Contour interaction for foveal acuity targets at different luminances

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Bedell, Harold E. ; Siderov, John ; Waugh, Sarah J. ; Zemanová, Romana ; Pluháček, František ; Musilová, Lenka (2013)
  • Publisher: Elsevier BV
  • Journal: Vision Research, volume 89, pages 90-95 (issn: 0042-6989)
  • Related identifiers: doi: 10.1016/j.visres.2013.07.009
  • Subject: Ophthalmology | Sensory Systems
    mesheuropmc: genetic structures

Single-letter visual acuity is impaired by nearby flanking stimuli, a phenomenon known as contour interaction. We showed previously that when foveal acuity is degraded by a reduction of letter contrast, both the magnitude and angular spatial extent of foveal contour interaction remain unchanged. In this study, we asked whether contour interaction also remains unchanged when foveal visual acuity is degraded by a reduction of the target’s background luminance.\ud \ud Percent correct letter identification was measured for isolated, near-threshold black Sloan letters and for letters surrounded by 4 flanking bars in 10 normal observers, 5 at Anglia Ruskin University, UK (ARU) and 5 at Palacky University, Czech Republic (PU). A stepwise reduction in the background luminance over 3 log units resulted in an approximately threefold increase in the near-threshold letter size. At each background luminance, black flanking bars with a width equal to 1 letter stroke were presented at separations between approximately 0.45 and 4.5 min arc (ARU) or 0.32 and 3.2 min arc (PU).\ud \ud The results indicate that the angular extent of contour interaction remains unchanged at approximately 4 min arc at all background luminances. On the other hand, the magnitude of contour interaction decreases systematically as luminance is reduced, from approximately a 50% reduction to a 30% reduction in percent correct. The constant angular extent and decreasing magnitude of contour interaction with a reduction of background luminance suggest foveal contour interaction is mediated by luminance-dependent lateral inhibition within a fixed angular region.
  • References (46)
    46 references, page 1 of 5

    Barlow, H.B., Fitzhugh, R. & Kuffler, S.W. (1957). Change of organization in the receptive fields of the cat‟s retina during dark adaptation. Journal of Physiology, 137, 338-354.

    Bouma, H. (1970). Interaction effects in parafoveal letter recognition. Nature, 226, 177-178.

    Cleland, B.G. & Enroth-Cugell, C. (1968). Quantitative aspects of sensitivity and summation in the cat retina. Journal of Physiology, 198, 237-250.

    Chung, S.T.L., Levi, D.M., & Legge, G.E. (2001). Spatial frequency and contrast properties of crowding. Vision Research, 41, 1833-1850.

    Dakin, S.C., Cass, J. Greenwood, J.A. & Bex, P.J. (2010). Probabilistic, positional averaging predicts object-level crowding effects with letter-like stimuli. Journal of Vision, 10(10):14, 1-16.

    Danilova, M.V., & Bondarko, V.M. (2007). Foveal contour interactions and crowding effects at the resolution limit of the visual system. Journal of Vision, 7(2):25, 1-18.

    Derrington, A.M. & Lennie, P. (1982). The influence of temporal frequency and adaptation level on receptive field organization of retinal ganglion cells in cat. Journal of Physiology, 333, 343- 366.

    Flom, M.C., Heath, G.C., & Takahashi, E. (1963). Contour interaction and visual resolution: contralateral effects. Science, 142, 979-980.

    Flom, M.C., Weymouth, F.W., & Kahneman, D. (1963). Visual resolution and contour interaction. Journal of the Optical Society of America, 53, 1026-1032.

    Freeman J., Chakravarthi, R., & Pelli, D.G. (2012). Substitution and pooling in crowding.

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