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Pi-Chun Huang, Goro Maehara, Robert F. Hess; A role for spatial alignments in early vision. Journal of Vision 2010;10(15):37. doi: 10.1167/10.15.37.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We set out to investigate the interaction between suprathreshold, spatially broadband stimuli in early vision. We wondered whether Foley's divisive inhobition model, derived for stimuli of different orientation, when applied to stimuli of different spatial frequency could predict the different masking effects from a sinewave versus a squarewave stimulus.
Methods: Odd man out paradigm was used to measure the contrast discrimination threshold of sinewave(S) for three types of contrast maskers; a sinewave (S), a squarewave(Q) and a missing fundamental waveform(M). We wondered if we could predict the response to a squarewave from a knowledge of the responses to a sinewave and missing fundamental.
Results: For S-S condition, a typical TvC function was found. For the S-Q condition, the TvC function exhibited less facilitation and more inhibition. For S-M configuration, no facilitatory effect was found at low pedestal contrasts and only limited inhibition at high pedestal contrasts. The effects of the squarewave masker could not be predicted, using Foley's model, from the responses of the sinewave and missing fundamental results; the squarewave masker exhibited more than the predicted amount of inhibition at high pedestal contrasts. However, when we phase-scrambled the squarewave and missing fundamental waveforms, Foley's model was able to predict the phase-scrambled squarewave result on the basis of the other two.
Conclusion: Our data concerning spatial frequency broadband stimuli, can be described by Foley's divisive model, but only for phase-scrambled stimuli. We conclude that the phase-alignment of spatial frequency components does not go unrecognized by early visual mechanisms.
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