NEUROTOXIC LESIONS OF THE PERIRHINAL CORTEX DO NOT MIMIC THE BEHAVIORAL-EFFECTS OF FORNIX TRANSECTION IN THE RAT

The effects of perirhinal (Prh) and fornix (Fx) lesions were compared on a series of spatial and nonspatial memory tests. These tests includ ed delayed nonmatching-to-position in an operant chamber, a spatial (l ever) discrimination and its subsequent reversals, delayed spatial alt ernation in a T-maze, and an object recognition memory test using both normal objects and 're configured' objects. As expected, the rats wit h fornix lesions were impaired on all of the spatial tests. Their perf ormance on the recognition test was, however, left intact. The perirhi nal lesions produced a quite different pattern of results. Animals wit h these lesions were unimpaired on all three spatial tasks, but displa yed evidence of an impairment on the object recognition test. This imp airment was restricted to the longer delay (15 min) and was only found with the normal objects. These findings suggest that the actions of t he perirhinal cortex and the hippocampus can be dissociated from one a nother.