Human Auditory and Adjacent Nonauditory Cerebral Cortices Are Hypermetabolic in Tinnitus as Measured by Functional Near-Infrared Spectroscopy (fNIRS)

Figure 6

Bar graph of quantified oxy-hemoglobin (HbO) concentration with standard errors in region of interest (ROI; (a)) and nonregion of interest (non-ROI; (b)) under conditions of silence (interstimulus rest; ISR) and stimulation (750 Hz, 8000 Hz, and broadband noise; BBN) between tinnitus (dark bars) and control (gray bars). The unit of concentration is micromolar (μM). Standard errors of the mean were calculated using the equation: with = sample standard deviation; = the number of values. Note the maintenance of HbO concentration in ROI (a) and the significant increase in non-ROI (b) during ISR in the tinnitus group as compared to control ( relative to tinnitus versus controls). Under conditions of stimulation, only BBN suppressed previously maintained HbO levels in tinnitus ROI (a), while all forms of auditory stimulation suppressed increased HbO during ISR in non-ROI ( relative to ISR in tinnitus). Under conditions of stimulation or rest, only the ROI (a) showed a difference between ISR and all forms of auditory stimulation ( relative to control ISR) and only during ISR significant differences were found between tinnitus and control; . Error bars represent average responses from 4–18 seconds recorded from all conditions across all groups.

(a)

(b)