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
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
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
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
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
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
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
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
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
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 -
"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."