Electrocortical activity and related phenomena associated with meditation practice: a literature review.

The state effects of meditation appear to include decreased electrocortical arousal. There is also evidence that meditators more readily demonstrate alpha and theta activity than nonmeditators, even when not meditating. It is not clear whether prospective meditators as a group already possessed this characteristic, or whether the state effects of meditation practice eventually generalize to become traits. However, certain individuals, namely the psychologically "healthy" and those with a capacity for relaxed absorbed attention, appear to be more favourably disposed to meditation. Meditators appear to show both stronger orienting and recovery responses to stressors while meditating than controls. Meditation practice may begin with left hemisphere type activity, which gives way to functioning more characteristic of the right hemisphere. However, it appears that during advanced meditation ("no thought") both left and right hemisphere activity are largely inhibited or suspended. Depending on the individual, inexperienced meditators may report sleep, hypnogogic reverie, trance or abreaction during practice. The evidence to date does not support the notion of unique state effects associated with the practice of meditation.