9221854 Gilbert A nerve cell in the sensory cortex of the brain is activated by stimuli that lie within a certain spatial area, called the "receptive field" of the cell. Evidence from work on the sense of touch on the body surface (somatosensory system) has shown that these receptive fields in adults are surprisingly dynamic in location and size, rather than having fixed characteristics for a given cell. Active sensory experience is important for defining the receptive field; a loss of sensation from the peripheral area reduces the size of receptive fields of cortical cells for that area, and persistent stimulation leads to an increase. Recent efforts have been to establish how connections in the neuronal pathway are modified when these plastic changes occur. This study is a novel application that parallels somatosensory approach, but uses the visual cortex to exploit known details of the visual pathway and intracortical connections. Here, changes in receptive fields in the visual system are studied when part of the visual field is made invisible (a scotoma). Anatomy and pharmacology will be used to examine connections to and within the cortex, to differentiate the contributions of such connections in the cortical dynamics. These studies will help elucidate the mechanisms of integrating information across space, and of cortical memory; the emphasis is on visual processing, but the results will have impact beyond visual neuroscience to sensory neuroscience in general, and to cognitive neuroscience. ***
