The contribution of the perirhinal cortex to anterograde and retrograde memory for objects and places in rats

The present thesis examined the effects of bilateral perirhinal cortex (PRh) lesions on rats' anterograde and retrograde memory for places and objects. Allocentric place memory was assessed using a standard water maze task and a test of novelty preference, which relies on the ability of rats to detect that an object has moved to a new location. Object-recognition memory was also assessed using a test of novelty preference, which, in this case, relies on the ability of rats to detect that an object is novel. The effects of aspiration and electrolytic PRh lesions were compared on most tests. Findings from the object-recognition tests suggest that the PRh is necessary to support anterograde, but not retrograde, object recognition. By contrast, findings from the place memory tests suggest that the functions of the PRh are important for retrograde, but not anterograde, place memory. Furthermore, on most tests, electrolytic PRh lesions were more effective than aspiration PRh lesions in revealing performance deficits. Evidence that electrolytic, but not aspiration, PRh lesions led to widespread neuronal activation in cortex is also presented and suggests that this lesion method may have adverse consequences for normal brain function that go beyond the functional effects of damage to the PRh. Current views of medial-temporal-lobe function are discussed and it is concluded that few models adequately capture the complex contribution of the PRh to learning and memory that is indicated by the present data