Reversing Synchronized Brain Circuits Using Targeted Auditory-Somatosensory Stimulation to Treat Phantom Percepts: A Randomized Clinical Trial.

Importance: Animal models have shown altered dorsal cochlear nucleus circuitry in animals that develop tinnitus; however, precise treatment using bisensory (auditory and somatosensory) stimuli can reverse altered neural patterns and lessen tinnitus. Objective: To confirm and extend the findings of a pilot study, which suggested an increased efficacy of bisensory stimulation, to a clinical trial with a greater duration and greater number of participants. Design, Setting, and Participants: This double-blind, crossover, single-center randomized clinical trial was conducted from March 2019, with a 3-month follow-up per participant ending in July 2022. Eligible adults were recruited from the University of Michigan Health System in Ann Arbor, Michigan. Eligibility criteria included bothersome tinnitus (Tinnitus Functional Index [TFI] score, ≥17 points), somatic tinnitus, normal to moderate hearing loss, and no other tinnitus treatments in the 6 months prior to the trial. Included participants were randomized to either treatment group 1, which received active (bisensory) treatment, or group 2, which received the control (auditory-only) treatment. Results were analyzed using intent-to-treat (ITT) and per protocol (PP) populations. Intervention: Precisely timed bisensory (combined auditory and somatosensory) treatment was delivered through a portable, custom, take-home device that was provided to each participant for daily, at-home treatments. Group 1 participants received 30 minutes per day of the bisensory treatment for 6 weeks, followed by a 6-week washout phase, and then 30 minutes per day of the auditory-only treatment followed by a second 6-week washout phase. Group 2 participants received the auditory-only treatment first, followed by a washout phase, and then the bisensory treatment followed by a second washout phase. Main Outcomes and Measures: Primary end points were changes in TFI score and tinnitus loudness level from baseline through week 6 and week 12. Results: Of 337 screened individuals, 99 (mean [SD] age, 47 [12.7] years; 59 males [60%]; 85 with non-Hispanic White [86%] race and ethnicity) were enrolled into the study and randomized to treatment group 1 (n = 49) or group 2 (n = 50). The active but not the control treatment resulted in clinically significant decreases in TFI scores at week 6 of phase 1 (ITT population: -12.0 [95% CI, -16.9 to -7.9] points; P < .001; PP population: -13.2 [95% CI, -16.0 to -10.5] points; P < .001). Decreases in tinnitus loudness level were greater than 6 dB sensation level (SL; >half as loud) at week 6 for the bisensory treatment group, with little effect for the auditory-only treatment control group at week 6 of phase 1 (ITT population: -5.8 [95% CI, -9.5 to -2.2] dB; P = .08; PP population: -7.2 [95% CI, -11.4 to -3.1] dB; P = .03), and up to 11 dB SL at week 12 of phase 2 (ITT population: -10.9 [95% CI, -15.2 to -6.5] dB; P = .001; PP population: -14.1 [95% CI, -18.4 to -9.8] dB; P < .001). Decreased tinnitus loudness level and TFI scores extended into the washout phase, indicating a prolonged treatment effect. Conclusions and Relevance: This trial found that precisely timed bisensory treatment using stimuli and timing developed in a validated animal model was effective for adults with somatic tinnitus. Prolonged reduction in tinnitus symptoms can result from using an extended treatment duration. Trial Registration: ClinicalTrials.gov Identifier: NCT03621735.

Bimodal Auditory Electrical Stimulation for the Treatment of Tinnitus: Preclinical and Clinical Studies.

Tinnitus, or the phantom perception of sound, arises from pathological neural activity. Neurophysiological research has shown increased spontaneous firing rates and synchronization along the auditory pathway correlate strongly with behavioral measures of tinnitus. Auditory neurons are plastic, enabling external stimuli to be utilized to elicit long-term changes to spontaneous firing and synchrony. Pathological plasticity can thus be reversed using bimodal auditory plus nonauditory stimulation to reduce tinnitus. This chapter discusses preclinical and clinical evidence for efficacy of bimodal stimulation treatments of tinnitus, with highlights on sham-controlled, double-blinded clinical trials. The results from these studies have shown some efficacy in reducing the severity of tinnitus, based on subjective and objective outcome measures including tinnitus questionnaires and psychophysical tinnitus measurements. While results of some studies have been positive, the degree of benefit and the populations that respond to treatment vary across the studies. Directions and implications of future studies are discussed.

Exploration of Head Related Transfer Function and Environmental Sounds as a Means to Improve Auditory Scanning for Children Requiring Augmentative and Alternative Communication.

Many individuals who require augmentative and alternative communication (AAC) cannot directly select items on computer-based displays. Individuals who also have visual impairments may need to rely on sequential announcement of array choices in auditory scanning. The method is challenging and there is a lack of research to improve this access method. Two potential solutions were tested: using environmental sounds to represent items (e.g., the sound of a clock ticking for a clock) and providing spatial cues regarding the organization of items (e.g., presenting auditory information and altering temporal and spectral features so that sounds are heard as left, right, up, or down relative to each other). The individual and combined effects of these cues were tested with typically developing 3-year-old children. After collecting and validating a set of stimulus sounds, 24 children participated in a within-subjects design with four conditions (spoken word label only, associated environmental sound only, spoken word label with spatial information, associated environmental sound plus spatial information). Dependent measures included reaction time (RT) and accuracy. Results indicated that the use of sounds without any spatial cues revealed slower RTs than any other conditions. Also, sounds regardless of spatial cues led to less accurate scores than words.

High- and Low-Frequency Decrement Contribution to Spectral Enhancement.

PURPOSE: The relative benefit of a single, flanking, high- or low-frequency decrement was assessed to better understand properties of spectral enhancement that may aid in algorithm design. METHOD: Detection thresholds were measured for intensity increments applied to a narrow target band of frequencies embedded in a broadband signal while 400-Hz-wide, 9- or 12-dB-deep intensity decrements were placed above, below, or on both sides of the target band. A mono condition with no decrements was used as a control. Eight participants with normal hearing and 8 participants with hearing impairment took part in this experiment. RESULTS: Performance improved in the presence of decrements for both groups and was equivalent for both high- or low-frequency decrements. Comparison with individually measured auditory filters revealed that participants with normal hearing made use of energy cues available within these filters, whereas some participants with hearing impairment, despite improved increment detection, underutilized this information. CONCLUSION: Inclusion of a single, adjacent, high- or low-frequency decrement improved increment detection but not to the same extent as when decrements flanked both sides.