ILLUSORY CONTOURS - TOWARD A NEURALLY BASED PERCEPTUAL THEORY

Although illusory contours were first described nearly a century ago, researchers have only recently begun to approach a consensus on the pr ocesses underlying their formation. Neurophysiological and psychophysi cal evidence indicate that neural mechanisms of the early visual corte x subserve illusory contour generation, although cognitive factors pla y important roles in determining the final percept. I summarize experi ments concerning the determinants of illusory contour strength and for m, concentrating on findings particularly relevant to modeling. After establishing arguments for the early generation of illusory contours, I provide an overview of formation theories, culminating with descript ions of neural models. The constraints that experimental data place on models are outlined, and neural models are evaluated with respect to these constraints. Throughout the review, I indicate where further exp erimental and modeling research are critical.