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Boris Sheliga, Christian Quaia, Edmond FitzGibbon, Bruce Cumming; Human short-latency ocular vergence responses in the absence of the binocular disparity signal.. Journal of Vision 2016;16(12):426. doi: https://doi.org/10.1167/16.12.426.
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We studied human short-latency vergence eye movements to sine wave stimuli moving in opposite directions (left vs. right; up vs. down) in the two eyes. The sine wave seen by each eye underwent a ¼-wavelength shift each successive video frame (at 150 Hz stimulus refresh rate). This arrangement eliminates changing disparity cues because the phase difference between the eyes alternated between 0° and 180°. We, nevertheless, observed robust short-latency vergence responses, whose sign was consistent with the interocular velocity differences. These responses were strongest for spatial frequencies (SFs) in the range of 0.42-0.62 cpd, much higher than the optimal SF for evoking either ocular-following (OFR) or disparity-vergence (DVR) responses. Restricting the images seen by each eye to just half of the visual hemifield, such that there was no binocular image overlap, weakened but by no means eliminated the responses. Further spatial separation of images seen by the two eyes did reduce the responses. However, even with a spatial gap of 4 sine wave periods responses were still significant. Observations with sine wave stimuli were corroborated using moving uncorrelated white noise stimuli: the lowest tested speeds of motion—mediated by high-SF channels (see Sheliga et al., JOV in press)—were the most effective in eliciting the ocular vergence responses. Our results show that the short-latency ocular vergence can be evoked by interocular velocity differences in the absence of the binocular disparity signal. The responses to differences in interocular vertical velocity presumably reflect the responses to such stimuli recently shown in area MT (Czuba et al., 2014), for which no other behavioral consequence was previously known.
Meeting abstract presented at VSS 2016
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