Speech Auditory Brainstem Response Research Articles

Assessment of Peripheral and Central Auditory Processing after Treatment for Idiopathic Sudden Sensorineural Hearing Loss.

Introduction When cases of idiopathic sudden sensorineural hearing loss (SSNHL) are treated successfully, most clinicians assume the normality and symmetry of the auditory processing. This assumption is based on the recovery of the detection ability on the part of the patients, but the auditory processing involves much more than detection alone. Since certain studies have suggested a possible involvement of the central auditory system during the acute phase of sudden hearing loss, the present study hypothesized that auditory processing would be asymmetric in people who have experienced sudden hearing loss. Objective To assess the physiologic and electrophysiological conditions of the cochlea and central auditory system, as well as behavioral discrimination, of three primary aspects of sound (intensity, frequency, and time) in subjects with normal ears and ears treated successfully for SSNHL. Methods The study included 19 SSNHL patients whose normal and treated ears were assessed for otoacoustic emissions, speech auditory brainstem response, intensity and pitch discrimination, and temporal resolution in a within-subject design. Results The otoacoustic emissions were poorer in the treated ears compared to the normal ears. Ear- and sex-dependent differences were observed regarding otoacoustic emissions and pitch discrimination. Conclusion The asymmetrical processing observed in the present study was not consistent with the hearing threshold values, which might suggest that the central auditory system would be affected regardless of the status of the peripheral hearing. Further experiments with larger samples, different recovery scenarios after treatment, and other assessments are required.

The Effects of a Home Personal Computer-based Auditory Training Program on the Binaural Listening Skills of Children With Specific Learning Disability: A Protocol for a Randomized Clinical Trial

Background and Objectives: A high prevalence of central auditory processing disorders has been reported in children with learning disabilities. One of the crucial auditory processing disorders in these children is a binaural processing problem. Binaural hearing leads to improved auditory performance in noisy situations. This research aims to develop an auditory training program based on binaural interaction at the brainstem level and to investigate its effect on the binaural listening skills of children with a specific learning disability. Methods: After developing the rehabilitation program and determining its validity, this intervention study is conducted in three stages. The first stage includes baseline assessments, the second stage includes the implementation of rehabilitation intervention and the third stage consists of the re-implementation of the tests of the first stage once immediately after intervention and then once after 45 days of training. Masking level differences (MLD), Persian auditory recognition of words in noise (PARWIN), and binaural speech-auditory brainstem response (Speech-ABR) tests are the primary outcome measures. Persian randomized dichotic digits test (PRDDT), Persian pediatric competing word test (PPCWT), Persian pediatric competing sentences test (PPCST), and Persian version of the auditory processing disorder questionnaire (APDQ-P) were included as secondary outcome measures. The sample size in each intervention and control group was 15 people and the duration of training was 3 months. Conclusion: Considering the importance of brainstem function in binaural hearing, it is recommended to investigate the effectiveness of the developed binaural interaction training program in improving hearing in background noise in children with specific learning disabilities.

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.

Assessing Auditory Processing in Children with Listening Difficulties: A Pilot Study.

Auditory processing disorders (APD) may be one of the problems experienced by children with listening difficulties (LiD). The combination of auditory behavioural and electrophysiological tests could help to provide a better understanding of the abilities/disabilities of children with LiD. The current study aimed to quantify the auditory processing abilities and function in children with LiD. Twenty children, ten with LiD (age = 8.46; SD = 1.39) and ten typically developing (TD) (age = 9.45; SD = 1.57) participated in this study. All children were evaluated with auditory processing tests as well as with attention and phonemic synthesis tasks. Electrophysiological measures were also conducted with click and speech auditory brainstem responses (ABR). Children with LiD performed significantly worse than TD children for most behavioural tasks, indicating shortcomings in functional auditory processing. Moreover, the click-ABR wave I amplitude was smaller, and the speech-ABR waves D and E latencies were longer for the LiD children compared to the results of TD children. No significant difference was found when evaluating neural correlates between groups. Combining behavioural testing with click-ABR and speech-ABR can highlight functional and neurophysiological deficiencies in children with learning and listening issues, especially at the brainstem level.

The Relationship between Contralateral Suppression of Transient Evoked Otoacoustic Emission and Unmasking of Speech Evoked Auditory Brainstem Response

Introduction Several studies have shown that efferent pathways of the auditory system improve perception of speech-in-noise. But, the majority of investigations assessing the role of efferent pathways on speech perception have used contralateral suppression of otoacoustic emissions as a measure of efferent activity. By studying the effect of efferent activity on the speech-evoked auditory brainstem response (ABR), some more light could be shed on the effect of efferent pathways on the encoding of speech in the auditory pathway. Objectives To investigate the relationship between contralateral suppression of transient evoked otoacoustic emission (CSTEOAE) and unmasking of speech ABR. Methods A total of 23 young adults participated in the study. The CSTEOAE was measured using linear clicks at 60 dB peSPL and white noise at 60 dB sound pressure level (SPL). The speech ABR was recorded using the syllable /da/ at 80 dB SPL in quiet, ipsilateral noise, and binaural noise conditions. In the ipsilateral noise condition, white noise was presented to the test ear at 60 dB SPL, and, in the binaural noise condition, two separate white noises were presented to both ears. Results The F0 amplitude of speech ABR was higher in quiet condition; however, the mean amplitude of F0 was not significantly different across conditions. Correlation analysis showed a significant positive correlation between the CSTEOAE and the magnitude of unmasking of F0 amplitude of speech ABR. Conclusions The findings of the present study suggests that the efferent pathways are involved in speech-in-noise processing.

Gender Effects on Binaural Speech Auditory Brainstem Response.

Background: The speech auditory brainstem response is a tool that provides direct information on how speech sound is temporally and spectrally coded by the auditory brainstem. Speech auditory brainstem response is influenced by many variables, but the effect of gender is unclear, particularly in the binaural recording. Studies on speech auditory brainstem response evoked by binaural stimulation are limited, but gender studies are even more limited and contradictory. This study aimed at examining the effect of gender on speech auditory brainstem response in adults.Methods: Time- and frequency-domain analyses of speech auditory brainstem response recordings of 30 healthy participants (15 women and 15 men) aged 18-35 years with normal hearing and no musical education were obtained. For each adult, speech auditory brainstem response was recorded with the syllable /da/ presented binaurally. Peaks of time (V, A, C, D, E, F, and O) and frequency (fundamental frequency, first formant frequency, and high frequency) domains of speech auditory brainstem response were compared between men and women.Results: V, A, and F peak latencies of women were significantly shorter than those of men (P < .05). However, no difference was found in the peak amplitude of the time (P > .05) or frequency domain between women and men (P > .05).Conclusion: Gender differences in binaural speech auditory brainstem response are significant in adults, particularly in the time domain. When speech stimuli are used for auditory brainstem responses, normative data specific to gender are required. Preliminary normative data from this study could serve as a reference for future studies on binaural speech auditory brainstem response among Turkish adults.

Evaluation of Auditory Efferent System using Speech Auditory Brainstem Response with Contralateral Noise

Evaluation of Auditory Efferent System using Speech Auditory Brainstem Response with Contralateral Noise

Effects of Spectral Shaping on Speech Auditory Brainstem Responses to Stop Consonant-Vowel Syllables.

Spectral shaping is employed by hearing aids to make consonantal information, such as formant transitions, audible for listeners with hearing loss. How manipulations of the stimuli, such as spectral shaping, may alter encoding in the auditory brainstem has not been thoroughly studied. The aim of this study was to determine how spectral shaping of synthetic consonant-vowel (CV) syllables, varying in their second formant (F2) onset frequency, may affect encoding of the syllables in the auditory brainstem. We employed a repeated measure design. Sixteen young adults (mean = 20.94 years, 6 males) and 11 older adults (mean = 58.60 years, 4 males) participated in this study. Speech-evoked auditory brainstem responses (speech-ABRs) were obtained from each participant using three CV exemplars selected from synthetic stimuli generated for a /ba-da-ga/ continuum. Brainstem responses were also recorded to corresponding three CV exemplars that were spectrally shaped to decrease low-frequency information and provide gain for middle and high frequencies according to a Desired Sensation Level function. In total, six grand average waveforms (3 phonemes [/ba/, /da/, /ga/] X 2 shaping conditions [unshaped, shaped]) were produced for each participant. Peak latencies and amplitudes, referenced to prestimulus baseline, were identified for 15 speech-ABR peaks. Peaks were marked manually using the program cursor on each individual waveform. Repeated-measures analysis of variances were used to determine the effects of shaping on the latencies and amplitudes of the speech-ABR peaks. Shaping effects produced changes within participants in ABR latencies and amplitudes involving onset and major peaks of the speech-ABR waveform for certain phonemes. Specifically, data from onset peaks showed that shaping decreased latency for /ga/ in older listeners, and decreased amplitude onset for /ba/ in younger listeners. Shaping also increased the amplitudes of major peaks for /ga/ stimuli in both groups. Encoding of speech in the ABR waveform may be more complex and multidimensional than a simple demarcation of source and filter information, and may also be influenced by cue intensity and age. These results suggest a more complex subcortical encoding of vocal tract filter information in the ABR waveform, which may also be influenced by cue intensity and age.

Comparing Sound-Field Speech-Auditory Brainstem Response Components between Cochlear Implant Users with Different Speech Recognition in Noise Scores

ObjectivesMany studies have suggested that cochlear implant (CI) users vary in terms of speech recognition in noise. Studies in this field attribute this variety partly to subcortical auditory processing. Studying speech-Auditory Brainstem Response (speech-ABR) provides good information about speech processing; thus, this work was designed to compare speech-ABR components between two groups of CI users with good and poor speech recognition in noise scores. Materials & MethodsThe present study was conducted on two groups of CI users aged 8-10 years old. The first group (CI-good) consisted of 15 children with prelingual CI who had good speech recognition in noise performance. The second group (CI-poor) was matched with the first group, but they had poor speech recognition in noise performance. The speech-ABR test in a sound-field presentation was performed for all the participants. Results The speech-ABR response showed more delay in C, D, E, F, O latencies in CI-poor than CI-good users (P <0.05), meanwhile no significant difference was observed in initial wave (V(t= -0.293, p= 0.771 and A (t= -1.051, p= 0.307). Analysis in spectral-domain showed a weaker representation of fundamental frequency as well as the first formant and high-frequency component of speech stimuli in the CI users with poor auditory performance.ConclusionsResults revealed that CI users who showed poor auditory performance in noise performance had deficits in encoding the periodic portion of speech signals at the brainstem level. Also, this study could be as physiological evidence for poorer pitch processing in CI users with poor speech recognition in noise performance.

On prediction of aided behavioural measures using speech auditory brainstem responses and decision trees.

Current clinical strategies to assess benefits from hearing aids (HAs) are based on self-reported questionnaires and speech-in-noise (SIN) tests; which require behavioural cooperation. Instead, objective measures based on Auditory Brainstem Responses (ABRs) to speech stimuli would not require the individuals' cooperation. Here, we re-analysed an existing dataset to predict behavioural measures with speech-ABRs using regression trees. Ninety-two HA users completed a self-reported questionnaire (SSQ-Speech) and performed two aided SIN tests: sentences in noise (BKB-SIN) and vowel-consonant-vowels (VCV) in noise. Speech-ABRs were evoked by a 40 ms [da] and recorded in 2x2 conditions: aided vs. unaided and quiet vs. background noise. For each recording condition, two sets of features were extracted: 1) amplitudes and latencies of speech-ABR peaks, 2) amplitudes and latencies of speech-ABR F0 encoding. Two regression trees were fitted for each of the three behavioural measures with either feature set and age, digit-span forward and backward, and pure tone average (PTA) as possible predictors. The PTA was the only predictor in the SSQ-Speech trees. In the BKB-SIN trees, performance was predicted by the aided latency of peak F in quiet for participants with PTAs between 43 and 61 dB HL. In the VCV trees, performance was predicted by the aided F0 encoding latency and the aided amplitude of peak VA in quiet for participants with PTAs ≤ 47 dB HL. These findings indicate that PTA was more informative than any speech-ABR measure, as these were relevant only for a subset of the participants. Therefore, speech-ABRs evoked by a 40 ms [da] are not a clinical predictor of behavioural measures in HA users.

Cortical and subcortical processing of speech in cochlear implant recipients with Auditory Neuropathy Spectrum Disorder

Abstract Background Cochlear implantation (CI) is now recognized as one of the possible lines of interventions in ANSD patients to improve their hearing and speech communication. Desynchronized of the auditory information is the most widely accepted mechanism in ANSD. Objectives To study speech processing in the brainstem level as measured by speech-auditory brainstem response (S-ABR) in ANSD and CAEP P1 in ANSD subjects fitted with CIs and the results will be compared to SNHL subjects fitted with unilateral CIs. Subjects and method A total number of 45 subjects were included classified into three groups (one control and two study groups). The control group 16 subjects, age ranged from 5 to 29.5 years with mean of (11.1 years) with normal peripheral hearing sensitivity. The study group comprised 29 children who underwent cochlear implantation. It was subdivided into two subgroups: Group (SNHL) ;their age ranged from2.9 to 15.5 years with mean of (7.7 years) and group (ANSD); Their age ranged from 3.2 to 29 years with mean of (9.3 years) They were subjected to detailed history taking, aided warble-tone sound field audiometry, Questionnaire and Speech-evoked potentials (P1 &amp;c-ABR) recording evoked by the 150-ms synthesized /da/ syllable stimulus. Results C-ABR waves were detected in 100% of control group, 75% of SNHL group and 53.8% of ANSD group. A statistically significant differences existed between the control group and the two study subgroups regarding the P1 latencies. While; there were no statistically significant differences between {SNHL group &amp;ANSD}. Sound-field S-ABR in the CI recipients showed delayed latencies in both SNHL group &amp;ANSD group comparable to the control group with more delay in ANSD group than SNHL group. Finally, the neural phase locking was significantly higher in CI recipients due to electrical artifact. Conclusions • There were no statistically significant differences between {SNHL group &amp; ANSD group} regarding P1 latency. • C-ABR waves were detected in 75% of SNHL group and 53.8% of ANSD group with delayed latencies and higher amplitude than control group with more delay in ANSD group than SNHL group. The findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech processing in ANSD subjects fitted with cochlear implant.

Speech ABR Findings in Auto Rickshaw Drivers Exposed to Occupational Noise.

Most of the persons with noise exposure will have clinically normal hearing threshold while experiencing reduced speech comprehension. The motive of this study is to assess the impact of occupational noise on the encoding of speech stimuli in the auditory system in the auto-rickshaw drivers and compare the auditory brainstem responses (ABR) using speech stimuli with that of controls. The study was done in experimental design, where speech evoked ABR was measured in 21 auto-drivers who were continuously exposed to higher levels of occupational noise, and they were compared to the results of 37 individuals who were not exposed to noise. Speech ABR was administered in both the groups and the absolute latencies and amplitudes of the peaks V, A, C, D, E, F and O were compared. The results revealed that there is a statistically significant difference (p < 0.05) in the latency of peak V (F(1,32) = 6.13, p < 0.05, = 0.12) and peak A (F(1,32) = 4.03, p < 0.05, = 0.08) between the control and experimental group. Similarly, there was a statistically significant difference seen in the amplitude of peak D (F(1,32) = 6.38, p < 0.05, = 0.12) and peak F (F(1,32) = 7.97, p < 0.05, = 0.15). Acknowledging how the speech signals are coded in the brainstem may aid in the timely detection and intervention of hearing-related issues, even in individuals having normal hearing acuity. The results indicate that there is damage at the level of the brainstem which will lead to poor speech understanding in those who are exposed to occupational noise. These indicators are present even before routine audiometry indicates a hearing loss.

Effects of auditory processing training on speech perception and brainstem plastisity in adolescents with autism spectrum disorders.

ObjectiveAutism spectrum disorder (ASD) is a neurodevelopmental disorder. A major problem of ASD is speech perception impairment in the presence of background noise. Additionally, researchers have reported temporal auditory processing impairment in patients with ASD. In the present study, we evaluated the effects of a temporal-based training program on improvement of speech perception in the presence of noise using the speech auditory brainstem response (sABR).Materials & MethodsTwenty-eight adolescents with high functional ASD with the mean age of 14.35±1.86 years were randomly selected and divided into an ASD group (11 males and three females) and a control group (13 males and one female). All the subjects had a normal hearing and intelligence threshold and had no history of neurological disorder.A speech perception test was performed in signal-to-noise ratios of 0 and +10. The intervention group received a temporal processingbased auditory training program, and the control group received a conventional training program. A P-value of <0.05 was considered significant.ResultsAfter training, speech perception in the presence of noise was significantly higher (P <0.001) and the latency of all sABR waves was lower in the intervention group compared to the control group.ConclusionImprovement of speech perception in noisy environments and the reduced latency of sABR waves following a temporal processingbased training program highlight the role of brainstem neural plasticity in speech processing.

Effect of Vowel Auditory Training on the Speech-In-Noise Perception among Older Adults with Normal Hearing.

Introduction:Aging reduces the ability to understand speech in noise. Hearing rehabilitation is one of the ways to help older people communicate effectively. This study aimed to investigate the effect of vowel auditory training on the improvement of speech-in-noise (SIN) perception among elderly listeners.Materials and Methods:This study was conducted on 36 elderly listeners (17 males and 15 females) with the mean±SD of 67.6±6.33. They had the normal peripheral auditory ability but had difficulties in SIN perception. The samples were randomly divided into two groups of intervention and control. The intervention group underwent vowel auditory training; however, the control group received no training.Results:After vowel auditory training, the intervention group showed significant changes in the results of the SIN test at two signal-to-noise ratios of 0 and -10 and the Iranian version of the Speech, Spatial, and Qualities of Hearing Scale, compared to the control group (P<0.001). Regarding the Speech Auditory Brainstem Response test, the F0 magnitude was higher in the intervention group (8.42±2.26), compared to the control group (6.68±1.87) (P<0.011).Conclusion:This study investigated the effect of vowel auditory training on the improvement of SIN perception which could be probably due to better F0 encoding and receiving. This ability enhancement resulted in the easier perception of speech and its more proper separation from background noise which in turn enhanced the ability of the old people to follow the speech of a specific person and track the discussion.

Noise-Induced Changes of the Auditory Brainstem Response to Speech\u2014a Measure of Neural Desynchronisation?

It is commonly assumed that difficulty in listening to speech in noise is at least partly due to deficits in neural temporal processing. Given that noise reduces the temporal fidelity of the auditory brainstem response (ABR) to speech, it has been suggested that the speech ABR may serve as an index of such neural deficits. However, the temporal fidelity of ABRs, to both speech and non-speech sounds, is also known to be influenced by the cochlear origin of the response, as responses from higher-frequency cochlear regions are faster and more synchronous than responses from lower-frequency regions. Thus, if noise caused a reweighting of response contributions from higher- to lower-frequency cochlear regions, the temporal fidelity of the aggregate response should be reduced even in the absence of any changes in neural processing. This ‘place mechanism’ has been demonstrated for non-speech ABRs. The aim of this study was to test whether it also applies to speech ABRs. We used the so-called ‘derived-band’ method to isolate response contributions from frequency-limited cochlear regions. Broadband and derived-band speech ABRs were measured both in quiet and in noise. Whilst the noise caused significant changes to the temporal properties of the broadband response, its effects on the derived-band responses were mostly restricted to the response amplitudes. Importantly, the amplitudes of the higher-frequency derived-band responses were much more strongly affected than those of the lower-frequency responses, suggesting that the noise indeed caused a reweighting effect. Our results indicate that, as for non-speech ABRs, the cochlear place mechanism can represent a potentially substantial confound to speech-ABR-in-noise measurements.

Sound-Field Speech Evoked Auditory Brainstem Response in Cochlear-Implant Recipients

Background and ObjectivesCurrently limited information is available on speech stimuli processing at the subcortical level in the recipients of cochlear implant (CI). Speech processing in the brainstem level is measured using speech-auditory brainstem response (S-ABR). The purpose of the present study was to measure the S-ABR components in the sound-field presentation in CI recipients, and compare with normal hearing (NH) children.Subjects and MethodsIn this descriptive-analytical study, participants were divided in two groups: patients with CIs; and NH group. The CI group consisted of 20 prelingual hearing impairment children (mean age=8.90 ± 0.79 years), with ipsilateral CIs (right side). The control group consisted of 20 healthy NH children, with comparable age and sex distribution. The S-ABR was evoked by the 40-ms synthesized /da/ syllable stimulus that was indicated in the sound-field presentation.ResultsSound-field S-ABR measured in the CI recipients indicated statistically significant delayed latencies, than in the NH group. In addition, these results demonstrated that the frequency following response peak amplitude was significantly higher in CI recipients, than in the NH counterparts (p<0.05). Finally, the neural phase locking were significantly lower in CI recipients (p<0.05). ConclusionsThe findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech process in CI recipients.

Encoding of speech in noise in adults using hearing aids: effect of noise reduction algorithm

Introduction: Subjects using hearing aids complains of difficulty in speech understanding in noise. Speech auditory brainstem response (S-ABR) provides cues for temporal and spectral encoding of speech in the brainstem.Objective: This work was designed to evaluate speech processing in patients fitted with hearing aid using S-ABR and to study the effect of noise reduction algorithm on speech processing in patients fitted with hearing aids.Materials and method: This study included 20 adults with mild to severe SNHL fitted with HA at least 3 months with aided threshold in all frequencies better than or equal to 30 dB. Hearing aid was used with all the subjects and was programed for each subject according to his audiogram followed by aided evaluation using S-ABR. Through sound field in four different test conditions with NR algorithm on in quiet and in the presence of noise then with the NR off in quiet and in the presence of noise were performed.Results: There was a statistically significant delay in the S-ABR onset and offset in noise compared to quiet. The effect of noise on S-ABR while the NR was on showed statistically significant difference in the onset response in both quiet and noise. When the NR was off, there was marked effect of noise on both the onset response and offset response.Conclusions: It was found that hearing aid users are vulnerable to noise regarding the speech encoding at the level of the brainstem. Noise reduction algorithm maintains the neural activity in response to speech and improves speech perception in noise.

Main Aspects of Peripheral and Central Hearing System Involvement in Unexplained HIV-Related Hearing Complaints.

Objective: Hearing abnormalities frequently occur in Human Immunodeficiency Virus (HIV) infected individuals. Both conductive and uni- or bilateral sensorineural hearing loss (SNHL) have been described along with other audiological and vestibular symptoms such as tinnitus, vertigo and balance disturbances. While frequent middle ear infections may explain impairment of peripheral hearing abilities, the exact etiology of cochlear, and central auditory processing deficits still remains unclear. Direct effects of HIV, opportunistic infections, ototoxic side effects of antiretroviral therapy (ART), and immunologic responses to the central nervous system involving the auditory pathway have been proposed. We aim to review the audiological profile in HIV infected adults related to the effects of HIV and HAART on the inner ear structures.Methods: We present a review of the literature on cases of HIV related SNHL in adult patients and studies conducted to investigate audiometric changes in such patients. Data on presentation, diagnosis and pathophysiology were reviewed.Results: Sensorineural hearing loss in the higher frequencies is a common form of hearing loss in HIV infected individuals throughout disease progression, along with decreased otoacoustic emission (OAE) responses, increased PTA hearing thresholds and prolonged latencies for auditory brainstem responses (ABR).Conclusion: HIV affects all stages of auditory perception in a way similar to accelerated aging of the auditory system. And we postulate that synaptic loss may be the first step, followed by cochlear damage and central pathology as the virus remains present in all the structures of the auditory pathway causing local inflammation and degeneration. Evaluation of hearing function among all patients diagnosed with HIV infection seems to be an accepted approach; it should include OAE testing, pure tone and speech audiometry, speech-in-noise tests and ABR measurements.

Enhancement of the Auditory Late Response (N1-P2) by Presentation of Stimuli From an Unexpected Location.

Passive electrophysiological protocols, such as the middle latency response and speech auditory brainstem response, are often advocated in the objective assessment of central auditory processing disorder (CAPD). However, few established electrophysiological protocols exist for CAPD assessment that have patients participate in active tasks which more closely approximate real-world listening. To this end, the present study used a discrimination task (i.e., oddball paradigm) to measure an enhancement of the auditory late response (N1-P2) that occurs when participants direct their auditory attention toward speech arising from an unexpected spatial location. To establish whether N1-P2 is enhanced when auditory attention is directed toward an unexpected location during a two-word discrimination task. In addition, it was also investigated whether any enhancements in this response were contingent on the stimulus being counted as part of the oddball paradigm. Prospective study with a repeated measures design. Ten normal hearing adults, with an age range of 18-24 years. The N1 and P2 latencies and peak-to-peak amplitudes were recorded during a P300 paradigm. A series of repeated measures of analysis of variance and a correlation analysis was performed. There was a significant effect of stimulus location, in which words arising from the unexpected location showed a larger N1-P2 peak-to-peak amplitude and an earlier N1 latency. This effect was seen regardless of whether or not participants had to count the word total in memory. These findings suggest that spatial enhancement of the N1-P2 is a fairly robust phenomenon in normal hearing adult listeners. Additional studies are needed to determine whether this enhancement is absent or reduced in patients with CAPD.

Speech Auditory Brainstem Responses: Effects of Background, Stimulus Duration, Consonant-Vowel, and Number of Epochs.

The aims of this study were to systematically explore the effects of stimulus duration, background (quiet versus noise), and three consonant-vowels on speech-auditory brainstem responses (ABRs). Additionally, the minimum number of epochs required to record speech-ABRs with clearly identifiable waveform components was assessed. The purpose was to evaluate whether shorter duration stimuli could be reliably used to record speech-ABRs both in quiet and in background noise to the three consonant-vowels, as opposed to longer duration stimuli that are commonly used in the literature. Shorter duration stimuli and a smaller number of epochs would require shorter test sessions and thus encourage the transition of the speech-ABR from research to clinical practice. Speech-ABRs in response to 40 msec [da], 50 msec [ba] [da] [ga], and 170 msec [ba] [da] [ga] stimuli were collected from 12 normal-hearing adults with confirmed normal click-ABRs. Monaural (right-ear) speech-ABRs were recorded to all stimuli in quiet and to 40 msec [da], 50 msec [ba] [da] [ga], and 170 msec [da] in a background of two-talker babble at +10 dB signal to noise ratio using a 2-channel electrode montage (Cz-Active, A1 and A2-reference, Fz-ground). Twelve thousand epochs (6000 per polarity) were collected for each stimulus and background from all participants. Latencies and amplitudes of speech-ABR peaks (V, A, D, E, F, O) were compared across backgrounds (quiet and noise) for all stimulus durations, across stimulus durations (50 and 170 msec) and across consonant-vowels ([ba], [da], and [ga]). Additionally, degree of phase locking to the stimulus fundamental frequency (in quiet versus noise) was evaluated for the frequency following response in speech-ABRs to the 170 msec [da]. Finally, the number of epochs required for a robust response was evaluated using Fsp statistic and bootstrap analysis at different epoch iterations. Background effect: the addition of background noise resulted in speech-ABRs with longer peak latencies and smaller peak amplitudes compared with speech-ABRs in quiet, irrespective of stimulus duration. However, there was no effect of background noise on the degree of phase locking of the frequency following response to the stimulus fundamental frequency in speech-ABRs to the 170 msec [da]. Duration effect: speech-ABR peak latencies and amplitudes did not differ in response to the 50 and 170 msec stimuli. Consonant-vowel effect: different consonant-vowels did not have an effect on speech-ABR peak latencies regardless of stimulus duration. Number of epochs: a larger number of epochs was required to record speech-ABRs in noise compared with in quiet, and a smaller number of epochs was required to record speech-ABRs to the 40 msec [da] compared with the 170 msec [da]. This is the first study that systematically investigated the clinical feasibility of speech-ABRs in terms of stimulus duration, background noise, and number of epochs. Speech-ABRs can be reliably recorded to the 40 msec [da] without compromising response quality even when presented in background noise. Because fewer epochs were needed for the 40 msec [da], this would be the optimal stimulus for clinical use. Finally, given that there was no effect of consonant-vowel on speech-ABR peak latencies, there is no evidence that speech-ABRs are suitable for assessing auditory discrimination of the stimuli used.