Large and small medial frontal cortex lesions and spatial performance of the rat.

Rats with sham operations, or small or large medial frontal cortex lesions were compared for the acquisition of a position habit and for learning a series of 4 position habit reversals. No differences were found during acquisition of the position habit. On the reversals, the rats with the larger lesions were markedly impaired, while less severe deficits or control-like performance characterized the rats with the smaller ablations. Analyses of the error scores showed that the rats with the larger lesions made more perseverative errors than the other groups and performed more sporadically even after breaking a previous position habit. These results confirm the hypothesis that a strong relationship exists between medial frontal cortex lesion features (depth and length) and performance. The differences found in acquisition vs. reversal learning, and the nature of the errors observed, also suggest that this part of the brain functions as more than simply a spatial analyzer.