WORKING-MEMORY, RESPONSE SELECTION, AND EFFORTFUL PROCESSING IN RATS WITH MEDIAL PREFRONTAL LESIONS

This study examined the effects of lesions of the prelimbic area of th e rat prefrontal cortex on acquisition and retention of nonmatching (N MTS) and matching-to-sample (MTS) tasks. Both tasks involved a referen ce and a working memory component, but only working memory was impaire d by the lesions. A comparison of the 2 tasks revealed quantitatively similar deficits in postoperatively trained rats. In preoperatively tr ained rats, however, the deficits were more important in the MTS task than in the NMTS task. In addition, an effect of interference between successive trials was observed in the NMTS task but not in the MTS tas k. Perseverative tendencies were observed in the MTS task only. These results suggest that prefrontal lesions induce working memory deficits as a result of poor temporal encoding and increased susceptibility to interference and impair effortful processing, such as that engaged in response selection mechanisms.