Sprague-Dawley rats were trained in a 2-way shuttle shock avoidance task and continuously monitored polygraphically with EEG, EOG and EMG using an automated sleep state analyzer. PS increases were observed following the daily training sessions (50 trials/day for two consecutive days) and for at least 7 days following the end of these training sessions. As well, there was an increase in the number of REMs. The number of REMs increased 4 hours prior to the onset of the increase in PS each day and remained high along with the elevated PS. A parallel PS deprivation study suggested that a vulnerable PS window occurs 9-12 hours after training in these rats. The results strengthen the idea that the PS related to learning is of a special nature with unique phasic characteristics.