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 influence of play behavior on the brain was investigated through plasticity and metaplasticity methodology. Regions in both cortical and sub-cortical areas were investigated. Animals in both studies either experienced play with juvenile partners or did not experience play by being paired with an adult. Play experience alone was shown to affect the plasticity in the prefrontal cortex, although it did not show structural changes to sub-cortical regions. If animals were given nicotine after play experiences, the affects of play in the prefrontal cortex were abolished. In addition, playful behaviors appear to prime some sub-cortical regions of the brain for expression of later plasticity. Thus, play appears to alter the structure of multiple brain areas, but do so in different ways. / ix, 67 leaves ; 29 cm