Region-of-interest (ROI) analyses. Percent signal change during the ultra-fast and moderately fast listening conditions plotted against individual behavioral performance during application of ultra-fast test materials – as determined prior to scanning – within three selected ROIs, i.e., right-hemispheric primary visual cortex (V1), left-hemispheric fusiform gyrus (FG), and ipsilateral inferior frontal gyrus (IFG). (Note, because of “ceiling effects”, the behavioral data bound to moderately fast utterances have not been included). Regression lines, correlation coefficients, and significance levels refer to the performance of the blind group during ultra-fast (dark blue lines or values, respectively) and moderately fast conditions (light blue; for further data see Additional file 13). As concerns the blind group, the three early-blind subjects are indicated by an extra-label (yellow values).