Spatial learning on the Morris Water Maze test after a short-term paradoxical sleep deprivation in the rat

Twelve rats were deprived of paradoxical sleep (PS) fur eight hours using t he small platform method. PS-deprived and control rats then learned either the standard allocentric version (using external cues) of the Morris Water Maze (MWM) or a delayed alternation version (changing the platform location between trials: MWMDA). Overall, rats learning the MWMDA made more quadran t entries than rats learning the allocentric version. Compared to other rat s, PS-deprived rats crossed more quadrants only in the MWMDA. These results show that MWMDA is a more complex task to learn and is more vulnerable to PS deprivation than allocentric spatial orientation. Since delayed alternat ion is dependent upon frontal structures, we propose that tasks involving t he frontal cortex are more sensitive to short-term PS deprivation than task s related to hippocampal structures. (C) 2000 Academic Press.