Processing mechanisms in visual cortex

Rockefeller University, New York NY

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Abstract

DESCRIPTION (provided by applicant): Adult primary visual cortex performs a high level analysis of the visual scene, mediating contour integration and surface segmentation. We propose to test the hypothesis that the primary visual cortex encodes information about complex visual shapes and that the properties of cortical neurons are experience dependent even in adulthood. Cortical receptive fields have higher order properties that represent the geometry of the visual world and these properties are mutable throughout life, allowing us to assimilate information during perceptual learning. The functional properties that show these changes are known as contextual influences, where the response of a cell to a local feature is dependent upon its global context. We will characterize the contextual influences seen in V1 and relate them to the geometry of visual scenes. We will determine the way in which visual experience further shapes the functional properties of visual cortical neurons. An important part of our study is to explore the role of top-down influences in shaping the response properties of V1 neurons. We will determine how higher order cognitive influences of attention; expectation and perceptual task interact with information about stimulus characteristics within V1. Our studies will include approaches that enable us to investigate cortical mechanisms at multiple scales, from single neurons, via single unit recordings in alert, behaving animals, to optical imaging of neuronal ensemble activity within a cortical area, to fMRI in human subjects. Psychophysical studies will help us define the nature of shape information encoded during perceptual learning, and will guide the physiological studies. Plasticity of V1 reflects an ongoing process, beginning with our early experience of the regularities of the world and continuing throughout our lives, to assimilate the specific patterns to which we become familiar. The properties of any cortical area, even in adults, are dynamic, being experience dependent and subject to top-down influences.