Neurophysiologic basis and specificity of fMRI

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DESCRIPTION (provided by applicant): Noninvasive assessment of brain function using blood-oxygen-level-dependent (BOLD) fMRI has gained enthusiastic and widespread acceptance among cognitive neuroscience investigators. This indirect approach to interrogating neural activity is based on work originating with Sherrington: the understanding that hemodynamic changes are coupled to neuronal activity. However, the extent to which the BOLD effect truly reflects and accurately localizes underlying neuronal activity remains unclear. The overall aim of this project is to optimize localization and characterization of brain activity, using noninvasive functional magnetic imaging (fMRI) and to assess the relationship of the optimized fMRI measurement to neuronal electrical activity. Ultimately these optimized measures will be implemented in humans for planning prior to surgical resection. The specific aims are: 1. Investigate differences in the discrete somatotopic representation of individual digits of the hand in primary somatosensory cortex (Area 3b) using BOLD and CBF-based fMRI to determine the relative specificity of the BOLD and CBF measurements. 2. Investigate differential activation of cortical layers in S1 using this somatosensory paradigm and CBF versus BOLD acquisition methods. 3. Identify Neural Correlates of BOLD-fMRI using multi-electrode survey of brain regions within monkey S1 exhibiting BOLD and CBF activation in response.