The effects of separate and combined perirhinal and prefrontal cortex lesions on spatial memory tasks in the rat

In order to compare the relative involvement of prefrontal and temporal reg ions in spatial memory, rats with bilateral electrolytic lesions of perirhi nal cortex, prefrontal cortex, or both regions were tested in the water and radial-arm maze. Perirhinal and prefrontal lesions produced similar perfor mance deficits during water-maze acquisition and in the radial-maze procedu re. Perirhinal cortex lesions also disrupted performance in a water-maze pr obe trial conducted 5 min after four training trials, whereas prefrontal le sions did not. Surprisingly, the combined-lesion group was not impaired dur ing water-maze acquisition and performed significantly better than the peri rhinal-lesioned group in the probe trial. This finding is interpreted in te rms of the executive function of prefrontal cortex and its possible role in switching behavior between different search strategies, only some of which may be dependent on perirhinal cortex.