fNIRS Analysis and Results.

(a) Photograph of the optode array on one participant and corresponding optode positions registered to an atlas brain. (b) Representative examples of the effect of two key signal processing stages: (upper panel) wavelet filtering successfully removes spikes from the optical signal, while leaving portions of the signal that are not contaminated by motion artifacts unchanged; (lower panel) for a hemodynamic response function showing substantial contamination by physiological noise, the hemodynamic signal separation technique successfully recovers a plausible functional response, plus an estimate of the systemic interference. (c) Group-average patterns of activation (normalized mean change in HbO between 6 and 20 s post onset) across the array for each stimulation condition. Channels within the predefined ROI (Ch# 6, 8, 10–13, 15, and 17) are highlighted. (d) Group-average hemodynamic response functions within the ROI for each stimulation condition. The shaded gray area shows the stimulation period. (e) Mean beta weights from the GLM analysis. Error bars show ±1 standard error, corrected to account for the repeated-measures nature of the design [57]. Asterisks denote a statistically significant difference between the conditions indicated (* p <. 05; ** p <. 01; *** p <. 001; Bonferroni corrected). (f) Assessment of a possible relationship between the suppressive effect of synchronous sounds on the fNIRS response from visual cortex (Beta_V-ONLY—Beta_AV-SYNC) and a corresponding reduction in the accuracy of visual target detection (Accuracy_V-ONLY − Accuracy_AV-SYNC). While Pearson’s correlation suggested a significant linear relationship (r = .46, p = .023, two-tailed), this result could not be confirmed by a robust regression analysis (p = .136).