THE PERCEPTUAL GROUPING CRITERION OF COLINEARITY IS REFLECTED BY ANISOTROPIES OF CONNECTIONS IN THE PRIMARY VISUAL-CORTEX

An important step in the processing of visual patterns is the segmenta tion of the retinal image. Neuronal responses evoked by the contours o f individual objects need to be identified and associated for further joint processing. These grouping operations are based on a number of G estalt criteria. Here we report that connections in the visual cortex of the cat exhibit a highly significant anisotropy, preferentially lin king neurons activated by contours that have similar orientation and a re aligned colinearly. These anatomical data suggest a close relation between the perceptual grouping criterion of colinearity and the topol ogy of tangential intracortical connections. We propose that tangentia l intracortical connections support perceptual grouping by modulating the saliency of distributed cortical responses in a context-dependent way. The present data are compatible with the hypothesis that the crit eria for this grouping operation are determined by the architecture of the tangential connections.