Extensive cytotoxic lesions involving both the rhinal cortices and area TE impair recognition but spare spatial alternation in the rat

Rats with cytotoxic lesions of the perirhinal, post-rhinal, and TE cortices (Rh + TE, n = 7) were compared with surgical control animals (n = 7) on a series of spontaneous object recognition tests. The Rh + TE group was associated with a failure to select the novel object. This recognition deficit contrasted with the apparently normal ability of the same animals to learn and perform a spatial working memory test (T-maze alternation). The animals were also tested on the acquisition of an automated visual discrimination task in which the stimuli were presented on a visual display unit (VDU) equipped with a touch screen, The animals with Rh + TE lesions showed only a borderline deficit on this task. These findings are consistent with other evidence implicating the rhinal region in recognition memory. More importantly, they also provide a dissociation between spatial working memory and object recognition and, hence, show that extensive rhinal lesions are not sufficient to disconnect the hippocampus functionally. (C) 1997 Elsevier Science Inc.