Auditory localization by subjects with unilateral tinnitus

What Do Mismatch Negativity (MMN) Responses Tell Us About Tinnitus?

Due to the heterogeneous causes, symptoms and associated comorbidities with tinnitus, there remains an unmet need for a clear biomarker of tinnitus presence. Previous research has suggested a "final pathway" of tinnitus presence, which occurs regardless of the specific mechanisms that resulted in alterations of auditory predictions and, eventually, tinnitus perception. Predictive inference mechanisms have been proposed as the possible basis for this final unifying pathway. A commonly used measure of prediction violation is mismatch negativity (MMN), an electrical potential generated in response to most stimuli that violate an established regularity. This narrative review discusses 16 studies comparing MMN between tinnitus and non-tinnitus groups. Methods varied considerably, including type of deviant, type of paradigm and carrier frequency. A minority of studies matched groups for age, sex and hearing, with few measuring hyperacusis. Frequency deviants were the most widely studied; at frequencies remote from tinnitus, MMN was consistently smaller in tinnitus groups, though hyperacusis or altered distress or attention could not be ruled out as explanatory factors. Few studies have used tinnitus-related frequencies; these showed larger MMN to upward frequency deviants above the tinnitus frequency, and larger MMN to upward intensity deviants at or close to the tinnitus frequency. However, the latter appears a correlate of hyperacusis rather than tinnitus, and tinnitus groups without hyperacusis instead show larger MMN to downward intensity deviants than controls. Other factors that affect MMN amplitudes included age, attention, and the specific characteristics of the range of stimuli across a particular experiment paradigm. As such, MMN cannot presently be considered a specific biomarker of tinnitus, but showed potential to objectively characterise a number of auditory processing traits relevant to tinnitus and hyperacusis.

A scoping review of the spatial perception of tinnitus and a guideline for the minimum reporting of tinnitus location

Tinnitus spatial localisation is an essential attribute of tinnitus perception and how it is separated from other ongoing neural activity. A scoping review was undertaken to determine how tinnitus localisation is reported, the role of the perceived spatial location of tinnitus on neurophysiology and if sound presented spatially can change tinnitus perception. Following reading of the full-text articles and including articles from reference lists, 46 articles were included for review. Six themes emerged from the results. 1. Where tinnitus was localised. 2. The effects of tinnitus on localisation. 3. The mechanisms underpinning tinnitus spatial location. 4. Masking. 5. Auditory training. 6. Multisensory training and virtual reality (VR). Tinnitus is much more complex than the often-used description of 'ringing in the ears'. Tinnitus can be heard anywhere in and around the head. Spatial sound presentation and perceptual training approaches may disrupt spatial selective attention to tinnitus and appear as changes in some of the neural networks involved in sound localisation. Where tinnitus is heard is a critical aspect of its perception, but its report, even in studies purporting to study localisation, is too general. A matrix for standardised minimum reporting of tinnitus location is recommended.

The interference of tinnitus on sound localization was related to the type of stimulus

Spatial processing is a major cognitive function of hearing. Sound source localization is an intuitive evaluation of spatial hearing. Current evidence of the effect of tinnitus on sound source localization remains limited. The present study aimed to investigate whether tinnitus affects the ability to localize sound in participants with normal hearing and whether the effect is related to the type of stimulus. Overall, 40 participants with tinnitus and another 40 control participants without tinnitus were evaluated. The sound source discrimination tasks were performed on the horizontal plane. Pure tone (PT, with single frequency) and monosyllable (MS, with spectrum information) were used as stimuli. The root-mean-square error (RMSE) score was calculated as the mean target response difference. When the stimuli were PTs, the RMSE scores of the control and tinnitus group were 11.77 ± 2.57° and 13.97 ± 4.18°, respectively. The control group performed significantly better than did the tinnitus group (t = 2.841, p = 0.006). When the stimuli were MS, the RMSE scores of the control and tinnitus groups were 7.12 ± 2.29° and 7.90 ± 2.33°, respectively. There was no significant difference between the two groups (t = 1.501, p = 0.137). Neither the effect of unilateral or bilateral tinnitus (PT: t = 0.763, p = 0.450; MS: t = 1.760, p = 0.086) nor the effect of tinnitus side (left/right, PT: t = 0.389, p = 0.703; MS: t = 1.407, p = 0.179) on sound localization ability were determined. The sound source localization ability gradually deteriorated with an increase in age (PT: r² = 0.153, p < 0.001; MS: r² = 0.516, p = 0.043). In conclusion, tinnitus interfered with the ability to localize PTs, but the ability to localize MS was not affected. Therefore, the interference of tinnitus in localizing sound sources is related to the type of stimulus.

Effect of tinnitus on sound localization ability in patients with normal hearing

OBJECTIVES

To determine whether tinnitus negatively impacts the accuracy of sound source localization in participants with normal hearing.

METHODS

Seventy-five participants with tinnitus and 74 without tinnitus were enrolled in this study. The accuracy of sound source discrimination on the horizontal plane was compared between the two participant groups. The test equipment consisted of 37 loudspeakers arranged in a 180° arc facing forward with 5° intervals between them. The stimuli were pure tones of 0.25, 0.5, 1, 2, 4, and 8kHz at 50dB SPL. The stimuli were divided into three groups: low frequency (LF: 0.25, 0.5, and 1kHz), 2kHz, and high frequency (HF: 4 and 8kHz) stimuli.

RESULTS

The Root Mean Square Error (RMSE) score of all the stimuli in the tinnitus group was significantly higher than that in the control group (13.45±3.34 vs. 11.44±2.56, p=4.115, t<0.001). The RMSE scores at LF, 2kHz, and HF were significantly higher in the tinnitus group than those in the control group (LF: 11.66±3.62 vs. 10.04±3.13, t=2.918, p=0.004; 2kHz: 16.63±5.45 vs. 14.43±4.52, t=2.690, p=0.008; HF: 13.42±4.74 vs. 11.14 ±3.68, t=3.292, p=0.001). Thus, the accuracy of sound source discrimination in participants with tinnitus was significantly worse than that in those without tinnitus, despite the stimuli frequency. There was no difference in the ability to localize the sound of the matched frequency and other frequencies (12.86±6.29 vs. 13.87±3.14, t=1.204, p=0.236). Additionally, there was no correlation observed between the loudness of tinnitus and RMSE scores (r=0.096, p=0.434), and the Tinnitus Handicap Inventory (THI) and RMSE scores (r=-0.056, p=0.648).

CONCLUSIONS

Our present data suggest that tinnitus negatively impacted sound source localization accuracy, even when participants had normal hearing. The matched pitch and loudness and the impact of tinnitus on patients' daily lives were not related to the sound source localization ability.

LEVEL OF EVIDENCE: 4

The Relationship Between Tinnitus Pitch, Audiogram Edge Frequency, and Auditory Stream Segregation Abilities in Individuals With Tinnitus

Purpose Around 80%-93% of the individuals with tinnitus have hearing loss. Researchers have found that tinnitus pitch was related to the frequencies of hearing loss, but unclear about the relationship between tinnitus pitch and audiometry edge frequency. The comorbidity of tinnitus and speech perception in noise problems had also been reported, but the relationship between tinnitus pitch and speech perception in noise had seldom been investigated. This study was designed to estimate the relationship between tinnitus pitch, audiogram edge frequency, and speech perception in noise. The speech perception in noise was measured using auditory stream segregation paradigm. Method Thirteen individuals with bilateral mild-to-severe tonal tinnitus and minimal-to-mild cochlear hearing loss were selected. Thirteen individuals with hearing loss without tinnitus were also selected. The audiogram of each participant with tinnitus was matched with that of the participant without tinnitus. Tinnitus pitch of the participants with tinnitus was measured and compared with audiogram edge frequency. The stream segregation thresholds were calculated at the participants' admitted tinnitus pitch and one octave below the tinnitus pitch. The stream segregation thresholds were estimated at fission and fusion boundary using pure-tone stimuli in ABA paradigm. Results High correlation between tinnitus pitch and audiogram edge frequency was noted. Overall stream segregation thresholds were higher for individuals with tinnitus. Higher thresholds indicated poorer stream segregation abilities. Within tinnitus participants, the thresholds were significantly lesser at frequency corresponding to admitted tinnitus pitch than at one octave below the tinnitus pitch. Conclusions The information from this study may be helpful in educating the patients about the relationship between hearing loss and tinnitus. The findings may also account for speech-perception-in-noise difficulties often reported by the individuals with tinnitus.

The impact of tinnitus distress on cognition

Tinnitus is the chronic perception of a phantom sound with different levels of related distress. Past research has elucidated interactions of tinnitus distress with audiological, affective and further clinical variables. The influence of tinnitus distress on cognition is underinvestigated. Our study aims at investigating specific influences of tinnitus distress and further associated predictors on cognition in a cohort of n = 146 out-ward clinical tinnitus patients. Age, educational level, hearing loss, Tinnitus Questionnaire (TQ) score, tinnitus duration, speech in noise (SIN), stress, anxiety and depression, and psychological well-being were included as predictors of a machine learning regression approach (elastic net) in three models with scores of a multiple choice vocabulary test (MWT-B), or two trail-making tests (TMT-A and TMT-B), as dependent variables. TQ scores predicted lower MWT-B scores and higher TMT-B test completion time. Stress, emotional, and psychological variables were not found to be relevant predictors in all models with the exception of small positive influences of SIN and depression on TMT-B. Effect sizes were small to medium for all models and predictors. Results are indicative of specific influence of tinnitus distress on cognitive performance, especially on general or crystallized intelligence and executive functions. More research is needed at the delicate intersection of tinnitus distress and cognitive skills needed in daily functioning.

Sensitivity to Interaural Phase in Older Hearing-Impaired Listeners Correlates With Nonauditory Trail Making Scores and With a Spatial Auditory Task of Unrelated Peripheral Origin

Interaural phase difference (IPD) discrimination upper frequency limits and just-noticeable differences (JNDs), interaural level difference (ILD) JNDs, and diotic intensity JNDs were measured for 20 older hearing-impaired listeners with matched moderate sloping to severe sensorineural hearing losses. The JNDs were measured using tone stimuli at 500 Hz. In addition to these auditory tests, the participants completed a cognitive test (Trail Making Test). Significant performance improvements in IPD discrimination were observed across test sessions. Strong correlations were found between IPD and ILD discrimination performance. Very strong correlations were observed between IPD discrimination and Trail Making performance as well as strong correlations between ILD discrimination and Trail Making performance. These relationships indicate that interindividual variability in IPD discrimination performance did not exclusively reflect deficits specific to any auditory processing, including early auditory processing of temporal information. The observed relationships between spatial audition and cognition may instead be attributable to a modality-general spatial processing deficit and/or individual differences in global processing speed.

Comparison of Amplitude Modulated Sounds and Pure Tones at the Tinnitus Frequency: Residual Tinnitus Suppression and Stimulus Evaluation

Recent studies have compared tinnitus suppression, or residual inhibition, between amplitude- and frequency-modulated (AM) sounds and noises or pure tones (PT). Results are indicative, yet inconclusive, of stronger tinnitus suppression of modulated sounds especially near the tinnitus frequency. Systematic comparison of AM sounds at the tinnitus frequency has not yet been studied in depth. The current study therefore aims at further advancing this line of research by contrasting tinnitus suppression profiles of AM and PT sounds at the matched tinnitus frequency (i.e., 10 and 40 Hz AM vs. PT). Participants with chronic, tonal tinnitus (n = 29) underwent comprehensive psychometric, audiometric, tinnitus matching, and acoustic stimulation procedures. Stimuli were presented for 3 minutes in two loudness regimes (60 dB sensation level [SL], minimum masking level [MML] + 6 dB, control sound: SL -6 dB) and amplitude modulated with 0, 10, or 40 Hz. Tinnitus loudness suppression was measured after the stimulation every 30 seconds. In addition, stimuli were rated regarding their valence and arousal. Results demonstrate only trends for better tinnitus suppression for the 10 Hz modulation and presentation level of 60 dB SL compared with PT, whereas nonsignificant results are reported for 40 Hz and MML + 6 dB, respectively. Furthermore, the 10 Hz AM at 60 dB SL and the 40 Hz AM at MML + 6 dB (trend) stimuli were better tolerated as elicited by valence ratings. We conclude that 10 Hz AM sounds at the tinnitus frequency may be useful to further elucidate the phenomenon of residual inhibition.

10 Hz Amplitude Modulated Sounds Induce Short-Term Tinnitus Suppression

Objectives: Acoustic stimulation or sound therapy is proposed as a main treatment option for chronic subjective tinnitus. To further probe the field of acoustic stimulations for tinnitus therapy, this exploratory study compared 10 Hz amplitude modulated (AM) sounds (two pure tones, noise, music, and frequency modulated (FM) sounds) and unmodulated sounds (pure tone, noise) regarding their temporary suppression of tinnitus loudness. First, it was hypothesized that modulated sounds elicit larger temporary loudness suppression (residual inhibition) than unmodulated sounds. Second, with manipulation of stimulus loudness and duration of the modulated sounds weaker or stronger effects of loudness suppression were expected, respectively. Methods: We recruited 29 participants with chronic tonal tinnitus from the multidisciplinary Tinnitus Clinic of the University of Regensburg. Participants underwent audiometric, psychometric and tinnitus pitch matching assessments followed by an acoustic stimulation experiment with a tinnitus loudness growth paradigm. In a first block participants were stimulated with all of the sounds for 3 min each and rated their subjective tinnitus loudness to the pre-stimulus loudness every 30 s after stimulus offset. The same procedure was deployed in the second block with the pure tone AM stimuli matched to the tinnitus frequency, manipulated in length (6 min), and loudness (reduced by 30 dB and linear fade out). Repeated measures mixed model analyses of variance (ANOVA) were calculated to assess differences in loudness growth between the stimuli for each block separately. Results: First, we found that all sounds elicit a short-term suppression of tinnitus loudness (seconds to minutes) with strongest suppression right after stimulus offset [F_{(6, 1331)} = 3.74, p < 0.01]. Second, similar to previous findings we found that AM sounds near the tinnitus frequency produce significantly stronger tinnitus loudness suppression than noise [vs. Pink noise: t₍₂₇₎ = -4.22, p < 0.0001]. Finally, variants of the AM sound matched to the tinnitus frequency reduced in sound level resulted in less suppression while there was no significant difference observed for a longer stimulation duration. Moreover, feasibility of the overall procedure could be confirmed as scores of both tinnitus loudness and questionnaires were lower after the experiment [tinnitus loudness: t₍₂₇₎ = 2.77, p < 0.01; Tinnitus Questionnaire: t₍₂₇₎ = 2.06, p < 0.05; Tinnitus Handicap Inventory: t₍₂₇₎ = 1.92, p = 0.065]. Conclusion: Taken together, these results imply that AM sounds, especially in or around the tinnitus frequency, may induce larger suppression than unmodulated sounds. Future studies should thus evaluate this approach in longitudinal studies and real life settings. Furthermore, the putative neural relation of these sound stimuli with a modulation rate in the EEG α band to the observed tinnitus suppression should be probed with respective neurophysiological methods.

Assessing Auditory Processing Deficits in Tinnitus and Hearing Impaired Patients with the Auditory Behavior Questionnaire

Background and Purpose: Auditory processing disorders (APD), tinnitus and hearing loss (HL) are typical issues reported by patients in audiologic clinics. These auditory impairments can be concomitant or mutually excluding. APD are not necessarily accompanied by significant HL, whereas many adults exhibit peripheral HL and typical cognitive deficits often associated with APD. Since HL, tinnitus and APD affects to several parts of the ascending auditory pathway from the periphery to the auditory cortex, there could be some interrelationship between them. For instance, tinnitus has been reported to degrade the auditory localization capacity. Tinnitus is believed to be triggered by deafferentation of normal peripheral input to the central auditory system. This peripheral deficit can be accompanied by HL or not, since a type of permanent cochlear damage (thus deafferentation) without an elevation of hearing thresholds might persist. Therefore, a combined study of APD, tinnitus and HL on the same cohort of patients can be audiologically relevant and worthy. Methods: Statistical analysis is applied to a cohort of 305 patients attending an audiology clinic in Madrid (Spain). This group of patients is first categorized in four subgroups, namely, HLTG (with tinnitus and HL), NHLTG (with tinnitus and without HL), HLNTG (with HL but no tinnitus), and NHLNTG (neither tinnitus nor HL). The statistical variables include Age, Average Auditory Threshold (ATT), for assessing HL, Tinnitus Handicap Inventory (THI), for measuring tinnitus, and a new 25-item Auditory Behavior Questionnaire (ABQ), for scoring APD. Factor analysis is applied to arrange these items into 4 subscales. The internal consistency reliability of this ABQ is confirmed by calculating Cronbach's coefficients α. The test-retest reliability is assessed by the intraclass correlation coefficients, ICC. Statistical techniques applied to the data set include descriptive analysis of variables and Spearman rank correlations (ρ) between them. Results: Overall reliability of ABQ is confirmed by an α value of 0.89 and by an ICC of 0.91. Regarding the internal consistency reliability, the four subscales prove a fairly good consistency with α coefficients above 0.7. Average values of statistical variables show significantly lower age of patients with tinnitus and no HL, which can provide a cue of noise overexposure of this segment of population. These younger patients show also decreased ABQ and similar THI in comparison with patients in the other subgroups. A strong correlation (ρ = 0.63) was found between AAT and Age for the HLNTG subgroup. For the HLTG subgroup, a moderate correlation (ρ = 0.44) was found between ABQ and THI. Conclusion: The utilized questionnaire (ABQ), together with AAT and THI, can help to study comorbid hearing impairments in patients regularly attending an audiological clinic.