Neurophysiological constraints on models of illusory contours.

Illusory contours can appear as interpolation between edges of the stimulus, as in the Kanizsa triangle, or run orthogonal to the inducing elements, as in the Ehrenstein illusion. Single-cell recordings from monkey visual cortex suggest that both are produced by the same mechanism. Neural border ownership coding, on the other hand, which shows a much larger range of context integration, might involve a different mechanism.