June 2004
Volume 4, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2004
Lateral interactions in orientation discrimination: Spatial frequency bandwidths
Author Affiliations
  • Lynn A. Olzak
    Department of Psychology, Miami University of Ohio, Oxford, OHUSA
  • Scott H. Gabree
    Department of Psychology, Miami University of Ohio, Oxford, OHUSA
  • Pentti I. Laurinen
    Department of Psychology, University of Helsinki, Helsinki, Finland
Journal of Vision August 2004, Vol.4, 776. doi:10.1167/4.8.776
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      Lynn A. Olzak, Scott H. Gabree, Pentti I. Laurinen; Lateral interactions in orientation discrimination: Spatial frequency bandwidths. Journal of Vision 2004;4(8):776. doi: 10.1167/4.8.776.

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Abstract

Surround gratings suppress the ability to make fine orientation discriminations on a center patch of grating when their spatial frequencies, orientations, and contrasts are similar. The interaction may be mediated by interactions among low-level analyzers, as posited in models of contrast-contrast. We measured the spatial frequency bandwidth of this effect. The patterns to be discriminated were vertical sinusoids of 4 cpd displayed in a sharp-edged 40-minute circular window, at a mean luminance of 19.8 cdm-0.5. In control conditions, no surround modulation was present. Modulated surrounds were simple vertical gratings that varied in spatial frequency ± >1 octave in 5 steps. Test and mask contrasts were held constant at 0.1. Each condition was run in a separate block of 80 trials. Differences to be discriminated were adjusted individually for each observer to yield a d′ of approximately 1.5 in control conditions. All observers were well-practiced. Difference thresholds were in the hyperacuity range and fixed for all conditions. A two-alternative signal-detection rating procedure was used to measure how discrimination performance changed as a function of center-surround similarity. The magnitude of interactions monotonically decreased with increasing differences between center and surround spatial frequency, returning to control levels at approximately ± 1 octave, with a half-amplitude, full bandwidth of approximately 0.75. Bandwidths were slightly asymmetric and narrower than either lateral-interaction bandwidths measured using apparent contrast tasks (Cannon & Fullenkamp, Vis. Res. 1991) or in estimates of spatially tuned channels in early vision (Wilson, MacFarlane & Phillips, Vis. Res. 1983) by overlaid masks. We conclude that the mechanisms underlying lateral interaction effects in orientation discriminations are different from those previously isolated or posited.

Olzak, L. A., Gabree, S. H., Laurinen, P. I.(2004). Lateral interactions in orientation discrimination: Spatial frequency bandwidths [Abstract]. Journal of Vision, 4( 8): 776, 776a, http://journalofvision.org/4/8/776/, doi:10.1167/4.8.776. [CrossRef]
Footnotes
 Supported by EY13953 to LAO
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