Effects of electrolytic lesions of the medial prefrontal cortex or its subfields on 4-arm baited, 8-arm radial maze, two-way active avoidance and conditioned fear tasks in the rat

The present study tested the effects of electrolytic lesions in two mPFC subregions, the dorsal anterior cingulate area (dACA) and prelimhic cortex, as well as the effects of a larger medial prefrontal cortex (mPFC) lesion which included both subregions, on 4-arm baited, 4-arm unbaited, 8-arm radial maze task and its reversal (Experiments 1 and 4), two-way active avoidance (Experiments 2 and 5) and conditioned emotional response (Experiments 3 and 6). Rats with large or small lesions of the mPFC learned the location of the 4 baited arms in the training and reversal stages of the radial maze task similarly to sham rats; indicating that these lesions did not affect animals' capacity to process and remember spatial information. dACA and mPFC lesions produced a transient deficit in the acquisition of the radial maze task, suggestive of an involvement of these regions in mnemonic processes. However, in view of the normal performance of these groups by the end of training and during reversal, this deficit is better interpreted as stemming from a difficulty to learn the memory-based strategy used to solve the task. Only mPFC lesion led to better avoidance performance at the beginning of training and tended to increase response during the presentation of a stimulus previously paired with shock, compared to sham rats. Both effects can be taken as an indication of reduced emotionality following mPFC lesion. The results are discussed in relation to known behavioral functions of the mPFC and the suggested functional specialization within this region.