Meditation changes the brain's activity frequency from the Beta to Theta.

THETA WAVES Theta waves (4-7 cps) occur in sleep and are dominant in our highest state of meditation. We normally only experience theta waves as we drift off to sleep, during some dreaming, and as we return from the depths of delta sleep. The pictures we perceive as we drift off and awaken are in theta wave. During theta wave meditations, we are in a waking dream where vivid imagery flashes before our inner vision. In this state, we are extremely receptive to information sent from the higher dimensions.
The Theta state is where intuition comes, instantaneous healings occur and accelerated learning occurs. Einstein trained himself to spend many hours in that state. It is where you feel one with All.

LSD , shrooms ect. put you in Theta state too. FYI

P.s. Cannabis alters the brain to produce Alpha waves.

http://holywine.blogspot.com/2006_01...e_archive.html