Neurophysiology of Meditation

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Neurophysiology of Meditation

 

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 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. "

 

M.P.BHATTATHIRY ( RETD. CHIEF TECHNICAL EXAMINER TO THE GOVT.

OF KERALA, INDIA