Volume 8, Number 3, Article 9, Pages 1-10 doi:10.1167/8.3.9 http://journalofvision.org/8/3/9/ ISSN 1534-7362
Resolution acuity for equiluminant gratings of S-cone positive or negative contrast in human vision
Margarita B. Zlatkova
Visual Science Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK
[e-mail]
Angel Vassilev
Institute of Neurobiology (Former Institute of Physiology), Bulgarian Academy of Sciences, Sofia, Bulgaria
[e-mail]
Roger S. Anderson
Visual Science Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK
[e-mail]
Abstract

We measured resolution acuity separately for gratings with positive (+S) and negative (−S) S-cone contrast at different eccentricities in the temporal retina to determine if the resolution performance is limited by a single bipolar opponent mechanism. Gratings were modulated from an achromatic background in either the 90 or 270 deg direction in DKL space. Two additional directions were tested to examine the effects of increased lens yellowing and macular pigment absence in the periphery. The gratings used slow temporally rising hue (co-sinusoidal step) to aid selective S-cone ON or OFF stimulation. Resolution acuity was measured using different luminance ratios of the grating bars with the background around the equiluminant point. The data displayed a plateau where the acuity was minimal and mediated by the sparse S-cone pathway, with observer performance rising on either side. The acuity at the minimum was consistently higher for +S gratings than −S gratings beyond 10 deg eccentricity. Above the resolution limit, an aliased pattern was detected for both types of gratings, indicating that the resolution acuity was limited by the density of postreceptoral neurons. The results suggest that the resolution of gratings with opposite S-cone contrast polarity is limited by separate and rectified mechanisms of different distribution.

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History
Received June 27, 2007; published March 12, 2008
Citation
Zlatkova, M. B., Vassilev, A., & Anderson, R. S. (2008). Resolution acuity for equiluminant gratings of S-cone positive or negative contrast in human vision. Journal of Vision, 8(3):9, 1-10, http://journalofvision.org/8/3/9/, doi:10.1167/8.3.9.
Keywords
color vision, resolution, color opponency, S-cone ON and OFF pathways, equiluminance
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