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Nicole D. Anderson, Kathryn M. Murphy, David G. Jones; Center-surround effects on orientation discrimination with visual noise stimuli. Journal of Vision 2002;2(7):222. doi: 10.1167/2.7.222.
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© ARVO (1962-2015); The Authors (2016-present)
Physiological and behavioural evidence suggests that responses to a target stimulus can be modulated by context. In the orientation domain, parallel elements in the surround can suppress responses to a center target, whereas orthogonal elements have less or no effect. We investigated the influence of contextual orientation information using a stimulus in which the amount of oriented signal was varied independent of contrast. Oriented elements within the pattern were drawn with a particular grey level for a limited spatial extent, and then randomly switched to a new grey level. Oriented centers (2 deg) were presented in the context of either a parallel or orthogonal surround. The subjects' task was to discriminate oriented centers from unoriented noise centers in a 2IFC task. With a uniform grey surround, only 12% orientation signal was required for accurate discrimination. With a strong parallel surround, twice as much oriented signal was required. This effect was reduced when the orientation strength of the surround signal was reduced or when a gap separated the center and surround. Thresholds were also elevated with an unoriented noise surround. When the surround signal was orthogonal, thresholds were not different from thresholds with a uniform grey surround. These results are consistent with previous physiological and behavioural results that suggest orientation information is pooled across a local spatial region in an orientation-specific manner.
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