Practice question

Scalp electroencephalographic rhythms are classified by dominant frequency: beta 13-30 Hz low amplitude for alertness, alpha 8-13 Hz moderate for relaxed wakefulness, theta 4-8 Hz for drowsiness, delta 0.5-4 Hz high amplitude slow waves for deep sleep. Frequency below 4 Hz signifies delta activity generated by prolonged hyperpolarization in thalamocortical circuits during restorative slow-wave sleep, also seen pathologically in encephalopathy. Therefore oscillations under 4 Hz belong to delta band, distinct from faster theta, alpha or beta rhythms reflecting higher arousal states.