Fig. 4.

Model predictions and empirical measurements on the relationship between behavioural sensitivity and the level of suppression. The left column shows proscriptive integration model simulation results that manipulated the inhibitory gain in the model: more suppression leads to higher model sensitivity for incongruent cues (top row), but not congruent (middle row) or single cues (bottom). The right column shows the results of MRS measurements that quantified GABA around V3B/KO and related this to between-subject differences in behavioural sensitivity. Consistent with the model simulations, we found a significant positive correlation between human observers’ GABA concentration in the voxel centred on V3B/KO and perceptual sensitivity to incongruent-cue stimuli (n = 18, Pearson’s correlation r = 0.75, P = 3.8e⁻⁴, CI_95% = [0.40, 0.91]; confidence intervals are corrected for multiple comparisons; top right), but not to congruent- or single-cue stimuli (n = 18, congruent: Pearson’s r = 0.10, P = 0.68, middle right; disparity: Pearson’s r = 0.03, P = 0.92; texture: Pearson’s r = 0.05, P = 0.85; bottom right). Asterisks highlight significant differences P < 0.05. Each datum represents measures from one participant; bivariate outliers are shown as empty circles