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Magda L. Michna, Kathy T. Mullen; The role of color vision in translation and radial global motion processing. Journal of Vision 2007;7(9):405. doi: https://doi.org/10.1167/7.9.405.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We address the issue of whether color vision can support both radial and translational global motion. Previous studies have argued that translational chromatic global motion is significantly impaired, however, these have not addressed the role of both contrast and coherence level in global motion discrimination, and/or have not used stimulus parameters appropriate for chromatic spatio-temporal contrast sensitivity. In addition, the chromatic contribution to radial motion has not been investigated.
Method: We analysed translational and radial global motion processing for random dot kinetograms (RDKs) calibrated for the selective activation of the L/M cone-opponent (red-green), S-cone-opponent (blue-yellow) or achromatic systems. Each RDK consisted of 50 Gaussian ‘dots’ (σ = 0.25deg.) presented using a limited lifetime paradigm in a circular window (12° diameter). ‘Dot’ speed was 5.4°/sec., and stimulus duration was 240msec. RDKs were presented in a Gaussian temporal window (σ=0.125sec). We measured direction discrimination thresholds (% coherence) using a method of constant stimuli over a wide range of stimulus contrasts scaled in multiples of detection threshold.
Results: We find that, for both chromatic and achromatic RDKs, coherence thresholds for discriminating global motion decrease as contrast increases. At higher contrasts, coherence thresholds for isoluminant red-green and S-cone isolating chromatic RDKs are similar to those for achromatic stimuli for both radial and translational motion, indicating that the chromatic system can perform as well in global motion processing as the luminance system.
Conclusion: We conclude that global motion processing is available to both red-green and blue-yellow color vision for both translational and radial motion stimuli.
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