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Neurophysiology of Meditation

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By simple definition, meditation is engagement in contemplation, especially of a spiritual or devotional nature. To elaborate further, meditation is an attempt to concentrate mind on a single form or an idea or an aspect of divinity at the exclusion of all other forms, thoughts, and ideas. The mind is focused inwards, and this effort of concentration acts as a stimulus to gain access to knowledge of 'object of meditation'. The aspirant makes an attempt to minimize perceptions through senses - inputs through special senses like touch, sight, hearing, etc. - by detaching mind from sense organs in the brain. This helps in controlling restlessness of mind, in favour of inner contemplation. The mind, as if, is made still. Meditation may be, therefore, taken as a 'passive' activity! But is it really so?

Tremendous changes observed in the human brain and nervous system during mediation run contrary to this belief of 'passivity' attached to meditation. Unprecedented progress and research in neurobiology, investigative neurology, and study of neurotransmitters in the last two decades has given a great fillip to the study of neuro-physiology of Meditation and Yoga. Altered State of Consciousness can be brought about by hypnosis, drugs (e. g. LSD), sleep, etc., but here we are trying to study a state specific science of altered consciousness brought about by meditation alone.

We shall attempt to review the progress in neurobiology in the recent years. An attempt is made to throw light on this new and fascinating subject. The terms used are technical, but, as far as possible, an attempt is made to simplify the description.

This attempt to explain the neurophysiology of meditation is purely hypothetical.

Meditation and Changes in Neurophysiology:

One of the ways to control physiological reactions to psychological stimuli is meditation, Yoga, Zen Buddhism etc. The scientists take Transcendental Meditation (TM) as the uniform technique, and base their observations on the study of the subjects engaged in this form of meditation. In summing up the results the scientists have come to conclusion that the effect of meditation is a "wakeful, hypo-metabolic state".

They have found that:

1) Yogis could slow both heart rate and rate of respiration,

2) Yogis could slow the rate of metabolism as confirmed by decreased oxygen consumption and carbon-di-oxide output.

3) Electro-Encephalo-Gram (EEG - recording of brain activity) in Yogis showed changes of calmness in the form of "alpha rhythm" during both eyes closed and eyes open recordings.

4) Their skin resistance to electric stimulation was increased (indicating increased tolerance to external stimuli).

Our usual 'defence-alarm' reaction to emotional and physical stress is in the form of "fright, flight, and fight" mediated through over-secretion of certain neuro-transmitters and neuro-modulators, namely adrenaline and dopamine by way of stimulation of sympathetic nervous system. Under the influence of these chemicals and hormones, we reflexively become panicky or aggressive, our blood pressure rises. Thus stress and anxiety is the end result if we allow our natural age-old sympathetic reactions to act and to come to surface. We try to run away, become fearful, or fight the situation. But today these 'defence-alarm' reactions have no place in our lives. Rather, they should be replaced by more calm and serene reactions of equanimity and fearlessness. The need is to just 'face the brute, and it will go away'. Such desirable reactions of non-aggression and peaceful attitude are generated by Yoga and meditation.

EEG Studies on Yogis and The Zen Meditations:

Yogis practising Raja-Yoga claim that during the state of samadhi they are oblivious to the internal and external stimuli, and they enjoy a calm ecstasy during that state. A study was undertaken to record the electrical activity of their brain during this state by means of a regular and useful test known as electroencephalography EEG. Physiological and experimental studies have demonstrated that the basis of conscious state of brain, among other things, is due to activation of "reticular system" in the brain-stem in response to internal and external stimuli. These stimuli bring about various changes during sleeping and wakeful states of the organism and these can be studied by EEG.

The study was carried out on four subjects during the state of concentration and meditation. Effects of external stimuli, like a loud gong, strong light, thermal simulation, and vibrations were studied. The results were compiled and analyzed. It was observed that two Yogis could keep their hands immersed in extremely cold water for about 50 minutes (raised pain threshold). During state of meditation, all of them showed persistent "alpha activity" in their EEG with increased amplitude wave pattern, both during 'eyes closed' and 'eyes open' recording. It was observed that these alpha activities could not be blocked by various sensory stimuli during meditation.
It was also observed that those, who had well-marked "alpha activity" in their resting EEG showed greater aptitude and zeal for maintaining the practice of Yoga. Similar observations and results were obtained when EEGs were recorded in persons adept in Zen Meditative technique. Can we say that only those persons who exhibit such recording of "alpha wave rhythm" in their EEG are fit for Yoga? and be designated as right candidates for meditation and Yoga practices? (Such experiments are indeed very few and the number of yogis examined is also very small. Therefore, scientifically and statistically these observations have only a tentative importance. Further research is definitely called for, albeit it will have its own limitations.)

Discussion and Conclusion

Neurotransmitters and Neuro-modulators: These are chemical substances released at the Neuronal Synapses (nerve junctions). They act by altering electrical membrane potential by opening up channels that permit diffusion of Sodium, Potassium, and Calcium ions in and out of the nerve cell. They not only transmit the message from one cell to another, but also selectively facilitate some information while inhibiting the other. Moreover, the action of Calcium ions permits transfer of electrical events into molecular changes that can alter functions of the nerve cells permanently, i.e. change cellular function to subserve a memory or learning response.

Neuro-modulators affect the neuro-transmitters by influencing neuronal plasticity, growth, or differentiation. Different types of receptors, as present in different regions of brain, can account for the complex and multiple effects of medication, meditation, concentration, and contemplation. This may be effected through actions of specific type of neuro-transmitter and neuro-receptor.

For example, a sub-type of glutamate receptor appears to mediate the function of brain plasticity, a process considered important in learning and memory.

Acetylcholine helps in memory, motivation, perception and cognition. It is also involved in attention and arousal functions of ascending reticular system. Decrease in the levels of this neuro-modulator leads to loss of memory, senile dementia - Alzheimer's disease.

Excess of serotonin, another important neuro-modulator, leads to hallucinations, as seen in LSD consumption, which causes increase in serotonin level. This discovery called attention to the correlation between behavior and variation in brain serotonin content. Selective depletion of serotonin, in animals, causes prolonged wakefulness. It also plays important role in circadian rhythm and sleep cycle.

Other neurotransmitters and modulators like nor-epinephrine cause changes in mood - excess leading to elation, and deficiency causing nervous depression. It also controls food intake, regulates temperature, and hormonal secretions.

Excess of dopamine level is responsible for schizophrenia and psychosis.

Nerve growth factor is a hormone like peptide that is responsible for the growth and maintenance of various brain structures.

The plausible hypothesis to explain the altered state of consciousness brought about by intense and prolonged mediation may be constructed as follows:

The evolutionary process adds higher centres to the primitive nervous system. These higher centres have inhibitory influence, in other words they suppress the functions of lower centres. Thus, the brain stem is controlled by the higher limbic system, and the limbic system in turn is controlled by still higher neo-cortex. The neuro-modulators with their influence on various neuro-transmitters effectively bring about this inhibitory modifications and inter-relations among various brain centres (hierarchy).

For instance, involuntary movements like tremors and chorea are suppressed by basal ganglia through the action of dopamine and acetylcholine synergy. Any imbalance in these neuro-modulators causes involuntary movements like chorea, tremors (Parkinson's Disease etc.). Similarly, loss of cortical control over the motor neurons of spinal cord leads to exaggerated muscle and tendon jerks due loss of inhibitory control of the higher motor cortex.

Neo-cortex keeps all the involuntary movements, hyper-reflexivity, rage, aggression, and similar animal tendencies under check so that it can effectively pursue its own highly developed activities of logic, memory, reason, language, calculations, judgement, and concepts, etc. Conscious, willful, imaginative functions are therefore, normal state of awareness of the human beings.

When meditation acts as a constant repetitive stimulus, certain qualitative and quantitative permanent changes develop in the nervous system. The neuro-transmitters and neuro-modulators may stimulate growth of dormant or latent neurons to develop a centre (or centres) which on the evolutionary ladder is/are still higher than the present day cerebral cortex. The brain may develop new connections and plasticity resulting in the capacity to think, to rationalize, and react in a different way to the sensory input than what is expected by present day physiologists. For want of name, we may label such higher center as 'God Module'. This higher centre will exert inhibitory control over the present day neo-cortex, and thereby, over the mind as a whole (consciousness, reasoning, conceptual thinking, willing, feeling, and doing, etc.)! The consciousness and all mental activities will hence be suppressed. The person will reach a state beyond mind itself - transcendental awareness!

"The spiritual ascent is from the least evolved state of consciousness to near perfect state, after which the mind itself will cease to be, and there will remain only non-dual experience."



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Last updated on 31-03-2007