Orientation-specificity of adaptation : isotropic adaptation is purely monocular

John Cass, Ameika Johnson, Peter J. Bex, David Alais

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    Abstract

    Numerous studies have found that prolonged exposure to grating stimuli reduces sensitivity to subsequently presented gratings, most evidently when the orientations of the adapting and test patterns are similar. The rate of sensitivity loss varies with angular difference indicating both the presence and bandwidths of psychophysical ‘orientation channels’. Here we study the orientation dependency of contrast adaptation measured both monoptically and dichoptically. Earlier psychophysical reports show that orientation bandwidths are broader at lower spatial frequencies, and we confirm this with a simple von Mises model using 0.25 vs. 2 c.p.d. gratings. When a single isotropic (orientation invariant) parameter is added to this model, however, we find no evidence for any difference in bandwidth with spatial frequency. Consistent with crossorientation masking effects, we find isotropic adaptation to be strongly low spatial frequency-biased. Surprisingly, unlike masking, we find that the effects of interocular adaptation are purely orientation-tuned, with no evidence of isotropic threshold elevation. This dissociation points to isotropic (or ‘cross-orientation’) adaptation being an earlier and more magnocellular-like process than that which supports orientation-tuned adaptation and suggests that isotropic masking and adaptation are likely mediated by separate mechanisms.
    Original languageEnglish
    Article numbere47425
    Number of pages13
    JournalPLoS One
    Volume7
    Issue number11
    DOIs
    Publication statusPublished - 2012

    Open Access - Access Right Statement

    ©2012 Cass et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

    Keywords

    • bandwith
    • orientation
    • spatial frequency

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