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Electroencephalogram (EEG) Changes during Meditation

The electroencephalogram (EEG) is the depiction of the electrical activity occurring at the surface of the brain. This activity appears on the screen as waveforms of varying frequency and amplitude measured in micro voltages.  Waveforms are classified according to frequency, amplitude, shape and at sites on the scalp. Classification of EEG waveform frequency includes alpha, beta, theta, and delta.

Normal EEG waveforms are defined by their frequency, amplitude and location; waves of 8 Hz and higher frequencies are normal in an awake adult.

Alpha waves generally are seen in all age groups but are most common in adults. They occur rhythmically on both sides of the head but are often slightly higher in amplitude on the nondominant side, especially in right-handed individuals. A normal alpha variant is noted when a harmonic of alpha frequency occurs in the posterior head regions. They tend to be present posteriorly more than anteriorly and are especially prominent with closed eyes and with relaxation.

Alpha activity disappears normally with attention (mental arithmetic, stress, opening eyes). In most it is as a normal waveform, except in alpha coma (hypoxic-ischemic encephalopathy) or destructive processes in the pons.

Beta waves are observed in all age groups;  are of small in amplitude, symmetric and more evident anteriorly. Barbiturates and benzodiazepines augment beta waves.

Theta waves are seen in sleep at any age. Theta and delta waves are slow waves.

Delta waves are slow waves with frequency of 3 Hz or less. They are normally seen in deep sleep, Delta waves are abnormal in the awake adult. They have the largest amplitude of all waves. Waves with a frequency of 7 Hz or less are classified as abnormal in awake adults.

In meditation, EEG is a physiological measure of neuro-feedback. It measures electrical activity of  voltage fluctuations from ionic current flows from within the brain

EEG frequency bands include: Alpha (α) for awake consciousness; and Beta (β) activity for sleep; Theta (θ) is for dream subconsciousness; and Delta (δ) is for deep sleep   unconsciousness or higher consciousness.

There is a drop in alpha activity and increased theta in meditative practices. The noticed effect of meditation with increase in delta and theta activity in most regions of the     brain, indicate the brain becomes deeply focused following Shambhavi Maha Mudra; it reflects a higher level of mental consciousness. Reduction in beta activity signifies lesser anxiety. Above all, all subjects showed a specific effect of meditative practices.


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