Cortical tinnitus evaluation using functional near-infrared spectroscopy

Functional near-infrared spectroscopy (fNIRS) estimates the cortical hemodynamic response induced by sound stimuli. fNIRS can be used to understand the symptomatology of tinnitus and consequently provide effective ways of evaluating and treating the symptom. Objective: Compare the changes in the oxy-hemoglobin and deoxy-hemoglobin concentration of individuals with and without tinnitus using auditory stimulation by fNIRS. Methods: A tinnitus group (n = 23) and a control group (n = 23) were evaluated by an auditory task for assessing sound-evoked auditory cortex activity. The fNIRS was composed of 20 channels arranged into 4x2 arrays over the frontal, temporal and parietal cortices. Then, a passive listening block-paradigm design was adopted with reoccurring blocks of tasks with 15 s interspersed with randomized silence periods between 15-25 s. Results: There was a significant difference in the condition (type of sound), region of interest (ROI) and channel. As well as significant interaction in group and condition, and group and channel. The Tinnitus Frequency decreased HbO levels, while other sounds (white noise - WN and 1KHZ) increased HbO levels. All conditions differed from each other, except 1KHz with Baseline (silence) in the control group. Regarding the channels, the frontal channels (1, 3, and 11) differed in the tinnitus group, while in the control group a difference was observed in the channels of the frontal, temporal and parietal regions. Conclusion: The type of sound presented, and brain region influenced the variations in HbO levels, but there was no difference between tinnitus and control participants. The tinnitus loudness, annoyance, and severity showed a weak correlation with variations in HbO levels.