Behavioural changes after ablation of subdivisions of the rat prefrontal cortex

Sham operated controls and four groups of rats subjected to ablation of various parts of their frontal cortex were compared in food and water intake and four behavioural tasks. The ablations were aimed at removing (1) the ventral prefrontal cortex, (2) the dorsal part of the medial prefrontal cortex, (3) the total medial prefrontal cortex, and (4) the anterior dorsolateral (non-prefrontal) cortex. Only two groups had a significantly impaired food and water intake: the ventral prefrontal and the non-prefrontal anterolateral. The latter group was not adipsic. Two variants of spontaneous alternation were administered in a T-maze: a non-cued version in which both arms were grey and a cued version in which one arm was white and the other black. While all ablated groups behaved like the control group on the non-cued test, the number of perseverative responses of the total anteromedial group was significantly increased in the cued version of the test. Significant group differences could be seen neither in a test of conditioned taste aversion nor in extinction of operantly conditioned bar presses. Finally, in a vertical hole-board exploration test the only significant group difference was a prolongation of the mean visit duration of the ventrally lesioned animals in comparison with all other groups. The results of the present study further indicate functional differentiation within the prefrontal cortex of the rat.