brain wave - (neurophysiology) rapid fluctuations of voltage between parts of the cerebral cortex that are detectable with an electroencephalographneurophysiology - the branch of neuroscience that studies the physiology of the nervous system alpha rhythm, alpha wave - the normal brainwave in the electroencephalogram of a person who is awake but relaxed; occurs with a frequency of 8-12 hertz beta rhythm, beta wave - the normal brainwave in the encephalogram of a person who is awake and alert; occurs with a frequency between 12 and 30 hertz delta rhythm, delta wave - the normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz) theta rhythm, theta wave - the normal brainwave in the encephalogram of a person who is awake but relaxed and drowsy; occurs with low frequency and low amplitude |