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Anthony D'Antona, Jan Kremers, Steven Shevell; A cortical and a sub-cortical origin of lateral interactions in perceived temporal variation. Journal of Vision 2008;8(6):358. doi: 10.1167/8.6.358.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Perception of a temporally-varying light is strongly affected by temporal variation within a surrounding field. The neural mechanism mediating this perceived lateral interaction has been posited to be center-surround antagonism in the LGN (Kremers et al., 2004) or at a cortical level (D'Antona & Shevell, 2007). To determine the neural locus, this study examined the contribution of monocular and/or binocular components to lateral interactions mediating perceived temporal variation. METHODS: Observers haploscopically viewed a central test stimulus (1 deg diam) with luminance varying over time. This stimulus had a surround (6 deg diam) that also varied in luminance at the same frequency. Center and surround were separated by a thin dark gap (0.2 deg). The center and surrounding stimuli were either presented to the same eye (monocular condition) or to opposite eyes (dichoptic condition). The central test stimulus always had Michelson contrast 0.5; the surround's contrast could be either 0.25 or 0.5. Stimuli were presented at 3.125, 6.25, or 12.5 Hz. The relative phase between the center and surround was varied in each condition. Observers adjusted the modulation depth of a separate temporally-varying matching field to match the perceived modulation depth in the central test area. RESULTS&CONCLUSIONS: Perceived modulation depth depended strongly on the relative phase between the center and surround in both the monocular and dichoptic conditions. The monocular conditions showed a somewhat larger influence from the surround compared to the dichoptic conditions. The results revealed both a weak monocular (plausibly LGN) and large binocular (central) component of lateral interaction. The monocular component was relatively flat as a function of temporal frequency, while the binocular component showed low-pass temporal-frequency tuning. These findings are consistent with two separate neural sites (monocular and binocular) underlying perceived temporal variation in context, with each site having a distinct strength and temporal-frequency tuning.
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