Perirhinal cortex lesions produce retrograde but not anterograde amnesia for allocentric spatial information: within-subjects examination.

Using a reference spatial memory task sensitive to hippocampal lesions, the same groups of rats were subjected to four successive experimental phases to investigate which aspects of spatial cognition are perirhinal cortex dependent. Results showed that the perirhinal cortex is not necessary for acquisition or for long-term spatial memory retention. However, the perirhinal cortex was differentially involved in spatial memory expression depending on whether the original learning took place in an intact brain or in a perirhinal damaged brain. Specifically, only when the lesions were made after learning was a profound impairment in the expression of preoperatively acquired spatial information observed. These results suggest that, in a normal brain, the perirhinal cortex plays an essential role in the expression of spatial information during the post-learning period.