Mapping Higher Level Visual Areas in Humans

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Mapping Higher Level Visual Areas in Humans Abstract With National Science Foundation support, Dr. Sereno and colleagues will conduct a three-year investigation aimed at generating comprehensive, high resolution maps of the borders and internal organization of intermediate and higher level human visual areas in occipital, parietal, temporal, frontal cortex using functional magnetic resonance imaging. The cerebral cortex of each hemisphere in humans contains more than one hundred distinct areas. Many of these areas are concerned with vision. The organization of lower level visual areas is well understood; but the location and number of higher level visual areas is much less clear and the goal of Dr. Sereno's project to produce insight into these areas. These maps he discovers will be made available to other researchers interested in determining how these visual areas differ in their functions. By analogy with the human genome project, this study will be carried out with the participation of a small group of 'professional subjects'. The first set of experiments extends traditional methods for mapping visual areas (phase-encoded, surface-based analysis using moving, windowed checkerboards, and a simple fixation task) by turning to more attentionally captivating windowed stimuli (television action programs, videos of moving faces and objects, more complex monitoring tasks). The second set of experiments extends the mapping stimulus set to include linguistic visual stimuli (reading short stories at systematically varying retinotopic locations). These two kinds of stimuli are better suited to activating higher visual areas, but at the same time, are capable of revealing their borders and internal structure. To successfully carry out high resolution mapping studies, it is crucial to correct the subtle spatial distortions present in functional scans before the data is overlaid onto a cortical surface reconstruction. Therefore, the third main part of the proposal focuses on improving distortion correction methods (including pre- and post-hoc corrections for static field inhomogeneities and gradient nonlinearities). The programs implementing these methods will be freely distributed to other imaging centers, in a manner similar to the way our cortical surface reconstruction programs (FreeSurfer) have been freely distributed and maintained. The findings from this research are expected to provide important new understanding into anatomical and functional organization of the human brain. These findings will have significant impact on clinical and basic neuroscience. In addition, several junior researchers will receive outstanding research experience.