Experience Dependent Plasticity of The Developing Cortex

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DESCRIPTION (provided by applicant): Our long-range research interest is to understand the functional organization of sensory cortex, its plasticity and their relationship to behavior. The target of our research is the somatosensory cortex of the rat, especially the subdivision that processes information from the facial whiskers known as Postero Medial Barrel Sub Field (PMBSF). Using chronic functional imaging and single unit recordings we have demonstrated that in the adult rat the size of a whisker functional representation (WFR) in the PMBSF is large and consequently overlaps extensively with the WFRs of other whiskers. Surprisingly, we found that this description of the WFRs is valid only in rats that live in a standard cage (SC). If rats are allowed out of the cage and thus are able to express innate behaviors that are not typically expressed in the SC, such as whisker-dependent navigation, the WFRs contract and weaken and thus minimize their overlap, but if the rat stays in its SC the WFRSs expand and strengthen. The contraction of WFRs was found both in adult deprived rats that experienced a removal of all whiskers except one (spared whisker) and were allowed a few minutes of navigation outside the cage, or in normal, non deprived adult rats that were spending a month in a naturalistic habitat (NH) - a new type of housing environment that imitates the rat's natural environment by enabling rats to engage in innate behaviors such as exploration, tunnel digging, subterranean navigation, foraging and social interactions. Because the cortex is especially sensitive to environmental influences during development, we propose to investigate the hypothesis that the ability to express innate behaviors since birth by being raised in the NH, may have anatomical, functional and behavioral consequences that would refine the cortex to be better optimized for whisker discrimination abilities compared to SC-raised rats. To test the hypothesis, we propose to compare the anatomy, neurophysiology and whisker-dependent discrimination behavior of NH-raised rats vs. SC-raised rats. Successful completion of the proposal would highlight the importance of expressing innate behaviors during development for the optimal maturation of cortical structure, function that is associated with this behavior. Such findings could have implications for the optimal treatment of developmental abnormalities of behavior in humans, and regeneration after injury or disease. Further, such results would help in reassessment of the appropriateness of SC-raised rats to serve as models for the normal human brain.