POSTTRIAL SLEEP IN OLD RATS TRAINED FOR A 2-WAY ACTIVE-AVOIDANCE TASK

Nine male Wistar rats aged 27 months were trained for a two-way active avoidance task and tested for retention the following day. At varianc e with young adult rats, most of which succeed in mastering the task, all old rats displayed a large majority of freezing responses througho ut the training and the retention sessions, thereby confirming the con dition of learning impairment of aged rats. Comparison of baseline and post-trial sleep indicated the presence of a transient, but marked, i ncrement in the average duration and total amount of post-trial slow-w ave sleep followed by waking, and of a decrease in total amount of qui et waking. On the other hand, variables of paradoxical sleep and of sl ow-wave sleep followed by paradoxical sleep or by transition sleep did not show significant variations. Because these sleep variables are kn own to undergo significant variations in learning in young adult rats, the present data confirm that the latter effects are related to memor y-processing events rather than to nonspecific effects of training. An additional outcome of training consisted in a marked post-trial decre ment in the number of spike-wave discharges, which are known to occur in old rats during periods of quiet waking. (C) 1997 Elsevier Science Inc.