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Keith Langley, Veronique Lefebvre, Peter Bex; The unveiling of transient channels at high spatial frequencies by contrast masking and contrast adaptation. Journal of Vision 2009;9(8):1081. doi: 10.1167/9.8.1081.
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© ARVO (1962-2015); The Authors (2016-present)
The lowpass spatio-temporal contrast sensitivity function (CSF) of the visual system for high spatial frequency signals has led some authors to posit that a single spatio-temporal channel is able to explain visual perception when testing at the higher spatial frequencies. We have re-examined this assumption through contrast masking and contrast adaptation experiments. When masking, the contrast of the mask as a function of temporal frequency (TF) was inversely scaled to a proportion of the CSF in an attempt to whiten the spatio-temporal masking response of the visual system's spatio-temporal processes. The detection contrast of 1 Hz and 10 Hz probes whose mean spatial frequency was 16.0 cpd, was then measured using a 2AFC paradigm. The mean luminance of the display monitor was 400 cd/m2. At low mask contrasts (multiples of 2 times threshold), and after inverting the contrast scaling of the masks, the masking functions for both probes were found to be lowpass functions of TF. For maskers whose contrast was set at a multiple of 16 times threshold contrast, however, the probes exhibited sustained and transient masking functions. In examining threshold contrast elevations as a function of adaptor (0–38 Hz) and test (0–19Hz) TFs for one-dimensional highpass spatial frequency signals, we further demonstrate the presence of an adaptable transient TF tuned channel whose peak lay around 12.0 Hz. Collectively, our results unveil significant transient but hidden characteristics of the visual system that we explain as an emergent property of an adaptable system in which transient and sustained processes lie in cascade.
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