Restricted lesions to ventral prefrontal subareas block reversal learning but not visual discrimination learning in rats

Previous studies have shown that extensive damage to the medial prefrontal cortex (mPFC) of rats causes reversal learning deficits. The mPFC of rats, however, consists of several subareas that are different from each other in both cytoarchitecture and neural connectivity, suggesting a functional dis sociation among the mPFC subareas. In the present study, selective lesions of the mPFC of rats were made with a specially designed microknife whose in tracranial placement could be controlled stereotaxically. Restricted lesion s were made to each of the 3 parts of the mPFC: the anterior cingulate area (AC) (including the medial precentral area, PrCm), the prelimbic area (PL) , and the infralimbic area (IL). One week after surgery, rats were trained in an aversively motivated Visual discrimination task in a novel rotating T -maze. After reaching the acquisition criterion, rats were trained in a rev ersal task in the same maze. No difference was found in acquisition between control and mPFC lesioned rats. However, lesions of either the PL or the I L produced a marked deficit in the reversal task. This behavioral deficit w as not found in rats with lesions of the AC. The results indicate that the mPFC of rats is not essential for discrimination learning, but that each of the 2 ventral subareas of the mPFC, FL, and IL, plays a critical role in r eversal learning. (C) 1998 Elsevier Science Inc.