Even though the pre-frontal and parietal lobes are inactivated during both REM sleep and meditation, meditation is different from sleeping or dreaming. It generates brainwaves in the Theta state, which is in a slightly higher frequency range than the Delta (sleeping) state. The state is on the border line between consciousness and sleeping. The anterior cingulate gyrus becomes underactive in meditation. The cingulate gyrus concentrates on internal stimuli, and contains the feeling of self. Curiously, this is the same area that becomes underactive in hypnosis (when the identity of self dissolved) and Schizophrenia (when own thoughts are confused with outside voices). Thus it doesn't seem to be accidental that in meditation, the sense of boundaries is lost and it induces a feeling of "at one" (union) with the universe.

Click for larger image

The physiological effects related to meditation are measurable and reliably repeatable. It includes the lowering of a subject's metabolic rate, decreasing blood pressure, pulse rate and muscle tension. Meditation can counteract the stress-induced fight-or-flight response and achieved a calmer and more relaxing state, which tends to strengthen the immune systems. One report showed that the subject could reduce oxygen intake to 1/3 of the normal resting state by allowing the parasympathetic nervous system to take over - an extraordinary feat, given that respiration is controlled by the autonomic nervous system, over which we ordinarily have no conscious control. Other studies suggest that meditation can help to alleviate bronchial asthma, hypertension, and insomnia. It is being recommended by more and more physicians as a way to prevent, slow or at least control the pain of chronic diseases like heart conditions, AIDS, cancer and infertility. It is now believed that the body produces more nitric oxide when deeply relaxed, and that this molecule acts as an antidote to cortisol (hormone associated with inflammation) and other potentially toxic stress hormones.

Meditation, nearly as old as humanity, has always been part of Eastern religions. Starting from 2nd century A.D. meditation became important part of Christian practice until early 1500s when Martin Luther disapproved mysticism. Jewish and Muslim meditations have established around 1000 A.D. Meditation was used as a medium to communicate with the higher being(s). Actually, the brain is playing trick on the practitioners by producing various illusions. Now the West is rediscovering the benefits of meditation. In its most modern forms, it has dropped the mantra bit that has the subject memorize a secret phrase or syllable; instead it only requires focusing on a sound or breathing. In fact, just closing the eyes in a quiet place (to block sensory inputs) and relaxing the mind (to minimize internal processing) would attain the same result without much ado.