FUNCTIONAL ORGANIZATION OF THE SOMATOSENSORY SYSTEM

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The proposed research addresses three long term goals. Studies will include New World owl monkeys, which offer clear technical advantages, and Old World macaques, which are more closely related to humans. 1) A major goal is to develop a better understanding of the organization of the somatosensory and motor systems in primates. We want to know how these systems are divided into nuclei, areas, and modules, and how these subdivisions are interconnected to form processing networks. Planned studies will combine electrophysiological microelectrode mapping procedures, histochemical architectonic methods, and multiple tracers in connection-tracing protocols in the same monkeys. A major effort will be to determine and compare connections of proposed subdivisions of somatosensory cortex of the lateral sulcus, posterior parietal cortex, and premotor cortex. 2) Related studies of adult plasticity in primates will determine the effects on sensory representations of partial deprivations as a result of cortical lesions, nerve damage, or spinal cord lesions. We will attempt to determine the contribution of neuronal growth and neurotransmitter regulation in plasticity by using molecular markers of neuron restructuring, tracers of axon-arbors and growth, and markers of molecules associated with neuronal activity and plasticity; 3) Other studies will examine the effects of fetal and early postnatal deprivation and damage on subsequent development of the somatosensory system in monkeys in order to understand the potential for developmental plasticity and reorganization in complex sensory systems. The three types of studies will provide a) a detailed and comprehensive model of sensorimotor processing that applies to humans: b) an understanding of the mechanisms of adult plasticity in the somatosensory system that can guide programs of therapy in humans, and c) an understanding of the extent and limits of developmental plasticity that can guide medical treatment and guidance of humans with prenatal defective and early postnatal injury.