Electrolytic lesions of the medial prefrontal cortex in rats disrupt performance on an analog of the Wisconsin Card Sorting Test, but do not disrupt latent inhibition: implications for animal models of schizophrenia

Abstract

The effects of electrolytic lesions of the medial prefrontal cortex (mPFC) or its subregions were investigated on two cognitive tests that may have relevance to the behavioral impairments of patients with schizophrenia. One task consisted of a delayed non-match-to-sample and reversal of the non-match-to-sample rule, in a Skinner box. The reversal component simulated the essential feature of rule shifting of the Wisconsin Card Sorting Test (WCST), which is a commonly used test for assessing 'frontal-like' deficits in schizophrenia. The second was latent inhibition, in which repeated pre-exposure to a stimulus without consequence retards subsequent associations with that stimulus. Latent inhibition is impaired in acute schizophrenic patients, and its disruption in the rat has been suggested to constitute an animal model of schizophrenia. Expts. 1 and 2 tested the effects of lesions of the dorsal anterior cingulate cortex (dACA) and mPFC, respectively, on the WCST analog. Expt. 3 tested the effects of lesions of the dACA or infralimbic cortex, and Expt. 4 tested the effects of mPFC lesion, on latent inhibition. Lesions of mPFC subregions had no effect. mPFC lesion produced transient deficits in the performance of the DNMS task and impaired the reversal from the non-match-to-sample to the match-to-sample rule, but left the latent inhibition effect intact. Possible relevance of this behavioral profile of mPFC lesion to the 'frontal syndrome' is discussed.