The objective of the proposed research is to determine principles of sensory coding of spatial information by examining how the somatosensory system integrates inputs from multiple points on the skin. Neurophysiological and psychological studies have shown that the nervous system often performs complex spatial and intensive transformations of these multiple-point stimuli which amplify or diminish their intensity, and increase or decrease the spatial resolution of the pattern. The development of chronic single-unit recording techniques, together with operant behavioral methods for measuring sensory discriminitive abilities in monkeys, will permit me to study the neurophysiological and psychophysical parameters of the transformation of spatial information in the same animal. The neurophysiological representation of light tactile stimuli presented at multiple points on the skin will be studied in primary somatosensory (S-I) cortex, dorsal column nuclei, and ventro-basal thalamus of awake, behaving rhesus monkeys. This investigation may yield answers to the following questions: How is stimulus intensity encoded in the somatosensory cortex? Does the nervous system integrate weak activity transmitted in three parallel channels in the same manner that it does strong activity in a single channel? How does the nervous system resolve two points on the skin? What are the neuronal mechanisms underlying feature-extracting properties of complex somatosensory cortical neurons? How do neural networks in the relay nuclei to the cortex integrate and transform spatial and intensive properties of multiple-point stimuli? What is the effect of attention on spatial integration and response magnitude? How are the primate dorsal column nuclei organized? Answers to these questions will be useful not only for understanding somatosensory function, but may be of general applicability to integration of multiple channels of information in other sensory systems.
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