Paradoxical sleep and memory (II): sleep circadian rhythmicity following enriched and impoverished environmental...

Sleep cycle circadian rhythmicity following either enriched or impoverished environmental rearing is examined in this study. Mice are reared in either super-enriched (SEE), regular-enriched (REE), social control (SC), or impoverished (IE) environments for 30 days. SEE and REE groups show a general increase in total slow-wave sleep (SWS) in the 24 hr cycle but the number of SWS episodes, mean duration of SWS episodes, and percent SWS of total sleep time (TST) is not significantly different from the SC groups for the Day cycle (0700--1900). Enriched rearing produces a selective and significant increase in the number of PS (Paradoxical sleep or REM sleep) episodes, mean duration of PS episodes, total amount of PS time, and percent PS/TST throughout the 24 hr cycle. IE reared mice also show a general increase in SWS primarily during the Day cycle but with rearing experience plays an important role in the developing of the basic rhythmicity during the sleep (PS-SWS)-wakefulness cycle, and (2) provide further support for our hypothesis that PS occurring over a prolonged time period is a requisite neurobiological mechanism for the processing, maintenance, and storage of long-term memory.