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Kenith V. Sobel, Randolph Blake, Tony A. Raissian; Binocular rivalry suppression does impede buildup of the motion aftereffect.. Journal of Vision 2004;4(8):243. doi: https://doi.org/10.1167/4.8.243.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Does binocular rivalry suppression interfere with build-up of the translational motion aftereffect (MAE)? Earlier work said “no” but we have re-examined the question taking into account the contrast-dependence of the MAE. METHODS AND RESULTS: After adapting to a drifting sinusoidal grating presented to one eye, a subsequently presented stationary grating appeared to drift slowly in the opposite direction. Observers indicated the duration of the MAE by pressing a key when the stationary grating ceased to generate illusory motion. For each of 4 observers, a contrast response curve was constructed from the mean MAE durations across varying levels of adapting contrast. Next, observers adapted with one eye to a drifting grating while, at the same time, the other eye viewed a high contrast, flickering radial checkerboard. The checkerboard was sufficiently dissimilar to trigger binocular rivalry, and sufficiently strong to suppress the drifting grating from visual awareness for most of the adaptation period. MAE duration was unaffected when the contrast of the adapting grating was high, replicating previous results. However, when the contrast of the adapting grating was lower, rivalry suppression did reduce the magnitude of the MAE and completely abolished it when adaptation contrast was very low. Results from adaptation regimes that mimicked rivalry alternations imply that suppression effectively reduces grating contrast by 0.5 log-units, a reduction too small to affect adaptation at high contrasts where the MAE is presumably near saturation. A similar overall pattern of results was obtained using a counterphase flickering test grating that putatively isolates the dynamic MAE. CONCLUSION: Evidently, neural events underlying rivalry suppression are initiated at an early site in visual processing, prior to those responsible for adaptation to translational motion. This conclusion does not rule out amplification of suppression at higher stages of visual processing.
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