Auditory Brainstem Response Latencies Research Articles

Effects of Korean red ginseng on auditory, cognitive, and liver functions in a naturally aged mouse model

BackgroundKorean Red Ginseng and ginsenosides have been studied for their efficacy against various diseases, including those related to aging. However, most aging studies use D-galactose to induce aging, which often does not accurately represent natural aging. This study aimed to verify improvements in auditory, cognitive, and liver function through administering red ginseng to an 18-month-old naturally aging mouse model. MethodsAuditory function was assessed using Auditory Brainstem Response (ABR) and Auditory Middle Latency Response (AMLR). Cognitive function was evaluated electrophysiologically with P300 and mismatch negativity (MMN), and behaviorally using the Y-maze. Additionally, biochemical tests and histological analysis were conducted to assess liver function. The effects of red ginseng on gene expression regulation were also examined in the cochlea, auditory cortex, and liver, focusing on age-related disease processes. ResultsRed ginseng significantly decreased hearing thresholds and improved central auditory function. It also enhanced cognitive behavior and function in response to external stimulation. Furthermore, red ginseng regulated alkaline phosphatase (ALP), albumin (Alb), and total protein (TP) levels, notably decreasing aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Hematoxylin and eosin (H&E) staining of liver tissue showed significant improvement in fat droplets. These effects appear to be mediated by the regulation of aging-related genes Dec, c-Jun, Stat5b, and Lims2. ConclusionThese results suggest that red ginseng improves auditory, cognitive, and liver functions in a naturally aged mouse model.

Audiological Characterization of Individuals with Cornelia de Lange Syndrome.

Introduction Cornelia de Lange Syndrome (CdLS) is a genetic disorder in which individuals may present sensorineural and/or conductive hearing loss, and the results of behavioral auditory assessments are not accurate. Objective To characterize the audiological profile of individuals with CdLS through behavioral, electroacoustic, and electrophysiological audiological assessments. Methods The study included 13 individuals of both sexes, aged between 3 and 26 years, with diagnoses confirmed through genetic studies. The following procedures were performed: medical history survey, otoscopy (pure-tone audiometry [PTA], speech audiometry, and acoustic immittance measures), and auditory brainstem response (ABR). Results In total 62.50% of the participants who underwent PTA had abnormal results (all of which were mild), with a predominance of bilateral conductive hearing loss (60%). Regarding tympanometry, 76.93% had abnormal results, most frequently type B (85.72% on the right and 88.89% on the left ear). Acoustic reflexes showed results compatible with tympanometry changes. Changes in ABR latency values compatible with middle-ear impairment were found in 8 of them (66.66%) - 3 had bilateral (37.50%), and 5 had unilateral impairments (62.50%). Conclusion Mild hearing loss was identified in 62.5% of the individuals with CdLS who underwent the behavioral audiological assessment. In the acoustic immittance measures, 76.9% of the participants presented a tympanometry curve characteristic of middle-ear changes. Acoustic reflexes were absent in 84.6% of the subjects. In the ABR, no changes were identified in auditory pathway integrity. On the other hand, changes in the absolute latency values were found, which are characteristic of conductive hearing loss.

Peripheral hearing sensitivity is similar between the sexes in a benthic turtle species despite the larger body size of males.

Sexually dimorphic hearing sensitivity has evolved in many vertebrate species, and the sex with a larger body size typically shows more sensitive hearing. However, generalizing this association is controversial. Research on sexually dimorphic hearing sensitivity contributes to an understanding of auditory sense functions, adaptations, and evolution among species. Therefore, the hypothesized association between body size and hearing needs further validation, especially in specific animal groups. In this study, we assessed hearing sensitivity by measuring auditory brainstem responses (ABRs) in both sexes of 3-year-old Chinese softshell turtles (Pelodiscus sinensis). In this species, male bodies are larger than those of female, and individuals spend most of their lives in the mud at the bottom of freshwater habitats. We found that for both sexes, the hearing sensitivity bandwidth was 0.2-0.9 kHz. Although males were significantly larger than females, no significant differences in ABR thresholds or latencies were found between males and females at the same stimulus frequency. These results indicate that P. sinensis hearing is only sensitive to low-frequency (typically <0.9 kHz) sound signals and that sexually dimorphic hearing sensitivity is not a trait that has evolved in P. sinensis. Physiological and environmental reasons may account for P. sinensis acoustic communication via low-frequency sound signals and the lack of sexually dimorphic hearing sensitivity in these benthic turtles. The results of this study refine our understanding of the adaptation and evolution of the vertebrate auditory system.

Charcot-Marie-Tooth Disease and Hearing Loss: A Systematic Review With Meta-Analysis.

To characterize the pattern of hearing loss in Charcot-Marie-Tooth (CMT) disease to help guide clinical management. CINAHL, PubMed, and Scopus. Two independent investigators selected studies on CMT patients with pure-tone average (PTA) and auditory brainstem response (ABR) data. Case reports, case series <5 patients, and data that overlapped with another study were excluded. Investigators performed data extraction, quality rating, and risk-of-bias assessment using the Newcastle-Ottawa Scale. Meta-analysis of mean difference using fixed/random effects models was used. Also, data were analyzed using a weighted one-way analysis of variance, with post-hoc Tukey's test for comparison. Ultimately, 6 prospective studies (N = 197) were included. The most common demyelinating subtype (CMT1A) had significantly prolonged ABR latency values across wave III (0.20 ms, 95% confidence interval [CI]: 0.05-0.35), wave V (0.20 ms, 95% CI: 0.01-0.39), waves I-III (0.20 ms, 95% CI: 0.01-0.39), and waves I-V (0.20 ms, 95% CI: 0.01-0.39) when compared to matched controls. The autosomal recessive demyelinating subtype (CMT4C) had significantly worse PTA when compared to the most common subtype (CMT1A) (Δ 28.93 dB, 95% CI 18.34-39.52) and nondemyelinating subtype (CMT2A) (Δ 28.3 dB, 95% CI: 15.98-40.62). Patients with CMT can present with a variety of phenotypes depending on the causative mutation. The ABR interpeak latency values for the most common demyelinating form of CMT are delayed when compared to matched controls. Most subtypes have normal hearing thresholds, apart from CMT4C, which presents with mild hearing loss on average.

Tone-burst elicited auditory brainstem responses in full-term and pre-term infants

Objective To investigate the reliability of tone-burst auditory brainstem response (TB-ABR) latencies and thresholds in pre-term and full-term infants. Design TB-ABRs to 500 Hz and 4000 Hz tone-burst stimuli were recorded at two-week intervals over the first six weeks of life in a group of full-term infants (40–46 weeks gestational age [GA]) and over ten weeks (36–46 weeks gestation) in a group of preterm infants. Linear mixed model analyses evaluated within-subject changes and the effects of the subject group, age at assessment, and stimulus frequency on ABR latency and threshold. Study sample Twenty-four infants participated. Nine were full-term (GA: 39–41 weeks) and fifteen were healthy pre-term (GA: 28–34 weeks) at birth. Results TB-ABR wave V latencies at 70 dBnHL decreased throughout the study (p < 0.001) in pre-term babies for both test frequencies by approximately 0.5 ms. There were, however, no group or GA (at birth) effects indicating that response latency normalized in these children by the due date. Similarly, TB-ABR threshold levels in the premature group were elevated (p = 0.001) by approximately 5 dB in pre-term evaluation but were equivalent to those of full-term participants in the post-term assessment period. Conclusions In healthy, pre-term infants, tone-burst ABR testing is reliable from 36 weeks gestation.

Auditory Neural Responses and Communicative Functioning in Children With Microcephaly Related to Congenital Zika Syndrome.

Children with microcephaly exhibit neurodevelopmental delays and compromised communicative functioning, yielding challenges for clinical assessment and informed intervention. This study characterized auditory neural function and communication abilities in children with microcephaly due to congenital Zika syndrome (CZS). Click-evoked auditory brainstem responses (ABR) at fast and slow stimulation rates and natural speech-evoked cortical auditory evoked potentials (CAEP) were recorded in 25 Brazilian children with microcephaly related to CZS ( M age: 5.93 ± 0.62 years) and a comparison group of 25 healthy children ( M age: 5.59 ± 0.80 years) matched on age, sex, ethnicity, and socioeconomic status. Communication abilities in daily life were evaluated using caregiver reports on Vineland Adaptive Behavior Scales-3. Caregivers of children with microcephaly reported significantly lower than typical adaptive functioning in the communication and socialization domains. ABR wave I latency did not differ significantly between the groups, suggesting comparable peripheral auditory function. ABR wave V absolute latency and waves I-V interwave latency were significantly shorter in the microcephaly group for both ears and rates. CAEP analyses identified reduced N2 amplitudes in children with microcephaly as well as limited evidence of speech sound differentiation, evidenced mainly by the N2 response latency. Conversely, in the comparison group, speech sound differences were observed for both the P1 and N2 latencies. Exploratory analyses in the microcephaly group indicated that more adaptive communication was associated with greater speech sound differences in the P1 and N2 amplitudes. The trimester of virus exposure did not have an effect on the ABRs or CAEPs. Microcephaly related to CZS is associated with alterations in subcortical and cortical auditory neural function. Reduced ABR latencies differ from previous reports, possibly due to the older age of this cohort and careful assessment of peripheral auditory function. Cortical speech sound detection and differentiation are present but reduced in children with microcephaly. Associations between communication performance in daily life and CAEPs highlight the value of auditory evoked potentials in assessing clinical populations with significant neurodevelopmental disabilities.

ABR-Attention: An Attention-Based Model for Precisely Localizing Auditory Brainstem Response.

Auditory Brainstem Response (ABR) is an evoked potential in the brainstem's neural centers in response to sound stimuli. Clinically, characteristic waves, especially Wave V latency, extracted from ABR can objectively indicate auditory loss and diagnose diseases. Several methods have been developed for the extraction of characteristic waves. To ensure the effectiveness of the method, most of the methods are time-consuming and rely on the heavy workloads of clinicians. To reduce the workload of clinicians, automated extraction methods have been developed. However, the above methods also have limitations. This study introduces a novel deep learning network for automatic extraction of Wave V latency, named ABR-Attention. ABR-Attention model includes a self-attention module, first and second-derivative attention module, and regressor module. Experiments are conducted on the accuracy with 10-fold cross-validation, the effects on different sound pressure levels (SPLs), the effects of different error scales and the effects of ablation. ABR-Attention shows efficacy in extracting Wave V latency of ABR, with an overall accuracy of 96.76 ± 0.41 % and an error scale of 0.1ms, and provides a new solution for objective localization of ABR characteristic waves.

Supra-Threshold LS CE-Chirp Auditory Brainstem Response in the Elderly

Introduction: Aging deteriorates peripheral and central auditory structures and functions. In elders, for an accurate audiological evaluation, it is important to explore beyond the cochlear receptor. Audiograms provide an estimation of hearing thresholds, while the amplitudes and latencies of supra-threshold auditory brainstem response (ABR) can offer noninvasive measures of the auditory pathways functioning. Regarding ABR, in young populations, level-specific chirp (LS CE-chirp) stimulus has been proposed as an alternative synchronizing method to obtain larger ABR responses than those evoked by clicks. However, the supra-threshold characteristics of chirp evoked ABR, and their association to hearing thresholds is relatively unknown in the elderly. The aim of this study was to evaluate supra-threshold LS CE-chirp ABRs in an aged population by comparing their features with click ABRs, and evaluating their relationship with audiometric hearing thresholds. Methods: We carried out a cross-sectional study to characterize the hearing of 125 adults aged over 65 years. We determined the audiometric hearing thresholds and supra-threshold ABRs elicited by LS CE-chirp and click stimuli at 80 dB nHL. We evaluated associations by means of partial correlations and covariate adjustment. We performed specific frequencies’ analysis and subgroup analysis per hearing level. Results: Wave V responses had significantly shorter latencies and larger amplitudes when elicited by LS CE-chirp as compared to click-evoked responses. Audiometric hearing thresholds correlated with age, but ABR characteristics did not. We found mild correlations between hearing thresholds and ABR characteristics, predominantly at higher frequencies and with chirp. We found scarce evidence of correlation between ABR characteristics and the average of behavioral hearing thresholds between 0.5 to 4 kHz (0.5–4 kHz PTA). After subgroup analysis according to the hearing level, no stronger or more significant correlations were found between ABR characteristics and 0.5–4 kHz PTA. Discussion: In this study, we found that supra-threshold LS CE-chirp ABR presented some of the previously described similitudes and differences with supra-threshold click ABR in younger populations. Although, the average amplitude and latency of wave V evoked by LS CE-chirp were larger and faster than those evoked by clicks, these results should be taken with caution at the individual level, and further studies are required to state that LS CE-chirp ABRs are better than click ABRs in elders for clinical evaluations. We did not find consistent associations between hearing thresholds and supra-threshold wave V features, suggesting that these measures should be considered independently in the elderly.

The auditory function in migraine model rats induced by postauricular nitroglycerin injection.

The mechanism by which migraines produce inner ear-related symptoms is not well understood. Previous studies have found that the latency of auditory brainstem response (ABR) in animal models of migraine has changed, but the threshold has not changed significantly. Therefore, it is necessary to establish a better animal model with both migraine and hearing loss to explore the relationship between migraine and auditory function deeply. In this study, the rat model of migraine was induced by postauricular injection of nitroglycerin (NTG), and the effect on the auditory function of the inner ear was explored by comparing with intraperitoneal injection of nitroglycerin. The rats were given the drug repeatedly on alternate days, a total of 5 dosing, with the body weight monitored during the drug administration. The tactile threshold of the rats' forepaw was measured using von-Frey filaments and auditory function was assessed by ABR. The results showed that the baseline tactile threshold of rats gradually decreased during the modeling process, and hyperalgesia appeared. Postauricular injection of NTG did not affect the weight gain of rats, while intraperitoneal injection of NTG showed slow or even negative weight gain. The ABR threshold of Click, 4 and 8 kHz of postauricular NTG injection rats increased, the latency was prolonged, and the ABR threshold in the right ear was higher than that in the left ear. We demonstrated that postauricular injection of nitroglycerin may be safer and more effective than intraperitoneal injection of nitroglycerin in the process of creating rat migraine model without affecting the weight gain. Postauricular injection of nitroglycerin has more damage to the auditory function of rats. Therefore, the migraine model rat induced by postauricular injection of nitroglycerin may be a new model of cochlear migraine.

Novelty detection in an auditory oddball task on freely moving rats

The relative importance or saliency of sensory inputs depend on the animal’s environmental context and the behavioural responses to these same inputs can vary over time. Here we show how freely moving rats, trained to discriminate between deviant tones embedded in a regular pattern of repeating stimuli and different variations of the classic oddball paradigm, can detect deviant tones, and this discriminability resembles the properties that are typical of neuronal adaptation described in previous studies. Moreover, the auditory brainstem response (ABR) latency decreases after training, a finding consistent with the notion that animals develop a type of plasticity to auditory stimuli. Our study suggests the existence of a form of long-term memory that may modulate the level of neuronal adaptation according to its behavioural relevance, and sets the ground for future experiments that will help to disentangle the functional mechanisms that govern behavioural habituation and its relation to neuronal adaptation.

Auditory Brainstem Response Testing in Children with Speech and Language Pathology: A Non-Randomized Observational Study

Introduction: The aim of this study was to compare auditory brainstem response (ABR) findings of normal-hearing preschool children with different types of speech and language pathology. Methods: This retrospective, non-randomized, cohort study was conducted at a tertiary speech and hearing rehabilitation institution according to STROBE guidelines. The study enrolled 123 preschool children diagnosed with speech language pathology and normal hearing. The participants included children with developmental language disorder, autism spectrum disorder, isolated articulation pathology, organic brain lesions, cognitive delay, and a group of very young children with clinically significant speech development delay. All patients underwent standard ABR procedures. Results: The latencies were the longest in the group of children with organic lesion, followed by the group of children with autism spectrum disorder, then the group with developmental language disorder, and the young children group. In the group of children with articulation pathology and the cognitive delay group, the latencies were the shortest. Conclusion: This study showed a connection between several groups of children with language pathology that includes comprehension problems and prolongation of ABR latencies.

Development of Machine-Learning Models for Tinnitus-Related Distress Classification Using Wavelet-Transformed Auditory Evoked Potential Signals and Clinical Data.

Tinnitus is a highly prevalent condition, affecting more than 1 in 7 adults in the EU and causing negative effects on sufferers' quality of life. In this study, we utilised data collected within the "UNITI" project, the largest EU tinnitus-related research programme. Initially, we extracted characteristics from both auditory brainstem response (ABR) and auditory middle latency response (AMLR) signals, which were derived from tinnitus patients. We then combined these features with the patients' clinical data, and integrated them to build machine learning models for the classification of individuals and their ears according to their level of tinnitus-related distress. Several models were developed and tested on different datasets to determine the most relevant features and achieve high performances. Specifically, seven widely used classifiers were utilised on all generated datasets: random forest (RF), linear, radial, and polynomial support vector machines (SVM), naive bayes (NB), neural networks (NN), and linear discriminant analysis (LDA). Results showed that features extracted from the wavelet-scattering transformed AMLR signals were the most informative data. In combination with the 15 LASSO-selected clinical features, the SVM classifier achieved optimal performance with an AUC value, sensitivity, and specificity of 92.53%, 84.84%, and 83.04%, respectively, indicating high discrimination performance between the two groups.

Changes in the cochlear and retrocochlear parts of the auditory system in 19-39 and 40-60 years old patients with type 1 diabetes mellitus.

Pathophysiological alterations in the cochlea and functional tests of the auditory pathway support that in diabetes both vasculopathy and neural changes could be present. The aim of our research was to study the differential effect of type 1 diabetes mellitus (T1DM) on two different age groups. Audiological investigation was carried out in 42 patients and 25 controls at the same age groups. Investigation of the conductive and sensorineural part of the hearing system by pure tone audiometry, distortion product otoacoustic emission measurement and acoustically evoked brainstem response registration were evaluated. Among the 19-39-year-old people the incidence of hearing impairment was not different in the diabetes and control groups. Among the 40-60-year-old people hearing impairment was more common in the diabetes group (75%) than in the control group (15,4%). Among patients with type 1 diabetes, the mean threshold values were higher in both age groups at all frequencies although significant difference was in 19-39 years old group: 500-4000Hz right ear, 4000Hz left ear, in 40-60 years old group: 4000-8000 Hz both ears. In the 19-39 years old diabetes group only at 8000 Hertz on the left side was a significant (p<0,05) difference in otoacoustic emissions. In the 40-60 years old diabetes group significantly less otoacoustic emissions at 8000 Hz on the right side (p<0,01) and at 4000-6000-8000 Hertz on the left side, (p<0,05, p<0,01, p<0,05 respectively) was present compared to the control group. According to ABR (auditory brainstem response) latencies and wave morphologies, a possible retrocochlear lesion arose in 15% of the 19-39 years old and 25% of the 40-60 years old diabetes group. According to our results, T1DM affects negatively the cochlear function and the neural part of the hearing system. The alterations are more and more detectable with aging.

Pathophysiological and Clinical Aspects of Hearing Loss Among 85-Year-Olds.

This study aimed to identify the prevalence of conductive/mixed and sensorineural hearing loss, with an attempt to differentiate between sensory and neural components in 85-year-olds. A comprehensive auditory test protocol, including pure-tone audiometry, speech audiometry, auditory brainstem response (ABR), and distortion product otoacoustic emission (DPOAE), was used to identify different types of hearing loss in 85-year-olds. This study comprised a subsample (n = 125) selected from an unscreened cohort of 85-year-olds born in 1930, within the Gothenburg H70 Birth Cohort Studies in Sweden. Test results were reported descriptively. Sensorineural hearing loss was present in one or both ears in almost all participants (98%), and the majority had absent DPOAEs. Only approximately 6% had additional conductive hearing loss, that is, mixed hearing loss. Approximately 20% of the participants with a pure-tone average at 0.5-4 kHz < 60 dB HL had worse word recognition scores compared with predicted scores by the Speech Intelligibility Index (SII), whereas only two participants were classified with neural dysfunction with the use of ABR. Sensorineural hearing loss, likely related to outer hair cell loss, was present in the vast majority of 85-year-olds. Conductive/mixed hearing loss appears to be relatively rare in advanced age. Poor word recognition scores in relation to SII-predicted scores were relatively common (20%) in 85-year-olds, whereas auditory neuropathy was only rarely identified (1.6%) by the use of ABR latencies. To explain abnormal word recognition and to identify the neural component of hearing loss among the older-old population, future research should consider factors such as listening effort and cognition among the older-old population.

The Correlation between Binaural Interaction Component of the Auditory Brainstem Response and Total Score of the Persian Version of the Spatial Hearing Questionnaire

Background and Aim: People with spatial hearing impairment have difficulty perception of speech in the presence of noise, sound localization, and estimating the distance from the sound source. In this study, the comparison between amplitude and latency of the Binaural Interaction Component of the Auditory Brainstem Response (ABR-BIC) with the total score of the Persian version of the Spatial Hearing Questionnaire (SHQ) in adults with normal hearing and moderate sensorineural hearing loss (SNHL) was evaluated. Methods: In this cross-sectional comparative study 55, 18–45-year-old individuals including 35 of normal hearing and 20 moderate SNHL participated. All participants underwent the assessments of medical history, otoscopy, conventional audiometry, tympanometry, SHQ questionnaire, and auditory brainstem response (ABR). Results: There was no significant correlation between the amplitude and latency of the ABR- BIC and the Persian version of the SHQ in normal groups (r=–0.085, r=0.116) and in moderate SNHL groups (r=0.030, r=0.119). The mean value of ABR-BIC range of people with normal hearing and SNHL is statistically significant (p=0.001). Conclusion: The results showed that the amplitude and latency of ABR-BIC were not correlated with the Persian version of the SHQ in people with normal hearing and with moderate SNHL but statistically significant between the mean amplitude and latency of ABR- BIC in people with normal hearing and people with hearing loss. Keywords: Auditory brainstem response; spatial hearing questionnaire; binaural interaction component; spatial hearing; spatial hearing disorder

Effects of latent iron deficiency on auditory neural maturation during early infancy in infants above 35 weeks' gestation.

Latent iron deficiency (LID) at birth is associated with prolonged latencies in auditory brainstem response (ABR), a surrogate for neural maturation. This study aimed to compare wave and inter-peak latencies of ABR at birth and at 4-6 months of age in infants ≥35 weeks of gestation with normal iron status (NIS) and LID. Neonates born at ≥35 weeks were screened. Cord ferritin value≤75ng/mL and >75ng/mL were classified as LID and NIS, respectively. ABR was performed within 48h of birth. The absolute latencies of waves I, III, and V, and inter-peak latencies I-III, III-V, and I-V were computed. Infants were reassessed at 4-6 months of age for hemoglobin, serum ferritin levels, and ABR latencies. In total, 160 neonates were enrolled. The mean (SD) birth weight and gestational age of the study population were 2843 (384) g and 38.3 (1.1) weeks, respectively. Approximately 122 infants completed follow-up until 4-6 months of age: 37 in the LID group and 85 in the NIS group. Overall, the wave and interpeak latencies in both groups at birth were comparable. At 4-6 months, the absolute latencies of waves I, III, and V, and inter-peak latencies I-III, III-V, and I-V were decreased and were comparable in both groups. Among small-for-gestational-age neonates, inter-peak latencies in I-III and I-V at birth were significantly longer in the LID group than in the NIS group. Nine (24.3%) infants in the LID group and none in the NIS group were iron-deficient at 4-6 months of age. There was no difference in wave or inter-peak latencies at birth and at 4-6 months of age in neonates aged ≥35 weeks with or without LID. However, infants with LID at birth have a significant risk of iron deficiency at 4-6 months of age. CTRI/2017/08/009379 (www.ctri.nic.in).

Analysis of the Latency of Auditory Brainstem Response Wave V in Infants According to Age, Hearing Threshold and Stimulus Intensity

Background and Objectives The latency of auditory brainstem response (ABR) wave V shifts depending on age, hearing threshold, and stimulus intensity. This study was performed to examine the latencies of ABR wave V in infants with normal hearing and sensorineural hearing loss.Subjects and Method The retrospective review of ABR of 318 infants (539 ears) was performed. The patients were divided into four groups according to age at the time of the ABR test (group A: 0-2 months, group B: 3-5 months, group C: 6-8 months, and group D: 9-11 months). The test was performed using click sound under sedation, with the stimulus intensity adjusted by 10 dB intervals. The latency of wave V was analyzed according to age, hearing threshold, and stimulus intensity.Results Normal hearing was detected in 320 ears (wave V threshold of 20 dBnHL or less) and sensorineural hearing loss was found in 219 ears. Wave V latencies decreased with increase in age and stimulus intensity in both normal hearing infants and hearing-impaired infants. The ears with higher thresholds showed longer latencies at the same stimulus intensity. The normative data of wave V latency of infants with varying hearing thresholds according to age and stimulus intensity could be determined.Conclusion The present study examined the latencies of ABR wave V of hearing-impaired and normal hearing infants according to age and stimulus intensity. The data will help audiologists to evaluate the hearing of infants who are referred for ABR test.

Effects of sex and gestational age on the auditory brainstem responses among two ears in moderate preterm infants

Objectives Auditory cortex in each hemisphere mostly receives the sounds from the opposite ear. The present study aimed at the contralateral dominance of auditory brainstem response (ABR) among the ears in preterm neonates by comparing sex and gestational age. Methods Transient Evoked Otoacoustic Emission (TEOAE) and Auditory Brainstem Response (ABR) were recorded at 3 months postconceptional age (PCA). The performance of two ears in ABR was compared. In addition, performance of each ear was analysed in females and males. A comparison of moderate gestational age also was performed. Twenty preterm neonates from 32 to 36 weeks gestational age admitted to the neonatal intensive care unit at Shafizadeh Children’s Hospital were participated. Results No significant asymmetry in ABR absolute latency and inter-peak intervals of right and left ears in preterm infants was noticed. Females and males did not demonstrate statistically significant values in ABR latencies. Moreover, the results of four gestational ages were not statistically different from each other. Conclusion The maturation of the auditory brainstem pathways most likely take places in both hemispheres simultaneously, independent of sex in preterm infants. Changes of gestational age in each month do not impact on the maturation of the auditory brain pathways.

GluA3 subunits are required for appropriate assembly of AMPAR GluA2 and GluA4 subunits on cochlear afferent synapses and for presynaptic ribbon modiolar-pillar morphology.

Cochlear sound encoding depends on α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs), but reliance on specific pore-forming subunits is unknown. With 5-week-old male C57BL/6J Gria3-knockout mice (i.e., subunit GluA3KO) we determined cochlear function, synapse ultrastructure, and AMPAR molecular anatomy at ribbon synapses between inner hair cells (IHCs) and spiral ganglion neurons. GluA3KO and wild-type (GluA3WT) mice reared in ambient sound pressure level (SPL) of 55-75 dB had similar auditory brainstem response (ABR) thresholds, wave-1 amplitudes, and latencies. Postsynaptic densities (PSDs), presynaptic ribbons, and synaptic vesicle sizes were all larger on the modiolar side of the IHCs from GluA3WT, but not GluA3KO, demonstrating GluA3 is required for modiolar-pillar synapse differentiation. Presynaptic ribbons juxtaposed with postsynaptic GluA2/4 subunits were similar in quantity, however, lone ribbons were more frequent in GluA3KO and GluA2-lacking synapses were observed only in GluA3KO. GluA2 and GluA4 immunofluorescence volumes were smaller on the pillar side than the modiolar side in GluA3KO, despite increased pillar-side PSD size. Overall, the fluorescent puncta volumes of GluA2 and GluA4 were smaller in GluA3KO than GluA3WT. However, GluA3KO contained less GluA2 and greater GluA4 immunofluorescence intensity relative to GluA3WT (threefold greater mean GluA4:GluA2 ratio). Thus, GluA3 is essential in development, as germline disruption of Gria3 caused anatomical synapse pathology before cochlear output became symptomatic by ABR. We propose the hearing loss in older male GluA3KO mice results from progressive synaptopathy evident in 5-week-old mice as decreased abundance of GluA2 subunits and an increase in GluA2-lacking, GluA4-monomeric Ca2+-permeable AMPARs.

The association of auditory function measures with low-level methylmercury from oceanic fish consumption and mercury vapor from amalgam: The Seychelles Child Development Study Nutrition 1 Cohort

BackgroundSome authors have reported that low-level exposure to methylmercury (MeHg) adversely impacts measures of auditory function. These reports, however, are not consistent in their findings. Consequently, we examined auditory function in a population exposed to low-level methylmercury (MeHg) exposure from fish consumption and to mercury vapor (Hg0) from dental amalgams. We analyzed their associations with the participants hearing acuity, absolute and interwave ABR latencies, and otoacoustic emissions (distortion product/DPOAE and click evoked/CEOAE). DesignWe administered an audiometry test battery to 246 participants from the Seychelles Child Development Study (SCDS) Nutrition Cohort 1 (NC1) at 9 years of age. The test battery included standard pure-tone audiometry, tympanometry, Auditory Brainstem Responses (ABR) and Distortion Product and Click Evoked Otoacoustic Emissions (DPOAE and CEOAE) testing. We measured prenatal MeHg exposure in maternal hair and postnatal MeHg in children’s hair. We approximated prenatal Hg0 exposure using maternal amalgam surface area and postnatal Hg0 using children amalgam surface area. Complete exposure records and audiometric data were available on 210 participants and in them we analyzed the association of MeHg and Hg0 exposures with auditory outcomes using covariate-adjusted linear regression models adjusted for sex and tympanometric pressure. ResultsHg exposures were similar for both sexes. Seven of the 210 evaluable participants examined had either a mild (5) or moderate (2) hearing loss. Four had a mild monaural hearing loss and 3 had either a mild (1) or moderate (2) bilateral hearing loss. No participant had greater than a moderate hearing loss in either ear. Hg exposures were higher in participants with either a mild or moderate hearing loss, but these differences were not statistically significant. Among the 210 with complete data, neither prenatal nor postnatal MeHg nor Hg0 exposure was statistically significantly associated with any of the ABR endpoints (p > 0.05 for all 72 associations). Neither prenatal nor postnatal Hg0 exposure was associated with any of the OAE endpoints (p > 0.05). MeHg exposure was statistically associated with 6 of the 56 DPOAE endpoints (p-values between 0.0001 and 0.023), but none of the 40 CEOAE endpoints. Two of the associations occurred with prenatal MeHg exposures and 1 of those would suggest a beneficial effect. Four of the other associations occurred with postnatal MeHg exposures with only 2 found in left ears of both males and females and the other 2 in the left and right ear of females at only one frequency. ConclusionOverall, these data do not present a clear and consistent pattern to suggest that the auditory system is negatively affected by low-level methylmercury exposure due to dietary consumption of oceanic fish or mercury vapor exposure from dental amalgams.