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Anthony D'Antona, Steven Shevell; Object segmentation cues influence perceived temporal variation. Journal of Vision 2007;7(9):1012. doi: 10.1167/7.9.1012.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Perception of temporally-varying light is strongly affected by temporally-varying surrounding light. Particularly, perceived modulation depth of a central light is suppressed by surrounding light varying at the same temporal frequency and phase as the central field. This suppression has been modeled by center-surround antagonism of receptive fields in the primate retino-geniculate pathway (Kremers et al, JOV 2004). Here, we question this explanation by showing that object segmentation cues (depth, illusory contours) alter perceived modulation.
METHOD: Observers matched the perceived modulation depth at the center of a 6° disc modulated in luminance at 2 Hz. In Experiment 1, the center of the field was contained within (1) 3 thin dark lines forming a triangle, (2) 3 ‘pac-men’ forming an illusory triangle, (3) 3 ‘pac-men’ rotated 180 degrees relative to (2) (‘pac-men’ control), or (4) nothing (control). In Experiment 2, the circular disc was viewed haploscopically and contained (1) a thin dark circular gap, (2) as (1) but with the gap perceived nearer than the circular field by stereo disparity (gap-only depth), (3) as (1) but with the gap and its interior both raised to the nearer depth plane (gap and interior depth), or (4) no gap (control).
RESULTS: In Experiment 1, perceived modulation depth was similar in the control and illusory-control conditions but clearly suppressed—almost identically—by the presence of either a real or illusory triangle. In Experiment 2, perceived modulation depth was suppressed greatest in the two conditions with the gap and its interior in the same depth plane. Suppression was reduced or abolished when only the gap was perceived in depth.
CONCLUSIONS: Suppression of perceived modulation by a temporally-varying surround cannot be explained by a simple receptive-field model. Cues to object segmentation (depth, real or illusory contours) modulate suppression, suggesting center-surround inhibition at the object level of visual processing.
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