The rhythmical electrical potential waves recorded from the human brain have been classified by their discoverer, Berger2 into two types: alpha-waves, and beta-waves. This classification is made on the basis of the duration and amplitude of the waves. Waves having a duration of about .10 sec. and an amplitude of about 20 microvolts fall into the category of alpha-waves. Waves having a duration of about .04 sec. and an amplitude of about 10 microvolts make up the beta-waves. In general, the beta-wave is formed on the sides of the larger and more predominant alpha-wave
