator. According to Li and team (2007) low levels of serotonin are highly associated with suicide.  Psychiatric disorders, particularly depression and anxiety, are often associated with impaired serotonergic function(Weinberg-Wolf, et al 2018). Meditation influence the brain’s production of serotonin levels (Li & He, 2007).

Meditation activates Endorphins and GABA (gamma aminobutyric acid). Endorphins are endogenous opioid peptides that function as neurotransmitters.
Endorphin seems to be released during meditation (Rokade, 2011) GABA or gamma-Aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. Elias and Wilson (1995) hypothesized that  transcendental meditation  produces changes in pituitary hormone secretion by enhancing hypothalamic GABAergic tone, and its anxiolytic effects by promoting GABAergic tone in specific areas of the brain.   

Meditation can lower cortisol level. Sudsuang and team (1991) found after meditation, serum cortisol levels were significantly reduced. Similar results were found by Brand and colleagues (2012) and Turakitwanakan and colleagues (2013).  Plasma Arginine vasopressin (AVP) elevation occurs through meditation (Jevning et al.,1992).

Mindfulness-based stress reduction may help reducing blood pressure levels and blood pressure reactivity to stress (Nyklíček et al., 2013). Brand and team (2012) highlight that mindfulness practice has a favorable influence both on biomarkers of stress regulation, such as cortisol secretion, and on sleep. Furthermore mindfulness practice is associated with increased experience of momentary positive emotions as well as greater appreciation of, and enhanced responsiveness to, pleasant daily-life activities (Geschwind et al., 2011). Hence meditation improves positive dimensions of mental health and improves prosociality.  

Meditation is a complex process that has neurological, psychological and biological effects. Numerous studies have revealed various neuro-physiological   neuro-chemical mechanism of meditation. These studies indicate that meditation has positive influence on cognition, sensory perception, affect and autonomic activity. 

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