Aging and Visual Spatial Integration

The current study evaluated the ability of 20 younger and 20 older adults to discriminate shapes depicted by Glass patterns. On any given trial, observers identified a particular pattern as either possessing a radial or concentric organization. Detecting a shape defined by a Glass pattern requires the successful detection of the orientations of its constituent local dipoles. In addition, long-range processes are needed to integrate the spatially separated dipoles into perceivable contours that have a particular (e.g., radial or concentric) organization. In the current experiment, the shapes were defined by either 40 or 200 oriented dipoles spread over an area with a diameter of either 6 or 25 degrees visual angle. Three amounts of visual noise were added to the patterns to manipulate task difficulty: 1) no added noise points, 2) low amounts of noise (a 1:1 ratio of randomlyplaced noise points and signal dipoles), and 3) large amounts of noise (a 5:1 ratio of randomly-placed noise points and signal dipoles). The results of the current study indicate that human observers, both younger and older, possess an effective ability to integrate visual information across space (using Glass patterns as stimuli). There is a small age-related deterioration in discrimination performance and this is most likely due to the deficits in orientation discrimination that accompany reductions in inhibitory GABA activity in visual cortex