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STRESS, THE BRAIN AND YOGA

Updated: Apr 10



How yoga might influence the brain and help develop greater resiliency to stress. Before discussing how yoga influences the brain let’s consider in more detail one area which may be affected by stress, namely the four parts of the cortex, and their major roles? The cerebral cortex is associated with higher level processes including thought, consciousness, emotion, reasoning, memory, and language. It enables the actual conscious thinking about stimuli. Divided into four parts or “lobes” each has a slightly different role as below: -

  1. Frontal Lobe - its main roles are in executive functioning, reflection, planning and language. It contains the Primary Motor Cortex (planning and coordinating movement), the Broca’s Area (speech and language), the Insula (body and emotional awareness), Pre-Frontal Cortex (decision making and high-level cognitive functioning), Anterior Cingulate Cortex (directs attention to what is significant and has a role in pain perception) and Orbito Frontal Cortex (social behaviour and planning of behaviour).

  2. Parietal Lobe – helps with spatial awareness (proprioception) and it contains the Somatosensory Cortex which registers and processes sensory information such as touch, temperature, and pain. It compares sensory information received with past experience which helps determine meaning in relationship to self.

  3. Temporal Lobe – has a role in auditory and visual processing and contains Wernicke’s Area which is important for speech comprehension and verbal memory.

  4. Occipital Lobe – this contains the Primary Visual Cortex, and its main role is in interpreting incoming visual information and making sense of and contextualising the environment we are in.

Stress Some stress can be useful for example helping us to react in dangerous situations, but continuous or chronic stress can alter the brain structure and how our brain functions. When the brain detects stress the hypothalamus signals to the body to respond via two mechanisms. The quickest is via the sympathetic nervous system The neurotransmitter norepinephrine (the locus coeruleus located in the pons, part of the hindbrain is the main site of the release) is released which activates our bodies stress response as part of our autonomous nervous system – the sympathetic system often known as our fight/flight response. The second response is via the Hypothalamic-pituitary-adrenal (HPA) axis which results in a cascade of hormones which ultimately stimulate the release of the hormone cortisol by the adrenal glands. What happens in a stressed brain? High levels of cortisol and inflammatory markers over a prolonged period can negatively affect the hippocampus, prefrontal cortex and other structures which impact mood, sleep, and memory (Innes and Selfie 2014). These negative effects can be explained as follows, . reducing the number of receptors and brain cells being made in the hippocampus thus reducing learning and memory and impacting the ability to encode and retrieve long term memory. The hippocampus is highly susceptible to cortisol and with prolonged high levels its receptors are damaged, and the hippocampus begins to atrophy leading to poor memory/attention span and a halt in neurogenesis in this area, “When people under stress experience severe memory problems – forgetting their way to work, going into the kitchen and then not remembering why they went in – it’s likely that what they’re experiencing is the very negative effect of stress on the function of the hippocampus due to decreased neurogenesis”, Peter Erikson, (The Plastic Mind by Sharon Begley pg. 87) The reduction in the number of brain cells being made in the hippocampus also reduces the ability to turn off the stress response because this is the area which inhibits the activity of the HPA axis (referred to above) which results in prolongation of the HPA axis and so it continues. . reducing activity in and shrinking in size of the prefrontal cortex located in the prefrontal lobe of the cerebral cortex which has a negative impact on executive functioning including decision making, rationalising, making judgments and assessments, modulating emotion and social interaction. The impact of chronic stress on this part of the brain effects our ability to reassess situations and find new ways of dealing with them. The prefrontal cortex works with the anterior cingulate cortex and insula to determine the importance of experiences, help us process somatic experience and sense of self and increased stress can cause dysregulation in these areas and hinder our ability to feel calmer, reappraise the stress triggers and feel better about ourselves. . increases activity in the amygdala, part of the limbic system located in the forebrain responsible for threat perception, emotions including fear, instinctual behaviours, and emotional memory. Often referred to as the “alarm bell” of the brain this receives information from the locus coeruleus (from where norepinephrine involved in the stress response is released). When stressed there is an increase in the activity levels of neurons in the amygdala which triggers more stress and fear, and the cycle continues unless this area is brought under control. Increased activity here is directly linked to reduced activity in the Prefrontal cortex which is unable to inhibit overactivity of the amygdala. Activation of the amygdala is necessary in emergencies but prolonged overactivation can lead to allostatic load and ill health. Other effects might be as follows- The Brocas area within the frontal lobe of the cerebral cortex is responsible for speech production and when stressed and feeing emotionally overwhelmed language becomes difficult as the blood flow to this is hindered. Norepinephrine released by the locus coeruleus which triggers the sympathetic stress response can impact the basal ganglia and reduce fine motor movement which may explain shaking when stressed. During chronic levels of stress, the locus coeruleus is overactive triggering the release of more norepinephrine and the stress response. Conversely reduced activity in the Dorsal raphe nucleus during stress means a reduction in the release of serotonin – a feel good neurotransmitter. High levels of stress can lead to higher levels of the major excitatory neurotransmitter glutamate which has a role in long term potentiation (neuroplastic coding) and encoding memories. Consequently, chronic stress can lead to strongly encoded pathways in the brain which become difficult to break. Ultimately in times of chronic/prolonged stress the Prefrontal cortex exhibits more excitatory activity and less inhibitory activity. There is less of an ability to down regulate, activate the para sympathetic circuits and feel calmer. Stress is associated with reduced hippocampal Gama Amino Butryic Acid (GABA)levels. The reduction in GABA, which is the primary inhibitory neurotransmitter may also reduce its role in inhibiting the amygdala and preventing inappropriate emotional and behavioural responses (Fan Jie et al 2018).

How yoga might influence the brain in such a way as to create greater resiliency to stress in the future. The interaction of the hippocampus, amygdala, prefrontal cortex, ANS and GABA referred to above provide a network which can be influenced by yoga practices which may reduce allostatic load, decrease stress, and improve future stress response. Yoga practices including asanas, breathing, mindfulness, meditation, and mudras may all impact how the brain responds to stress. Slow controlled yoga breathing techniques such as coherent breathing activate the para sympathetic nervous response (rest and digest) immediately invoking a feeling of calm, increasing HRV, greater vagal tone and emotional resiliency/reactivity to stress. As Dr Luciano Bernardi (2015) also discovered this significantly impacts the insula which works with the prefrontal cortex and processes how our body feels both in sensation and form, movement, and awareness of movement. Stronger prefrontal cortical functioning is associated with reduced cognitive decline. Research by Streeter et al 2012 revealed that slow breathing used during yoga increases GABA levels which reduces stress. Ujjayi breathing can cause an increase in release of GABA even more so than normal slow breathing, via a unique activation of the Nucleus Tractus Solitarius (NTS) where the SARS in the lungs send messages to the vagus and then to the NTS. Increased GABA as the main inhibitory neurotransmitter can help improve stress resilience. Yoga asana practices and movement can support the pathway between the cerebellum and PFC (reduced connectivity here is linked to mental health issues and stress). Working on balancing asanas is ideal and hand movements (including mudras) are relevant as they improve the sensory and motor real estate. When sequencing asanas to practice, planning new movements is preferable rather than the repetition of perhaps an ashtanga practice (Aelst et al. May 2020). In a study by Afonso et al 2017 healthy elderly women practicing hatha yoga for 8 years were shown to have increased prefrontal cortical thickness improving awareness, memory, executive function and therefore control over the amygdala and better stress resilience. Yoga asanas and physical movement can increase serotonin levels- our feel-good neurotransmitter enhancing mood and resiliency to stress. A study by Lim et al 2015 revealed that 90 minutes of yoga once a week for 12 weeks compared with a control group showed increased serotonin. Furthermore “studies also suggest that yoga practices reduce stress-induced allostatic load in three stress reactive systems: the ANS, the HPA axis, and the GABAergic system” (Streeter et al 2021 pg. 574). In a randomized controlled MRS study on the effect of walking and 12 weeks of Iyengar yoga asanas it was revealed that the yoga group saw greater increases in mood and resilience and increase in thalamic GABA activities (Streeter et al 2010). Yoga asanas build resilience in several ways! Yoga asanas and Yoga Nidra have been shown to increase dopamine levels (kjaer et al 2002), a feel-good neurotransmitter which activates neurons of the Pre-Frontal Cortex and elevates mood/concentration. Yoga improves the release of feel-good neurotransmitters including GABA, dopamine, oxytocin, and serotonin calming us down and reducing stress and creating awareness of techniques which may build resiliency to future stress. Mindfulness and breathing slowly including breathing techniques such as ujjayi breathing and activities such as naming emotions as they arise can reduce overactivity in the amygdala, reducing our fear-based stress response and emotional reactivity to future stress. A 2018 Rotterdam study showed decreased right amygdala activity following the practice of yoga over a five-year period. The right amygdala is associated with poor emotional regulation, so this suggests yoga enables better emotional regulation and response to stressors. Chanting Om which involves slow breathing and increasing vagal tone may also boost executive reasoning, memory and emotional resilience as revealed. In a 2011 study by Kalyani et al, Om chanting led to significant deactivation in the right amygdala (associated with emotional reactivity and resilience to stress). Mindfulness meditations as part of yoga can increase body awareness and reduce activity in the limbic system, develop more grey matter in the hippocampus, and reduce emotional overactivity. Yoga therapy can include the practice of yoga (asanas, breathing, mindfulness) in ways outlined above and give us tools to better regulate our nervous system and build future resiliency – when to use our SNS for clarity/alertness and when to activate our PNS for calm and stress relief. Furthermore, yoga’s influence on the brain also outlined above, and its strengthening of the prefrontal cortex and reduction in overactivity of the amygdala can help to provide transformational shifts and improve future resiliency.

If stress is something you are currently experiencing then feel free to get in touch to find out more about how yoga therapy with me might be able to help you. . Innes and Selfie 2014 “Meditating as a therapeutic intervention for adults at risk for Alzheimer’s disease” Frontiers in Psychiatry 2014 . The Plastic Mind, Sharon Begley . Fan Jie et al 2018 “Stress in regulation of GABA Amygdala system and relevance to neuropsychiatric diseases” Front. Neurosci. 2018 . Dr Luciano Bernardi et al (2015) “Slow breathing and hypoxic challenge, cardio respiration consequences and their central neural substrates” Plos One May 2015 . Streeter et al 2012 “Effects of yoga on the ANS, GABBA, and allostasis in epilepsy, depression and PTSD” Medical Hypothesis Jan 2012 . Aelst et al May 2020 “Long term ashtanga yoga practices decrease medical temporal and brainstem glucose metabolism relative to years of experience”, EJNMMI Research May 2020 . Lim et al 2015 “Regular yoga practice improves antioxidant status, immune function, and stress hormone releases…” Journal of alternative and complimentary medicine. . Streeter et al 2010 “Effects of yoga versus walking on mood, anxiety and brain GABA levels”, Journal of alternative and complimentary medicine. Nov 2010 . Kjaer et al 2002, “Increased dopamine tone during meditation – induced change of consciousness” Cognitive Brain Research 2002 . Gotink et al 2018 Meditation and Yoga are associated with smaller right amygdala volume: The Rotterdam study, APA PsycNET . Kalyani et al, “Neurohemodynamic correlates of “OM” chanting”, NCBI 2011 . Afonso et al “Greater cortical thickness in elderly female yoga practitioners a cross-sectional study” 2017 PubMed







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