The prefrontal cortex (PFC) has long been thought to be the seat of social behaviours in mammals. Lesions of the orbitofrontal cortex (OFC), a subregion of the PFC, are known to cause social deficits in humans. Interestingly, social deficits are also seen in rats with OFC lesions. Rats that are deprived of peer play during development exhibit behaviour similar to OFC-ablated animals. Another subregion of the PFC, the medial prefrontal cortex (mPFC) is interconnected with the OFC. The mPFC and OFC have been shown to be reciprocally responsive to a variety of inuences, in terms of dendritic morphology. It was hypothesized that social experiences are necessary for the proper development of the OFC, and that, because of the interconnectivity, the mPFC would also be sensitive to social experience. The social condition in which juvenile rats were raised was manipulated, and the OFC and mPFC were shown to be differentially responsive to specific aspects of social experience. It was already known that OFC lesions produce specific social deficits, but the contribution of the mPFC to the production of social behaviour was unknown. To investigate the contribution of the mPFC to the performance of social behaviour, animals were given mPFC lesions, and their social play behaviour was quantified. mPFC-ablated animals had altered play patterns that were distinct from those seen in the OFC-ablated animals. It was concluded that the OFC and mPFC are differentially responsive to social stimuli during development, and that the OFC and mPFC make discrete contributions to the production of social behaviour. The results were interpreted in an evolutionary context. / x, 93 leaves : ill. ; 29 cm.

The current studies investigate the behavioral and anatomical changes after lesions at different ages of the cingulate cortex. Rats received lesions of the posterior cingulate cortex (PCing) or the anterior and posterior cingulate cortex (Total) at: postnatal day 4 (P4); day 10 (P10), or in adulthood (P120). Rats were trained in the Morris water maze, the Whishaw reaching task, conditioned taste aversion (CTA), and their activity was monitored over 48 hours. The general finding was a significant behavioral recovery on P10 animals regardless the size of the lesion. This recovery was associated with an increase in dendritic arborization in P10 animals with the PCing removed and a partial regeneration of the midline tissue in the Total P10 animals. These results suggest that damage to the cingulate cortex at P10 is associated with substantial behavioral and anatomical plasticity and that removal of the frontal midline tissue stimulates a regenerative process in more posterior cortex that does not occur otherwise. / ix, 111 leaves : ill. ; 29 cm.