The Spatiotemporal Properties of the Craik-O'Brien-Cornsweet Effect Are Consistent with 'filling-in'

The Craik-O'Brien-Cornsweet effect (COCE) is an illusion in which luminance discontinuities give rise to illusory brightness. One hypothesised mechanism for the induction of illusory brightness is that the cortex constructs a brightness percept from edge information by a lateral 'filling-in' process. A requirement for the filling-in hypothesis is that ability of the illusion to form would be limited by the speed of propagation of the filling-in. The results presented here from three methods indicate that in the case of COCE gratings brightness information propagates at a fixed speed across the central visual field of about 19 degrees/s, and across visual areas V1 or V2 at 155 or 205 (+/- 20) mm/s, respectively.