The long-term objective of the proposed research is to determine the relative roles of juvenile and adult behavior patterns in the development of cortical representational areas in primary (S1) and secondary (S2) somatosensory cortex. The animal model for this research is the star nosed mole, which has perhaps the most sensitive and highly developed sense of touch among mammals. Each of the eleven tactile nasal appendages or """"""""rays"""""""" that ring the mole's nostrils is represented in both the S1 and S2 somatosensory areas by a stripe of tissue visible in sections processed for histochemical markers. The pattern of cortical magnification across the nasal rays does not match anatomical parameters of the ray, such as size or innervation density, but instead prescisely matches the pattern of behavioral use of the rays during search for prey and feeding. This suggests behaviors play a role in shaping the cortical representation. The goals of the proposed research are 1) determine the developmental mechanisms by which the patterns of cortical specialization in S1 and S2 are matched to the behavior patterns, 2) identify the functional circuitry of the cortical representations, including intrinsic, intercortical and callosal connections between areas, and 3) determine the effects of changes in the behavior patterns or surgical alteration of the nose on subsequent cortical development. Initial studies will relate the time course of prenatal and postnatal nose development to the emergence of nose related patterns in the cortex, and concurrently determine when the nose is first used for tactile explorations. Previous research on a range of species suggests that cortical specializations, such as barrels in rodent cortex, develop and become fixed during early critical periods. However, the nose of the star nosed mole does not fully develop until weeks after birth, after expected critical periods. Do relatively late emerging behavior patterns influence subsequenct cortical organization, or is the pattern of magnification independently matched to the adult behaviors during early development? By establishing the time course of pattern formation in the nose and cortex and then subsequently disrupting the normal development by altering the nose, the relative role of use dependent influences and possible critical periods can be determined. Few animal models have sensory systems in which discrete brain characters are correlated with specific patterns of behavior. The influence of early behaviors on brain development and learning remains an important public health issue. Results will be interpreted in a comparative framework to identify principles that may be generalized to other species and other sensory systems.
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