Neurobiology of Meditation: Effects of regular meditation on the Brain
17 August 2015
Meditation induces a highly integrative state that may be conducive to therapeutic processing.
A brain is an intricate structure that controls all the voluntary and involuntary movements and enables conscious communication with various autonomic and other structures within the body. Different parts of the brain control different functions. For example, Frontal lobe is responsible for short-term memory formation, motivation, emotional behavior, problem solving and judgement. Parietal lobe is involved in language processing and sensory information integration such as taste, temperature and touch. Temporal lobe controls processing of auditory information from the ears, comprehend and understand speech and emotional associations. Occipital lobe is responsible for vision. The normal functioning of these structures is extremely important for the maintenance of constant internal environment or homeostasis. Disruption of this internal environment may lead to cellular malfunction and hence many serious neurological ailments. For centuries, meditation and other yogic practices have claimed to treat many physiological and psychological ailments without any known side-effects, unlike most of the modern marketable drugs that exhibit neurotoxicity. In recent years, meditation has received greater attention for it’s role in strengthening neuronal communication, long-term psychological and physical well-being, musculoskeletal strengthening, increasing parasympathetic function and cognition, selective activation of specific brain structures and neurochemical systems, improving metabolic profile, reducing oxidative stress, gene related disorders and lowering blood pressure and curing heart related problems.
How Brain Works
- Cingulate Cortex (CC) is known to play a significant role during meditation. Neurons of Cingulate Cortex have a specific property of relaying ‘control signals’ in the multiple areas of the brain during meditation. They help to maintain focus, avoid distraction from external events (our thoughts) and keeps cognitive control during meditation. The strengthening of Cingulate Cortex, especially anterior part, during mindfulness practice have been shown to be effective in disorders like Bipolar and ADHD (attention-deficit/hyperactivity disorder). However, some researchers claim that Cingulate Cortex activates only in the novice meditators but not in the experienced meditators while others have mentioned it’s deactivating role in Zen meditators thereby blurring the role of CC in meditation.
- Many conspicuous changes were also observed in the hippocampus during meditation in functional neuroimaging studies using PET and fMRI. Hippocampus is a part of the limbic system which helps in the formation and storing of different kinds of memories. Stress in the cells of Dentate Gyrus, region of Hippocampus, has been shown to cause anxiety, depression and other clinical disorders. Hippocampal atrophy is very prominent in these conditions that leads to cognitive decline. Some studies have shown that meditation helps in slowing the rate of hippocampal atrophy, increases consolidation of existing memories and the formation of the new memories while others have shown improvement in the cognitive ability in some epileptic patients after 8 weeks of meditating activity. This was due to increased neural connections/communications, increased hippocampal white matter efficiency and other neuro-plastic changes associated with meditation training.
- The mindfulness meditation also strengthens hypothalamic circuit causing positive physiological changes in the body through the release of useful hormones and neurotransmitters that stimulates adjoining neural circuits thereby activating parasympathetic system. This activation can thus regulate various bodily activities such as decrease in respiration rate, decrease in heart rate and overall decrease in stress hormone levels.
Changes in the Brain Structure
- Morphometric neuroimaging analysis in meditation practitioners have revealed neuroanatomical changes in the brain. Results from such studies have shown that meditators, compared to non-meditators, have large brain volume, greater concentration of grey and white matter, greater number of neurons/glia fibers in a given region, greater white matter fiber density, greater axonal integrity and myelination and higher index of gyrification (greater cortical surface area per unit volume).
- To prove the influential role of meditation in sensory experience such as pain, researchers from Wake forest University have shown that after 4 days of mindfulness meditation, the meditators experienced less pain than non-meditators. This is because meditators were able to block pain sensory activation centers located in somatosensory cortex, activate evaluative regions such as pre-frontal cortex and deactivate thalamic regions involved in thalamo-cortical interactions. Thalamus relays sensory and motor information to and from the cerebral cortex. During meditation, there is a constant increase in the reticular nuclear activity of the thalamus which secretes neurotransmitter GABA (γ-amino butyric acid) thereby decreasing sensory input to the parietal lobe causing a feedback loop to focus attention.
- According to Richard W. Maxwell, author of Physiological foundation of Yoga Chakra expression, chakras are the gap junction proteins and kundalini Shakti is the electrical conductance activated at the base of the spine that increases Central Nervous System (CNS) function when activated. Meditation increases the prevalence of chakras (gap junctions) and kundalini Shakti increasing neuron-neuron and neuron-glia communication allowing full electrical conductance in the spine and brain cells. This is also the mechanism of action for acupuncture, which is known to focus on these gap junction proteins or chakras for treatment.
Effects of Regular Meditation on the Brain
- Meditation induces a highly integrative state that may be conducive to therapeutic processing.
- Regular practice promotes structural changes in the brain regions important for emotion processing.
- Increases attention and decreases distractibility.
- Less rumination/self-focus and increased bodily awareness.
- Decreases reactivity to socially threatening faces.
- Increases pro-social behavior and improves clinical disorders.
- Increases blood flow and prolactin upregulation, reduces concentration of plasma cortisol, lactate, growth hormone and triiodothyronine (these are stressor biomarkers)- this decrease is mediated by changes in hypothalamo-anterior pituitary function during meditation.
- Keeps serum cholesterol concentration low.
- Develops skillful optimization and control over autonomic nervous system in response to stressors thereby helping the meditator stay relaxed with less efforts, and facilitate rapid recovery of bodily systems under stress.
- Increases blood flow in the prefrontal cortex of novice meditators and upregulation of serotonin during meditation.
The different types of meditation techniques may have a distinctive effect in the different areas of the brain. Some are strict and austere (for example Zen meditation) while others take a more relaxed approach. These diverse forms of meditation practices activate various centers in the brain regulating numerous neural activities thereby providing a positive feedback loop. Future studies are required to understand how these diverse forms of meditation effects different areas of the brain and whether the morphological alterations in the brain is the result of single meditative technique or is the amalgamation of several techniques.
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Written by Shaunik Sharma, Neuroscience Researcher at Iowa State University, U.S.A.