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Christian Quaia, Boris Sheliga, Lance Optican, Bruce Cumming; Noise plaids reveal differences between motion and disparity computations. Journal of Vision 2013;13(9):963. doi: https://doi.org/10.1167/13.9.963.
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© ARVO (1962-2015); The Authors (2016-present)
Unidisparity plaids (in which one of two gratings has zero disparity) elicit short-latency disparity vergence responses (DVRs) that can be used to study how the brain extracts pattern disparity. Similarly, unikinetic plaids (in which one of the two gratings is static) elicit short-latency ocular following responses (OFRs) that can be used to study pattern motion. A close comparison of these results reveals differences in the pattern computation (DVRs are maximal when the two gratings have the same spatial frequency, which is not the case for OFRs). To investigate this further we measured, in three human subjects, DVRs and OFRs to a novel unidisparity/unikinetic plaid composed by summing two 1-D random line patterns. For the DVR, the zero-disparity noise pattern was replaced with a binocularly uncorrelated noise pattern, which abolished the responses to pattern disparity. For the OFR the stationary grating consisted (equivalently) of a new noise pattern on every frame, but this produced a response in the same direction as a stationary noise pattern. We also summed a correlated noise pattern containing disparity with an anticorrelated noise pattern at zero disparity. This reversed the direction of the pattern component in the DVR. When we studied the OFR with a two-frame motion stimulus containing an anticorrelated stationary component, there was no appreciable response in the pattern direction. However, with careful selection of parameters in stimuli containing many successive frames, we were able to observe reversed pattern responses when the contrast of the stationary pattern alternated between frames. These experiments demonstrate responses to pattern disparity/motion even in stimuli where an "Intersection of Constraints" is not well defined. An explanation based on channels narrowly tuned for spatial and temporal frequency is possible, but the differences between responses to disparity and motion indicate that a single explanation cannot be applied to both systems.
Meeting abstract presented at VSS 2013
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