title: Orientation enhancement in early visual processing can explain time course of brightness contrast and White's illusion.
abstract: Dynamics of orientation tuning in V1 indicates that computational model of V1 should not only comprise of bank of static spatially oriented filters but also include the contribution for dynamical response facilitation or suppression along orientation. Time evolution of orientation response in V1 can emerge due to time- dependent excitation and lateral inhibition in the orientation domain. Lateral inhibition in the orientation domain suggests that Ernst Mach's proposition can be applied for the enhancement of initial orientation distribution that is generated due to interaction of visual stimulus with spatially oriented filters and subcortical temporal filter. Oriented spatial filtering that appears much early (<70 ms) in the sequence of visual information processing can account for many of the brightness illusions observed at steady state. It is therefore expected that time evolution of orientation response might be reflecting in the brightness percept over time. Our numerical study suggests that only spatio-temporal filtering at early phase can explain experimentally observed temporal dynamics of brightness contrast illusion. But, enhancement of orientation response at early phase of visual processing is the key mechanism that can guide visual system to predict the brightness by "Max-rule" or "Winner Takes All" (WTA) estimation and thus producing White's illusions at any exposure.
authors: Saha Institute of Nuclear Physics, Kolkata 700064, India. subhajit.karmakar@saha.ac.in
authors: Subhajit
authors: S
authors: Karmakar
authors: Sandip
authors: S
authors: Sarkar
mesh_terms: D003198:Computer Simulation; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009903:Optical Illusions / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010775:Photic Stimulation; D011237:Predictive Value of Tests; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D013997:Time Factors