Visual cortex in primates includes dozens of visual areas arranged in a richly interconnected hierarchical network. This proposal involves physiological recordings from macaque monkeys to study form vision, anatomical experiments in the macaque to determine connectivity patterns, and systematic comparisons between the organization of human and macaque visual cortex. Experiments on form vision will involve recordings from neurons in areas V1, V2, and V4 of alert monkeys. One project will measure neural responses to an ensemble of contour stimuli (bars, curves, angles, and intersections) and grating stimuli (e.g., concentric, radial, and hyperbolic gratings). Comparisons across visual areas will test whether receptive field properties become progressively more complex in going from area V1 to V2 to V4. Another project will study the representation of three-dimensional shapes in area V4. Neural responses to simulated bumps, indentations, and flat surfaces will be analyzed to determine whether cells in V4 explicitly represent the sign of surface curvature. Neuroanatomical studies will examine the connections of parieto-occipital areas V3A, PIP, MIP, DP, and newly discovered LOP. Patterns of connectivity will be analyzed in relation to identifiable architectonic borders and will be visualized on cortical flat maps. Shape-based deformations applied to cortical maps will be used to compensate for individual variability in cortical convolutions. Interspecies comparisons will be made by deforming flat maps of macaque cortex to match the shape of the human cortical man. These deformations will be guided by gyral and sulcal landmarks identifiable in both species and by visual areas strongly suspected to be homologous. Comparisons between regions of functional specialization on the human map and area boundaries on the deformed map of the macaque will provide an objective basis for evaluating additional candidate homologies. Collectively, these experiments should reveal important principles of organization and function in primate visual cortex that are relevant to the understanding and treatment of functional deficits resulting from strokes and other neurological disorders.
Showing the most recent 10 out of 40 publications
