Changes in sleep episodes duration and brief awakenings after sleep deprivation. A. Duration of episodes of drowsiness, SWS, NREM, REM and total (NREM + REM) sleep during baseline (BSL) and recovery (Rec) sleep, plotted in 1-hour intervals beginning at sleep onset. Values (in minutes or seconds) are expressed as mean (± SEM, n = 6). For drowsiness, SWS and NREM an episode was defined as a period of continuous drowsiness or SWS lasting > 16 seconds and occurring without any waking interruption lasting > 16 seconds. A REM episode was defined as any occurrence of one or more consecutive epochs of REM sleep preceded and followed by any other behavioral state (no interruptions allowed). B. Number of brief awakenings during baseline (BSL) and recovery (Rec) sleep plotted in 1-hour intervals beginning at sleep onset. Values are expressed as mean (± SEM, n = 6) number of brief awakenings per hour of sleep. A brief awakening was defined as a brief waking period (<16 seconds) preceded and followed by at least one 4-sec epoch of SWS or drowsiness. Triangles depict significant difference between recovery sleep relative to the same circadian time during baseline sleep. Note that the number of brief awakenings at the beginning of recovery sleep shows a trend to be lower (p < 0.07, paired t-test) than at the beginning of baseline sleep.