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Frédéric Devinck, Thorsten Hansen, Karl Gegenfurtner; The spatiotemporal properties of the achromatic and chromatic Craik-O'Brien-Cornsweet effect. Journal of Vision 2007;7(9):677. doi: https://doi.org/10.1167/7.9.677.
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© ARVO (1962-2015); The Authors (2016-present)
The Craik-O'Brien-Cornsweet effect (COCE) is a visual phenomenon in which a difference in brightness is observed between two equal luminance regions separated by a luminance defined edge consisting of both sharp and gradual discontinuity. This effect is also shown with isoluminant colors. It has been hypothesized that the COCE is mediated by a cortical filling-in process. According to this hypothesis, filling-in needs some finite amount of time for the brightness or color to spread from the locations corresponding to both edges of a COCE grating into the space between them. Consequently, if the COCE relies on a neural spreading effect it should proceed at finite speed, and exhibit some temporal tuning as a function of the width of the area enclosed by the contours. In the present study, temporal frequency thresholds were determined at three spatial frequencies ranged from 0.05 to 2 cpd. Observers varied the temporal frequency of a COCE grating to determine the maximum temporal frequency at which temporal brightness or color modulation is perceived. In the achromatic COCE, contours were determined along the luminance axis of the DKL color space; in the chromatic COCE, contours were modulated along the L-M- or S-cone axis. Two contrasts were used (0.1 and 1). For the achromatic condition at low contrast, the data showed that the temporal frequency for an induction effect increased with an increasing spatial frequency, while it was constant for the high contrast condition. For both chromatic COCE, the modulation in chromaticity at low contrast decreased when the spatial frequency increased, while it was constant in the high contrast condition. Our results are consistent with the spatial filtering properties of the luminance and chromatic systems, but they suggest that temporal filling-in may not operate under all conditions.
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