Objective: Brain activity preceding rapid eye movements (REM) during human REM sleep has remained poorly understood. Slow negative brain potential (pre-REM negativity) appears before REMs. Current sources of this potential were investigated to identify brain activity immediately preceding REMs.
Methods: In this study, 22 young healthy volunteers (20-25 years old) participated. Polysomnograms were recorded during normal nocturnal sleep. Brain potentials between 200ms before and 50ms after the onset of REMs and pseudo-triggers (3000ms before the onset of REMs) were averaged. Standardized low-resolution brain electromagnetic tomography (sLORETA) was used to estimate current sources of pre-REM negativity.
Results: Pre-REM negativity appeared with the maximal amplitude at right prefrontal sites immediately before REMs. However, this negativity did not appear before pseudo-triggers. Current sources of the pre-REM negativity were estimated in the ventromedial prefrontal cortex, uncus, insula, anterior cingulated cortex, basal forebrain, parahippocampal gyrus, premotor cortex and frontal eye field.
Conclusions: The pre-REM negativity reflects brain activity coupled with the occurrence of REMs. Results of this study suggest that emotion, memory, and motor-related brain activity might occur before REMs.
Significance: Pre-REM negativity is expected to be a psychophysiological index for elucidating functions of REM sleep.