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PloS One 2023Noise exposure can destroy the synaptic connections between hair cells and auditory nerve fibers without damaging the hair cells, and this synaptic loss could contribute...
Noise exposure can destroy the synaptic connections between hair cells and auditory nerve fibers without damaging the hair cells, and this synaptic loss could contribute to difficult hearing in noisy environments. In this study, we investigated whether delivering lithium chloride to the round-window can regenerate synaptic loss of cochlea after acoustic overexposure. Our rat animal model of noise-induced cochlear synaptopathy caused about 50% loss of synapses in the cochlear basal region without damaging hair cells. We locally delivered a single treatment of poloxamer 407 (vehicle) containing lithium chloride (either 1 mM or 2 mM) to the round-window niche 24 hours after noise exposure. Controls included animals exposed to noise who received only the vehicle. Auditory brainstem responses were measured 3 days, 1 week, and 2 weeks post-exposure treatment, and cochleas were harvested 1 week and 2 weeks post-exposure treatment for histological analysis. As documented by confocal microscopy of immunostained ribbon synapses, local delivery of 2 mM lithium chloride produced synaptic regeneration coupled with corresponding functional recovery, as seen in the suprathreshold amplitude of auditory brainstem response wave 1. Western blot analyses revealed that 2 mM lithium chloride suppressed N-methyl-D-aspartate (NMDA) receptor expression 7 days after noise-exposure. Thus, round-window delivery of lithium chloride using poloxamer 407 reduces cochlear synaptic loss after acoustic overexposure by inhibiting NMDA receptor activity in rat model.
Topics: Rats; Animals; Receptors, N-Methyl-D-Aspartate; Lithium Chloride; Hearing Loss, Noise-Induced; Poloxamer; Auditory Threshold; Cochlea; Synapses; Evoked Potentials, Auditory, Brain Stem
PubMed: 37216352
DOI: 10.1371/journal.pone.0284626 -
PloS One 2023Pathophysiological alterations in the cochlea and functional tests of the auditory pathway support that in diabetes both vasculopathy and neural changes could be...
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.
Topics: Humans; Young Adult; Adult; Middle Aged; Diabetes Mellitus, Type 1; Cochlea; Hearing; Otoacoustic Emissions, Spontaneous; Hearing Loss; Audiometry, Pure-Tone; Evoked Potentials, Auditory, Brain Stem; Auditory Threshold
PubMed: 37205672
DOI: 10.1371/journal.pone.0285740 -
Ear and HearingSingle-ear hearing measurements, such as better-ear, worse-ear or left/right ear, are often used as outcomes in auditory research, yet, measurements in the two ears of...
OBJECTIVE
Single-ear hearing measurements, such as better-ear, worse-ear or left/right ear, are often used as outcomes in auditory research, yet, measurements in the two ears of the same individual are often strongly but not perfectly correlated. We propose a both-ear method using the Generalized Estimating Equation approach for analysis of correlated binary ear data to evaluate determinants of ear-specific outcomes that includes information from both ears of the same individual.
DESIGN
We first theoretically evaluated bias in odds ratio (OR) estimates based on worse-ear and better-ear hearing outcomes. A simulation study was conducted to compare the finite sample performances of single-ear and both-ear methods in logistic regression models. As an illustrative example, the single-ear and both-ear methods were applied to estimate the association of Dietary Approaches to Stop Hypertension adherence scores with hearing threshold elevation among 3135 women, aged 48 to 68 years, in the Nurses' Health Study II.
RESULTS
Based on statistical theories, the worse-ear and better-ear methods could bias the OR estimates. The simulation results led to the same conclusion. In addition, the simulation results showed that the both-ear method had satisfactory finite sample performance and was more efficient than the single-ear method. In the illustrative example, the confidence intervals of the estimated ORs for the association of Dietary Approaches to Stop Hypertension scores and hearing threshold elevation using the both-ear method were narrower, indicating greater precision, than for those obtained using the other methods.
CONCLUSIONS
The worse-ear and better-ear methods may lead to biased estimates, and the left/right ear method typically results in less-efficient estimates. In certain settings, the both-ear method using the Generalized Estimating Equation approach for analyses of audiometric data may be preferable to the single-ear methods.
Topics: Audiometry, Pure-Tone; Auditory Threshold; Female; Hearing; Humans
PubMed: 35302530
DOI: 10.1097/AUD.0000000000001216 -
BioMed Research International 2022The efficacy of tympanum injection and posterior auricular injection in diabetes with sudden hearing loss (SHL) was analyzed. A mobile terminal-based portable pure tone... (Randomized Controlled Trial)
Randomized Controlled Trial
The efficacy of tympanum injection and posterior auricular injection in diabetes with sudden hearing loss (SHL) was analyzed. A mobile terminal-based portable pure tone audiometry system and its processing method were established. Based on mobile terminals, a portable pure tone audiometry system including an Android system, pure sound signal generation, pure tone hearing threshold, and client module was established. A masking model and self-adaptive algorithm were used to detect and reduce noise. Besides, the performance of the portable pure tone audiometry system was detected. A total of 46 diabetes patients with SHL diagnosed at the otolaryngology department in BeiChen Hospital between August 2019 and November 2021 were selected as the research objects and randomly divided into the retroauricular group (posterior auricular injection) and the tympanic group (tympanum injection). Each group included 23 cases. All patients received pure tone audiometry (PTA) before and after the treatment. The changes in fasting blood glucose (FPG), 2h postprandial blood glucose (2hPG), and glycosylated hemoglobin (HbA1c) of the patients were monitored before and after the treatment. Besides, tinnitus loudness visual analog scale (VAS), pain VAS, efficacy, and the incidence of adverse reactions of the patients in two groups were compared. The results indicated that the hear threshold error detected by the medical audiometer and a portable pure tone audiometry system was within 2dB. Before the optimization, there was an error of about 10dB between the hear thresholds detected by the self-adaptive algorithm and a medical audiometer. After the treatment, the hear threshold and average PTA of the patients in the retroauricular and the tympanic groups under different frequencies were both reduced compared with those before the treatment ( < 0.05). The tinnitus VAS score in the retroauricular group was decreased more notably than that in tympanic group ( < 0.01), and the pain VAS score was much lower than that in the tympanic group ( < 0.001). The comparison of FPG, 2hPG, HbA1c, the proportions of cured, significantly effective, effective, ineffective patients, and the total effective rate in the patients in the retroauricular and the tympanic groups before and after the treatment all showed no statistical differences ( > 0.05). The incidence of adverse reactions in tympanic group after the treatment was dramatically higher than that in retroauricular group ( < 0.001). The above results demonstrated that posterior auricular injection showed potential application values in the treatment of SHL with diabetes and established a portable pure tone audiometry system as well as its noise processing method.
Topics: Audiometry, Pure-Tone; Auditory Threshold; Blood Glucose; Diabetes Mellitus; Ear, Middle; Glycated Hemoglobin; Hearing Loss, Sudden; Humans; Pain; Tinnitus
PubMed: 35909479
DOI: 10.1155/2022/8494868 -
The Journal of the Acoustical Society... Dec 2021Although clinical use of the auditory brainstem response (ABR) to detect retrocochlear disorders has been largely replaced by imaging in recent years, the discovery of... (Review)
Review
Although clinical use of the auditory brainstem response (ABR) to detect retrocochlear disorders has been largely replaced by imaging in recent years, the discovery of cochlear synaptopathy has thrown this foundational measure of auditory function back into the spotlight. Whereas modern imaging now allows for the noninvasive detection of vestibular schwannomas, imaging technology is not currently capable of detecting cochlear synaptopathy, the loss of the synaptic connections between the inner hair cells and afferent auditory nerve fibers. However, animal models indicate that the amplitude of the first wave of the ABR, a far-field evoked potential generated by the synchronous firing of auditory nerve fibers, is highly correlated with synaptic integrity. This has led to many studies investigating the use of the ABR as a metric of synaptopathy in humans. However, these studies have yielded mixed results, leading to a lack of consensus about the utility of the ABR as an indicator of synaptopathy. This review summarizes the animal and human studies that have investigated the ABR as a measure of cochlear synaptic function, discusses factors that may have contributed to the mixed findings and the lessons learned, and provides recommendations for future use of this metric in the research and clinical settings.
Topics: Animals; Auditory Threshold; Cochlea; Cochlear Nerve; Evoked Potentials, Auditory, Brain Stem; Hearing Loss, Noise-Induced; Humans; Noise
PubMed: 34972291
DOI: 10.1121/10.0007484 -
International Journal of Molecular... Jul 2023The auditory brainstem response (ABR) is a scalp recording of potentials produced by sound stimulation, and is commonly used as an indicator of auditory function....
The auditory brainstem response (ABR) is a scalp recording of potentials produced by sound stimulation, and is commonly used as an indicator of auditory function. However, the ABR threshold, which is the lowest audible sound pressure, cannot be objectively determined since it is determined visually using a measurer, and this has been a problem for several decades. Although various algorithms have been developed to objectively determine ABR thresholds, they remain lacking in terms of accuracy, efficiency, and convenience. Accordingly, we proposed an improved algorithm based on the mutual covariance at adjacent sound pressure levels. An ideal ABR waveform with clearly defined waves I-V was created; moreover, using this waveform as a standard template, the experimentally obtained ABR waveform was inspected for disturbances based on mutual covariance. The ABR testing was repeated if the value was below the established cross-covariance reference value. Our proposed method allowed more efficient objective determination of ABR thresholds and a smaller burden on experimental animals.
Topics: Mice; Animals; Evoked Potentials, Auditory, Brain Stem; Acoustic Stimulation; Auditory Threshold; Hearing; Disease Models, Animal
PubMed: 37511152
DOI: 10.3390/ijms241411393 -
Journal of the Association For Research... Dec 2022The middle-ear system relies on a balance of mass and stiffness characteristics for transmitting sound from the external environment to the cochlea and auditory neural...
The middle-ear system relies on a balance of mass and stiffness characteristics for transmitting sound from the external environment to the cochlea and auditory neural pathway. Phase is one aspect of sound that, when transmitted and encoded by both ears, contributes to binaural cue sensitivity and spatial hearing. The study aims were (i) to investigate the effects of middle-ear stiffness on the auditory brainstem neural encoding of phase in human adults with normal pure-tone thresholds and (ii) to investigate the relationships between middle-ear stiffness-induced changes in wideband acoustic immittance and neural encoding of phase. The auditory brainstem neural encoding of phase was measured using the auditory steady-state response (ASSR) with and without middle-ear stiffness elicited via contralateral activation of the middle-ear muscle reflex (MEMR). Middle-ear stiffness was quantified using a wideband acoustic immittance assay of acoustic absorbance. Statistical analyses demonstrated decreased ASSR phase lag and decreased acoustic absorbance with contralateral activation of the MEMR, consistent with increased middle-ear stiffness changing the auditory brainstem neural encoding of phase. There were no statistically significant correlations between stiffness-induced changes in wideband acoustic absorbance and ASSR phase. The findings of this study may have important implications for understanding binaural cue sensitivity and horizontal plane sound localization in audiologic and otologic clinical populations that demonstrate changes in middle-ear stiffness, including cochlear implant recipients who use combined electric and binaural acoustic hearing and otosclerosis patients.
Topics: Adult; Humans; Ear, Middle; Hearing Tests; Hearing; Cochlear Nerve; Brain Stem; Auditory Threshold; Acoustic Stimulation
PubMed: 36214911
DOI: 10.1007/s10162-022-00872-0 -
American Journal of Audiology Dec 2022Normative auditory brainstem response (ABR) data for infants and young children are available for 0.25-4 kHz, limiting clinical assessment to this range. As such, the...
PURPOSE
Normative auditory brainstem response (ABR) data for infants and young children are available for 0.25-4 kHz, limiting clinical assessment to this range. As such, the high-frequency hearing sensitivity of infants and young children remains unknown until behavioral testing can be completed, often not until late preschool or early school ages. The purpose of this study was to obtain normative ABR data at 6 and 8 kHz in young infants.
METHOD
Participants were 173 full-term infants seen clinically for ABR testing at 0.4-6.7 months chronological age ( = 1.4 months, = 1.0), 97% of whom were ≤ 12 weeks chronological age. Stimuli included 6 and 8 kHz tone bursts presented at a rate of 27.7/s or 30.7/s using Blackman window gating with six cycles (6 kHz) or eight cycles (8 kHz) rise/fall time and no plateau. Presentation levels included 20, 40, and 60 dB nHL. The ABR threshold was estimated in 5- to 10-dB steps.
RESULTS
As previously observed with lower frequency stimuli, ABR waveforms obtained in response to 6 and 8 kHz tone bursts decreased in latency with increasing intensity and increasing age. Latency was shorter for 8-kHz tone bursts than 6-kHz tone bursts. Data tables are presented for clinical reference for infants ≤ 4 weeks, 4.1-8 weeks, and 8.1-12 weeks chronological age including median ABR latency for Waves I, III, and V and the upper and lower boundaries of the 90% prediction interval. Interpeak Latencies I-III, III-V, and I-V are also reported.
CONCLUSION
The results from this study demonstrate that ABR assessment at 6 and 8 kHz is feasible for young infants within a standard clinical appointment and provide reference data for clinical interpretation of ABR waveforms for frequencies above 4 kHz.
Topics: Infant; Child; Humans; Child, Preschool; Evoked Potentials, Auditory, Brain Stem; Audiometry, Pure-Tone; Auditory Threshold; Hearing; Acoustic Stimulation
PubMed: 36442042
DOI: 10.1044/2022_AJA-22-00100 -
Journal of Neurophysiology Apr 2021Permanent threshold elevation after noise exposure or aging is caused by loss of sensory cells; however, animal studies show that hair cell loss is often preceded by...
Permanent threshold elevation after noise exposure or aging is caused by loss of sensory cells; however, animal studies show that hair cell loss is often preceded by degeneration of the synapses between sensory cells and auditory nerve fibers. Silencing these neurons is likely to degrade auditory processing and may contribute to difficulties understanding speech in noisy backgrounds. Reduction of suprathreshold ABR amplitudes can be used to quantify synaptopathy in inbred mice. However, ABR amplitudes are highly variable in humans, and thus more challenging to use. Since noise-induced neuropathy preferentially targets fibers with high thresholds and low spontaneous rate and because phase locking to temporal envelopes is particularly strong in these fibers, measuring envelope following responses (EFRs) might be a more robust measure of cochlear synaptopathy. A recent auditory model further suggests that modulation of carrier tones with rectangular envelopes should be less sensitive to cochlear amplifier dysfunction and, therefore, a better metric of cochlear neural damage than sinusoidal amplitude modulation. In this study, we measure performance scores on a variety of difficult word-recognition tasks among listeners with normal audiograms and assess correlations with EFR magnitudes to rectangular versus sinusoidal modulation. Higher harmonics of EFR magnitudes evoked by a rectangular-envelope stimulus were significantly correlated with word scores, whereas those evoked by sinusoidally modulated tones did not. These results support previous reports that individual differences in synaptopathy may be a source of speech recognition variability despite the presence of normal thresholds at standard audiometric frequencies. Recent studies suggest that millions of people may be at risk of permanent impairment from cochlear synaptopathy, the age-related and noise-induced degeneration of neural connections in the inner ear. This study examines electrophysiological responses to stimuli designed to improve detection of neural damage in subjects with normal hearing sensitivity. The resultant correlations with word recognition performance are consistent with a contribution of cochlear neural damage to deficits in hearing in noise abilities.
Topics: Acoustic Stimulation; Adolescent; Adult; Age Factors; Aging; Audiometry; Auditory Threshold; Cochlea; Cochlear Nerve; Female; Humans; Male; Middle Aged; Noise; Recognition, Psychology; Speech Perception; Young Adult
PubMed: 33656936
DOI: 10.1152/jn.00620.2020 -
Brain Structure & Function Jul 2023Tinnitus is one of the main hearing impairments often associated with pure-tone hearing loss, and typically manifested in the perception of phantom sounds. Nevertheless,...
Tinnitus is one of the main hearing impairments often associated with pure-tone hearing loss, and typically manifested in the perception of phantom sounds. Nevertheless, tinnitus has traditionally been studied in isolation without necessarily considering auditory ghosting and hearing loss as part of the same syndrome. Hence, in the present neuroanatomical study, we attempted to pave the way toward a better understanding of the tinnitus syndrome, and compared two groups of almost perfectly matched individuals with (TIHL) and without (NTHL) pure-tone tinnitus, but both characterized by pure-tone hearing loss. The two groups were homogenized in terms of sample size, age, gender, handedness, education, and hearing loss. Furthermore, since the assessment of pure-tone hearing thresholds alone is not sufficient to describe the full spectrum of hearing abilities, the two groups were also harmonized for supra-threshold hearing estimates which were collected using temporal compression, frequency selectivity und speech-in-noise tasks. Regions-of-interest (ROI) analyses based on key brain structures identified in previous neuroimaging studies showed that the TIHL group exhibited increased cortical volume (CV) and surface area (CSA) of the right supramarginal gyrus and posterior planum temporale (PT) as well as CSA of the left middle-anterior part of the superior temporal sulcus (STS). The TIHL group also demonstrated larger volumes of the left amygdala and of the left head and body of the hippocampus. Notably, vertex-wise multiple linear regression analyses additionally brought to light that CSA of a specific cluster, which was located in the left middle-anterior part of the STS and overlapped with the one found to be significant in the between-group analyses, was positively associated with tinnitus distress level. Furthermore, distress also positively correlated with CSA of gray matter vertices in the right dorsal prefrontal cortex and the right posterior STS, whereas tinnitus duration was positively associated with CSA and CV of the right angular gyrus (AG) and posterior part of the STS. These results provide new insights into the critical gray matter architecture of the tinnitus syndrome matrix responsible for the emergence, maintenance and distress of auditory phantom sensations.
Topics: Humans; Tinnitus; Hearing Loss; Brain; Hearing; Comorbidity; Audiometry, Pure-Tone; Auditory Threshold
PubMed: 37349539
DOI: 10.1007/s00429-023-02669-0