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Elena Gheorghiu, Frederick A. A. Kingdom, Emma Witney; Size and shape-frequency after-effects: same or different mechanism?. Journal of Vision 2008;8(6):936. doi: https://doi.org/10.1167/8.6.936.
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Aim. The size, or luminance spatial frequency after-effect (LFAE) is the phenomenon in which adaptation to a luminance grating of given spatial frequency causes a shift in the perceived spatial frequency of a grating away from that of the adapting grating (Blakemore & Sutton, 1969, Science, 166, 245–7).The analogous shape-frequency after-effect (or SFAE) is the phenomenon in which adaptation to a sine-wave-shaped contour causes a shift in the apparent shape-frequency of a test contour away from that of the adapting stimulus (Gheorghiu & Kingdom, 2007, Vis.Res., 47, 834–44). It is widely believed that the LFAE is mediated by luminance-spatial-frequency-selective channels, while it has been suggested that the SFAE is mediated by curvature-selective channels. However it is possible that the SFAE is mediated by the same mechanism as underlies the LFAE, in spite of the fact that the stimuli involved have little Fourier energy in common. Methods. We measured both SFAEs and LFAEs using a conventional staircase procedure. The contour-shape stimuli were sine-wave-shaped contours and edges; luminance stimuli were sine-wave, square-wave and line luminance gratings. The rationale was that if the after-effects were reduced when adaptor and test stimuli were of a different class (shape versus luminance), this suggested that the SFAE and LFAE were mediated by different mechanisms. Results. While similar-sized after-effects were found for same-class adaptor-and-test stimuli (either shape or luminance), the after-effects were greatly reduced for different-class adaptor-and-test stimuli (shape adaptors and luminance tests, or vice-versa). Conclusion. SFAEs are mediated by different mechanisms to the LFAE.
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