Scoring of sleep and wakefulness by behavioral analysis from video recordings in rhesus monkeys: comparison with...

Extensive work on sleep-wake cycles in non-human primates has been carried out using conventional EEG scoring. In this study, simultaneous somnopolygrams and video recordings at 1 frame/s were performed on 6 adult rhesus monkeys (Macaca mulatta) during a 24 h period. Wakefulness, NREM sleep and REM sleep were scored by analysis of animal behavior from video data, using characteristic criteria for each state of vigilance. Results were then compared with those of conventional EEG scoring. Values of the total amount for each state obtained by the two scoring methods during the light and the dark periods were significantly closely related (P < 0.001) with a high correlation coefficient for wakefulness (r1 = 0.99956), for NREM sleep (r1 = 0.99641) and for REM sleep (r1 = 0.98708). Moreover, the epoch by epoch analysis between both methods showed a high concordance with percent agreement values of 95.68% for wakefulness, 93.52% for NREM sleep and 94.02% for REM sleep. The number of REM sleep episodes was similarly defined. The patterns of successive sleep-wake cycles determined from both scorings were superimposable, as were the frequent state changes for the same time segments. The video method's main limitation was that the 4 stages of NREM sleep could not be differentiated. Reliability and advantages of sleep-wake scoring by behavioral analysis are discussed. These results suggest that the video methodology is relevant as a non-invasive technique complementary to conventional EEG analysis for sleep studies in rhesus monkeys.