Fig 1.
Configuration of channels (numbers) with identified detectors (red circles) and emitters (blue circles) over the right and left cortical hemispheres. There are 8 detectors and 7 sources resulting in 22 channels per hemisphere. Interconnected blocks with the solid yellow line represent the region of interest (ROI; primary auditory regions; channels 13, 15, 23, and 29). Interconnected blocks with white line represent the n-1 non-region of interest (non-ROI; (channels 3, 5, 34, and 39)). T3 and T4 are the reference points of the International 10–20 System [16].
Table 1.
Corresponding Brodmann Areas and cortical regions for each channel.
Fig 2.
Schematic of block auditory testing paradigm. Participants passively listened to randomly selected pure tones (750 or 8000Hz) or broadband noise (BBN) for 18 seconds each, immediately followed or preceded by an inter-stimulus rest period (ISR) consisting of silence/absence of auditory stimulation for 18 seconds, for a total experiment run time of 18 minutes. A 60-second pre- and a separate 60-second post-stimulation paradigm baseline periods of silence were recorded from which the RSFC was derived. Black downward arrow depicts the four second wait period to allow activation levels to return to baseline.
Fig 3.
Demonstration of high and low correlated channels for participants during auditory pre-stimulation.
The HbO concentration data (μM) of tinnitus participant number 10 in the pre-stimulation condition of (a) two highly correlated channels (channels 13 and 10; r = 0.952) and (b) two lowly correlated channels (channels 13 and 25; r = -0.089). (c) Mean hemodynamic response for channels 13 and 10 for the tinnitus and control groups with the standard deviation at select time points.
Fig 4.
ICC analysis for reproducibility.
(a) Recordings from two channels (same as Fig 3) with arrows depicting examples of the snippets used for ICC analysis. The green arrow represents snippets beginning at the start and the black arrow represents snippets terminating at the end. (b) Mean ICC results of all participants for all connectivity pairs and for connectivity pairs involving the ROI are shown. Top panel depicts results of the beginning snippets and the bottom panel depicts results for the ending snippets. Black horizontal lines indicate the thresholds for the grading scale with abbreviations in top left bar graph serving as a legend (P = poor, F = fair, G = good, and E = excellent).”
Fig 5.
Pre-stimulation and change in ROI connectivity.
Mean connections of each channel to the four pooled ROI. Black lines separate the channels into lobes. Labels in (a) serve as a legend (F = frontal, T = temporal, P = parietal, O = occipital). The mean values in the pre-stimulation condition for (a) controls and (b) tinnitus. The mean change from pre- to post-stimulation in (c) controls and (d) tinnitus. Number of statistically significant connections (e) and average connectivity (f) to the ROI and to the “n-1” non-ROI for the depicted conditions for both control and tinnitus participants. In the pre-stimulation conditions ((a) and (b)), each hemisphere contains two values equivalent to one at the locations of the ROI since the connectivity of a channel to itself results in a connection of one. In the change plots ((c) and (d)), the areas corresponding to the ROI show a connectivity of 0. Asterisks denote significance level, one (*): p<0.05; two (**): p<0.01; three (***): p<0.001.
Fig 6.
Average connectivity of ROI to the various cortical regions under multiple conditions.
Y-axis indicates which type of participant and which condition (change refers to post-stimulation minus pre-stimulation). The X-axis indicates the measured region. Warmer colors in the left panel denote high connectivity, and in the right panel they denote increases in connectivity. Cooler colors in the left panel denote low connectivity and in the right panel they denote decreases in connectivity. To create the right panel, the numbers in the left panel underwent Fisher Transformation, were subsequently subtracted, and then transformed back to Pearson correlation coefficients. F = frontal, FT = fronto-temporal, FP = fronto-parietal, TP = temporo-parietal, T = temporal, P = parietal, OP = occipito-parietal, OT = occipito-temporal O = occipital.
Table 2.
Statistically significant differences in regional connectivity.
Fig 7.
Change from pre- to post-stimulation of connections involving all measured channels.
The top-left of the plot represents controls and the bottom right represents tinnitus, with the shaded boxes in middle diagonal separating the two groups. Size of each circle represents the percentage of connections that involved the two matching regions (legend on the left side of the plot for reference). The color of the circle indicates the average change of those connections (warmer colors are increased connectivity; cooler colors are decreased connectivity). The hashed region of the circle indicates the proportion of those connections that involved regions on opposite hemispheres (bilateral connections; unshaded area is unilateral only). Connections shown are one standard deviation above the mean in absolute magnitude (n = 170 in controls, n = 162 in tinnitus).
Table 3.
Connectivity between tinnitus and controls across specific cortical brain regions.