Neural generators of brain potentials before rapid eye movements during human REM sleep: A study using sLORETA

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 200 ms before and 50 ms after the onset of REMs and pseudo-triggers (3000 ms 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.