Anterograde and retrograde memory for object discriminations and places inrats with perirhinal cortex lesions

Three experiments examined the effects of perirhinal cortex lesions on rats ' retrograde and anterograde memory for object-discriminations and water-ma ze place-memory problems. In Experiment 1, rats learned two object-discrimi nations - the first was learned 2 weeks before surgery and the second 24 h before surgery. Rats with perirhinal cortex lesions displayed mildly impair ed retention of both object discriminations, with no evidence of a temporal gradient. They also learned a new discrimination at a normal rate, but wer e impaired on a retention test 24 fi later. In Experiment 2, rats learned t wo water-maze place problems, conducted in different rooms - the first was learned 4 weeks before surgery and the second during the week immediately b efore surgery. Rats with perirhinal cortex lesions displayed deficits on th e early retention trials of both place problems, but they quickly relearned both problems. In Experiment 3, rats with perirhinal cortex lesions learne d a new place problem at a normal rate and performed as well as control rat s on a retention test 3 weeks later. Although some of the results are consi stent with the conclusion that perirhinal damage disrupts storage or retrie val of place information acquired before surgery, additional considerations suggest instead a role for perirhinal cortex in the representation of nons patial information that makes a useful but nonessential contribution to wat er-maze performance. (C) 2000 Elsevier Science B.V. All rights reserved.