Individual differences in functional connectivity from the auditory cortex increase in deafness.

A. Significant differences in the inter-individual variability of the AC FC values between deaf and hearing groups (p < .05, corrected for multiple comparisons) are presented on inflated cortical hemispheres. These are found in the left STG (including the auditory association cortex), bilateral IFG (including part of Broca’s area), paracentral lobule and the medial superior frontal gyrus, along with the dorsal visual stream. B. The ratio of the within-group variability of AC FC between the deaf and hearing groups is presented (within areas showing variability between the groups. Most areas showing change in variability between the groups display larger individual differences in deafness, including the left auditory cortex and Broca’s area. C. Differences in native signing deaf subgroup and hearing group in their interindividual variability of the auditory cortex FC values (p < .05, corrected for multiple comparisons) replicate the effect of the mixed deaf group (panel A). D. The ratio of the variability of auditory cortex FC between the native signing deaf and hearing (within areas showing variability difference between the groups). No area showed increased individual differences for the hearing group. Native-signing deaf participants have higher individual differences, despite having no delay in language acquisition. Anatomical marks: SMA = Supplementary Motor Area; IFG = Inferior Frontal Gyrus; STG = Superior Temporal Gyrus. The regions outlined in white show some of the language-sensitive regions identified by Fedorenko et al. (2010), including the IFG, the anterior and the posterior temporal parcellations.

Individual variability in deafness is related to brain plasticity. A. ANOVA main effect showing which regions are reorganized in deafness (group difference between the deaf and hearing in AC FC; p < .05, corrected for multiple comparisons). B. Direct comparison of AC FC between deaf and hearing groups (p < .05, corrected for multiple comparisons) broadly replicated previous findings, showing broad reorganization in deafness. C. Correlation between regions that show increased individual differences (Figure 1A) with the regions that show reorganization in deafness (panel A) is shown as a red line (r = 0.3) compared with a spatial permutation test (distribution in black); the brain patterns of FC reorganization and of increased individual differences are correlated, suggesting increased individual differences characterizes plasticity in deafness. D. The ratio of the intra-group variability of AC FC between the deaf and hearing groups is shown within areas showing reorganization group-level changes to FC). No area showed increased individual differences for the hearing group. Among the areas showing change in AC FC in deafness, individual differences are overall increased or stable.

Anatomical marks: SMA = Supplementary Motor Area; IFG = Inferior Frontal Gyrus; STG = Superior Temporal Gyrus.

Auditory cortex FC variability comparison between delayed signing deaf and native signing deaf individuals shows an effect of delayed language acquisition on individual differences. A. Differences in delayed and native signing deaf subgroups in their interindividual variability of the auditory cortex FC values (p < .05, corrected for multiple comparisons) show changes to individual differences in several left-hemispheric regions (no effects are found in the right hemisphere). B. The ratio of the variability of auditory cortex FC between the delayed signing and native signing deaf (within areas showing variability between the subgroups in the left hemisphere) shows that individual differences increase due to delayed language acquisition in the inferior frontal junction and orbitofrontal cortex, but that early-onset sign language exposure stabilizes connectivity between the auditory cortex and the supramarginal gyrus and dorsal medial visual cortex (cuneus and precuneus).

Anatomical marks: PoS = Parietooccipital Sulcus; IFJ = Inferior Frontal Junction; SMG = Supramarginal Gyrus.

Participants’ demographic information.

Auditory cortex FC variability difference between delayed signing deaf and hearing individuals. A. Differences in delayed signing deaf subgroup and hearing group in their interindividual variability of the auditory cortex FC values (p < .05, corrected for multiple comparisons). B. The ratio of the variability of auditory cortex FC between the delayed signing deaf and hearing (within areas showing variability difference between the groups) replicates the effects seen in when comparing the hearing and mixed deaf group. No significant increase in variability were found for the hearing group.

Anatomical marks: SMA = Supplementary Motor Area; IFG = Inferior Frontal Gyrus; STG = Superior Temporal Gyrus.

MNI coordinates for the FC variability analyses.

Age of sign language acquisition for the delayed signing deaf group.