November 2002
Volume 2, Issue 7
Free
Vision Sciences Society Annual Meeting Abstract  |   November 2002
Center-surround effects on orientation discrimination with visual noise stimuli
Author Affiliations
  • Nicole D. Anderson
    McMaster University, Canada
Journal of Vision November 2002, Vol.2, 222. doi:10.1167/2.7.222
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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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Abstract

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.

Anderson, N. D., Murphy, K. M., Jones, D. G.(2002). Center-surround effects on orientation discrimination with visual noise stimuli [Abstract]. Journal of Vision, 2( 7): 222, 222a, http://journalofvision.org/2/7/222/, doi:10.1167/2.7.222. [CrossRef]
Footnotes
 Supported by grants from NSERC and PREA.
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