Comparing the spatial-frequency response of first-order and second-order lateral visual interactions: grating induction and contrast-contrast.
The magnitudes of two suprathreshold lateral spatial-interaction effects--grating induction and contrast--contrast--were compared with regard to their dependence upon inducing-grating spatial frequency. Both effects cause the contrast of target stimuli embedded in surrounding patterns to be matched nonveridically. The magnitudes of each effect were measured in a common unit that indexed the degree of nonveridical contrast matching across a large range of target-grating contrasts (+/- 0.80). Grating induction was a low-pass effect with respect to spatial frequency, whereas contrast-contrast was bandpass, peaking at approximately 4.0 cycles deg(-1). The magnitude of grating induction exceeded that of contrast--contrast, both overall and at their optimal frequencies (0.03125 and 4.0 cycles deg(-1), respectively); the two effects are equipotent at an inducing-grating spatial frequency of 1.0 cycle deg(-1). A significant negative correlation between the magnitudes of the two effects suggests a link whereby activation of second-order normalization mechanisms may inhibit first-order mechanisms.
McCourt
Mark E
ME
Department of Psychology, Center for Visual Neuroscience, North Dakota State University, Fargo, ND 58105-5075, USA. mark.mccourt@ndsu.nodak.edu
D015350:Contrast Sensitivity; D006801:Humans; D008027:Light; D010775:Photic Stimulation / Q000379:methods; D011581:Psychological Tests; D012684:Sensory Thresholds; D013028:Space Perception