Energy model for contrast detection: spatial-frequency and orientation selectivity in grating summation.
Models of spatial vision usually assume a "front-end" of spatial-frequency and orientation selective channels. Subthreshold-summation studies have provided some of the strongest support for this notion. We applied a single-channel energy model and a multiple-channels probability-summation model to explore subthreshold-summation phenomena. We measured the contrast thresholds for detection of two superimposed Gabor patches as a function of the spatial-frequency and orientation difference between the components. The stimuli were centred 7.5 deg above the fixation point and were windowed by a Gaussian function with one of two different spatial spreads. We have shown that the spatial-frequency and orientation selectivity in subthreshold summation of Gabor patches is determined by the similarity (cross-correlation) between the stimulus components. A single-channel energy model as well as a multiple-channels probability-summation model could explain the summation data.
Manahilov
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V
Department of Vision Sciences, Glasgow Caledonian University, City Campus, Cowcaddens Road, Glasgow, G4 0BA, Scotland, UK. vma@gcal.ac.uk
Simpson
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WA
D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008432:Mathematical Computing; D008954:Models, Biological; D016011:Normal Distribution; D009949:Orientation / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*