Implementation and Long-Term Evaluation of a Hearing Aid Supported Tinnitus Treatment Using Notched Environmental Sounds.

Recent work has shown that sharp spectral edges in acoustic stimuli might have advantageous effects in the treatment of tonal tinnitus. In the course of this paper, we evaluate the long-term effects of spectrally notched hearing aids on the subjective tinnitus distress. By merging recent experimental work with a computational tinnitus model, we modified the commercially available behind-the-ear hearing aids so that a frequency band of 0.5 octaves, centered on the patient's individual tinnitus frequency, was blocked out. Those hearing aids employ a steep notch filter that filters environmental sounds to suppress the tinnitus-related changes in neural firing by lateral inhibition. The computational model reveals a renormalization of pathologically increased neural response reliability and synchrony in response to spectrally modified input. The target group, fitted with spectrally notched hearing aids, was matched with a comparable control group, fitted with standard hearing aids of the same type but without a notch filter. We analyze the subjective self-assessment by tinnitus questionnaires, and we monitor the objective distress correlates in auditory evoked response phase data. Both, subjective and objective results show a noticeable trend of a larger therapeutic benefit for notched hearing correction.

Free-field evoked auditory brainstem responses in cochlear implant users.

The importance of binaural cues in auditory stream formation and sound source segregation is widely accepted. When treating one ear with a cochlear implant (CI) the peripheral auditory system gets partially replaced and processing delays get added potentially, thus important interaural time differences get altered. However, these effects are not fully understood, leaving a lack of systematic binaural fitting strategies with respect to an optimal binaural fusion. To get new insights into such alterations, we suggest a novel method of free-field auditory brainstem evoked responses (ABRs) analysis in CI users. This method does not bypass the technically induced intrinsic delays of the sound processor while leaving the whole electrode array active, thus the most natural way of stimulation is provided. We compared the ABRs collected of 12 CI users and 12 normal hearing listeners using two different stimuli (chirp, click) at four different intensities each. We analyzed the ABRs using the average of 2000 trials as well as a single trial analysis and found consistent results in the ABRs' amplitudes and latencies, as well as in single trial relationships between both groups. This method provides a new perspective into the natural CI users' ABRs and can be useful in future research regarding binaural interaction and fusion.

Neurodynamic evaluation of hearing aid features using EEG correlates of listening effort.

In this study, we propose a novel estimate of listening effort using electroencephalographic data. This method is a translation of our past findings, gained from the evoked electroencephalographic activity, to the oscillatory EEG activity. To test this technique, electroencephalographic data from experienced hearing aid users with moderate hearing loss were recorded, wearing hearing aids. The investigated hearing aid settings were: a directional microphone combined with a noise reduction algorithm in a medium and a strong setting, the noise reduction setting turned off, and a setting using omnidirectional microphones without any noise reduction. The results suggest that the electroencephalographic estimate of listening effort seems to be a useful tool to map the exerted effort of the participants. In addition, the results indicate that a directional processing mode can reduce the listening effort in multitalker listening situations.

A multidisciplinary systematic review of the treatment for chronic idiopathic tinnitus.

The majority of tinnitus patients are affected by chronic idiopathic tinnitus, and almost 60 different treatment modalities have been reported. The present study is a multidisciplinary systematic analysis of the evidence for the different forms of treatment for chronic tinnitus. The results are used to form the basis of an S3 guideline. A systematic search was carried out in PubMed and the Cochrane Library. The basis for presenting the level of evidence was the evidence classification of the Oxford Centre of Evidence-based Medicine. Whenever available, randomised controlled trials were given preference for discussing therapeutic issues. All systematic reviews and meta-analyses were assessed for their methodological quality, and effect size was taken into account. As the need for patient counselling is self-evident, specific tinnitus counselling should be performed. Due to the high level of evidence, validated tinnitus-specific, cognitive behavioural therapy is strongly recommended. In addition, auditory therapeutic measures can be recommended for the treatment of concomitant hearing loss and comorbidities; those should also be treated with drugs whenever appropriate. In particular, depression should be treated, with pharmacological support if necessary. If needed, psychiatric treatment should also be given on a case-by-case basis. With simultaneous deafness or hearing loss bordering on deafness, a CI can also be indicated. For auditory therapeutic measures, transcranial magnetic or direct current stimulation and specific forms of acoustic stimulation (noiser/masker, retraining therapy, music, and coordinated reset) for the treatment of chronic tinnitus the currently available evidence is not yet sufficient for supporting their recommendation.

Detection of binaural interaction in free-field evoked auditory brainstem responses by time-scale representations.

The so called ß-wave of the binaural interaction component (BIC) in auditory brainstem responses (ABR) has been shown to be an objective measure for binaural interaction (BI). This component is the arithmetical difference between the sum of the monaurally evoked ABRs and the binaurally evoked ABR. Unfortunately, these neural responses are known to be very fragile and as a result the calculated BIC. An additional issue is, that the findings of this measurement are predominantly needed in people with hearing loss who may use hearing devices like hearing aids (HA) or cochlear implants (CI), thus they are not able to use headphones (like in conventional ABR measurements) during the detection of possible BI. This is a crucial problem, because it is known that factors like the interaural time delay (ITD) between the receiving ears are responsible for solving tasks like sound source localization or sound source separation, but specially designed measurements to coordinate the fitting of HAs or CIs with respect to BI are still missing. In this paper, we introduce a new measurement setup that is able to detect BI depending on different ITDs in free-field evoked responses by using the more reliable instantaneous phase in the time-scale representation. With this pilot study we are able to demonstrate a decreasing BI with an increasing ITD using the wavelet phase synchronization stability analysis in ten normal hearing subjects.

Dysfunctional long term habituation to exogeneous tinnitus-matched sounds in patients with high tinnitus distress.

During the last years, the demand of accurate diagnostic tools for individualized tinnitus treatment gradually increased. Today several different psychometric instruments for the estimation of the patients degree of decompensation with clinical relevance have emerged. All of these tools are questionnaires for a subjective self-assessment and have deficits in comparability due to severe differences in their factor structure in the anamnesis. Those questionnaires thus they are only of limited value in the design of an individualized therapeutic approach. Objective diagnostic tools for the categorization of the patients' distress level are lacking in clinical routine. Scientific approaches yet demonstrated the feasibility of individual distress assessment by objective markers in the EEG. In this article we present the preliminary results of our study of a use of habituation correlates as objective indicator for the decompensation degree in high-distress tinnitus patients.

Evaluation of an objective listening effort measure in a selective, multi-speaker listening task using different hearing aid settings.

Speaker recognition in a multi-speaker environment is a complex listening task that requires effort to be solved. Especially people with hearing loss show an increased listening effort in demanding listening situations compared to normal hearing people. However, a standardized method to quantify listening effort does not exist yet. Recently we have shown a possible way to determine listening effort objectively. The aim of this study was to validate the proposed objective measure in a challenging, true-to-life listening situation, and to get an insight on the influence of different hearing aid (HA) settings on the listening effort using the proposed measure. To achieve this we investigated the influence of four different HA settings and two different listening task difficulties (LTD) on the listening effort of people with hearing loss in a selective, real-speech listening task. HA setting A, B and C all had an adaptive compression with static characteristic, but differed in the gain and compression settings (more and less gain and more and less linear). Setting D had an adaptive compression whose characteristic was situation-dependent. To quantify the listening effort the ongoing oscillatory EEG activity was recorded as the basis to calculate the objective measure (OLEosc). By way of comparison a subjective listening effort score was determined on an individual basis (SLEscr). The results show that the OLEosc maps the SLEscr well in every of the tested conditions. Furthermore, the results also suggest that OLEosc might be more sensitive to small variances in listening effort than the employed subjective rating scale.

Objective assessment of listening effort in the oscillatory EEG: comparison of different hearing aid configurations.

An objective estimate of listening effort could support the hearing aid fitting procedure. Most of the digital hearing aids have already hearing aid settings which are supposed to reduce the listening effort, but the effects of these settings on the individual's listening effort remain unclear. In this study, we propose an objective estimate of listening effort using electroencephalographic data. The new method is based on the phase distribution of the ongoing oscillatory EEG activity. We hypothesize that for a non-effortful listening environment the phase is rather uniformly distributed on the unit circle than for a demanding condition. To prove if the phase is uniformly distributed around the unit circle, the Rayleigh Test was applied to the phase of the EEG. This method was tested in 14 hearing impaired subjects (moderate hearing loss, 65.64 ±7.93 yrs, 7 female). The tested hearing aid settings were a directional microphone combined with a noise reduction algorithm in a medium and a strong setting, the noise reduction setting turned off as well as a setting using omnidirectional microphones. Noise embedded sentences (Oldenburg Sentence Test, OlSa) were used as test materials. The task of the subject was to repeat each sentence. The results indicate that the objective estimate of listening effort maps the subjectively rated effort and for a listening situation like the presented one, the strong setting of the directional microphone requires the smallest effort.

Neural correlates of listening effort related factors: influence of age and hearing impairment.

In the last years, there has been a rising interest to find an objective method to estimate listening effort. Previously, we have shown that the wavelet phase synchronization stability (WPSS), gained from the instantaneous phase of auditory late responses (ALRs), could serve as a feasible measure for listening effort related factors. In the current study, we examined if the WPSS reflects the listening effort in young as well as middle-aged subjects and in persons with a different degree of hearing loss. To evoke ALR sequences, we generated syllabic paradigms with a different level of difficulty to evoke ALR sequences. We expected, due to the varying task demand, that the subjects require a measurable difference in the amount of effort to solve the paradigms. Additionally, a possible age and/or hearing loss related effect on the neural correlates of listening effort was investigated. The results indicate, that WPSS reflects the listening effort related factors needed to solve an auditory task. A further finding was that the reaction time data and the N1 wave amplitude information hardly yield any correlate of the invested listening effort. In addition, we noticed an age as well as hearing sensitivity related effect on the listening effort.

The effects of age and hearing impairment on the extraction of listening effort correlates.

In clinical practice, an objective method to assess listening effort is still not available. The benefit of such a measure would be to reduce the listening effort in hearing impaired persons by an adequate adaption of their personal hearing aids. In foregoing studies, we have shown that the wavelet phase synchronization stability (WPSS) of auditory late responses (ALRs) could serve as a feasible measure of listening effort. Here, tonal and noise embedded syllabic paradigms were employed to achieve ALR sequences in normal hearing subjects. The aims of this ongoing study were 1) to extract the WPSS of ALR sequences in hearing impaired persons, middle-aged normal hearing persons and younger normal hearing subjects, 2) to investigate possible age-related influences on the WPSS and 3) to examine a feasible influence of the hearing loss on the WPSS. It is concluded, that the WPSS of ALR sequences can be extracted in normal hearing as well as in hearing impaired persons. An age related effect regarding the WPSS was not noticeable and the intergroup comparison of the difference of the WPSS showed a tendency to be larger for the hearing impaired compared to the normal hearing middle-aged subjects. The latest can be interpreted that this subject group showed a larger effort to solve the auditory paradigms.

Alterations in Event Related Potentials (ERP) associated with tinnitus distress and attention.

Tinnitus related distress corresponds to different degrees of attention paid to the tinnitus. Shifting attention to a signal other than the tinnitus is therefore particularly difficult for patients with high tinnitus related distress. As attention effects on Event Related Potentials (ERP) have been shown this should be reflected in ERP measurements (N100, phase locking). In order to prove this hypothesis single sweep ERP recordings were obtained in 41 tinnitus patients as well as 10 control subjects during a period of time when attention was shifted to a tone (attended) and during a second phase (unattended) when they did not focus attention to the tone. Whereas tinnitus patients with low distress showed a significant reduction in both N100 amplitude and phase locking when comparing the attended and unattended measurement condition a group of patients with high tinnitus related distress did not show such ERP alterations. Using single sweep ERP measurements the results of our study show, that attention in high tinnitus related distress patients is captured by their tinnitus significantly more than in low distress patients. Furthermore our results provide the basis for future neurofeedback based tinnitus therapies aiming at maximizing the ability to shift attention away from the tinnitus.