The ultradian rhythm of alternating cerebral hemispheric activity.

This review covers cognitive and electroencephalographic studies of the ultradian rhythm of alternating cerebral hemispheric activity found in humans and animals. This endogenous alternation of right and left dominance ranges in periodicity from about 25 to 300 min with peaks between 90-200 min during waking and around 100 min during sleep. Studies of lateralized EEG activity during sleep are reported as correlates of the REM-NREM sleep cycle. Studies of lateralized ultradian rhythms of EEG during wakefulness reveal a correlation between hemispheric dominance and the nasal cycle. The rhythm of cerebral dominance has also been identified with tests of lateralized cognitive performance using left and right hemisphere dependent tasks. Awakening from REM or NREM sleep is associated with different effects on left or right hemispheric dominance. This rhythm plays an important role in cognitive performance, memory processes, visual perception, levels of arousal and performance, mood, and individual and social behavior.