a pattern of high-frequency brain waves (beta waves) observed in normal persons upon sensory stimulation, especially with light, or when they are engaging in purposeful mental activity.
Origin of beta rhythm
1935–40; earlier beta waves, translation of German Betawellen; see alpha rhythm
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The second most common waveform occurring in electroencephalograms of the adult brain, characteristically having a frequency from 13 to 30 hertz. It is associated with an alert waking state but can also occur as a sign of anxiety or apprehension.beta wave
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.