Comparing contrast-modulated and luminance-modulated masking: effects of spatial frequency and phase.
Comparing contrast-modulated and luminance-modulated masking: effects of spatial frequency and phase.
复制标题
比较对比度调制和亮度调制掩蔽：空间频率和相位的影响。
作者：
Willis,A;Smallman,HS;Harris,JM
The masking of a sinusoidal test grating by contrast-modulated (CM) gratings could, in principle, be attributable to the presence of a distortion product, injected into the stimulus during some nonlinear transformation at an early level of visual processing (eg Nachmias, 1989Vision Research29137 – 142). If so, CM gratings and luminance-modulated (LM) gratings of similar effective contrast and spatial frequency should mask the detection of sinusoids in a similar fashion. We compared the effects of masking by 1 cycle deg−1CM gratings [both simple beats (8 + 9 cycles deg−1) and amplitude-modulated gratings (8 + 9 + 10 cycles deg−1)], with those of masking by 1 cycle deg−1LM gratings of low contrast. We found that: (i) CM and low-contrast LM grating masks yielded similar spatial-frequency tuning functions around the modulation frequency of 1 cycle deg−1; (ii) low-contrast LM gratings masked the detection of test sinusoids in a highly phase-dependent fashion, while masking by CM gratings did not vary systematically with relative spatial phase. The results suggest that masking produced by CM gratings cannot simply be explained by the presence of a distortion product at the beat or modulation frequency.
