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Pi-Chun Huang, Goro Maehara, Keith A. May, Robert F. Hess; Pattern masking: The importance of remote spatial frequencies and their phase alignment. Journal of Vision 2012;12(2):14. doi: 10.1167/12.2.14.
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© 2016 Association for Research in Vision and Ophthalmology.
To assess the effects of spatial frequency and phase alignment of mask components in pattern masking, target threshold vs. mask contrast (TvC) functions for a sine-wave grating (S) target were measured for five types of mask: a sine-wave grating (S), a square-wave grating (Q), a missing fundamental square-wave grating (M), harmonic complexes consisting of phase-scrambled harmonics of a square wave (Qp), and harmonic complexes consisting of phase-scrambled harmonics of a missing fundamental square wave (Mp). Target and masks had the same fundamental frequency (0.46 cpd) and the target was added in phase with the fundamental frequency component of the mask. Under monocular viewing conditions, the strength of masking depends on phase relationships among mask spatial frequencies far removed from that of the target, at least 3 times the target frequency, only when there are common target and mask spatial frequencies. Under dichoptic viewing conditions, S and Q masks produced similar masking to each other and the phase-scrambled masks (Qp and Mp) produced less masking. The results suggest that pattern masking is spatial frequency broadband in nature and sensitive to the phase alignments of spatial components.
Notes: *Fixed parameter. Numobs: Number of data points used to fit the data. x 2: The reduced chi-squared statistics were calculated according to the following formula, x reduced 2 = 1 v ∑ ( J o b s − J p r e d ) 2 σ 2 , where v is the number of degrees of freedom, given by Numobs − n − 1, with n being the number of fitted parameters, and σ is the known variance of the observation (here, we used averaged variance). x Q/Qp,Mp 2: The same equation as previously mentioned. The degrees of freedom are 7–1.
Notes: *Fixed parameter. Numobs: Number of data points used to fit the data. x S,M/Mp 2: The reduced chi-squared statistics were calculated as in Table A1. x Q/Qp 2: The same equation as previously mentioned. The degree of freedom is 7–1.
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