Amount and time course of behavioral states during sleep deprivation and subsequent recovery. A. Amount and time course of vigilance states during 6 hours of sleep deprivation (SD) and the first 8 hours of recovery sleep (Rec) and values during baseline (BSL). Values plotted as mean duration (± SEM, n = 6) of each state in 2-hour intervals expressed as percentage of total recording time. Triangle indicates a significant difference between the duration of vigilance state in BSL versus Rec. B. Latency to the first epoch scored as SWS or drowsiness during BSL and after SD. The latency to drowsiness was defined as the interval between lights-off during baseline or the end of 6 hours of SD and the first epoch of drowsiness. Values are plotted as mean (± SEM, n = 6) number of minutes from dark onset (BSL) or from the end of SD. Note the trend toward a decrease in SWS latency (p = 0.087, paired t-test) and the significant (p = 0.016, paired t-test) decrease in latency to drowsiness after SD.