Head hemodynamics and systemic responses during auditory stimulation

FIGURE 1. Experimental procedure. (a) Graphic of the stimulation process showing the 20 single stimuli (S1–S20) in each trial for each intensity and the 30‐s inter‐stimulus rest (b) graphic of the auditory stimulation protocol of Muñoz‐Caracuel et al. (2021) showing the 7 single stimuli (S1–S7) in each trial for each intensity and the rest period (14 ± 2 s) (c) fNIRS montage of the experiment showing the channels formed by the sources and detectors with a standard distance of 3 cm. The circles in red correspond to the location of light sources, the circles in blue to the light detectors. The lines in yellow correspond to the channels recording the right auditory cortex, in orange the left auditory cortex, and in green the visual channel.

FIGURE 2. Peripheral signals. (a) Amplitude changes for: electrodermal activity (EDA), heart rate (HR), absolute peripheral pulse (PPG), pulse transit time (PTT_1) in the five auditory intensities (70.9, 77.9, 84.5, 89.5, and 94.5 dBA), and PTT_2 for Muñoz‐Caracuel et al. (2021) PTT data. (b) Normalized power spectral density of the PPG signal for present (PPG_1), and Muñoz‐Caracuel (PPG_2) experiments. The selected windows for the statistical analysis are labeled in gray.

FIGURE 3. Median, mean values, and a rain cloud plot for the median values of the significant peripheral vascular measurements in the present experiment. (a) Absolute PPG signal by intensity. (b) LF/HF ratio for the PSD of the PPG signal by intensity. (c) LFnu for the PSD of the PPG signal by intensity. (d) PTT by intensity. Median: red, mean: blue. PPG, photoplethysmography; PSD, power spectral density; PTT, pulse transit time.

FIGURE 4. Median, mean values, and a rain cloud plot for the median values of the significant peripheral vascular measurements for Muñoz‐Caracuel data. (a) LF/HF ratio for the PSD of the PPG signal by intensity. (b) LFnu for the PSD of the PPG signal by intensity. (c) PTT by intensity. Median: red, mean: blue. PPG, photoplethysmography; PSD, power spectral density; PTT, pulse transit time.

FIGURE 5. Median, mean values, and a rain cloud plot for the median values of the significant peripheral cardiac measurements. (a) Heart rate (HR) signal for the effect of time window. (b) HR of the first time window by intensity. (c) Root mean square of successive differences (RMSSD) by intensity. Median: red, mean: blue.

FIGURE 6. Oxyhemoglobin changes. Average change in the oxyhemoglobin (ΔHbO) for the five auditory intensities (70.9, 77.9, 84.5, 89.5, and 94.5 dBA) in the three regions of interest (LAC, left auditory cortex; RAC, right auditory cortex; VSC, visual cortex). The selected windows for the statistical analysis are marked in gray. The sensitivity maps obtained with the fNIRS montage, as indicated by AtlasViewer software, are inserted.

FIGURE 7. Median, mean values, and a rain cloud plot of the median values for the significant oxyhemoglobin results. (a) ΔHbO for the first time window, with the collapse of the ROIS, for the five auditory stimuli, and (b) ΔHbO in the second time window, with the collapse of the ROIS, for the five auditory stimuli. Median: red, mean: blue.

FIGURE 8. Deoxyhemoglobin changes. Average change in the deoxyhemoglobin (ΔHbR) for the five auditory intensities (70.9, 77.9, 84.5, 89.5, and 94.5 dBA) in the three regions of interest (LAC, left auditory cortex; RAC, right auditory cortex; VSC, visual cortex). The selected windows for the statistical analysis are marked in gray. The sensitivity maps obtained with the fNIRS montage, as indicated by AtlasViewer software, are inserted.

FIGURE 9. Median, mean values, and a rain cloud plot of the median values for the significant deoxyhemoglobin results. (a) ΔHbR signal in the first time window with the five auditory intensities collapsed, for the three ROIS. (b) ΔHbR signal in the second time window with the five auditory intensities collapsed, for the three ROIS. (c) ΔHbR in the second time window, with the collapse of the ROIS, for the five auditory stimuli. (d) ΔHbR of the five auditory stimuli in the visual channel. Median: red, mean: blue.

FIGURE 10. Total hemoglobin changes. Average change in the total hemoglobin (ΔHbT) for the five auditory intensities (70.9, 77.9, 84.5, 89.5, and 94.5 dBA) in the three regions of interest (LAC, left auditory cortex; RAC, right auditory cortex; VSC, visual cortex). The selected windows for the statistical analysis are marked in gray. The sensitivity maps obtained with the fNIRS montage, as indicated by AtlasViewer software, are inserted.

FIGURE 11. Median, mean values, and a rain cloud plot of the median values for the significant total hemoglobin results. (a) ΔHbT in the first time windows with the collapse of the ROIS, for the five auditory stimuli, and (b) ΔHbT in the second time window, with the ROIS collapsed, for the five auditory stimuli. Median: red, mean: blue.

FIGURE 12. Changes in oxy, deoxyhemoglobin, and total hemoglobin after subtraction of the regressed visual channel activity. Hemodynamic response for ΔHbO, ΔHbR, and ΔHbT, for the five auditory intensities (70.9, 77.9, 84.5, 89.5, and 94.5 dBA), with the values of the regression of the visual channel activity vs auditory cortex activity subtracted from the fNIRS activity in left auditory cortex (LAC) and right auditory cortex (RAC). The sensitivity maps obtained with the fNIRS montage, as indicated by AtlasViewer software, are inserted.