Abstract
The spatial context has strong effects on visual processing. Psychophysics and modeling studies have provided evidence that the surround context can systematically modulate the perception of center stimuli. For motion direction, these center-surround interactions are considered to come from spatio-directional interactions between direction of motion tuned neurons, which are attributed to the middle temporal (MT) area. Here, we investigated through psychophysics experiments on human subjects changes with spatial separation in center-surround inhibition and motion direction interactions. Center-surround motion repulsion effects were measured under near-and far-surround conditions. Using a simple physiological model of the repulsion effect we extracted theoretical population parameters of surround inhibition strength and tuning widths with spatial distance. All 11 subjects showed clear motion repulsion effects under the near-surround condition, while only 10 subjects showed clear motion repulsion effects under the far-surround condition. The model predicted human performance well. Surround inhibition under the near-surround condition was significantly stronger than that under the far-surround condition, and the tuning widths were smaller under the near-surround condition. These results demonstrate that spatial separation can both modulate the surround inhibition strength and surround to center tuning width.
Highlights
Contextual interactions in visual processing are ubiquitous across a large panel of feature processing aspects and contribute to binding or segregating spatial elements in the visual field (Spillmann and Werner, 1996; Albright and Stoner, 2002; Kingdom et al, 2014; Tadin, 2015)
Psychophysics studies on center-surround motion processing have indicated that surround effects are selective for the motion direction, and the motion repulsion effect in this configuration is attributed to the suppressive interactions between motion sensitive neurons with non-overlapping receptive fields (Kim and Wilson, 1997; Tzvetanov and Womelsdorf, 2008; Tzvetanov, 2012)
We found that near- and far-surround motion discrimination tasks led to different motion repulsion results
Summary
Contextual interactions in visual processing are ubiquitous across a large panel of feature processing aspects and contribute to binding or segregating spatial elements in the visual field (Spillmann and Werner, 1996; Albright and Stoner, 2002; Kingdom et al, 2014; Tadin, 2015). By applying center-surround configuration stimuli, the strongest suppressive effects appear when the surround motion has the same direction as the center target, and by contrast, surround stimuli facilitate neuronal responses to the center target if it moves in the opposite direction than that in the center (Allman et al, 1985a,b; Born and Tootell, 1992; Murakami and Shimojo, 1995, 1996) This effect is spatially selective, with the strongest effect found when the surround is adjacent to the center, and as the surround is moved further away, the suppressive effects decrease in amplitude, which explains the decrease in motion repulsion with center-surround separation (Kim and Wilson, 1997)
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