Boynton GM, Demb JB, Glover GH, and Heeger DJ, Neural Basis of Contrast Discrimination, Vision Research, 39:257-269, 1999.
Abstract: Psychophysical contrast increment thresholds were compared with neuronal responses, measured using functional magnetic resonance imaging (fMRI), to test the hypothesis that pattern discrimination judgments are limited by neuronal signals in early visual cortical areas. FMRI was used to measure human brain activity as a function of stimulus contrast, in each of several identifiable visual cortical areas. Contrast increment thresholds were measured for the same stimuli across a range of baseline contrasts. FMRI responses in visual areas V1, V2d, and V3d were found to be consistent with the psychophysical judgments, i.e., a contrast increment was detected when the fMRI responses in each of these brain areas increased by a criterion amount. Thus, the pooled activity of large numbers of neurons can reasonably well predict behavioral performance.