SEQUENTIAL HYPOTHESIS OF SLEEP FUNCTION .5. LENGTHENING OF POSTTRIAL SS EPISODES IN REMINISCENT RATS

Rats failing to learn a two-way active avoidance task during the train ing session were tested for performance the following day. One group o f rats maintained its low level of avoidances (non improving or NI rat s), while the remaining rats dramatically improved their avoidance sco re (improving or I rats). EEG recording during the posttrial period de monstrated significant variations in the sleep structure of I rats, in comparison with NI rats. The main change consisted in an increase in the average duration of the episodes of slow wave sleep followed by wa kefulness or by paradoxical sleep. These variations occurred in the th ird hour of the posttrial period, while an increment in the amount of PS was observed in the sixth hour. In I rats, but not in NI rats, comp arable variations emerged from the comparison of baseline sleep (deter mined the day before training) with posttrial sleep. The data are in a greement with the main postulate of the sequential hypothesis of sleep function which attributes a primary role to slow wave sleep in the pr ocessing of newly acquired memories.