A key visual function known as contrast adaptation has been well studied and utilized to deduce the selectivity of the visual brain. In a recent study, researchers found a discrepancy between the effects of contrast adaptation on perception and the functional magnetic resonance imaging BOLD response adaptation, whereby psychophysically measured selectivity for adaptation to chromatic and achromatic stimuli was greater than that for adaptation as measured by BOLD signals. For a study, they sought to evaluate the neural effects of contrast adaptation using magnetoencephalography (MEG) recordings of neural responses to identical chromatic and achromatic adaptation circumstances to ascertain whether BOLD adaptation or MEG better reflects the reported perceptual effects.
Achromatic, L-M isolating, and S-cone isolating radial sinusoids were shown to participants before and after adjusting to each of the three contrast orientations. Two measures of the MEG response—the overall response amplitude and a novel time-resolved measure of the contrast response function—derived from a classification analysis in conjunction with multidimensional scaling—were used to assess adaptation-related changes in the neural response to a variety of stimulus contrast amplitudes.
Each case’s within-stimulus adaptation effects on the contrast response functions displayed a pattern of contrast-gain effects or effects that combined contrast-gain and response-gain. Cross-stimulus adaptation conditions demonstrated that, in early, ventral, and dorsal visual cortical regions were strongly stimulus selective, in line with the perceptual effects.
Reference: jov.arvojournals.org/article.aspx?articleid=2783653
