Illusory contours and linear filters.
The border between two abutting gratings is sometimes referred to as an illusory contour. In the Fourier spectrum of such a pattern there is no energy corresponding to the precise orientation of this contour. Neuronal responses elicited by such stimuli are therefore thought to be incompatible with linear filtering. The present investigation tested this notion. Abutting gratings were Fourier analyzed and passed through spatial and temporal filters with properties comparable with those of cortical neurons. It was found that the distribution of amplitudes in the Fourier spectrum is such that these stimuli may indeed stimulate neurons based on linear filtering. In the case of drifting stimuli the amount of stimulation may be maximal when the illusory contour is at the optimal orientation for bars with less stimulation on either side of this orientation.
Skottun
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BC
D002540:Cerebral Cortex / Q000502:physiology; D003198:Computer Simulation; D006801:Humans; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology; D009903:Optical Illusions / Q000502:physiology*