Evidence for a paradoxical sleep window for place learning in the Morris water maze.

Sprague-Dawley rats were given 4 consecutive days of training in the hidden platform version of the Morris water maze. They were then given paradoxical sleep deprivation (PSD) for 12 h either immediately after each training session or after a 12-h delay. The former group showed impaired learning on the second day of training compared to the 12-h-delayed PSD group or a nondeprived control group. In a second experiment, three groups of rats were trained as before and then given PSD for a 4-h interval beginning either immediately after, 4 h after, or 8 h after the end of each training session. Only rats exposed to PSD during the period beginning 4 h after the end of training each day showed an acquisition deficit. In a third experiment, rats were trained in a visible platform version of the water maze and exposed to PSD for a 12-h period either beginning immediately after the last training trial each day or after a 12-h rest delay. Neither of these groups was impaired on the task compared to a non-PSD control group. These results suggest that there is a PS window for place, but not cue, learning in the Morris water maze.