ABSENCE OF CONTOUR LINKING IN PERIPHERAL-VISION

Human foveal vision is subserved initially by groups of spatial, tempo ral and orientational 'filters', the outputs of which are combined to define perceptual objects, Although a great deal is known about the fi ltering properties of individual cortical cells, relatively little is known about the nature of this 'linking' process. One recent approach( 1) has shown that the process can be thought of in terms of an associa tion field whose strength is determined conjointly by the orientation and distance of the object. Here we describe a fundamental difference in this feature-linking process in central and peripheral parts of the visual field, which provides insight into the ways that foveal and pe ripheral visual perception differ(2,3). In the fovea, performance can be explained only by intercellular Linking operations whereas in the p eriphery intracellular filtering will suffice. This difference represe nts a substantial economy in cortical neuronal processing of periphera l visual information and may allow a recent theory of intercellular bi nding to be tested(4-7).