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Sunwoo Kwon, Thomas Albright, Sergei Gepshtein; Invariants of center-surround interactions. Journal of Vision 2014;14(10):258. doi: https://doi.org/10.1167/14.10.258.
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© ARVO (1962-2015); The Authors (2016-present)
Sensitivity to visual stimuli depends on their spatial and temporal context. Effects of temporal context (as in motion adaptation) that appear to be contradictory in narrow samples of stimuli follow a simple invariant pattern when viewed broadly. Thus, local gains and losses of sensitivity caused by motion adaptation added up to a global shift of the spatiotemporal contrast sensitivity function (CSF; Kelly, 1979) when studied over the full domain of CSF (Gepshtein, Lesmes & Albright, 2013). Similarly contradictory results are commonly observed in studies of spatial contextual modulation ("center-surround interactions") in narrow samples of stimuli. We asked whether a simpler pattern of sensitivity changes can be discovered in center-surround interactions when they are studied broadly, across the domain of CSF. We measured contrast sensitivity using direction discrimination in drifting Gabor patches with or without surrounding gratings. Center stimuli were sampled from a constant-speed "slice" of CSF (i.e., at constant ratio of temporal to spatial frequencies). When the surround was present, its spatiotemporal frequency and contrast were fixed within an experiment, its orientations was either collinear or orthogonal to the center, and its motion direction was either same or opposite to the center. The results varied across observers when center and surround moved in the same direction, possibly due to individual effects of motion capture. But the results were invariant across observers for all other conditions. What looked like a different pattern of gains and losses of sensitivity for every observer in narrow samples of stimuli, could be succinctly described as shifts of CSF following the same pattern across observers. At low surround contrasts, increasing surround frequency shifted the peak of CSF towards higher center frequencies. And at high surround contrasts, increasing surround frequency shifted the peak of CSF towards lower center frequencies.
Meeting abstract presented at VSS 2014
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