Cochlear summating potential to broadband clicks detected from the human external auditory meatus. A study of subjects with normal hearing for age

Effects of age and noise exposure history on auditory nerve response amplitudes: A systematic review, study, and meta-analysis

Auditory nerve (AN) function has been hypothesized to deteriorate with age and noise exposure. Here, we perform a systematic review of published studies and find that the evidence for age-related deficits in AN function is largely consistent across the literature, but there are inconsistent findings among studies of noise exposure history. Further, evidence from animal studies suggests that the greatest deficits in AN response amplitudes are found in noise-exposed aged mice, but a test of the interaction between effects of age and noise exposure on AN function has not been conducted in humans. We report a study of our own examining differences in the response amplitude of the compound action potential N1 (CAP N1) between younger and older adults with and without a self-reported history of noise exposure in a large sample of human participants (63 younger adults 18-30 years of age, 103 older adults 50-86 years of age). CAP N1 response amplitudes were smaller in older than younger adults. Noise exposure history did not appear to predict CAP N1 response amplitudes, nor did the effect of noise exposure history interact with age. We then incorporated our results into two meta-analyses of published studies of age and noise exposure history effects on AN response amplitudes in neurotypical human samples. The meta-analyses found that age effects across studies are robust (r = -0.407), but noise exposure effects are weak (r = -0.152). We conclude that noise exposure effects may be highly variable depending on sample characteristics, study design, and statistical approach, and researchers should be cautious when interpreting results. The underlying pathology of age-related and noise-induced changes in AN function are difficult to determine in living humans, creating a need for longitudinal studies of changes in AN function across the lifespan and histological examination of the AN from temporal bones collected post-mortem.

Effects of Age and Noise Exposure History on Auditory Nerve Response Amplitudes: A Systematic Review, Study, and Meta-Analysis

Auditory nerve (AN) function has been hypothesized to deteriorate with age and noise exposure. Here, we perform a systematic review of published studies and find that the evidence for age-related deficits in AN function is largely consistent across the literature, but there are inconsistent findings among studies of noise exposure history. Further, evidence from animal studies suggests that the greatest deficits in AN response amplitudes are found in noise-exposed aged mice, but a test of the interaction between effects of age and noise exposure on AN function has not been conducted in humans. We report a study of our own examining differences in the response amplitude of the compound action potential N1 (CAP N1) between younger and older adults with and without a self-reported history of noise exposure in a large sample of human participants (63 younger adults 18-30 years of age, 103 older adults 50-86 years of age). CAP N1 response amplitudes were smaller in older than younger adults. Noise exposure history did not appear to predict CAP N1 response amplitudes, nor did the effect of noise exposure history interact with age. We then incorporated our results into two meta-analyses of published studies of age and noise exposure history effects on AN response amplitudes in neurotypical human samples. The meta-analyses found that age effects across studies are robust (r=-0.407), but noise-exposure effects are weak (r=-0.152). We conclude that noise-exposure effects may be highly variable depending on sample characteristics, study design, and statistical approach, and researchers should be cautious when interpreting results. The underlying pathology of age-related and noise-induced changes in AN function are difficult to determine in living humans, creating a need for longitudinal studies of changes in AN function across the lifespan and histological examination of the AN from temporal bones collected post-mortem.

Lack of neural contributions to the summating potential in humans with Meniere's disease

Objective

To investigate the electrophysiology of the cochlear summating potential (SP) in patients with Meniere's disease (MD). Although long considered a purely hair cell potential, recent studies show a neural contribution to the SP. Patients with MD have an enhanced SP compared to those without the disease. Consequently, this study was to determine if the enhancement of the SP was in whole or part due to neural dysfunction.

Design

Study participants included 41 adults with MD and 53 subjects with auditory neuropathy spectrum disorder (ANSD), undergoing surgery where the round window was accessible. ANSD is a condition with known neural dysfunction, and thus represents a control group for the study. The ANSD subjects and 17 of the MD subjects were undergoing cochlear implantation (CI) surgery; the remaining MD subjects were undergoing either endolymphatic sac decompression or labyrinthectomy to alleviate the symptoms of MD. Electrocochleography was recorded from the round window using high intensity (90 dB nHL) tone bursts. The SP and compound action potential (CAP) were measured to high frequencies (> = 2 kHz) and the SP, cochlear microphonic (CM) and auditory nerve neurophonic (ANN) to low frequencies. Linear mixed models were used to assess differences between MD and ANSD subjects.

Results

Across frequencies, the MD subjects had smaller alternating current (AC) response than the ANSD subjects (F = 31.61,534, p < 0.001), but the SP magnitudes were larger (F = 94.31,534, p < 0.001). For frequencies less than 4 kHz the SP magnitude in the MD group was significantly correlated with the magnitude of the CM (p's < 0.001) but not in the ANSD group (p's > 0.05). Finally, the relative proportions of both ANN and CAP were greater in MD compared to ANSD subjects. The shapes of the waveforms in the MD subjects showed the presence of multiple components contributing to the SP, including outer and inner hair cells and neural activity.

Conclusion

The results support the view that the increased negative polarity SP in MD subjects is due to a change in the operating point of hair cells rather than a loss of neural contribution. The steady-state SP to tones in human subjects is a mixture of different sources with different polarities.

Electrocochleographic recording in Asian adults: Preliminary normative data and demographic analyses

OBJECTIVE

Electrocochleography (ECochG) is valuable to diagnose Meniere's disease objectively. The aim of the present study was to provide preliminary normative data for ECochG among Asian adults. The influences of ethnicity (Malay versus Chinese) and gender on ECochG results were also studied.

METHODS

Twenty-two Malay adults (10 men and 12 women) and twenty Chinese participants (10 men and 10 women) aged between 20 and 49 years participated in this study. Extratympanic ECochG (ET-ECochG) was recorded according to standard non-invasive procedure. Summating potential (SP) amplitude, action potential (AP) amplitude and SP/AP ratio were analyzed accordingly.

RESULTS

ET-ECochG results were found to be comparable between left and right ears (p > 0.05). No notable differences in ET-ECochG results were found between Malay and Chinese groups (p > 0.05). No significant influence of gender on ET-ECochG outcomes was also noted (p > 0.05). The derived normative data for Asian adults (84 ears) are consistent with previous reports.

CONCLUSION

The present study provides preliminary normative data for ET-ECochG among Asian adults. The ECochG components do not appear to be influenced by either ethnicity or gender. The derived normative data can be used for clinical applications and as the reference for future studies involving Asian population.

Adaptation Duration Dissociates Category-, Image-, and Person-Specific Processes on Face-Evoked Event-Related Potentials

Several studies demonstrated that face perception is biased by the prior presentation of another face, a phenomenon termed as face-related after-effect (FAE). FAE is linked to a neural signal-reduction at occipito-temporal areas and it can be observed in the amplitude modulation of the early event-related potential (ERP) components. Recently, macaque single-cell recording studies suggested that manipulating the duration of the adaptor makes the selective adaptation of different visual motion processing steps possible. To date, however, only a few studies tested the effects of adaptor duration on the electrophysiological correlates of human face processing directly. The goal of the current study was to test the effect of adaptor duration on the image-, identity-, and generic category-specific face processing steps. To this end, in a two-alternative forced choice familiarity decision task we used five adaptor durations (ranging from 200-5000 ms) and four adaptor categories: adaptor and test were identical images-Repetition Suppression (RS); adaptor and test were different images of the Same Identity (SameID); adaptor and test images depicted Different Identities (DiffID); the adaptor was a Fourier phase-randomized image (No). Behaviorally, a strong priming effect was observed in both accuracy and response times for RS compared with both DiffID and No. The electrophysiological results suggest that rapid adaptation leads to a category-specific modulation of P100, N170, and N250. In addition, both identity and image-specific processes affected the N250 component during rapid adaptation. On the other hand, prolonged (5000 ms) adaptation enhanced, and extended category-specific adaptation processes over all tested ERP components. Additionally, prolonged adaptation led to the emergence of image-, and identity-specific modulations on the N170 and P2 components as well. In other words, there was a clear dissociation among category, identity-, and image-specific processing steps in the case of longer (3500 and 5000 ms) but not for shorter durations (< 3500 ms), reflected in the gradual reduction of N170 and enhancement of P2 in the No, DiffID, SameID, and RS conditions. Our findings imply that by manipulating adaptation duration one can dissociate the various steps of human face processing, reflected in the ERP response.

Phase noise reveals early category-specific modulation of the event-related potentials

Previous studies have found that the amplitude of the early event-related potential (ERP) components evoked by faces, such as N170 and P2, changes systematically as a function of noise added to the stimuli. This change has been linked to an increased perceptual processing demand and to enhanced difficulty in perceptual decision making about faces. However, to date it has not yet been tested whether noise manipulation affects the neural correlates of decisions about face and non-face stimuli similarly. To this end, we measured the ERPs for faces and cars at three different phase noise levels. Subjects performed the same two-alternative age-discrimination task on stimuli chosen from young–old morphing continua that were created from faces as well as cars and were calibrated to lead to similar performances at each noise-level. Adding phase noise to the stimuli reduced performance and enhanced response latency for the two categories to the same extent. Parallel to that, phase noise reduced the amplitude and prolonged the latency of the face-specific N170 component. The amplitude of the P1 showed category-specific noise dependence: it was enhanced over the right hemisphere for cars and over the left hemisphere for faces as a result of adding phase noise to the stimuli, but remained stable across noise levels for cars over the left and for faces over the right hemisphere. Moreover, noise modulation altered the category-selectivity of the N170, while the P2 ERP component, typically associated with task decision difficulty, was larger for the more noisy stimuli regardless of stimulus category. Our results suggest that the category-specificity of noise-induced modulations of ERP responses starts at around 100 ms post-stimulus.

Electrophysiological evidence of atypical visual change detection in adults with autism

Although atypical change detection processes have been highlighted in the auditory modality in autism spectrum disorder (ASD), little is known about these processes in the visual modality. The aim of the present study was therefore to investigate visual change detection in adults with ASD, taking into account the salience of change, in order to determine whether this ability is affected in this disorder. Thirteen adults with ASD and 13 controls were presented with a passive visual three stimuli oddball paradigm. The findings revealed atypical visual change processing in ASD. Whereas controls displayed a vMMN in response to deviant and a novelty P3 in response to novel stimuli, patients with ASD displayed a novelty P3 in response to both deviant and novel stimuli. These results thus suggested atypical orientation of attention toward unattended minor changes in ASD that might contribute to the intolerance of change.

Audiovestibular testing in patients with Meniere's disease

In this article, the present state of the art with respect to audiovestibular testing for Meniere's disease (MD) is reviewed. There is no gold standard for MD diagnosis, and the classic dictum is that even the "best" tests yield positive results in only two-thirds of patients with MD. Still, we advocate the use and further investigation of advanced audiovestibular testing in patients with MD in an attempt to answer the questions that confront any clinician who cares for patients with audiovestibular symptoms.

Increased Frequency of Left-Handedness in Patients with Unilateral Coronal Synostosis

Objective:

Left-handedness reportedly has been more common in persons with neurological afflictions (e.g., stroke) and malformations (e.g., cleft lip with or without cleft palate) that demonstrate marked unilateral involvement. Coronal synostosis is also more frequently unilateral, affecting the right side more commonly than the left. We sought to compare left-handedness in patients with unilateral coronal synostosis versus healthy controls.

Subjects:

All patients aged 3 years or older with nonsyndromic unilateral coronal synostosis and healthy controls recruited by pediatricians blinded to the study.

Main Outcome Measures:

Prospective data obtained for all participants included age, gender, and handedness. In patients with unilateral coronal synostosis, the side of synostosis and age at surgery were documented. Left-handedness in the study and control groups was compared using chi-square analysis. Left-handedness also was analyzed in the study group according to side of fusion.

Results:

Eighty-six patients with nonsyndromic unilateral coronal synostosis comprised the study group; there were 96 controls. The mean ages of the study (8.8 years) and control groups (9.8 years) were not statistically different (p > .05). There were more girls in the study group (67%) than in the control group (56%), but this difference was not statistically significant (p > .05). Left-handedness was documented in 30.2% of the study group and 11.4% of the control group (p < .005). Left-handedness was twice as common in patients with left versus right unilateral coronal synostosis (44.4% versus 20.4%; p < .05).

Conclusions:

Left-handedness is nearly three times more common in patients with unilateral coronal synostosis than in controls and four times more likely in patients with left-sided fusion.

Increased prevalence of left-handedness in hemifacial microsomia

Ten percent of people are left handed, but a higher frequency has been associated with certain craniofacial malformations, such as cleft lip and unilateral coronal synostosis. The purpose of this study was to determine the frequency of left-handedness in patients with hemifacial microsomia (HFM). Patients with HFM were identified in our craniofacial database. Normal controls were recruited by local pediatricians. Data gathered included age, sex, and handedness (determined by writing and/or drawing); the orbit, mandible, ear, nerve, and soft tissue (OMENS)-plus score and side of involvement were tabulated for patients with HFM. Hand preference was compared between the groups using chi analysis; possible correlations were analyzed between handedness and age, sex, the OMENS score, extracraniofacial findings, and side of involvement. One hundred seventy-eight patients with HFM were identified; 92 (51%) were excluded. Of the 86 included, 48% were boys (n = 47) and the mean age at inquiry was 13.5 years. Predominant side of involvement was right in 49% (n = 42) and left in 38% (n = 33). Eleven patients (13%) had severe involvement of both sides. Expanded-spectrum HFM was documented in 41% of patients. Ninety-six children were in the control group; 44% were boys (n = 42), and the mean age was 10 years. The difference in age between the groups was significant (P < 0.05), but sex differences were not. Patients with HFM were more likely to be left handed for writing compared with the control group (26% vs. 11%; P < 0.05). The frequency was higher, 36%, in those with bilateral involvement (P > 0.05). There was no correlation with predominant side or OMENS score. This study confirms that this disorder affects cerebral lateralization.

The interaction between ear and sex differences and stimulus rate

Evoked otoacoustic emissions (EOAEs) are produced by the cochlea in response to acoustic stimuli and provide an objective and non-invasive measure of cochlear function. A new technique, based on maximum length sequences (MLSs), enables stimulus rates of up to 5000 clicks/s to be used. Conventional EOAE amplitude differs between ears and sexes, female subjects having responses of greater amplitude than male subjects and right ears larger responses than left ears. As a prerequisite to clinical use it is necessary to establish if these differences occur with the MLS OAE technique and whether they change with stimulus rate. Eighty ears of normally hearing adults between the ages of 18 and 40 years were tested. MLS OAEs were recorded at eight stimulus rates ranging from 40/s to 5000/s. Two stimulus levels and two recordings were made at each stimulus rate. Female subjects were found to have statistically significantly larger MLS OAEs than male subjects and gave larger amplitude responses in the right ears. The difference was not significant between male right and left ears. A rate effect was also demonstrated with the amplitude of the MLS OAEs decreasing with an increase in rate. The study provides normative data for MLS OAE testing and shows that females have MLS OAEs of larger amplitude than males and that as the click stimulus rate increases the significance of this difference decreases. Female right ears also have MLS OAEs of greater amplitude than female left ears.

The effects of high stimulus rate on the electrocochleogram in normal-hearing subjects

The use of high stimulus rates has the potential to improve the electrocochleogram's (ECochG) sensitivity and specificity in endolymphatic hydrops and Menière's disease, but is currently hindered by the absence of an acceptable normative database. In response, this study recorded click-evoked ECochG tracings from 51 normal-hearing subjects (102 ears), between 18 and 60 years of age, at 7.1, 51.1, 101.1 and 151.1 clicks/s using a tympanic membrane electrode. As stimulus rate increased, various statistically significant (p < 0.05) changes were observed. In general, summating potential (SP) latency and amplitude and action potential (AP) latency increased, SP/AP amplitude ratio and waveform width increased but then plateaued, and AP amplitude fluctuated. While providing the largest contribution to a high-stimulus-rate ECochG normative database published to date, potential clinical limitations were identified and a possible solution proposed.

Relations among hand preference, craniofacial asymmetry, and ear advantage in young subjects

The relations for hand preference with craniofacial asymmetry and ear advantage, and between craniofacial asymmetry and ear advantage were investigated in young healthy subjects. Ear advantage was recorded as duration of hearing, craniofacial asymmetry by computerized tomography in 44 right-handed and 38 left-handed male and female high school students. Right-handers had a right ear advantage and a larger left craniofacial region, whereas left-handers had a left ear advantage and a larger right craniofacial region. These results are consistent with the speculation that hand preference may be related to craniofacial and consequently aural asymmetries.

Correlations between hand preference and durations of hearing for right and left ears in young healthy subjects

In this study, to test an inference from the 1991 Previc hypothesis that right-handers have a right-ear advantage, the durations of hearing for the right and left ears were compared for 81 right- and 45 left-handed high school students. In the present study, right-handedness was associated with a right-ear advantage and left-handedness was associated with a left-ear advantage. In addition, there was a significant positive correlation between the durations of hearing for the right and left ears and the scores for right-handedness for right-handed subjects. The durations of hearing for the right and left ears were negatively correlated with the left-handedness for left-handed subjects. These results suggest hand preference may be related to asymmetry of aural sensitivity.

Click evoked otoacoustic emissions: inter-aural and gender differences in newborns

Click evoked otoacoustic emissions (CEOAEs) are an objective and reliable method of assessing cochlear status, particularly suitable for newborns. This study aimed to assess CEOAE inter-aural and gender differences. Other non-auditory factors, such as infant's head size and weight, were considered. Band averaged CEOAEs were analyzed for 120 healthy, full term newborns, 61 females and 59 males. The babies were randomly selected from the nursery and tested in a quiet room away from the ward, using an Otodynamic ILO 92 system. The CEOAEs of the females were significantly larger than those of the males. For the frequency bands 2, 3, and 4 kHz and for the overall response, the emissions were larger in the right ear, for both males and females. These inter-aural differences were more pronounced in male subjects than in female subjects. These findings may reflect the accumulating evidence that differences exist in efferent cochlear inhibition.

Evidence that inner hair cells are the major source of cochlear summating potentials

The role of the inner hair cells (IHCs) in generating the cochlear summating potentials (SP) was assessed by measuring SP, cochlear nerve action potentials (CAP), cochlear microphonics (CM) and 2f1-f2 distortion product otoacoustic emissions (DPOAEs) in 15 chinchillas with either acute chemical de-afferentation, accomplished by applying kainic acid to the round window, or surgical de-afferentation and basal IHC loss, which developed within two months after sectioning the auditory nerve. In the auditory nerve sectioned ears, type I ganglion cells disappeared whereas most, if not all, type II ganglion cells were still present. Histological analysis of surface preparations and sections through the modiolus verified the de-afferentation in both models and showed a large IHC loss at the base of the cochlea in the ears with the auditory nerve sectioned while other structures of the cochlea remained intact. Unoperated (left) ears of 9 animals served as controls. CM and DPOAEs were normal in all ears whereas the CAP was substantially depressed in de-afferented ears. Comparisons among the SP input-output functions suggest that (1) the IHCs are the major generator of SP recorded from the round window in chinchilla, in particular at low to moderate stimulus levels, (2) the SP recorded from the round window largely reflects the responses from hair cells at the base of the cochlea, and (3) kainic acid results in an increase of SP amplitude to high-level stimuli whereas the SP to low- to moderate-level stimuli remains in the normal range.

Electrocochleography with postural changes in perilymphatic fistula. Animal studies

The present study investigated the effect of altering body position on electrocochleographic findings in the presence and absence of perilymphatic fistula. Three groups of guinea pigs included 1) 10 normal control animals, 2) 10 experimental animals with induced perilymphatic fistula, and 3) 10 control animals with induced perilymphatic fistula. In the first two groups, animals were successively tested in three positions: first with the ventral aspect down, again after 30 minutes with the test ear up, and again after 15 minutes with the test ear down. In the third group, body position was not altered. Stimuli consisted of clicks and 6,000-Hz tone bursts. Data analysis included summating potential (SP) amplitude, action potential (AP) amplitude, and AP threshold for the click stimuli. Only the normal control group showed a significant effect of body position for the SP/AP amplitude ratio. Average change was greater in the experimental group, but high variability precluded statistical significance. Both fistulized animal groups exhibited high variability in the SP/AP amplitude ratio, with and without postural change. The SP/AP amplitude ratio and SP amplitude were significantly larger for the two fistulized groups than for the normal control group. No significant change in threshold occurred across positions for any group.

A speculation about the parallel ear asymmetries and sex differences in hearing sensitivity and otoacoustic emissions

Hearing sensitivity and the prevalence of spontaneous otoacoustic emissions show parallel ear and sex differences in humans. Here it is proposed that these lateral asymmetries and sex differences may all result from differences in the 'strength' of the efferent inhibition delivered to individual cochleas. Specifically, it is proposed that the amount of efferent inhibition is relatively less in right ears and in females than in left ears and males. While it is unclear why or how ear asymmetries or sex differences would develop in the efferent system, by assuming that they do, one can begin to explain a number of basic facts of hearing. It is even possible that the lateral asymmetry in the efferent system may be related to the well-known cortical asymmetries that are believed to underlie speech perception, speech production, and other human abilities.

Interpretation of electrocochleography in Menière's disease and normal subjects

Electrocochleographic recordings were obtained from 20 subjects with normal hearing and 10 subjects with Menière's disease by using an eardrum electrode. Stimuli included clicks and 6,000-Hz tone bursts. Results were not significantly different between the two groups for summating potential (SP) amplitude, action potential (AP) amplitude, or the SP/AP amplitude ratio. Interpreting the results in light of symptoms on the date of assessment or hearing threshold did not appear to improve separation between the two groups. Various SP/AP amplitude ratio criteria have been proposed in order to separate normal patients from those with Menière's disease. Applying these proposed criteria to our data did not successfully separate the two groups.

The I' potential of the brain-stem auditory-evoked potential

We have consistently recorded a positive wave which precedes wave I, and is called I', within the human brain-stem auditory-evoked potential. It is postulated that I' represents initial neural activity of the auditory nerve, which presumably has as its origin auditory nerve dendrites. Thus, I' may represent a summed far-field dendritic potential from currents of excitatory postsynaptic potentials. We report latency and amplitude values of I'.