MODULATION OF NEURONAL RESPONSES IN SOMATOSENSORY CORTEX

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DESCRIPTION: (Adapted from the Investigator's Abstract) In tactile object recognition we attend to and remember selected features sequentially touched while integrating the information leading to recognition. To understand this complex process we propose using whole-brain functional magnetic resonance imaging (fMRI) in humans and single neuron recording studies in monkeys, who are trained on tactile memory tasks, to investigate the functional anatomy of the sensory and cognitive processes underlying tactile attention and memory. We propose five interrelated fMRI experiments that will determine: (a) the extent of primary somatosensory cortex dedicated to selective activation of the receptors in each fingertip (Exps 1-2), (b) the network of cortical areas engaged by the cognitive processes of tactile attention (Exps 3-4), and (c) the network associated with tactile memory (Exp 5). The first two experiments test the hypothesis that attention involves dynamic modulation of recorded somatotopic maps. The second two experiments focus on the nature of the functional anatomy engaged by attention to the stimulus attributes of vibration frequency, surface roughness and tactile stimulus duration. The fifth experiment examines the functional anatomy engaged during a working memory task for vibration frequency. Overlapping foci identified in Exps 3-5 will suggest a possible network for tactile object recognition because these regions will be common to memory and attention processes. Two neurophysiology studies (Exps 6a, 6b) will record the neural correlates of sensory and working memory in frontal and somatosensory cortex, areas likely to be identified in the fMRI studies. Thus, these observations of single neurons will show differential activity during delay intervals for remembered tactile stimuli and, therefore, highlight the likely temporal dynamics underlying the functional anatomy in the human studies.