Neurophysiology of Meditation

By M.P.BHATTATHIRY 


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."