Peripheral Hearing Thresholds Research Articles

Associations of sleep characteristics in late midlife with late-life hearing loss in the Atherosclerosis Risk in Communities-Sleep Heart Health Study (ARIC-SHHS)

ObjectivesThis study investigated associations of late midlife sleep characteristics with late-life hearing, which adds to the existing cross-sectional evidence and is novel in examining polysomnographic sleep measures and central auditory processing. MethodsA subset of Atherosclerosis Risk in Communities Study participants underwent sleep assessment in the Sleep Heart Health Study in 1996-1998 and hearing assessment in 2016-2017. Peripheral hearing thresholds (0.5-4kHz) assessed by pure-tone audiometry were averaged to calculate speech-frequency pure-tone average in better-hearing ear (higher pure-tone average=worse hearing). Central auditory processing was measured by the Quick Speech-in-Noise Test (lower score=worse performance). Sleep was measured using polysomnography (time spent in stage 1, stage 2, stage 3/4, rapid eye movement sleep; sleep-disordered breathing [apnea-hypopnea index ≥5]) and self-report (habitual sleep duration; excessive daytime sleepiness [Epworth Sleepiness Scale 10]). Linear regression models adjusted for demographic and lifestyle factors with additional adjustment for cardiovascular factors. ResultsAmong 719 Atherosclerosis Risk in Communities-Sleep Heart Health Study participants (61 ± 5years, 54% female, 100% White), worse speech-frequency pure-tone average was found with sleep-disordered breathing (2.51dB, 95% confidence interval: 0.27, 4.75) and excessive daytime sleepiness (3.35 dB, 95% confidence interval: 0.81, 5.90). Every additional hour of sleep when sleeping >8 hours was associated with worse Quick Speech-in-Noise score (1.61 points, 95% confidence interval: 0.03, 3.19). Every 10-minute increase in rapid eye movement sleep was associated with 0.14-point better Quick Speech-in-Noise score (95% confidence interval: 0.02, 0.25). ConclusionsSleep abnormalities might be risk factors for late-life hearing loss. Future longitudinal studies are needed to confirm these novel findings and clarify the mechanisms.

Speech understanding and extended high-frequency hearing sensitivity in blast-exposed veteransa).

Auditory difficulties reported by normal-hearing Veterans with a history of blast exposure are primarily thought to stem from processing deficits in the central nervous system. However, previous work on speech understanding in noise difficulties in this patient population have only considered peripheral hearing thresholds in the standard audiometric range. Recent research suggests that variability in extended high-frequency (EHF; >8 kHz) hearing sensitivity may contribute to speech understanding deficits in normal-hearing individuals. Therefore, this work was designed to identify the effects of blast exposure on several common clinical speech understanding measures and EHF hearing sensitivity. This work also aimed to determine whether variability in EHF hearing sensitivity contributes to speech understanding difficulties in normal-hearing blast-exposed Veterans. Data from 41 normal- or near-normal-hearing Veterans with a history of blast exposure and 31 normal- or near-normal-hearing control participants with no history of head injury were employed in this study. Analysis identified an effect of blast exposure on several speech understanding measures but showed no statistically significant differences in EHF thresholds between participant groups. Data showed that variability in EHF hearing sensitivity did not contribute to group-related differences in speech understanding, although study limitations impact interpretation of these results.

Developmental PCB Exposure Disrupts Synaptic Transmission and Connectivity in the Rat Auditory Cortex, Independent of Its Effects on Peripheral Hearing Threshold.

Polychlorinated biphenyls (PCBs) are enduring environmental toxicants and exposure is associated with neurodevelopmental deficits. The auditory system appears particularly sensitive, as previous work has shown that developmental PCB exposure causes both hearing loss and gross disruptions in the organization of the rat auditory cortex. However, the mechanisms underlying PCB-induced changes are not known, nor is it known whether the central effects of PCBs are a consequence of peripheral hearing loss. Here, we study changes in both peripheral and central auditory function in rats with developmental PCB exposure using a combination of optical and electrophysiological approaches. Female rats were exposed to an environmental PCB mixture in utero and until weaning. At adulthood, auditory brainstem responses (ABRs) were measured, and synaptic currents were recorded in slices from auditory cortex layer 2/3 neurons. Spontaneous IPSCs (sIPSCs) and miniature IPSCs (mIPSCs) were more frequent in PCB-exposed rats compared with controls and the normal relationship between IPSC parameters and peripheral hearing was eliminated in PCB-exposed rats. No changes in spontaneous EPSCs were found. Conversely, when synaptic currents were evoked by laser photostimulation of caged-glutamate, PCB exposure did not affect evoked inhibitory transmission, but increased the total excitatory charge, the number and distance of sites that evoke a significant response. Together, these findings indicate that early developmental exposure to PCBs causes long-lasting changes in both inhibitory and excitatory neurotransmission in the auditory cortex that are independent of peripheral hearing changes, suggesting the effects are because of the direct impact of PCBs on the developing auditory cortex.

The peripheral hearing and central auditory processing skills of individuals with subjective memory complaints

AbstractBackgroundWith no cure or effective treatment currently in sight, it is critical to identify those factors that may prevent or delay cognitive decline and dementia in older adults, it is important to focus on potentially modifiable risk factors. Untreated hearing loss contributes up to about 9% of the modifiable risk factors in mid‐life (Livingston et al., 2017).MethodA total of 95 participants were recruited from the larger Western Australia Memory Study and were classified as SMCs (N = 61; 20 males and 41 females, mean age 71.47 + 7.19 years) and non‐SMCs (N = 34; 10 males, 24 females, mean age 68.85 + 7.70 years). All participants completed a peripheral hearing assessment, a CAP assessment battery (Dichotic Digits, Duration Pattern Test, Dichotic Sentence Identification, Synthetic Sentence Identification with Ipsilateral Competing Message and the Quick‐Speech‐in‐Noise) and a cognitive screening assessment.ResultThe SMCs group performed significantly poorer than the control group on Synthetic Sentence Identification with Ipsilateral Competing Message ‐10dB and ‐20 dB Signal to Noise Ratio conditions. No significant differences were found between the two groups on the peripheral hearing threshold measurements.ConclusionThe results suggest that individuals with SMCs perform poorly in CAP assessments in comparison to the controls. The poor CAP in SMC individuals may result in a greater cost to their finite pool of cognitive resources. The CAP results provide yet another biomarker that supports the hypothesis that SMCs may be a primary indication on neuropathological changes in the brain affecting various functions. Longitudinal follow up of individuals with SMCs and decreased CAP abilities should inform whether this group is at higher risk of developing dementia as compared to non‐SMCs and to those SMC individuals without CAP difficulties.

The Peripheral Hearing and Central Auditory Processing Skills of Individuals With Subjective Memory Complaints

PurposeThis study examined the central auditory processing (CAP) assessment results of adults between 45 and 85 years of age with probable pre-clinical Alzheimer’s disease – i.e., individuals with subjective memory complaints (SMCs) as compared to those who were not reporting significant levels of memory complaints (non-SMCs). It was hypothesized that the SMC group would perform significantly poorer on tests of central auditory skills compared to participants with non-SMCs (control group).MethodsA total of 95 participants were recruited from the larger Western Australia Memory Study and were classified as SMCs (N = 61; 20 males and 41 females, mean age 71.47 ±7.18 years) and non-SMCs (N = 34; 10 males, 24 females, mean age 68.85 ±7.69 years). All participants completed a peripheral hearing assessment, a CAP assessment battery including Dichotic Digits, Duration Pattern Test, Dichotic Sentence Identification, Synthetic Sentence Identification with Ipsilateral Competing Message (SSI-ICM) and the Quick-Speech-in-Noise, and a cognitive screening assessment.ResultsThe SMCs group performed significantly poorer than the control group on SSI-ICM −10 and −20 dB signal-to-noise conditions. No significant differences were found between the two groups on the peripheral hearing threshold measurements and other CAP assessments.ConclusionsThe results suggest that individuals with SMCs perform poorly on specific CAP assessments in comparison to the controls. The poor CAP in SMC individuals may result in a higher cost to their finite pool of cognitive resources. The CAP results provide yet another biomarker that supports the hypothesis that SMCs may be a primary indication of neuropathological changes in the brain. Longitudinal follow up of individuals with SMCs, and decreased CAP abilities should inform whether this group is at higher risk of developing dementia as compared to non-SMCs and those SMC individuals without CAP difficulties.

Electrophysiological assessment of auditory processing disorder in children with non-syndromic cleft lip and/or palate.

ObjectivesCleft lip and/or palate is a common congenital craniofacial malformation found worldwide. A frequently associated disorder is conductive hearing loss, and this disorder has been thoroughly investigated in children with non-syndromic cleft lip and/or palate (NSCL/P). However, analysis of auditory processing function is rarely reported for this population, although this issue should not be ignored since abnormal auditory cortical structures have been found in populations with cleft disorders. The present study utilized electrophysiological tests to assess the auditory status of a large group of children with NSCL/P, and investigated whether this group had less robust central auditory processing abilities compared to craniofacially normal children.Methods146 children with NSCL/P who had normal peripheral hearing thresholds, and 60 craniofacially normal children aged from 6 to 15 years, were recruited. Electrophysiological tests, including auditory brainstem response (ABR), P1-N1-P2 complex, and P300 component recording, were conducted.ResultsABR and N1 wave latencies were significantly prolonged in children with NSCL/P. An atypical developmental trend was found for long latency potentials in children with cleft compared to control group children. Children with unilateral cleft lip and palate showed a greater level of abnormal results compared with other cleft subgroups, whereas the cleft lip subgroup had the most robust responses for all tests.ConclusionChildren with NSCL/P may have slower than normal neural transmission times between the peripheral auditory nerve and brainstem. Possible delayed development of myelination and synaptogenesis may also influence auditory processing function in this population. Present research outcomes were consistent with previous, smaller sample size, electrophysiological studies on infants and children with cleft lip/palate disorders. In view of the these findings, and reports of educational disadvantage associated with cleft disorders, further research that focuses on the auditory processing abilities of children with cleft lip/palate disorder is warranted.

Diabetes-Associated Changes in Cortical Auditory-Evoked Potentials in Relation to Normal Aging

(1) To characterize the influence of type 2 diabetes mellitus (DM) on cortical auditory-evoked potentials (CAEPs) separate from the effects of normal aging, and (2) to determine whether the disease-related effects are modified by insulin dependence. A cross-sectional study was conducted in a large cohort of Veterans to investigate the relationships among type 2 DM, age, and CAEPs in randomly selected participants with (N = 108) and without (N = 114) the disease and who had no more than a moderate hearing loss. Participants with DM were classified as insulin-dependent (IDDM, N = 47) or noninsulin-dependent (NIDDM, N = 61). Other DM measures included concurrent serum glucose, HbA1c, and duration of disease. CAEPs were evoked using a passive homogeneous paradigm (single repeating stimulus) by suprathreshold tones presented to the right ear, left ear, or both ears. Outcome measures were adjusted for the pure-tone threshold average for frequencies of 0.5, 1, and 2 kHz and analyzed for differences in age effects between participant groups using multiple regression. There is little variation across test ear conditions (left, right, binaural) on any CAEP peak in any of the groups. Among no-DM controls, P2 latency increases about 9 msec per decade of life. DM is associated with an additional delay in the P2 latency of 7 and 9 msec for the IDDM and NIDDM groups, respectively. Moreover, the slope of the function relating P2 latency with age is similar across participant groups and thus the DM effect appears constant across age. Effects on N1 latency are considerably weaker, with age effects of less than 4 msec per decade across all groups, and DM effects of only 2 (IDDM) or 3 msec (NIDDM). In the NIDDM group, the slope relating N1 latency to age is steeper relative to that observed for the no-DM group, providing some evidence of accelerated "aging" for this CAEP peak. DM does not substantially reduce N1-P2 amplitude and age relationships with N1-P2 amplitude are effectively absent. There is no association between pure-tone average at 0.5, 1, and 2 kHz and any aspect of CAEPs in this cohort. In a large cohort of Veterans, we found that type 2 DM is associated with prolonged N1 and P2 latencies regardless of whether insulin is required to manage the disease and independent of peripheral hearing thresholds. The DM-related effects on CAEP latencies are threefold greater for P2 compared with N1, and there is little support that at the cortical level, IDDM participants had poorer responses compared with NIDDM participants, although their responses were more variable. Overall, these results indicate that DM is associated with slowed preattentive neural conduction. Moreover, the observed 7 to 9 msec P2 latency delay due to DM is substantial compared with normal age changes in P2, which are 9 msec per decade of life in this cohort. Results also suggest that whereas N1 latency changes with age are more pronounced among individuals with DM versus without DM, there was no evidence for more rapid aging of P2 among patients with DM. Thus, the damage responsible for the major DM-related differences may occur early in the DM disease process. These cross-sectional results should be verified using a longitudinal study design.

Position-dependent hearing in three species of bushcrickets (Tettigoniidae, Orthoptera).

A primary task of auditory systems is the localization of sound sources in space. Sound source localization in azimuth is usually based on temporal or intensity differences of sounds between the bilaterally arranged ears. In mammals, localization in elevation is possible by transfer functions at the ear, especially the pinnae. Although insects are able to locate sound sources, little attention is given to the mechanisms of acoustic orientation to elevated positions. Here we comparatively analyse the peripheral hearing thresholds of three species of bushcrickets in respect to sound source positions in space. The hearing thresholds across frequencies depend on the location of a sound source in the three-dimensional hearing space in front of the animal. Thresholds differ for different azimuthal positions and for different positions in elevation. This position-dependent frequency tuning is species specific. Largest differences in thresholds between positions are found in Ancylecha fenestrata. Correspondingly, A. fenestrata has a rather complex ear morphology including cuticular folds covering the anterior tympanal membrane. The position-dependent tuning might contribute to sound source localization in the habitats. Acoustic orientation might be a selective factor for the evolution of morphological structures at the bushcricket ear and, speculatively, even for frequency fractioning in the ear.

Effects of tea drinking on auditory functions in aged subjects.

The purpose of this study was to investigate the effects of Oolong tea drinking on the auditory functions in aged subjects. Retrospective cohort study was conducted on 265 subjects who were older than 55 years old. Tea drinking was determined from responses to a medical and food consumption questionnaires. The effects of Oolong tea drinking on pure tone thresholds (PTAs) for peripheral hearing and pitch pattern sequence (PPS) scores for central hearing were analyzed. Results showed that, before adjusting for other factors, PTAs were not significantly different between "non-tea drinkers" and "Oolong tea drinkes". But, the mean PPS score was higher in the "Oolong tea drinkers" (74.5 ± 12.7%) than in the "non-tea drinkers" (68.4 ± 13.9%). After adjusting for age, gender, waist circumference, and other variables, Oolong tea drinking (coefficient (β) ± standard error (SE) = 2.60 ± 0.67, P<0.001) was positively associated with PPS score, but not with PTAs, by multivariate linear regression analysis. In subgroup analysis for PPS score by gender, Oolong tea drinking showed a significant positive association with PPS score in males (β± SE=4.75 ± 0.95, P<0.001), but showed association of borderline significance with PPS score in females (β± SE=1.57 ± 0.94, P=0.097), with adjustment of other risk factors. In conclusion, Oolong tea drinking was associated with better central auditory function, but not with peripheral hearing thresholds, especially in male aged subjects.

Brain Stem Responses to Speech in Younger and Older Adults

This experiment was designed to evaluate whether neural encoding of speech features at the brain stem level is altered in the aging auditory system. In addition, the effect of minimal peripheral hearing loss on the auditory brain stem response (ABR) evoked by speech stimuli and interactions with aging were examined. Speech-evoked ABRs (S-ABRs) were recorded using a synthetic 40-msec /da/ stimulus from both ears of participants in two groups: normal-hearing younger adults (n = 19) and normal-hearing older adults (n = 18). Latencies and amplitude for S-ABR peaks representing neural responses to the onset and offset of the speech syllable as well as a sustained frequency following response to the vowel content were analyzed. The role of hearing threshold differences between groups and the reduced overall stimulus level on the S-ABR were also examined. In addition, click-evoked ABRs (C-ABRs) were obtained from all participants, and age-group differences in the neural response to both types of stimuli at the brain stem level were compared. S-ABR latencies, amplitudes, and sustained response mean data were obtained for younger adults and older adults. Older adults were found to have significantly smaller C-ABRs with longer latencies, despite all latencies falling within normal limits. Older adults also had significantly smaller onset and offset responses for the S-ABR, with significantly delayed offset latencies in response to this synthetic consonant-vowel syllable. Many of the C-ABR and S-ABR variables were found to significantly correlate with high-frequency audiometric thresholds, and few of the group differences remained significant when this was taken into account. The remaining significant S-ABR effects were decreased amplitude at the onset and significantly delayed offset responses in the older group. These effects were different from those of simply decreasing the overall stimulus level, which caused significant shifts in latency across the entire S-ABR. Results of this study partially supported the hypothesis of age-related differences in neural processing of speech at the brain stem level. There were significant delays in the timing of the offset portion of the S-ABR in older listeners compared with their younger counterparts, even after accounting for the differences in peripheral hearing threshold between groups. There were also significant reductions in amplitude of the S-ABR at the onset. These results are consistent with a reduction in neural synchrony in older adults to transient components of both speech and nonspeech sounds. However, sustained components of the S-ABR, which follow the harmonic components of the syllable, showed group differences but were not significant after adjusting for peripheral hearing loss, suggesting that they may be more affected by hearing sensitivity and other peripheral changes. These results support further investigation into the ability of the aging auditory system to encode temporal cues at the brain stem level, particularly the response to speech stimulus offset and its relationship to speech perception and temporal processing abilities.

Auditory brainstem responses are impaired in EphA4 and ephrin-B2 deficient mice

The Eph receptor tyrosine kinases and their membrane-anchored ligands, ephrins, are signaling proteins that act as axon guidance molecules during chick auditory brainstem development. We recently showed that Eph proteins also affect patterns of neural activation in the mammalian brainstem. However, functional deficits in the brainstems of mutant mice have not been assessed physiologically. The present study characterizes neural activation in Eph protein deficient mice in the auditory brainstem response (ABR). We recorded the ABR of EphA4 and ephrin-B2 mutant mice, aged postnatal day 18–20, and compared them to wild type controls. The peripheral hearing threshold of EphA4 −/− mice was 75% higher than that of controls. Waveform amplitudes of peak 1 (P1) were 54% lower in EphA4 −/− mice than in controls. The peripheral hearing thresholds in ephrin-B2 lacZ/ + mice were also elevated, with a mean value 20% higher than that of controls. These ephrin-B2 lacZ/ + mice showed a 38% smaller P1 amplitude. Significant differences in latency to waveform peaks were also observed. These elevated thresholds and reduced peak amplitudes provide evidence for hearing deficits in both of these mutant mouse lines, and further emphasize an important role for Eph family proteins in the formation of functional auditory circuitry.

Severe hearing loss in Dlx1 mutant mice

The Dlx homeobox gene family participates in regulating middle and inner ear development. A significant role for Dlx1, in particular, has been demonstrated in the development of the middle ear ossicles, but the functional consequences of Dlx1 gene mutation on hearing thresholds has not been assessed. The present study characterizes auditory brainstem responses to click and tonal stimuli in a non-lethal variant of a Dlx1 gene knockout. We found that peripheral hearing thresholds for click and tonal stimuli were significantly elevated in homozygous Dlx1 knockout ( Dlx1 −/−) compared to both heterozygous (Dlx1 +/−) and wild type ( Dlx1 +/+) mice. Thus, abnormal morphogenesis of the incus and stapes that has been documented previously with histological measures is now known to result in a severe peripheral hearing deficit.

Development of human peripheral hearing revealed by brainstem auditory evoked potentials

Development of human peripheral hearing from birth to 6 years was investigated by recording brainstem auditory evoked potentials (BAEPs). The threshold of BAEPs decreased rapidly during the first 3 months after birth (2.7 dB/week during the neonatal period, 2.6 dB/month at 1-3 months), after which further decrease occurred more slowly but continued through 1 year of age (0.26 dB/month at 3-12 months). A few days after birth, the threshold was 18 dB higher compared to the adults, and progressively decreased to 10, 5 and 2 dB at 1, 3 and 12 months, respectively. The latencies of waves I and V decreased as a function of age at a rate of 0.01 and 0.05 ms/week during the neonatal period, 0.02 and 0.10 ms/month at 1-3 months and 0.014 and 0.076 ms/month at 3-12 months, respectively. Adult latency value was attained by 2 and 4 years for waves I and V, respectively. These findings suggest that although the ear is reported to be almost adult-like at birth, the immaturity in neural functional properties limits auditory sensitivity during early childhood. It appears that human peripheral hearing threshold decreases rapidly through the third postnatal month and thereafter continues to improve slowly through early childhood. It is postulated that the first 3 months after birth are likely to be a critical period in postnatal development of human peripheral hearing.

Acoustic reflex abnormalities in behaviorally disturbed and language delayed children.

Contralateral and ipsilateral acoustic reflex thresholds were measured in 62 subjects referred for suspected delays in development of language, learning disabilities, or disorders of auditory processing, with normal peripheral hearing thresholds and normal tympanometry. Thirty-two percent of the subjects in this study showed abnormal contralateral and ipsilateral acoustic reflex thresholds. Both contralateral and ipsilateral acoustic reflex thresholds were involved when subjects showed abnormal reflex thresholds. Although a high percentage of abnormal acoustic reflexes occurred in this population, no strong correlation could be found with specific areas of language delay. A slight positive correlation was found between abnormal acoustic reflexes and delayed psychomotor development. Increased or absent acoustic reflex thresholds are usually associated with peripheral or low brain stem pathologies. While not conclusive, these results suggest brain stem involvement in this population.