Components Of Auditory Brainstem Response Research Articles

Auditory brainstem responses are resistant to pharmacological modulation in Sprague Dawley wild-type and Neurexin1α knockout rats

Sensory processing in the auditory brainstem can be studied with auditory brainstem responses (ABRs) across species. There is, however, a limited understanding of ABRs as tools to assess the effect of pharmacological interventions. Therefore, we set out to understand how pharmacological agents that target key transmitter systems of the auditory brainstem circuitry affect ABRs in rats. Given previous studies, demonstrating that Nrxn1α KO Sprague Dawley rats show substantial auditory processing deficits and altered sensitivity to GABAergic modulators, we used both Nrxn1α KO and wild-type littermates in our study. First, we probed how different commonly used anesthetics (isoflurane, ketamine/xylazine, medetomidine) affect ABRs. In the next step, we assessed the effects of different pharmacological compounds (diazepam, gaboxadol, retigabine, nicotine, baclofen, and bitopertin) either under isoflurane or medetomidine anesthesia. We found that under our experimental conditions, ABRs are largely unaffected by diverse pharmacological modulation. Significant modulation was observed with (i) nicotine, affecting the late ABRs components at 90 dB stimulus intensity under isoflurane anesthesia in both genotypes and (ii) retigabine, showing a slight decrease in late ABRs deflections at 80 dB stimulus intensity, mainly in isoflurane anesthetized Nrxn1α KO rats. Our study suggests that ABRs in anesthetized rats are resistant to a wide range of pharmacological modulators, which has important implications for the applicability of ABRs to study auditory brainstem physiology.

Attention modulates cortical, but not subcortical responses

Organisms often need to attend to one signal within a crowded acoustic scene. While attentional effects in the auditory cortex are robust, what happens subcortically remains mysterious. We combined previous electroencephalography paradigms to measure whether attention modulates subcortical as well as cortical responses. Participants heard competing, temporally interleaved low and high melodies. Each melody had notes repeating at 2 Hz, with an overall note rate of 4 Hz. Participants attended to either the high- or low-pitched melody and responded whenever a 3-note pattern repeated in that stream. From past work, we expected to see strong cortical EEG responses at 2 Hz, but with a phase that shifted depending on which melody listeners attended. Importantly, we engineered the notes so that (1) low and high melodies excited different cochlear regions, and (2) each pitch period of each note elicited an auditory brainstem response (ABR). This allowed us to test whether attention altered responses along the ascending pathway in the brainstem. We found phase shifts in cortical responses with shifts of attention. While we found robust ABRs, we saw no evidence that attention modulated any of the ABR components. These results suggest that attentional effects in subcortical structures are weak, at best.

Can auditory evoked responses elicited to click and/or verbal sound identify children with or at risk of central auditory processing disorder: A scoping review.

(Central) auditory processing disorders, (C)APDs are clinically identified using behavioral tests. However, changes in attention and motivation may easily affect true identification. Although auditory electrophysiological tests, such as Auditory Brainstem Responses (ABR), are independent of most confounding cognitive factors, there is no consensus that click and/or speech-evoked ABR can be used to identify children with or at-risk of (C)APDs due to heterogeneity among studies. This study aimed to review the possibility of using ABR evoked by click and/or speech stimuli to identify children with or at risk of (C)APDs. The online databases of PubMed, Web of Science, Medline, Embase, and CINAHL were explored using combined keywords for all English and French articles published until April 2021. Additional gray literature was also included such as conference abstracts, dissertations, and editorials in ProQuest Dissertations. Thirteen papers met the eligibility criteria and were included in the scoping review. Fourteen papers were cross-sectional and two were interventional studies. Eleven papers used click stimuli to assess children with/at risk of (C)APDs, and speech stimuli were utilized in the remaining studies. Despite the diversity of the results, especially in click ABR assessments, most studies indicated increases in the wave latencies and/or decreases in the wave amplitudes of click ABR in children with/at risk of (C)APDs. The results of speech ABR assessments were more consistent, as prolongation of the transient components of speech ABR was observed in these children, while sustained components remained almost unchanged. Although both click and speech-evoked ABRs could be used to assess children with (C)APDs, it appears that speech-evoked ABR assessments yield more reliable findings. These findings, however, should be interpreted with caution given the heterogeneity among studies. Well-designed studies on children with confirmed (C)APDs using standard diagnostic and assessment protocols are recommended.

The Effect of Tinnitus and Related Characteristics on Subcortical Auditory Processing.

The primary aim of this study was to evaluate whether individuals with tinnitus exhibited evidence of reduced inhibition and increased excitation at the subcortical auditory processing level. Based on the proposed mechanism of tinnitus generation, including peripheral auditory insult that triggers reduced inhibition and subcortical hyperactivity, it was hypothesized that a tinnitus group would yield reduced amplitudes for the most peripheral auditory brainstem response (ABR) component (wave I) and larger amplitudes for the most central ABR component (wave V) relative to controls matched on factors of age, sex, and hearing loss. Further, this study assessed the relative influence of tinnitus presence versus other related individual characteristics, including hearing loss, age, noise exposure history, and speech perception in noise on these ABR outcomes. Subcortical processing was examined using click-evoked ABR in an independent groups experimental design. A group of adults who perceived daily unilateral or bilateral tinnitus were matched with a control group counterpart without tinnitus by age, hearing, and sex (in each group n = 18; 10 females, 8 males). Amplitudes for ABR waves I, III, V, and the V/I ratio were compared between groups by independent t-tests. The relative influence of tinnitus (presence/absence), age (in years), noise exposure history (subjective self-report), hearing loss (audiometric thresholds), and speech perception in noise (SNR-50) was determined based on the proportional reduction in error associated with accounting for each variable of interest using multiple regression. Between-group trends were consistent with smaller amplitudes for all ABR components in individuals with tinnitus. Contrary to our hypotheses, however, none of the tinnitus compared with control group differences in ABR outcomes were statistically significant. In the multiple regression models, none of the factors including tinnitus presence, age, noise exposure history, hearing loss, and speech perception in noise significantly predicted ABR V/I ratio outcomes. The presence of reduced inhibition and subcortical hyperactivity in the tinnitus group was not supported in the current study. There were trends in ABR outcomes consistent with reduced peripheral to central brainstem auditory activity in the tinnitus group, but none of the group differences reached significance. It should also be noted that the tinnitus group had poorer extended high-frequency thresholds compared with controls. Regardless, neither tinnitus presence nor any of the proposed related characteristics were found to significantly influence the ABR V/I ratio. These findings suggest that either reduced subcortical inhibition was not a primary underlying mechanism for the tinnitus perceived by these subjects, or that ABR was not a reliable indicator of reduced subcortical inhibition possibly due to characteristics of the sample including a skewed distributions toward young and normal hearing individuals with little tinnitus distress.

Speech in noise performance in individuals with misophonia and hyperacusis using behavioral and auditory brainstem response

Hyperacusis is reduced tolerance to everyday environmental sounds, whereas misophonia is a relatively unknown disorder in which characterized by intense and excessive emotional responses to specific “trigger” sounds. Few studies have investigated ability of speech in noise (SiN) and examined them using auditory brainstem responses (ABR)—which is used to measure early auditory processing and overall hearing function in human listeners, in particular for the sound sensitivity disorders of misophonia and hyperacusis. The primary aim of this study was to investigate the relationships between SiN performance and ABR components, specifically for group differences. A total of 60 participants were categorized into three groups: 13 with misophonia, 12 with hyperacusis, and 35 control group. Our findings indicated that (1) the misophonia group showed poor speech in noise performance than control and hyperacusis groups at 20 and 5 SNR; (2) both hyperacusis and misophonia groups showed enhanced wave I amplitude compared with the control group; and (3) the misophonia group showed prolonged wave V latency compared to the other two groups. Additionally, delayed ABR wave V latency in misophonia group was correlated with decreased speech-in-noise performance score, suggesting possible delays in processing of speech sounds in this group leading to poorer performance.

Auditory brainstem responses in adults with autism spectrum disorder

ObjectiveTo investigate possible differences in the auditory peripheral and brainstem functions between adults with autism spectrum disorder (ASD) and neurotypical (NT) adults. MethodsClick-evoked auditory brainstem responses (ABRs) were obtained from 17 high-functioning ASD adults (aged 21–38 years) and 20 NT adults (aged 22–36 years). A relatively large number of stimulus presentations (6000) were adopted, and ABRs by horizontal and vertical electrode montages were evaluated, in order to allow precise evaluations of early ABR components. ResultsWaves I, II, III, and V were identified in the vertical electrode montage, and wave I and the summating potential (SP) in electrocochleograms were identified in the horizontal electrode montage. There were no significant group differences in the wave I, II, III, and V latencies or the interpeak latencies (IPLs) in the vertical electrode montage. In the horizontal montage, the ASD adults exhibited significantly shortened SP latencies compared with the NT adults, whereas there was no significant group difference in the wave I latency. ConclusionThe ASD adults may have the abnormalities of processing more in the peripheral auditory system than in the brainstem. SignificanceThe current study suggests that the peripheral abnormality is associated with ASD.

Experimental study of potential adverse effects on the auditory system of rabbits exposed to short-term GSM-1800 radiation

Purpose The effects of the electromagnetic (EM) radiation emitted by a mobile phone on the central auditory system of rabbits are investigated in this paper. Auditory brainstem response (ABR) measurements were performed before and after short-term exposure to EM radiation. Materials and methods Excitation was provided by a GSM-1800 emitter placed in contact with the (randomly selected) ear of the anesthetized rabbit/subject. The latency of waves I, II, III, IV, V and the interpeak latencies I-III, I-V, III-V were recorded, for both ears, before (baseline recordings) and after 1, 15, 30, 45 and 60 minutes of exposure to the EM radiation. The repeated measures one-way analysis of variance (ANOVA) followed by the post hoc Tukey test for pairwise comparisons was performed in order to decide about the significance of the results. Results The statistical tests indicated that, as regards the ear ipsilateral to the radiating module, the mean latencies of waves I, II, III, IV, V, I-III, I-IV after 60 min exposure, the mean latencies of waves I, III, IV, V, I-III, I-IV after 45 min exposure and the mean latencies of waves I, III, IV, V, I-IV after 30 min exposure, were significantly prolonged compared to the corresponding baseline values. Statistically significant differences were also found for certain peak and interpeak latencies for 60 min exposure as compared with the corresponding results for 1 min and 15 min exposure. No statistically significant delay was observed for the latencies before and after the exposure, for the ear contralateral to the radiation source. Conclusions Although we found that more than 30 min exposure to GSM-1800 radiation resulted in prolongation of certain ABR components of rabbits, further investigation may be needed into the potential adverse effects on the auditory pathways.

Binaural interaction component of the auditory brainstem response in children with autism spectrum disorder

IntroductionThere is ample evidence that auditory dysfunction is a common feature of autism spectrum disorder (ASD). Binaural interaction component (BIC) manifests binaural interaction and is valid and proven response which reflects ongoing binaural processing. ObjectivesTo investigate the differences in binaural interaction component of auditory brainstem response (ABR-BIC) between children with autism spectrum disorder (ASD) and normal peers and to correlate between ABR-BIC amplitudes and the acquired communication skills in ASD children. MethodsASD was diagnosed according to the criteria of 5th edition of diagnostic and statistical manual of mental disorders (DSM-V) and all children with ASD underwent test of acquired communication skills (TACS). Click evoked ABRs were elicited by left monaural, right monaural and binaural stimulation at intensity of 65 dBnHL in all participants. ABR-BIC was then calculated as the difference between the binaurally evoked ABR waveform and a predicted binaural waveform created by algebraically summing the left and right monaurally evoked ABRs. The difference in amplitudes that gives rise to ABR-BIC is at IV-VI waves. ResultsABR-BIC amplitudes were demonstrated to be significantly reduced in the ASD group compared to the control group. There was significant positive correlation between ABR-BIC amplitude and the language and social scores in TACS. ConclusionThis study provided an objective evidence of binaural processing disorder in children with ASD.

Perceptual Encoding in Auditory Brainstem Responses: Effects of Stimulus Frequency.

A central question about auditory perception concerns how acoustic information is represented at different stages of processing. The auditory brainstem response (ABR) provides a potentially useful index of the earliest stages of this process. However, it is unclear how basic acoustic characteristics (e.g., differences in tones spanning a wide range of frequencies) are indexed by ABR components. This study addresses this by investigating how ABR amplitude and latency track stimulus frequency for tones ranging from 250 to 8000 Hz. In a repeated-measures experimental design, listeners were presented with brief tones (250, 500, 1000, 2000, 4000, and 8000 Hz) in random order while electroencephalography was recorded. ABR latencies and amplitudes for Wave V (6-9 ms) and in the time window following the Wave V peak (labeled as Wave VI; 9-12 ms) were measured. Wave V latency decreased with increasing frequency, replicating previous work. In addition, Waves V and VI amplitudes tracked differences in tone frequency, with a nonlinear response from 250 to 8000 Hz and a clear log-linear response to tones from 500 to 8000 Hz. Results demonstrate that the ABR provides a useful measure of early perceptual encoding for stimuli varying in frequency and that the tonotopic organization of the auditory system is preserved at this stage of processing for stimuli from 500 to 8000 Hz. Such a measure may serve as a useful clinical tool for evaluating a listener's ability to encode specific frequencies in sounds. https://doi.org/10.23641/asha.6987422.

Supra-threshold auditory brainstem response amplitudes in humans: Test-retest reliability, electrode montage and noise exposure

The auditory brainstem response (ABR) is a sub-cortical evoked potential in which a series of well-defined waves occur in the first 10 ms after the onset of an auditory stimulus. Wave V of the ABR, particularly wave V latency, has been shown to be remarkably stable over time in individual listeners. However, little attention has been paid to the reliability of wave I, which reflects auditory nerve activity. This ABR component has attracted interest recently, as wave I amplitude has been identified as a possible non-invasive measure of noise-induced cochlear synaptopathy. The current study aimed to determine whether ABR wave I amplitude has sufficient test-retest reliability to detect impaired auditory nerve function in an otherwise normal-hearing listener. Thirty normal-hearing females were tested, divided equally into low- and high-noise exposure groups. The stimulus was an 80 dB nHL click. ABR recordings were made from the ipsilateral mastoid and from the ear canal (using a tiptrode). Although there was some variability between listeners, wave I amplitude had high test-retest reliability, with an intraclass correlation coefficient (ICC) comparable to that for wave V amplitude. There were slight gains in reliability for wave I amplitude when recording from the ear canal (ICC of 0.88) compared to the mastoid (ICC of 0.85). The summating potential (SP) and ratio of SP to wave I were also quantified and found to be much less reliable than measures of wave I and V amplitude. Finally, we found no significant differences in the amplitude of any wave components between low- and high-noise exposure groups. We conclude that, if the other sources of between-subject variability can be controlled, wave I amplitude is sufficiently reliable to accurately characterize individual differences in auditory nerve function.

Brainstem Evoked Potential Indices of Subcortical Auditory Processing After Mild Traumatic Brain Injury.

The primary aim of this study was to assess subcortical auditory processing in individuals with chronic symptoms after mild traumatic brain injury (mTBI) by measuring auditory brainstem responses (ABRs) to standard click and complex speech stimuli. Consistent with reports in the literature of auditory problems after mTBI (despite normal-hearing thresholds), it was hypothesized that individuals with mTBI would have evidence of impaired neural encoding in the auditory brainstem compared to noninjured controls, as evidenced by delayed latencies and reduced amplitudes of ABR components. We further hypothesized that the speech-evoked ABR would be more sensitive than the click-evoked ABR to group differences because of its complex nature, particularly when recorded in a background noise condition. Click- and speech-ABRs were collected in 32 individuals diagnosed with mTBI in the past 3 to 18 months. All mTBI participants were experiencing ongoing injury symptoms for which they were seeking rehabilitation through a brain injury rehabilitation management program. The same data were collected in a group of 32 age- and gender-matched controls with no history of head injury. ABRs were recorded in both left and right ears for all participants in all conditions. Speech-ABRs were collected in both quiet and in a background of continuous 20-talker babble ipsilateral noise. Peak latencies and amplitudes were compared between groups and across subgroups of mTBI participants categorized by their behavioral auditory test performance. Click-ABR results were not significantly different between the mTBI and control groups. However, when comparing the control group to only those mTBI subjects with measurably decreased performance on auditory behavioral tests, small differences emerged, including delayed latencies for waves I, III, and V. Similarly, few significant group differences were observed for peak amplitudes and latencies of the speech-ABR when comparing at the whole group level but were again observed between controls and those mTBI subjects with abnormal behavioral auditory test performance. These differences were seen for the onset portions of the speech-ABR waveforms in quiet and were close to significant for the onset wave. Across groups, quiet versus noise comparisons were significant for most speech-ABR measures but the noise condition did not reveal more group differences than speech-ABR in quiet, likely because of variability and overall small amplitudes in this condition for both groups. The outcomes of this study indicate that subcortical neural encoding of auditory information is affected in a significant portion of individuals with long-term problems after mTBI. These subcortical differences appear to relate to performance on tests of auditory processing and perception, even in the absence of significant hearing loss on the audiogram. While confounds of age and slight differences in audiometric thresholds cannot be ruled out, these preliminary results are consistent with the idea that mTBI can result in neuronal changes within the subcortical auditory pathway that appear to relate to functional auditory outcomes. Although further research is needed, clinical audiological evaluation of individuals with ongoing post-mTBI symptoms is warranted for identification of individuals who may benefit from auditory rehabilitation as part of their overall treatment plan.

High-pass filtering obscures stimulus encoding characteristics of the auditory brainstem response: Evidence from click and tone stimuli

The auditory brainstem response (ABR) is an electrophysiological measure of early auditory processing. While previous work has examined ABRs to clicks, tones, speech, and music, it remains unclear how changes in acoustic properties (e.g., frequency) map onto specific changes in ABR components. This may be partly due to filtering during data processing. High-pass filtering can severely distort cortical and subcortical responses, potentially obfuscating how stimuli are encoded. To address this, we measured ABRs to a wide range of pure tones (250 to 8000 Hz) and examined how high-pass filtering affects tone- and click-evoked ABRs. In Experiment 1, various high-pass filter settings (0.1-300 Hz) were applied to click-evoked ABRs. In Experiment 2, ABRs to brief tones across a six-step frequency continuum were collected, and the same high-pass filter settings were applied. Results indicate that excessive high-pass filtering diminishes the amplitude of ABR components, consistent with previous findings. In addition, filtering can obscure true effects of stimulus frequency. With appropriate filters, we find that the amplitude of wave V tracks stimulus frequency log-linearly, demonstrating that tonotopic organization is preserved and easily detectable early in processing. Future ABR work should minimize the use of high-pass filters when studying the encoding of acoustic information.

Peripheral and central auditory assessment in among the elderly

Abstract Introduction: Presbycusis can affect different portions of the auditory system, causing impacts of varying degrees of seriousness on the daily routine of elderly persons. It is essential that the extent of the deficit as well as the degree of handicap is evaluated, so that the hearing of the elderly can be effectively rehabilitated, improving their quality of life. Purpose: To characterize the peripheral and central hearing of elderly individuals and assess their auditory handicaps. Methods: A cross sectional observational study was performed. We evaluated 83 elderly persons (60-85 years; 33 men, 50 women) with normal hearing or sensorineural hearing loss. Individuals were divided into 3 groups according to the 3 to 6kHz hearing thresholds: G1 - mean of 0 to 39 dBHL (80 ears); G2 - mean of 40 to 59 dBHL (48 ears); G3 - mean of 60 to 120dBHL (38 ears). All individuals responded to the Hearing Handicap Inventory for the Elderly (HHIE), and underwent Pure Tone Audiometry, Auditory Brainstem Response (ABR) and Long Latency Response (P300) evaluation. Results: Men had higher auditory thresholds at frequencies from 500 to 12,000Hz (with a statistical difference between 2-8 kHz) and also significantly greater latencies for ABR components. There was no difference between genders for the P300 evaluation. Comparison between groups showed: a statistically significant difference for age; greater ABR wave latencies and interwave intervals; that questionnaire scores worsened as hearing threshold declined; and similar P300 latencies. Conclusions: Elderly people have impairment throughout the auditory pathway (peripheral and central). The P300 was less accurate at identifying the losses that come with age. The HHIE demonstrated negative effects on the social life of elderly people, agreeing with the hearing thresholds found.

Abnormalities in Auditory Efferent Activities in Children with Selective Mutism

Two efferent feedback pathways to the auditory periphery may play a role in monitoring self-vocalization: the middle-ear acoustic reflex (MEAR) and the medial olivocochlear bundle (MOCB) reflex. Since most studies regarding the role of auditory efferent activity during self-vocalization were conducted in animals, human data are scarce. The working premise of the current study was that selective mutism (SM), a rare psychiatric disorder characterized by consistent failure to speak in specific social situations despite the ability to speak normally in other situations, may serve as a human model for studying the potential involvement of auditory efferent activity during self-vocalization. For this purpose, auditory efferent function was assessed in a group of 31 children with SM and compared to that of a group of 31 normally developing control children (mean age 8.9 and 8.8 years, respectively). All children exhibited normal hearing thresholds and type A tympanograms. MEAR and MOCB functions were evaluated by means of acoustic reflex thresholds and decay functions and the suppression of transient-evoked otoacoustic emissions, respectively. Auditory afferent function was tested by means of auditory brainstem responses (ABR). Results indicated a significantly higher proportion of children with abnormal MEAR and MOCB function in the SM group (58.6 and 38%, respectively) compared to controls (9.7 and 8%, respectively). The prevalence of abnormal MEAR and/or MOCB function was significantly higher in the SM group (71%) compared to controls (16%). Intact afferent function manifested in normal absolute and interpeak latencies of ABR components in all children. The finding of aberrant efferent auditory function in a large proportion of children with SM provides further support for the notion that MEAR and MOCB may play a significant role in the process of self-vocalization.

Electrophysiological Measures of Auditory Processing in Patients with Multiple Sclerosis

Previous studies demonstrated that patients with multiple sclerosis (MS) experience more hearing loss than age-matched control subjects. Patients with MS also exhibit deficits processing auditory stimuli, including speech in a background of noise. These findings suggest that auditory deficits in the MS population can result from damage to central neural pathways in addition to peripheral hearing structures. To assess auditory processing functions in patients with MS, this study used auditory event-related potentials (AERPs)—specifically, the auditory brain stem response (ABR) and long-latency AERPs including the P300. AERPs recorded from 20 patients with MS were compared to AERPs from 20 healthy control subjects. When ABR stimuli (clicks) were presented monaurally, there were no significant differences between groups in component latencies or amplitudes for waves I through V. However, binaural presentation of the same stimuli elicited wave V ABR components significantly greater in amplitude for the control group compared with the MS group. Long-latency AERP results showed no significant differences between groups for N100 latency and amplitude or for P300 latency. P300 component amplitude was significantly greater for control subjects compared with patients with MS. It is probable that neural degeneration and impaired neural transmission within the MS group contributed to these AERP results. AERPs are useful tools that can be used to assess peripheral and central auditory functions as well as cognitive processing abilities in patients with MS. AERPs could be used to evaluate neural integrity, disease progression, and treatment efficacy in this population.

Vestibular hearing and neural synchronization.

Objectives. Vestibular hearing as an auditory sensitivity of the saccule in the human ear is revealed by cervical vestibular evoked myogenic potentials (cVEMPs). The range of the vestibular hearing lies in the low frequency. Also, the amplitude of an auditory brainstem response component depends on the amount of synchronized neural activity, and the auditory nerve fibers' responses have the best synchronization with the low frequency. Thus, the aim of this study was to investigate correlation between vestibular hearing using cVEMPs and neural synchronization via slow wave Auditory Brainstem Responses (sABR). Study Design. This case-control survey was consisted of twenty-two dizzy patients, compared to twenty healthy controls. Methods. Intervention comprised of Pure Tone Audiometry (PTA), Impedance acoustic metry (IA), Videonystagmography (VNG), fast wave ABR (fABR), sABR, and cVEMPs. Results. The affected ears of the dizzy patients had the abnormal findings of cVEMPs (insecure vestibular hearing) and the abnormal findings of sABR (decreased neural synchronization). Comparison of the cVEMPs at affected ears versus unaffected ears and the normal persons revealed significant differences (P < 0.05). Conclusion. Safe vestibular hearing was effective in the improvement of the neural synchronization.

An electrophysiological approach to tinnitus interpretation

Serotonin seems to play a central role in tinnitus. The intensity dependence of auditory evoked potential (IDAP) is considered an index of central serotonergic activity in the auditory cortex. The higher the steepness of the N1/P2 component amplitude-stimulus function slope (N1/P2 ASF slope as calculated by IDAP), the lower the central serotonergic activity. Similarly, the N1 amplitude-stimulus function slope (N1 ASF slope) was investigated. Auditory brainstem responses (ABR) examine the auditory system functionality from the periphery and through the brainstem, where serotonergic projections have been identified. Assessing whether tinnitus perception neurotransmitters activity inbalance could be investigated by an electrophysiological approach. Ten normoacousic tinnitus patients and 14 healthy controls were included in the study. Subjects underwent EEG (IDAP) recording, ABR recording and psychometric questionnaires administration. N1/P2 ASF slope and N1ASF slope tended to have a greater steepness in patients. N1ASF slope was significantly correlated with ABR wave V and interpeak III-V latencies in patients. ABR wave V and interpeak III-V latencies were significantly longer in patients than in controls. N1/P2 ASF slope, N1 ASF slope and ABR components appear to be useful electrophysiologic methods to study possible functional alterations related to the serotonergic activity.

Electrophysiological differences in sensorineural hearing loss patients with and without problem-tinnitus

EnAbstract Objects Problem-tinnitus refers to tinnitus that is sufficiently severe to produce a major disruption in the patient’s life; tinnitus of such severity involves a number of regions of the auditory system and other brain systems may also play an essential role. Auditory brainstem responses (ABR) and event-related potentials (ERP) were recorded from sensorineural hearing loss (SNHL) patients with problem-tinnitus and were then compared with responses from normal hearing and hearing loss tinnitus-free patients. Aim To study whether differences exist in ABR and/or ERP parameters in SNHL patients with and without problem-tinnitus when matched as closely as possible for hearing loss, age, and sex to investigate the mechanism responsible for tinnitus. Materials and Methods Ninety participants were included in this study. They were divided into two groups: the study group included 66 participants with bilateral symmetrical SNHL that did not exceed a moderate degree. The study group was divided into two subgroups: 36 patients had problem-tinnitus and 30 patients were tinnitus-free (SNHL, age, and sex matched). Participants in each of these subgroups were compared with each other and were also compared with 24 healthy individuals in the control group (age and sex matched with the study group). All participants were subjected to a basic audiological evaluation and electrophysiological tests (ABR and ERP). Results This work had shown a higher prevalence of ABR abnormalities in tinnitus patients in comparison with either the control group or the SNHL tinnitus-free group. Statistically significant differences were found in III–V and I–V interpeak latencies and in the VI amplitude ratio in problem-tinnitus female patients compared with tinnitus-free female patients. Meanwhile, in problem tinnitus male patients when compared with tinnitus-free male patients at III–V interpeak latencies and at VI amplitude ratio. As regards the results of ERP in this work, an increase in latency and amplitude reduction were found. Statistically significant differences were observed regarding both the mean latency values of waves N1, P2, and P300 and the amplitude mean values of P2 and P300 when we compared the problem-tinnitus subgroup with either the tinnitus-free subgroup or the control group (both female and male patients. Conclusion A variety of ABR and ERP components are altered in tinnitus patients; this would indicate impairment in both the central auditory pathway and central auditory processing. Thus, it is suggested that this form of ABR, ERP testing could be considered as an objective measure to complement behavioral, audiologic, and other physiologic methods of assessing tinnitus, rather than a single definitive tinnitus measure in an attempt to supplement and thereby extend knowledge of the nature and origins of tinnitus. Furthermore, these results provide the basis for future neurofeedback-based tinnitus therapies aiming at maximizing the ability to shift attention away from the tinnitus.

Assessment of inter-examiner agreement and variability in the manual classification of auditory brainstem response

BackgroundThe analysis of the Auditory Brainstem Response (ABR) is of fundamental importance to the investigation of the auditory system behaviour, though its interpretation has a subjective nature because of the manual process employed in its study and the clinical experience required for its analysis. When analysing the ABR, clinicians are often interested in the identification of ABR signal components referred to as Jewett waves. In particular, the detection and study of the time when these waves occur (i.e., the wave latency) is a practical tool for the diagnosis of disorders affecting the auditory system. Significant differences in inter-examiner results may lead to completely distinct clinical interpretations of the state of the auditory system. In this context, the aim of this research was to evaluate the inter-examiner agreement and variability in the manual classification of ABR.MethodsA total of 160 ABR data samples were collected, for four different stimulus intensity (80dBHL, 60dBHL, 40dBHL and 20dBHL), from 10 normal-hearing subjects (5 men and 5 women, from 20 to 52 years). Four examiners with expertise in the manual classification of ABR components participated in the study. The Bland-Altman statistical method was employed for the assessment of inter-examiner agreement and variability. The mean, standard deviation and error for the bias, which is the difference between examiners’ annotations, were estimated for each pair of examiners. Scatter plots and histograms were employed for data visualization and analysis.ResultsIn most comparisons the differences between examiner’s annotations were below 0.1 ms, which is clinically acceptable. In four cases, it was found a large error and standard deviation (>0.1 ms) that indicate the presence of outliers and thus, discrepancies between examiners.ConclusionsOur results quantify the inter-examiner agreement and variability of the manual analysis of ABR data, and they also allows for the determination of different patterns of manual ABR analysis.

Analysis of the variability of auditory brainstem response components through linear regression

The analysis of the Auditory Brainstem Response (ABR) is of fundamental importance to the investigation of the auditory system behavior, though its interpretation has a subjective nature because of the manual process employed in its study and the clinical experience required for its analysis. When analyzing the ABR, clinicians are often interested in the identification of ABR signal components referred to as Jewett waves. In particular, the detection and study of the time when these waves occur (i.e., the wave latency) is a practical tool for the diagnosis of disorders affecting the auditory system. In this context, the aim of this research is to compare ABR manual/visual analysis provided by different examiners. Methods: The ABR data were collected from 10 normal-hearing subjects (5 men and 5 women, from 20 to 52 years). A total of 160 data samples were analyzed and a pair- wise comparison between four distinct examiners was executed. We carried out a statistical study aiming to identify significant differences between assessments provided by the examiners. For this, we used Linear Regression in conjunction with Bootstrap, as a method for evaluating the relation between the responses given by the examiners. Results: The analysis suggests agreement among examiners however reveals differences between assessments of the variability of the waves. We quantified the magnitude of the obtained wave latency differences and 18% of the investigated waves presented substantial differences (large and moderate) and of these 3.79% were considered not acceptable for the clinical practice. Conclusions: Our results characterize the variability of the manual analysis of ABR data and the necessity of establishing unified standards and protocols for the analysis of these data. These results may also contribute to the validation and development of automatic systems that are employed in the early diagnosis of hearing loss.