Figure 7. Degraded speech perception performance is predicted by intra-regional activations and inter-regional connectivity.

(A) BS, A1, and IFG activity and their inter-regional interactions (pooled across all interference conditions) account for 81% of the variance (adj-R²) in behavioral QuickSIN scores. Cortico-collicular (BS-A1) and cortico-cortical (A1-IFG) neural interactions are also strong predictors of perception. Lines connecting ROIs show pairwise source terms that interacted in the GLME (solid lines, significant; dotted lines, n.s.) Statistical flags within ROIs reflect the main effect of that source in the GLME. (B) QuickSIN scores for “good” (n=6) vs. “poor” (n=5) SIN performers (median split of scores). Despite all having normal hearing, certain listeners obtain better (~1 dB lower) SIN thresholds indicating individual differences in SIN perception. (C) Functional connectivity in the brainstem-cortical speech network that differentiates “good” vs. “poor” SIN performers. Values represent the magnitude of connectivity computed via phase transfer entropy (Lobier et al., 2014). Statistical flags represent group contrasts at each connection. Feedforward (BS→A1) and feedback (IFG→A1) towards primary auditory cortex (A1) is stronger in “good” relative to “poor” perceivers. ^†p < 0.1; *p < 0.05; **p ≤ 0.01