Enhancement of REM sleep during extraocular light exposure in humans

This study examined the effects on sleep of light administered to an extrao cular site. A 3-h photic stimulus was applied to the popliteal region durin g sleep in 14 human subjects. Each subject also underwent a control stimulu s condition during a separate laboratory session. The proportion of rapid e ye movement (REM) sleep during the 3-h light administration session increas ed by an average of 31% relative to the control condition. The frequency bu t not the duration of REM episodes was altered during light exposure, there by shortening the REM/non-REM (NREM) cycle length. No other sleep stages we re significantly affected during light administration nor was sleep archite cture altered after the light-exposure interval. These results confirm that extraocular light is transduced into a signal that is received and process ed by the human central nervous system. In addition, they expand to a novel sensory modality previous findings that REM sleep can be enhanced by senso ry stimulation.