The REM Cycle in Altered Sleep/Wake Schedules

Abstract

ABSTRACTThe length and rhythmicity of the REM cycle was studied using data from three laboratories. In the three studies, 25 subjects obtained their sleep in naps under three different sleep/wake schedules: 60/160 min (N =8), 30/60 min (N =10), and 60/120 min (N =7), over a period of 40 hrs to 10 days. Previous results from these subjects (Moses, Lubin, Johnson, & Naitoh, 1977) indicated that the REM cycle is sleep‐dependent, rather than an expression of an ongoing Basic Rest‐Activity Cycle (BRAC). As a further test of the sleep‐dependent hypothesis, autocorrelation and r2 analysis was applied to the compressed sleep (i.e., all wake time between and within sleep periods subtracted) of the baseline, nap, and recovery conditions. Compared to baseline, there were no significant differences in nap REM cycle length in the 60/160 and 60/120 groups; the 30/60 group had significantly shorter cycles. It appeared that this REM cycle shortening was due to the significantly shorter REM episodes in this group. The nap r2 values were significantly lower than baseline in the 30/60 and 60/120 groups, indicating increased variability in the timing of REM episodes during naps. All the nap r2 values, however, were significantly larger than those obtained from a random distribution of sleep stages.To further examine the effects of the degree of sleep fragmentation on REM cycle rhythmicity, two additional groups of subjects whose sleep was fragmented by either REM or SWS deprivation were compared to the nap groups. REM deprivation was the most disruptive of REM cycle rhythmicity; the r2 values for REM deprivation were significantly less than those for napping or SWS deprivation.These data offer further support that the REM cycle is a sleep‐dependent rhythm and is not an expression of an ongoing BRAC.