Polygraphic analysis of the sleep-wake states and the REM sleep periodicity in domesticated pigs (Sus scrofa).

Electrocorticography and concurrent electromyography were used during a total of nineteen 24 hr periods in three juvenile pigs in order to establish the quantitative duration of the sleep-wake states and the REM sleep cycles. Wakefulness (W), drowsiness (DR), slow-wave sleep (SWS) and paradoxical sleep (REM) occupied respectively 46.5%, 15.9%, 26.7% and 10.9% of the 24 hr period. Mean duration of episodes was 4.1 min for DR, 6.2 min for SWS and 3.3 min for REM. Sleep cycles (SC) duration was 13.1 min. Near 80% of the SC were nocturnal. Analysis of variance showed a significant difference between diurnal and nocturnal duration of SC (day less than night), as well as between day-time and night-time duration of DR (day greater than night), SWS (day less than night) and REM (day less than night). A strong negative correlation was also found between the mean duration of SC and the number of SC per day.