7 September 2013
Dr Fred Travis' Conscious Thoughts chart shows the difference in brain waves during three different commonly used types of meditation—concentration, contemplation, and Transcendental Meditation. During concentration-types of meditation there are fast (20-50 Hz) gamma waves on the surface of the mind. During contemplation, slow theta waves (4-8 Hz) are seen. During Transcendental Meditation, highly coherent alpha waves in the 8-10 Hz range occur.