Prof. J.P.N. Mishra
Studies of brain physiology during meditation have most frequently employed the electroencephalograph (EEG) for the measurement of brain wave electrical activity It has been reported that most meditative practices the EEG patterns exhibit a slowing and synchronization of brain waves, with alpha waves predominating. More advanced practitioners of meditation demonstrate an even greater slowing of their brain waves, with the possible emergence of theta wave patterns. These patterns are consistent with deep relaxation. Alpha rhythm is the classical EEG correlate for a state of relaxed wakefulness, also described as relaxed vigilance (Niedermeyer & Da Silva 1993). Indeed, emotional tension attenuates or blocks the alpha rhythm. Theta activity is associated with emotional processes and indicates relative maturity of the mechanisms linking the cortex, the thalamus, and the hypothalamus; theta rhythm also occurs during a state of maximal awareness (Niedermeyer & Da Silva 1993). Apparently, an alpha wave pattern is most conducive to creativity and to the assimilation of new concepts, while the theta response seems to be a stage at which the mind is capable of deep insights and intuition. It is significant to note that practiced meditators can continue to exhibit alpha and theta waves after the meditation period has ended (Wallace et al 1971). Our findings are also in the conformity of earlier explained mechanism, and it can be concluded that practice of yoga and preksha meditation combine results in reduction in electrical activities in neuronal units of brain. The meditation practice decreases muscle reflex time (Warshal 1980, Robertson 1983). Significant reductions in reflex time provides possible neurological evidence for the improved motor performance skills reported in other studies on meditation, such as higher performance on perceptual-motor speed tests, static motor performance tests, and physical task tests of balance. Meditation may somehow accelerate neural conduction or augment the release of neurotransmitters, thereby decreasing synaptic time, resulting in a change in muscle firing threshold and pattern. These findings appear consistent with the development of a heightened sensitivity of the human central nervous system and suggest a neural mechanism underlying the motor performance improvements of those who meditate.
Timmons et al 1972 compared different types of breathing during meditation and discovered that diaphragmatic or deep breathing was associated more with an EEG alpha response than thoracic breathing. Meditative traditions place a great deal of importance on breathing; indeed, breath becomes the object of awareness in most methods. Specifically, Taoist and Zen traditions of meditation have historically placed great value in abdominal breathing, consistent with the popular belief that the vital center is located in the abdomen (Huard 1971). The study by Timmons and collaborators validates the merit of deep abdominal breathing. The cortex of the brain is popularly believed to consist of two halves, the left and right hemispheres. Although simplistic, activities such as speech, logical thinking, analysis, sense of time are thought to function in the left hemisphere, while the ability to recognize faces and comprehend maps is thought to function in the right hemisphere. On the physiological level, it has been demonstrated that the two hemispheres of the cortex are specialized for different modes of information-processing; the left hemisphere operates primarily in a verbal, intellectual, sequential mode, while the right hemisphere operates primarily in a spatial oriented mode. The right hemisphere concerns space more than time and intuition more than logic or language. The right lobe also houses the purported center of motor skills connected with spatial awareness. Most people, under scientific measurement, demonstrate a marked preponderance towards left hemisphere usage.
Several authors hypothesize that systems of meditation alter consciousness by inhibiting' cognitive functions associated with the dominant or left cortical hemisphere. Ornstein (1975), for example, states that meditation "turns off" the verbal, linear, analytic style of information processing associated with the normal waking state. By inhibiting the left cortical hemisphere, the sense of time and logic no longer dominate consciousness during meditation. In association with this repression of the left hemisphere occurs a hypothesized shift to the right hemispheric manner of experience, described as holistic, receptive, and beyond language or logic. Since it is nonlinear, the right cortical hemisphere devalues the concept of cause and effect. Davidson (1976) argues that meditation leads to the development of right hemisphere associated abilities. This assertion has been verified by several research projects; meditators show faster reaction times on simple visual reaction time tasks, thus demonstrating that meditation facilitates right hemisphere specific abilities (Appelle & Oswald 1974, Holt et al 1978, Pagano & Frumkin 1977). Furthermore, EEG alpha and theta wave coherence is most marked in the right cortical hemisphere during the practice of meditation (Gaylord et al 1989).
Other analyses suggest the existence of synchronization patterns both between corresponding areas of the two cortical hemispheres and within individual hemispheres (Glueck & Stroebel 1978). Some tests indicate that the EEG activation patterns in meditators display a greater flexibility in shifting between hemispheres in response to the demands of specific tasks (Bennet & Trinder 1977); this represents an integration of the left and right hemispheres of the brain, synchronizing the logical with the intuitive.
