FUNCTIONAL MAPPING OF THE VISUAL CORTEX

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The long range goal of this Project is to use functional magnetic resonance imaging (FMRI) to identify the brain mechanisms responsible for normal vision and for brain-related visual pathologies. Since FMRI is relatively new, this project also seeks to develop and extend the application of this technology to brain systems and problems not previously studied in this way. Fortunately, the neural basis of vision in monkeys is sufficiently well understood to provide a solid background for interpreting the results of FMRI experiments and for comparing and interrelating visual mechanisms in human and simian species. To this end, the Specific Aims of the Project are: 1) to determine the parametric relationships between the FMRI signal and visual stimulation, 2) to use FMRI to study the functional specialization of cerebral cortex by creating maps of retinotopic and functionally selective activation within and among different cortical visual areas in both humans and monkeys, 3) to identify cortical "association" areas involved in the integration of visual information with other modalities such as audition, 4) to explore the potential application of FMRI in the assessment of specific visual deficits resulting from retinal or cortical pathology. To accomplish these aims, both a clinical MR scanner (G.E. Signa) and a high magnetic field strength research MR scanner (Bruker 3 tesla) will be used to image cortical activation during computer controlled visual stimulation delivered via a custom designed optical system. Using novel computer algorithms, the 3-dimensional patterns of activation will be displayed on unfolded, two-dimensional maps of the cortical surface. These results will provide brain maps of the functional specialization of a significant portion of the cerebral cortex. The results will also provide new insight into the relationships between physical brain mechanisms and both normal and impaired perceptual experience. Ultimately, these techniques will be used to study brain activation in a small number of subjects with well characterized visual deficits thereby leading to a subsequent proposal that will specifically address clinical issues. Finally, the testing and refinement of the FMRI technology will contribute significantly to the development of a powerful new tool for medical science.