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Remy Allard, Jocelyn Faubert; No dedicated color motion system. Journal of Vision 2014;14(10):19. doi: 10.1167/14.10.19.
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© ARVO (1962-2015); The Authors (2016-present)
The existence of a color motion system distinct from both the luminance and feature tracking motion systems remains controversial. In the current study, we used a mask known to affect luminance-defined motion processing but which should not affect distinct color-defined motion processing: a static, luminance-defined pedestal at high contrast. To neutralize feature tracking, the motion (3.75 Hz) was presented in the near periphery (2 to 3 degrees of eccentricity) at a spatial frequency (~1 cpd) beyond the attentional resolution acuity. The results showed that, in a direction discrimination task, the luminance-defined pedestal affected luminance- and color-defined contrast thresholds by similar proportions (~10x at the highest pedestal contrast) and that this masking was orientation specific as a similar mask orthogonal to the signal modulation had little impact on luminance- and color-defined contrast thresholds. Given that L- and M-cone pathways merge at a processing level that is not orientation specific (i.e., ganglion cells, which have center-surround receptive fields), the masking of a luminance pedestal must interfere with higher processing stages within the luminance pathway where cells are orientation selective (e.g., simple cells). Furthermore, a static luminance-defined mask should not generate any substantial response from cells sensitive to luminance-defined motion (e.g., complex cells), so even if distinct luminance and color motion pathways merged after independent motion extractions, a static, luminance-defined mask should not impair color-defined motion processing. The similar vulnerabilities of luminance- and color-defined motion processing to a static, luminance-defined mask suggest that, when the feature tracking is neutralized, luminance- and color-defined motions are processed by the same motion system. We conclude that there is no dedicated color motion system.
Meeting abstract presented at VSS 2014
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