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Vivian Holten, Sjoerd M. Stuit, Maarten J. van der Smagt, Stella F. Donker, Frans A.J. Verstraten; Interocular competition at higher levels of motion processing. Journal of Vision 2014;14(10):382. doi: https://doi.org/10.1167/14.10.382.
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© ARVO (1962-2015); The Authors (2016-present)
Binocular rivalry is thought to occur at multiple stages along the visual processing hierarchy. Although monocular channels in primary visual cortex have been suggested to play an important role, recent studies have hinted at monocular information being available to higher-level visual (motion) areas. These areas, such as the medial superior temporal area (MST), are involved in the processing of radial optic flow. It is known that cells in these areas are selectively tuned to either expansion or contraction, while areas earlier in the visual hierarchy cannot distinguish between these two directions. Previous studies have shown that MST cells tuned to expansion outnumber those tuned to contraction. If monocular information reaches higher-level visual areas, one might expect that these tuning differences play a role in binocular rivalry. Here we question whether the time it takes to reach awareness differs between expanding and contracting optic flow. We used breaking continuous flash suppression to measure the duration until expanding or contracting optic flow broke suppression. Observers viewed the stimuli (3.6° radius) through a mirror stereoscope mounted on a chin rest. A white frame and a noise pattern (subtending 4.9° x 4.9°) surrounded the stimuli to facilitate binocular fusion. During the experiment, one eye viewed a mask (refresh rate 10Hz), which was created by filtering pink (1/f) noise using a low-pass filter (σ = 1.5), while the other eye viewed an either expanding or contracting radial optic flow pattern with a quadratic speed gradient (speed 2.7 deg/s). Observers pressed one of the two response keys to discriminate the optic flow direction as soon as possible within 6-second trials. The results show that expanding optic flow breaks suppression faster than contracting optic flow. These results may, for instance, reflect the larger prevalence of cells tuned to expansion in MST, suggesting monocular contributions to higher-level motion processing.
Meeting abstract presented at VSS 2014
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