ORIENTATION MAPS OF SUBJECTIVE CONTOURS IN VISUAL-CORTEX

Responses to subjective contours in visual cortical areas V1 and V2 in adult cats were investigated by optical imaging of intrinsic signals and single-unit recording. Both V1 and V2 contain maps of the orientat ion of subjective gratings that have their basis in specific kinds of neuronal responses to subjective orientations. A greater proportion of neurons in V2 than in V1 show a robust response to subjective edges. Through the use of subjective stimuli in which the orientation of the luminance component is invariant, an unmasked V1 response to subjectiv e edges alone can be demonstrated. The data indicate that the processi ng of subjective contours begins as early as V1 and continues progress ively in higher cortical areas.