NEURAL MECHANISMS OF TACTILE SPATIO-TEMPORAL INTEGRATION

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This proposal describes a series of experiments in humans and monkeys that investigate neural integration of tactile spatio- temporally ordered stimuli. A fundamental goal of the proposed research is to understand this neural processing at the level of activation of cortical areas, and at the level of specific patterns neuronal activity within those areas. To achieve this goal, functional magnetic resonance imaging (fMRI) will be used to map the human somatosensory cortex, and multi-electrode recording will be used to record neural response patterns in the monkey somatosensory cortex. This project has three specific aims. First, to define human cortical areas activated by tactile motion stimuli. Use of an event-related design in a 3 Tesla fMRI scanner will permit mapping as a function of individual behavioral responses. Second, to examine rapid neural integration of tactile motion stimuli in the monkey/postcentral gyrus (PoCG) and a higher cortical area. Multi-electrode recording techniques will record patterns of action potential firing from over millimeters of the cortex during the presentation of tactile apparent motion stimuli. This will permit the analysis of distributed coding schemes and the organization of individual tactile receptive fields. Third, to examine cortical activation during spatio-temporally ordered stimuli that do not evoke the percept of motion. Using fMRI and multi-electrode techniques, we will examine cortical activation evoked by a continuum of stimuli, ranging from apparent motion stimuli to perceptually stable stimuli. By mapping these activation patterns, we will gain insight into both the emergence of neural coding supporting motion perception, and into the neural mechanisms, that support a variety of spatio-temporal perceptual interactions. These studies will expand our understanding of rapid spatio-temporal tactile integration, an important topic in the design of successful tactile prosthetics. Further, they will provide direct comparisons between the neural processing in humans and monkeys, a comparison that will expand our knowledge of the connections between human function and the most important clinical and scientific model system, the non-human primate.