Abstract
PURPOSE: An array of luminance-defined rectangles (“Mondrians”) changing shape and contrast irregularly over time induce strong interocular suppression 1. To investigate the nature and locus of neural events underlying this potent stimulus, we measured the influence of channel-specific Mondrian adaptation on binocular rivalry.
METHODS: Observers dichoptically viewed orthogonally oriented gratings, one defined by chromatic contrast and the other by luminance contrast. A tracking procedure was used to measure durations of exclusive visibility of each rival grating during 30-second viewing periods. Immediately preceding some tracking periods, observers adapted for one minute to a dynamic Mondrian display tailored to favor activation of magnocellular (MC) or parvocellular (PC) channels. MC-biased adaptation employed dynamic, achromatic Mondrian patches each of which was one of two gray values (equal-energy-spectrum ‘whites’); PC-biased adaptation employed dynamic patches composed of two equiluminant chromaticities. Adaptation involved: 1) binocular exposure to achromatic or to equiluminant Mondrian patches, 2) same eye exposure in which achromatic (or equiluminant) Mondrian patches were presented only to the eye that viewed the luminance (or the equiluminant) grating during rivalry, 3) different eye exposure in which achromatic (or equiluminant) Mondrian patches were presented only to the eye that viewed the equiluminant (or luminance) grating during rivalry, or 4) exposure of both eyes to an uncontoured, mean luminance field (baseline).
RESULT AND CONCLUSION: Relative to baseline rivalry (no Mondrian adaptation), adaptation to achromatic Mondrians biased rivalry dominance in favor of the equiluminant grating; adaptation to equiluminant Mondrians biased dominance in favor of the luminance grating. This channel-specific adaptation effect was observed only in same-eye conditions, meaning that adaptation did not transfer interocularly. Evidently adaptation to dynamic Mondrians, whether targeting MC or PC channels, transpires at early stages of visual processing prior to binocular integration, perhaps contributing to their capacity to induce potent interocular suppression.
Tsuchiya & Koch (2005) Nature Neurosci.