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Elena Gheorghiu, Frederick Kingdom, Rickul Varshney; Global not local motion direction tuning of curvature encoding mechanisms. Journal of Vision 2009;9(8):651. doi: 10.1167/9.8.651.
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© ARVO (1962-2015); The Authors (2016-present)
Aim. The shape-frequency and shape-amplitude after-effects, or SFAE and SAAE, are phenomena in which adaptation to a sine-wave-shaped contour causes a shift in respectively the apparent shape-frequency and shape-amplitude of a test contour in a direction away from that of the adapting stimulus. SFAEs and SAAEs are useful for probing curvature encoding in human vision. Here we have investigated motion direction selectivity of curvature-encoding mechanisms as a function of temporal frequency. We have examined whether curvature encoding mechanisms are tuned for: (i) global motion direction, (b) local motion direction, and (c) the local motion of texture-surround inhibition. Methods. SFAEs and SAAEs were measured as a function of temporal frequency for adapting and test contours that were either the same or different in motion direction, the rationale being that if the after-effects were smaller when adaptor and test differed in their motion direction then curvature encoders must be selective for motion direction. Results. SFAEs and SAAEs (i) show selectivity to global motion direction; (ii) increase in magnitude with global temporal frequency; (iii) show no selectivity to local motion direction; (iv) show no tuning for local motion of texture-surround inhibition. Conclusion. Curvature is encoded by mechanisms that are selective to global not local motion direction.
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