May 2008
Volume 8, Issue 6
Free
Meeting Abstract  |   May 2008
Orientation difference, spatial separation, intervening stimuli: What degrades stereoacuity and what doesn't
Author Affiliations
  • Bart Farell
    Institute for Sensory Research, Syracuse University
  • Fernandez Julian
    Institute for Sensory Research, Syracuse University
Journal of Vision May 2008, Vol.8, 91. doi:10.1167/8.6.91
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      Bart Farell, Fernandez Julian; Orientation difference, spatial separation, intervening stimuli: What degrades stereoacuity and what doesn't. Journal of Vision 2008;8(6):91. doi: 10.1167/8.6.91.

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      © 2015 Association for Research in Vision and Ophthalmology.

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Abstract

Stereoacuity varies with relative stimulus orientation: As the orientation difference between two stimuli increases, so does the minimum disparity required for discriminating the depth difference between the stimuli (Farell, 2006, J.Neurosci.). For neighboring stimuli, this effect might be due to local contour interactions. To evaluate this possibility, we varied the spatial separation between filtered noise patches presented at various retinal eccentricities. To further determine how orientation difference affects stereoacuity, we interposed irrelevant noise patches of various orientations and disparities between the two stimuli to be judged. Noise patches had spatial frequencies of 1 c/d ±2 octaves and orientations confined to ±15° of the mean. The difference in mean orientation between the two test patches varied between 0° and 90°. Test patches were horizontally separated (center to center) by 2.2, 4.5, 6.7, or 9° of visual angle. Subjects judged whether the farther patch was on the left or the right. Stereoacuity for all subjects fell gradually as eccentricity and stimulus separation increased (though thresholds could not be measured at 9° separation for all subjects). Stereoacuity fell with orientation difference at approximately the same rate at all eccentricities and separations. This argues against local interactions as the source of the orientation effect. Interposed noise patches had no systematic effect on stereoacuity regardless of their relative orientations or depths (except for improved performance when all orientations were identical and spacing was close). A difference in stimulus orientation interferes with optimal stereoacuity directly. This effect is not mediated by local contour interactions between the stimuli. Nor can local interactions overcome this interference: Intervening stimuli with orientations intermediate between those of the target stimuli do not improve stereoacuity via transitive processing across small local orientation differences. Therefore, the locus of the orientation effect is to be found in the relative disparity computation itself.

Farell, B. Julian, F. (2008). Orientation difference spatial separation, intervening stimuli: What degrades stereoacuity and what doesn't [Abstract]. Journal of Vision, 8(6):91, 91a, http://journalofvision.org/8/6/91/, doi:10.1167/8.6.91. [CrossRef]
© 2008 ARVO
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