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International audience; Presbycusis, or age-related hearing loss (ARHL), is a major public health issue. About half the phenotypic variance has been attributed to genetic factors. Here, we assessed the contribution to presbycusis of ultrarare pathogenic variants, considered indicative of Mendelian forms. We focused on severe presbycusis without environmental or comorbidity risk factors and studied multiplex family age-related hearing loss (mARHL) and simplex/sporadic age-related hearing loss (sARHL) cases and controls with normal hearing by whole-exome sequencing. Ultrarare variants (allele frequency [AF] < 0.0001) of 35 genes responsible for autosomal dominant early-onset forms of deafness, predicted to be pathogenic, were detected in 25.7% of mARHL and 22.7% of sARHL cases vs. 7.5% of controls ( P = 0.001); half were previously unknown (AF < 0.000002). MYO6 , MYO7A , PTPRQ , and TECTA variants were present in 8.9% of ARHL cases but less than 1% of controls. Evidence for a causal role of variants in presbycusis was provided by pathogenicity prediction programs, documented haploinsufficiency, three-dimensional structure/function analyses, cell biology experiments, and reported early effects. We also established Tmc1 N321I/+ mice, carrying the TMC1 :p.(Asn327Ile) variant detected in an mARHL case, as a mouse model for a monogenic form of presbycusis. Deafness gene variants can thus result in a continuum of auditory phenotypes. Our findings demonstrate that the genetics of presbycusis is shaped by not only well-studied polygenic risk factors of small effect size revealed by common variants but also, ultrarare variants likely resulting in monogenic forms, thereby paving the way for treatment with emerging inner ear gene therapy.

Background It has been suggested that age-related hearing loss (ARHL) and Alzheimer's disease (AD) are commonly associated. Objective The Alzheimer Disease, Presbycusis and Hearing Aids (ADPHA) clinical trial assessed the influence of hearing aids (HAs) on patients affected by ARHL and AD, as judged by behavioral symptoms and functional abilities, as well as patient and caregiver quality of life (QoL). Methods A multicenter double-blind randomized placebo-controlled trial, with a semi-crossover procedure over 12 months, was conducted from 2006 to 2012. For the first 6 months, the active group was treated with active HAs and the placebo group with inactive HAs. For the last 6 months, HAs in the placebo group were activated. Assessment was conducted at baseline, 6 months, and 12 months. We performed intergroup and intragroup comparisons. Behavioral symptoms were assessed by neuropsychiatric inventory (NPI), functional abilities by instrumental activities of daily living, and QoL by Zarit, Alzheimer's disease related quality of life, and simplified Duke scales. Results Fifty-one patients were included and randomized: 22 in active group (mean NPI 17.6; mean age 83±6.2) and 26 in placebo group (mean NPI 25.8; mean age 82.3±7.2) were fitted with HAs. At 6-month follow-up, all scores worsened without significant difference between the two groups. In placebo group, activation of HAs had no effect on the change of these scores. Conclusion These findings do not provide evidence of improvement in behavioral symptoms, functional status, or QoL of hearing impaired AD patients and their caregivers after 6 months of HA use. However, we cannot exclude that HAs may have a positive effect in patients aged less than 75 years.

Background/objective This study evaluated the cognitive benefit of hearing aids (HA) in older patients with Alzheimer's disease (AD) and hearing loss (HL) after a 6- and 12-month period of utilization. Methods A multicenter double-blind randomized placebo-controlled trial was conducted in patients aged more than 65 years. A group was equipped with active HA for 6 months (active group) and a second group had placebo HA for 6 months (placebo group) followed by a secondary activation phase for a further 6 months (semi crossover procedure). Both groups were retested after a 12-month period. The primary endpoint was the change from baseline of the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS Cog) after a 6-month period in both groups and after 6 months of secondary HA activation in the placebo group. A smaller cognitive decline should be obtained with HA use; an increase in ADAS Cog score of less than 6 points was defined a success. Results Fifty-one patients aged 68 to 99 years were included; 38 attended the 6-month visit: 18 in the active group and 20 in the placebo group. At 6 months, 14 (82.4%) successes were noticed in the active group, and 15 (88.2%) in the placebo group (p = 1.0); delta ADAS Cog in the active group was 1.8±5.3 and 1.3±5.3 in the placebo group (p = 0.8). In the placebo group, after the secondary HA activation, no significant improvement was observed. Conclusion No significant effect of HA use was observed after 6 months of follow-up in patients with AD and HL.

Depuis la loi du 12 juillet 1971 instaurant le numerus clausus et la selection en fin de premiere annee de medecine, le nombre de medecins formes a subi d’importantes variations : plus de 8 000 formes par an en 1972, 3 500 en 1993 et plus de 8 000 en 2018. Les critiques nombreuses sur le taux d’echec et l’existence de zones sous-denses en medecins ont conduit a proposer la suppression du numerus clausus a compter de la rentree universitaire 2020. Cet article retrace l’evolution des textes legislatifs et reglementaires relatifs a la selection des etudiants en medecine depuis 1971.

Objective To measure noise levels generated by repetitive transcranial magnetic stimulation. Intervention Repetitive transcranial magnetic stimulation (rTMS). Main outcome measures rTMS noise levels measured in equivalent continuous sound level (LAeq) and in peak level (LC, peak), as a function of maximum power output of the equipment. Methods rTMS noise levels were measured for an active and a corresponding sham coil, as a function of distance and percentage power output of a MagPro X100 system (Medtronic) and compared with occupational noise exposure standards, using parameters classically used for rTMS tinnitus treatment. Results Significant differences in frequency composition and intensity levels were observed between sham and active coil noises. The active coil noise reached, at 50% power, 96 LAeq (peak at 132 LC, peak), varying by 3.9 LAeq (3.9 LC, peak) per 10% of power increase, whereas the sham coil reached 87 LAeq (114 LC, peak), varying by 3.2 LAeq (3.6 LC, peak) per 10% of power increase. Conclusion rTMS noise levels differ significantly between active and sham coils, and can go beyond the American and European legal occupational noise limits, hence making ear protection a specific issue, particularly relevant to rTMS treatment for tinnitus.

Background The guidelines for use of repetitive transcranial magnetic stimulation (rTMS) advise frequent updating of rTMS safety guidelines and recommendations. Although rTMS can produce sound of more than 120 dB C, which is sufficient to induce hearing loss, the effect of rTMS noise on the hearing of both patients and rTMS practitioners is understudied. Objective This study investigated the effects of rTMS noise on subjects’ hearing using otoacoustic emissions evoked by clicks (transiently evoked otoacoustic emissions, TEOAEs), which is an objective and sensitive method of cochlear exploration. Methods Hearing thresholds and TEOAEs were recorded in 24 normal-hearing healthy subjects before and after a real or sham rTMS session (a single 20-minute session applied to the superior temporal gyrus with 1200 pulses at 100% of the individual motor threshold). Results No significant difference in hearing thresholds was observed between subjects exposed to real or sham rTMS. However, the difference in TEOAE amplitude between pre- and post-rTMS sessions increased significantly with rTMS noise for those subjects the least protected by earplugs, showing a post-rTMS slight decrease of TEOAE amplitude for high rTMS intensities and hence minor hearing function alteration. However, this correlation was no longer found 1 hour after the rTMS session. Conclusions These findings suggest that, even when rTMS is used within normal safety limits and with good hearing protection, rTMS noise can transiently disturb hearing mechanisms in normal-hearing healthy subjects. This transient effect of rTMS on hearing may be an important consideration for Institutional Review Boards when rTMS is used at higher stimulation intensities.

Although EAS electrode arrays are shorter, they have the same number of electrodes as conventional implant arrays. The possibility of channel interaction already exists with a standard length electrode array. As electrodes on an EAS array are closer together, the likelihood of channel interaction is even greater. To compensate for this, we proposed to deactivate several channels on the electrode array, on the premise that the reduction in speech intelligibility due to fewer channels would be offset by the low frequency residual hearing. Recent studies have demonstrated that low frequency residual hearing provides significant benefit for speech understanding (Dorman et al., 2005; Turner et al., 2004). This study aims to determine the number of channels necessary to provide good speech understanding according to the degree of low frequency residual hearing, particularly the boundary or cutoff frequency (Fc) between acoustic and electrical stimulation. This study utilized an acoustic simulation of an EAS device in normal-hearing subjects.

This paper reviews psychoacoustical and electrophysiological evidence for reorganization of the human central auditory system in case of auditory deprivation and rehabilitation.To investigate the plasticity of cortical tonotopic maps in cochlear-damaged subjects.Frequency discrimination scores were analysed in subjects with high frequency hearing loss to test for potential perceptual correlates of auditory deprivation- and rehabilitation-induced plasticity. In cochlear implant patients, electrically evoked auditory cortical responses were obtained using EEG to study scalp potential maps.Perceptual changes in frequency discrimination were observed at the lesion-edge frequency of steeply sloping hearing loss. Although these results are not direct proof of cortical plasticity, no peripheral phenomenon has been found to explain them. The reversal of such auditory deprivation-induced plasticity, a phenomenon that may be termed rehabilitation plasticity, can be studied in hearing-impaired subjects fitted with a hearing aid. Cochlear implant subjects provide another interesting model for studying rehabilitation plasticity in that even profound to total deafness is made partially reversible by cochlear implantation. We found that the auditory cortex of deaf subjects with at least 3 months of cochlear implant experience is organized in a way similar to the tonotopy described in normal-hearing subjects.

Restoration of auditory input through the use of hearing aids has been proposed as a potentially important means of altering tinnitus among those tinnitus sufferers who experience significant sensorineural hearing loss. In animal models of neural plasticity induced by noise trauma, high-frequency stimulation in deafferented regions of the auditory spectrum has been shown to modulate cortical reorganization after hearing loss, a result which suggests that the neural basis of tinnitus is subject to interference by acoustic stimulation. This study drew on deafferentation models to investigate the effect of hearing aids on the psychoacoustic properties of the tinnitus sensation, using both conventional amplification and high-bandwidth amplification regimes. The tinnitus percept was affected only weakly in the conventional amplification group, and was not at all affected in the high-bandwidth group. The changes observed under conventional, low-to-medium frequency amplification may indicate that the perceptual characteristics of tinnitus depend on the pattern of sensory inputs - notably a contrast in activity between adjacent central auditory regions of more and less afferent activity - while the absence of modifications in the high-bandwidth amplification group suggests limit on the tractability of the tinnitus percept. This limit to the malleability of the tinnitus percept may arise from either the extent of hearing deficits or the duration and robustness of the neuroplastic changes that originally give rise to tinnitus.

Anatomical and physiological changes may occur under different circumstances, reflecting the plasticity of the human central and peripheral auditory system: deprivation of peripheral auditory input (plasticity induced by hearing deprivation), chronic exposition to sound in deaf subjects (plasticity induced by auditory rehabilitation), or auditory learning (learning-induced plasticity). In this review, we focus on auditory deprivation and rehabilitation-induced plasticity. We first describe some perceptual correlates of cortical plasticity induced by sensory deprivation, and then we present some of our original results showing the influence of hearing aids on perceptual performances of sensorineural hearing impaired listeners. These results are in line with the auditory acclimatization phenomenon (i.e. in monaurally fitted listeners, the aided ear performs better than the unaided ear for fine processing of high-intensity sounds). They also suggest that the auditory acclimatization phenomenon is lateralized...

Speech elicited auditory brainstem responses (Speech ABR) have been shown to be an objective measurement of speech processing in the brainstem. Given the simultaneous stimulation and recording, and the similarities between the recording and the speech stimulus envelope, there is a great risk of artefactual recordings. This study sought to systematically investigate the source of artefactual contamination in Speech ABR response. In a first part, we measured the sound level thresholds over which artefactual responses were obtained, for different types of transducers and experimental setup parameters. A watermelon model was used to model the human head susceptibility to electromagnetic artefact. It was found that impedances between the electrodes had a great effect on electromagnetic susceptibility and that the most prominent artefact is due to the transducer's electromagnetic leakage. The only artefact-free condition was obtained with insert-earphones shielded in a Faraday cage linked to common ground. In a second part of the study, using the previously defined artefact-free condition, we recorded speech ABR in unilateral deaf subjects and bilateral normal hearing subjects. In an additional control condition, Speech ABR was recorded with the insert-earphones used to deliver the stimulation, unplugged from the ears, so that the subjects did not perceive the stimulus. No responses were obtained from the deaf ear of unilaterally hearing impaired subjects, nor in the insert-out-of-the-ear condition in all the subjects, showing that Speech ABR reflects the functioning of the auditory pathways.

Objectives The present study was aimed to compare gain and speech intelligibility measured in quiet and in noise between the Signia hearing aid and the Vibrant Soundbridge (VSB), both devices using the same sound processing technology. Patients A prospective longitudinal study was performed. Six patients with a steeply sloping high-frequency hearing loss were selected. Intervention The protocol comprised 3 months' hearing aid use, VSB implantation, and 3 months' VSB use. Main outcome measures Patient performances were evaluated unaided and aided by audiologic assessments, including free-field thresholds and word recognition tasks in quiet and in noise. Results Statistical analysis revealed a slight decrease in overall frequencies in pure-tone audiometry after surgery; however, this decrease did not exceed 5 dB and was not different from the changes that occurred in the contralateral nonimplanted ear. The measures of aided and unaided hearing thresholds showed statistically significant larger gains with the VSB than with the hearing aid. In quiet, speech performances were poorer unaided than with either device. Because of ceiling effects, statistically significant higher scores with the VSB than with the hearing aid were only observed at the lowest intensity level. In noise, speech intelligibility was reported to be better with the VSB compared with both unaided and with the hearing aid at 5 signal-to-noise ratios. Conclusion This prospective study demonstrated that direct-drive stimulation provided by the VSB allows better speech performances than acoustic stimulation for rehabilitation of patients with steeply sloping high-frequency hearing losses.

Objective To investigate the temporal relationship between speech auditory brainstem responses and acoustic pattern of the phoneme /ba/. Methods Speech elicited auditory brainstem responses (Speech ABR) to /ba/ were recorded in 23 normal-hearing subjects. Effect of stimulus intensity was assessed on Speech ABR components latencies in 11 subjects. The effect of different transducers on electromagnetic leakage was also measured. Results Speech ABR showed a reproducible onset response (OR) 6 ms after stimulus onset. The frequency following response (FFR) waveform mimicked the 500 Hz low pass filtered temporal waveform of phoneme /ba/ with a latency shift of 14.6 ms. In addition, the OR and FFR latencies decreased with increasing stimulus intensity, with a greater rate for FFR (−1.4 ms/10 dB) than for OR (−0.6 ms/10 dB). Conclusions A close relationship was found between the pattern of the acoustic stimulus and the FFR temporal structure. Furthermore, differences in latency behaviour suggest different generation mechanisms for FFR and OR. Significance The results provided further insight into the temporal encoding of basic speech stimulus at the brainstem level in humans.

The present study investigates the relationship between auditory steady-state responses (ASSRs) and loudness growth function. ASSR amplitudes were compared to the perceived loudness level at frequencies of 500 and 2000 Hz in 11 normal-hearing subjects. As a first step, loudness growth function was estimated for the two test frequencies. Then ASSR amplitude was recorded for each of the two frequencies at different stimulus intensities, each corresponding to a loudness level as given by the first part of the study. Normalized results show that the ASSR amplitude correlates well with the loudness function (R2 = 0.81). A stepwise multiple linear regression confirmed these results with loudness explaining almost all the ASSR amplitude (loudness R2 = 0.81, p

Cochlear damages have been shown to induce changes in tonotopic maps in the central auditory system of animals; neurons deprived from peripheral inputs start to respond to stimuli with frequencies close to the cutoff frequency (Fc) or "edge" of the hearing loss, which then become over-represented at the neural level. Here, we review findings, which reveal a possible psychophysical correlate of such central over-representation in human listeners with sensorineural hearing loss. These findings concur to demonstrate a local improvement in difference limens for frequency (DLFs) at or near Fc. This effect has now been observed in several studies and subjects with varied audiometric characteristics, including high- and low-frequency, and symmetric and asymmetric hearing losses. The presence of cochlear dead region or a steeply sloping hearing loss appear as a necessary condition for its occurrence. The effect cannot be explained simply by more prominent loudness cues or spontaneous otoacoustic emissions (SOAEs) near the audiogram edge. Overall, the data are consistent with local changes in pitch discrimination performance near the hearing-loss cutoff frequency being a result of the neural over-representation of that frequency region in the central auditory system. Further work is needed to confirm this hypothesis, and investigate other possible perceptual correlates of injury-related cortical plasticity in both humans and animals.

The purpose of this study was to distinguish the effects of different parameters on latencies of wave IIIe, wave Ve, and interpeak interval IIIe–Ve of electrical auditory brainstem responses (EABRs). EABRs were recorded from all the intra-cochlear electrodes in eight adult HiRes90K ® cochlear implant users. The relationship between latencies and stimulation sites in the cochlea was characterized to assess activity along the auditory pathway. Audiograms before implantation, psychophysics at first fitting and duration of deafness were used to describe the influence of deafness on latencies. A decreasing baso-apical latency gradient was found for waves IIIe and Ve, while the interpeak interval IIIe–Ve remained the same along the electrode array. Electrical stimulation enabling to stimulate various parts of the cochlea at the same time, this could indicate an anatomical way of compensating for the delay the acoustic wave takes to reach the cochlea apex in a non-implanted ear. However, psychophysical levels were also found to increase at the cochlear base showing that the latency gradient could result from an increasing gradient of neural degeneration toward the base. Correlations of EABR latencies with psychophysics, audiometric data and duration of deafness show that factors linked to deafness have indeed an influence on EABR latencies. The possible explanations for the latency shift observed, whether they are anatomical and/or pathological, are exposed.

Although measurement of the detection limits of the 80Hz auditory steady-state response (ASSR) has proven to be a reasonably reliable tool in estimating hearing sensitivity in the mid-conventional audiometric frequencies (e.g. 1000 and 2000Hz), results in the literature suggest potentially diminishing performance at 500Hz and above 4000Hz. The primary goal of this work was to examine the accuracy of threshold estimation via ASSR measurement for carriers more toward the audiometric extremes. At the same time, different stimulus and recording protocols than those commonly employed in ASSR testing were examined. Using a two-channel recording system, ASSRs were obtained from 15 normal-hearing young adults for an amplitude-modulated carrier of 250Hz and repeated tone bursts of 10000–16000Hz, gated using a Blackman window. Results attest to the ability to record ASSRs to a wide range of carrier frequencies but also suggest that accuracy of threshold estimation suffers toward the audiometric extremes. Feasibilit...

Several studies have already demonstrated that patients with steeply sloping hearing loss of cochlear origin exhibit an improvement in frequency discrimination performance at or around the cut-off frequency. This enhancement cannot be explained in terms of peripheral mechanisms and should rather be interpreted in terms of central reorganization: i.e., injury-induced cortical plasticity. However, the reversibility and time course of such reorganization has not yet been described. The main goal of the present study was therefore to investigate the occurrence of rehabilitation plasticity associated with hearing-aid fitting in human subjects. Nine subjects with steeply sloping hearing loss and who were candidates for auditory rehabilitation were tested. Discrimination-limen-for-frequency (DLF) enhancement was investigated at the frequency with the best DLF (bDLF) for each individual subject before and during auditory rehabilitation (at 1 month, 3 months and 6 months). From 1 month on, frequency discrimination performance decreased significantly at the bDLF frequency, while remaining stable at other frequencies. This normalization may reflect a new central reorganization reversing the initial injury-induced changes in the cortical map. A correlation between subject's age and alteration in DLF at 1 month was also found, suggesting that plasticity operates faster in younger patients.

The aim of the present study was to investigate the simple reaction time (RT) performance of patients with steeply sloping sensorineural hearing loss. This kind of hearing loss has the particularity of inducing a reorganization of the primary auditory cortex (Dietrich et al, ), the edge frequency of the loss being over-represented. It is assumed that a consequence of this plasticity could be reflected in an improvement in frequency discrimination performances around the edge of the loss (McDermott et al, ). In the present study we used pure tones equalized in loudness to investigate whether RT might be altered at the cut-off frequency (Fc) of the loss, or at the frequency that presented the best discrimination-limen-for-frequency (bDLF). The effect of auditory rehabilitation on RT was also studied. A great variability in RT was noted in all our subjects. Our results demonstrated that RT was unmodified at Fc or bDLF, be it before or after hearing aid fitting. However, an improvement in the correlation betw...

Tinnitus can be a very troubling complaint but its impact may vary between individuals, both in the perceived severity and the aspects of life affected. The International Tinnitus Inventory (ITI) is an eight-item questionnaire based on the commonest patient reported complaints attributed to tinnitus. It is modelled on the International Outcomes Inventory - Hearing Aids (IOI-HA) to be brief, have a clear and simple response format and be comparable across languages. The psychometric properties of the English and French versions have been examined in this paper. Preliminary results show that the ITI is a robust questionnaire. It is unifactorial, has a good response rate and high internal consistency and it is easy to interpret. Responses from the inventory relate to hearing level but not to other demographic factors. The ITI is a simple and patient friendly measure which can be a helpful tool to highlight the predominant tinnitus-related complaint(s) of the individual, thus providing useful information not only about the tinnitus but also to help plan and assess a rehabilitation programme.

Benzodiazepines (Bzd) are known to interact with GABAergic inhibitory neurotransmission. Previous research on their effect on human auditory efferent pathways--through evoked otoacoustic emissions suppression by contralateral acoustic stimulation (CAS)--indicated a decrease in medial olivocochlear (MOC) efferent system inhibitory activity, after oral intake of oxazepam--representative of the Bzd drug class. To date, this pharmacological effect was only assessed in the right ear. Since a leftward asymmetry of Bzd receptors localization in human auditory cortex has been described recently, we explored in this study the hypothesis of an asymmetrical action of Bzd on MOC efferent functioning. The results revealed a significant difference of Bzd effect probing the right ear versus the left ear, with CAS-induced suppression being less effective in the right than left ear after oxazepam intake. This finding raises the question of possible neurochemical left-right asymmetry in the descending auditory pathways. The potential localization of this asymmetry is discussed.

Active cochlear micromechanisms, involved in auditory sensitivity, are modulated by the medial olivocochlear efferent system, which projects directly onto the organ of Corti. Both processes can be assessed non-invasively by means of evoked otoacoustic emissions. Animal experiments have revealed top-down control from the auditory cortex to peripheral auditory receptor, supported by anatomical descriptions of descending auditory pathways from auditory areas to the medial olivocochlear efferent system and organ of Corti. Through recording of evoked otoacoustic emissions during presurgical functional brain mapping for refractory epilepsy, we showed that corticofugal modulation of peripheral auditory activity also exists in humans. In 10 epileptic patients, electrical stimulation of the contralateral auditory cortex led to a significant decrease in evoked otoacoustic emission amplitude, whereas no change occurred under stimulation of non-auditory contralateral areas. These findings provide evidence of a cortico-olivocochlear pathway, originating in the auditory cortex and modulating contralateral active cochlear micromechanisms via the medial olivocochlear efferent system, in humans.

Presented are results relevant to extending the utility of the auditory steady-state response (ASSR) in threshold estimation at high-frequency carriers and to the accuracy of thresholds estimated using modulation frequencies near 40 versus 80 Hz. Initially, efforts were directed at confirming various findings reported in the literature apropos effects of several basic ASSR parameters. Results supplement others’ observations suggesting that ASSR detection limits overestimate behavioral thresholds for conventional audiometric (carrier) frequencies from 500 to 4000 Hz. Further investigation revealed even greater errors of threshold estimates for 8000 and 12 000 Hz, by about 14 and 22 dB on average, respectively. Although suggesting high-frequency ASSR testing to be efficacious, technical advances and additional work is needed to establish clinical utility. Comparison of effects of modulation frequency suggested ASSR thresholds with 40 Hz modulation to fall closer to behavioral threshold than those estimated ...

Clinical reports on autism describe abnormal responses to auditory stimuli such as intolerance to sounds. The present study assessed subjective perception of loudness in subjects with autism compared to healthy controls, using two psychoacoustic tests. First, the auditory dynamic range was evaluated at six different tone frequencies. Secondly, loudness growth as a function of the intensity level of a 1 kHz tone was estimated. Verbal responses from a group of 11 children and adolescents with autism were compared to responses of 11 age- and gender- matched healthy controls. Smaller auditory dynamic ranges were found in the autistic group than in the control group, as well as increased perception of loudness, indicating hyperacusis in subjects with autism.

The auditory nerve's electrically evoked compound action potential is recorded in deaf patients equipped with the Nucleus^(R) 24 cochlear implant using a reverse telemetry system (NRT(TM)). Since the threshold of the NRT response (NRT-T) is thought to reflect the psychophysics needed for programming cochlear implants, efforts have been made by specialized management teams to develop its use. This study aimed at developing a valid tool, based on artificial neural networks (ANN) technology, for automatic estimation of NRT-T. The ANN used was a single layer perceptron, trained with 120 NRT traces. Learning traces differed from data used for the validation. A total of 550 NRT traces from 11 cochlear implant subjects were analyzed separately by the system and by a group of physicians with expertise in NRT analysis. Both worked to determine 37 NRT-T values, using the response amplitude growth function (AGF) (linear regression of response amplitudes obtained at decreasing stimulus intensity levels). The validity of the system was assessed by comparing the NRT-T values automatically determined by the system with those determined by the physicians. A strong correlation was found between automatic and physician-obtained NRT-T values (Pearson r correlation coefficient >0.9). ANOVA statistics confirmed that automatic NRT-Ts did not differ from physician-obtained values (F=0.08999, P=0.03). Moreover, the average error between NRT-Ts predicted by the system and NRT-Ts measured by the physicians (3.6 stimulation units) did not differ significantly from the average error between NRT-Ts measured by each of the three physicians (4.2 stimulation units). In conclusion, the automatic system developed in this study was found to be as efficient as human experts for fitting the amplitude growth function and estimating NRT-T, with the advantage of considerable time-saving.

Patients with steeply sloping hearing losses of cochlear origin may exhibit enhanced difference limens for frequency (DLFs) near the cut-off frequency (Fc) of their hearing loss. This effect has been related to observations in deafened animals of an over-representation of Fc in the primary auditory cortex. However, alternative interpretations in terms of peripheral mechanisms have not been eliminated. In the present study, we assessed the possible role of two peripheral mechanisms [loudness cues and spontaneous otoacoustic emissions (SOAEs)] in a group of patients with high-frequency hearing loss. We tested first whether the DLF enhancement effect was still observed under conditions where subjects could not rely on loudness cues to perform the frequency discrimination task. To achieve this, we adjusted the nominal level of each stimulus so that it fell on an equal loudness contour measured at very fine (1/8 octave) frequency intervals, and we roved the level of each stimulus over a large range (12 dB). Under these conditions, the DLF enhancement was still observed in all patients; this demonstrates that the effect cannot be explained simply by loudness cues. We then screened the patients for SOAEs to test whether the DLF enhancement effect could be explained by the presence of such emissions in the vicinity of the Fc. None of the patients exhibited SOAEs. Finally, we tested whether the patients had cochlear dead regions, i.e. regions lacking functional inner hair cells and/or auditory nerve fibres. Using a refined version of a non-invasive clinical test for the identification of dead regions, we assessed the presence of such regions in fine frequency steps (1/4 octave) up to very high frequencies. All of the patients had cochlear dead regions. The first two findings support the hypothesis that DLF enhancement is due to injury-induced central reorganization in the auditory system. The last one is consistent with neurophysiological data in animals, which suggest that complete deprivation from auditory input at certain cochlear sites may be a necessary condition for the occurrence of injury-induced cortical reorganization.

In 1997, Don and his co-workers described a new method for evaluating the auditory brainstem response (ABR)—yielding the stacked-wave-V ABR—which may permit the reliable detection of even small vestibular schwannomas (VSs). However, this method requires a masking technique that may not be readily available to the clinician. Furthermore, relatively high-level noise is required and may be annoying to the patient. An alternative method that might permit the same manipulation of the ABR was thus explored whereby tone-bursts (TBs) were used to obtain frequency-specific ABRs. The goal of the study was to determine whether TBs could be used to achieve the sort of de-convolution and subsequent enhancement of wave V reported with the original method of Don et al. First, the TB-stacked ABR (wave V) was compared to that obtained using derived narrowband masked ABRs in young normal-hearing subjects. Second, the TB method was employed in subjects with unilateral VSs and in patients with unilateral sensory hearing loss...

Objective The purpose of the study was to test for differences in late electrically evoked auditory potentials between subjects exhibiting “good” versus “poor” speech recognition performances with their cochlear implants. Methods Late auditory evoked responses were measured in 30 subjects equipped with the Digisonic (MXM, Antibes, France) cochlear implant, 15 of whom had “good” speech recognition scores (i.e., more than 89% correct phoneme identification without lip reading). The 15 other subjects had poorer speech recognition scores (i.e., less than 85%). Results Differences in N1P2 amplitude, as well as P1, N1, and P2 latencies, and N1-P1 and N1-P2 latency intervals were tested. Wave P2 latency was found to be significantly different between the two groups (P = .016), being shorter in “good” than in “poor” performers. The strength of the statistical relationship between electrophysiological and speech recognition variables (r2 = 17%) was substantially smaller than that observed using electrically evoked auditory brainstem response (EABR) for the same implanted device (r2 = 49% for the EABR wave III–V latency interval). Conclusions Some characteristics of late electrically evoked auditory potentials differ significantly among cochlear implant users depending on their speech recognition performance. However, the relationship between electrophysiological and speech recognition variables is more pronounced when early (brainstem) rather than late (cortical) evoked responses are considered.

In order to test the hypothesis of a role of cochlear efferent activity in intensity perception in humans, loudness functions, loudness integration, and loudness summation were measured in the absence and in the presence of contralateral noise in normal-hearing subjects. Additionally, relationships with the effect of the noise on evoked otoacoustic emissions (EOAEs) were tested, and comparisons with vestibular neurotomy patients were performed. Overall, the results failed to demonstrate significant effects of contralateral noise stimulation on loudness functions and loudness integration. Furthermore, no significant differences were found in vestibular neurotomy patients. A significant effect of contralateral noise on loudness summation was noted, but was not related to the effect on otoacoustic emissions. The present results fail to support the notion that efferent influences onto the cochlear compression have a significant perceptual effect.

The inner ear contains receptor cells that oscillate spontaneously, generating waves that propagate backward in the cochlea, ultimately causing sound to be radiated into the ear canal--the spontaneous otoacoustic emissions (SOAEs). Except in rare conditions, these internally generated signals appear to go unheard. The intensity of SOAEs admittedly hovers near the threshold of detection, but they are essentially continuous and perhaps last a lifetime. The hypothesis is tested that the frequency difference limen (DL(F)) is affected by SOAEs. The results show that the DL(F) systematically improves near SOAE frequencies, determined ipsi- or contralaterally to the SOAEs, arguing for a central effect. The results are discussed in the context of central plasticity.

In this study, an original psychometric procedure was used in order to characterize in more detail than in previous studies the different perceptual components of tinnitus, i.e. auditory sensations which are perceived in the absence of a corresponding external acoustic stimulus. Ten subjects with chronic tinnitus were asked to rate on a numeric scale the contribution of elementary pitch sensations evoked by isolated frequency components to their overall tinnitus sensation. The resulting ‘internal tinnitus spectra’, which represented the estimated perceptual contribution to the tinnitus sensation as a function of frequency over a large range of frequencies, were found to occupy a wide frequency range corresponding largely to that at which hearing thresholds were abnormally elevated. In most cases, they exhibited a broad peak falling within the hearing loss range. This pattern of result suggests that in subjects with high-frequency hearing loss, tinnitus sensations, when present, resemble those evoked by high-frequency noise bands with, in some cases, a superimposed tonal-like pitch. These results confirm and extend earlier results in the literature and agree with the patients’ reports; their practical implications for the design of future studies on tinnitus and theoretical implications for the understanding of the neurophysiological mechanisms underlying tinnitus are discussed. The results of an additional experiment showed that the internal tinnitus spectrum could be altered by perceptual training in a fine frequency discrimination task with tones in the frequency range of the main peak of the tinnitus spectrum.

The influence of hearing loss and aging on the perceptual organization of sound sequences was investigated by comparing the ability of young normal-hearing subjects and elderly subjects having either impaired or normal hearing for their age to form perceptual auditory streams from sequences of harmonic complex tones as a function of differences in fundamental frequency (F0). The sequences consisted of repeating triplets of harmonic complex tones separated by a silence (ABA-). In conditions in which the F0s of the A and B tone were so low that the harmonics could not be individually resolved by the peripheral auditory system even in the young normal-hearing subjects, those subjects showed similar stream segregation performance to the elderly hearing-impaired subjects. In contrast, when the F0s of the tones were high enough for the harmonics to be largely resolved at the auditory periphery in normal-hearing subjects, but presumably unresolved in the elderly subjects, the former showed significantly more stream segregation than the latter. These results, which cannot be consistently explained in terms of age differences, suggest that auditory stream segregation is adversely affected by reduced peripheral frequency selectivity of elderly individuals. This finding has implications for the understanding of the listening difficulties experienced by elderly individuals in cocktail-party situations.

Objective: Response from spiral ganglion cells to electrical stimulation via the Nucleus 24 cochlear implant can be measured using the neural response telemetry system. The purpose of this study was to assess, in children, the correlation between the neural response threshold and the behavioral levels used for cochlear implant programming process. Methods: The neural response telemetry test was administered to 23 children (mean age at implantation: 4 years) with the Nucleus 24 cochlear implant. Four intra-cochlear electrodes (electrodes 5, 10, 15 and 20) were tested. The neural response threshold at 3, 6, 9 and 12 months post-implantation was compared with the behavioral threshold and the maximum comfort level estimated during the same periods: a Pearson's correlation test was performed for each tested electrode. Results: On apical electrodes, the correlation with the behavioral threshold remained significant from 3 to 12 months post-implantation ( r ranging from 0.696 to 0.909, P 0.05), and the correlation with the maximum comfort level was also significant throughout the study period, except on electrode 15 at 9 months (tendency to significance). On basal and intermediate electrodes, statistical correlations were found only at some points of time; nonetheless, at 12 months post-implantation, a significant correlation with behavioral levels could be clearly demonstrated both on electrode 15 ( r =0.914–0.778, P 0.05) and on electrode 10 ( r =0.845–0.720, P 0.05). Conclusions: This preliminary study suggests that the correlation between the neural response threshold and behavioral levels may improve from the base towards the apex of the cochlea. However, a significant correlation can be demonstrated for all tested electrodes at 12 months post-implantation. During the first months post-implantation care must be exercised when interpreting neural response telemetry measurements: a positive test does not necessarily mean that the stimulus delivered to the acoustic nerve will be centrally processed with the result of an auditory perception.

Genetically-transferred hearing impairments account for more than 50% of cases of pediatric sensorineural hearing defects. Multiple clinical aspects are involved in genetic hearing impairment, including the involvement of other organs, genetic inheritance, and the degree and age at onset of hearing loss. Diagnosis relies on family history, on the systematic investigation of the symptomatology including an associated syndrome, and audiometry testing in parents and siblings. Analysis of the connexin 26 gene is also indicated, as it is frequently involved in this disorder. Further genetic analysis in affected families will aid in detecting other as yet unidentified genes responsible for hearing impairment.

Difficulty in filtering relevant auditory information in background noise is one of the features of autism. Auditory filtering processes can be investigated at the peripheral level as they are hypothesized to involve active cochlear mechanisms which are regulated by the efferent activity of the medial olivocochlear (MOC) system. The aim of the present work was therefore to assess these peripheral auditory processes in 22 children and adolescents with autism compared with age- and gender-matched normal controls. Active cochlear mechanisms were evaluated with transiently evoked otoacoustic emissions (TEOAEs) and MOC system efficiency was assessed via TEOAEs which are decreased when stimulating the contralateral ear with noise. The MOC system evaluation was performed on 18 of the 22 children. In both studies, results were analysed according to age (from 4 to 10 years and from 11 to 20 years). The main result concerns the asymmetry of the efferent system which differs in individuals with autism. Several neural processes might be hypothesized as involved in the results obtained as the MOC system which originates in the brainstem received regulating controls from upper brain structures including auditory cortex. Lateralization abnormalities at the auditory periphery may reflect indirectly a problem at a higher level of auditory processing. A second important result shows a decrease in TEOAE amplitude with age, in patients, that may correspond to a decrease in hearing sensitivity.

The mammalian auditory system contains descending pathways that originate in the cortex and relay at various intermediate levels before reaching the peripheral sensory organ of Corti. The last link in this chain consists of the olivocochlear bundle. The activity of this bundle can be measured through otoacoustic emissions, which are acoustic signatures of the cochlear biomechanical activity. In the present study, it was hypothesized that frequency-specific activation of the olivocochlear bundle in the contralateral ear would show up as frequency-specific variations in otoacoustic emission amplitude in the ipsilateral ear. Two groups of young adult subjects participated in this experiment. Evoked otoacoustic emissions were recorded in the ipsilateral ear at two test frequencies (1 and 2 kHz). Subjects had to detect probe tones at a given frequency in background noise in the contralateral ear. Larger efferent activation was measured at test frequencies on which attention is focused. This result provides evidence for an influence of attention on the auditory periphery via descending projections.

Diagnosis of hearing impairment is possible during the first days of life. Hearing tests are noninvasive and should not be delayed when hearing loss is suspected. Among children's hearing impairments, conductive hearing loss is the most frequent; it is generally acquired and reversible. At the opposite pole, sensorineural hearing loss has more severe consequences because it is irreversible and often present from birth. Early diagnosis and treatment are necessary in all cases to prevent speech delay. In cases with sensorineural hearing impairment, hearing aid fitting, or even cochlear implantation, and intensive speech therapy will help deaf children learn speech, with the view of optimal social and professional integration.

In this study, increases in loudness with increases in bandwidth, termed loudness summation, were derived from loudness growth functions estimated using a loudness-scaling procedure. The results revealed that at equal loudness category, categorical loudness summation was generally larger in normal-hearing than in hearing-impaired subjects; furthermore, the increase in loudness summation at intermediate loudness levels observed in the former, was absent in the latter. These results, in broad agreement with recent data from the literature, can be explained in the light of physiological data on cochlear compression. One implication of these results regarding hearing aid fitting was that channel-by-channel loudness normalization was effective only when the incoming sound was closed in bandwidth to one of the test stimuli.

The present study aimed to test whether central, across-channel, informational auditory processing abilities are altered by hearing loss. The informational masking effect exerted on a 1 kHz tone-pip by a simultaneous four-tone masker, whose spectral content changed within as well as across trials, was measured in the left and right ears of normal-hearing subjects and hearing-impaired subjects with either symmetrical or asymmetrical hearing loss between the two ears. In the subjects with normal-hearing or symmetrical hearing loss, the level of the masker was set to 40 dB SL in each ear, in the subjects with asymmetrical hearing loss, the masker was set to 40 dB SL in the best ear and loudness-balanced in the other ear. The results failed to reveal significant differences in informational masking between normal-hearing and hearing-impaired subjects. However, in subjects with asymmetric hearing loss, less informational masking was observed in the ear with the more elevated absolute thresholds than in the opposite ear. Since the latter finding can be explained in terms of across-ear differences in loudness recruitment, it is suggested that central, across-channel, informational processing abilities are not substantially different in hearing-impaired than in normal-hearing ears.

The efficiency of sets of acoustical features discriminating pathological voices from control voices is reported. Two strategies were compared. The first (called the 'distance strategy') was built upon a statistical distance of voice features to reference values obtained for a set of healthy (reference) voices. The second strategy (called the 'range strategy') is based on the position inside or outside normal ranges established from a reference population; results based on this strategy were presented in a previous paper. Reference values were calculated from a database of 200 healthy voices distributed into 10-year age groups ranging from 20 to 70. Comparisons were made using a second database of 220 voices, including 65 control, 51 functional dysphonia, 50 with nodules on the vocal folds and 54 recurrent nerve palsy. The phonetic material was compared of 17 French vowels: 11 vowels in a sentence, three isolated vowels and three segments (beginning, middle and end) of the sustained vowel /a/. Four acoustical features were considered for each vowel: the voice fundamental (f0) and the first three formant frequencies. Acoustical features were calculated on an ILS (Interactive Laboratory System) analysis system (workstation). The separation of each pathological group from the control group, using sets of acoustical features, was statistically assessed. From the strategy point of view, results indicated that (i) the fundamental frequency f0 was the best measure to separate normal from pathological voices with the distance strategy; (ii) when the formants were taken, the range strategy performed better in separating the voices. For classification of pathologies, the best separation coefficients were obtained with nodules and the worst with recurrent nerve palsy. Overall, it was seen that the separation between control and pathological voices was most efficient when measured using the distance strategy for f0. The range strategy was useful with formant frequencies.

It is well established that low-level broad band noise can elicit an amplitude decrease in evoked otoacoustic emissions recorded in the opposite ear. However, the influence of the temporal characteristics of the contralateral stimulus on this effect remains largely unknown. In the present study, otoacoustic emissions evoked by 60 dB SPL clicks were recorded in 19 normal-hearing subjects using the Otodynamics ILO88, successively in absence and presence of a contralateral noise that was either steady or modulated sinusoidally in amplitude at different depths (from 25% to 100% in 25 point steps) and rates (from 50 Hz to 800 Hz in half-octave steps). The energy was kept constant whatever the modulation depth. The results showed that the evoked otoacoustic-emission attenuation effect induced by contralateral stimulation varied depending on the modulation depth and frequency of the contralateral amplitude-modulated noise. The largest suppression effect was observed at the 100 Hz modulation frequency and the 100% modulation depth. The 50 Hz modulation resulted in less suppression than with unmodulated noise. An interpretation of these results in terms of the influence of temporal amplitude fluctuations falling within a certain range on medial olivocochlear bundle activity is discussed.

The auditory sensory end organ is under the control of the central nervous system via efferent projections. Contralateral suppression of otoacoustic emissions (acoustic signatures of the cochlear biomechanical activity) provides a non-invasive approach to assess olivocochlear efferent activity in humans. Using this approach, the present study compared professional musicians with musically-inexperienced subjects. The results revealed stronger bilateral cochlear suppression, suggesting larger efferent influences in both ears, in musicians. Furthermore, in indicating no difference in left/right asymmetry of efferent-mediated suppression between the two groups, the present findings suggest that the observed differences in olivocochlear activity reflect bilaterally-enhanced activity of the cortical auditory structures in musicians rather than differences in cerebral hemispheric asymmetry between the two groups.

The aim of this study was to test for differences between normal-hearing and hearing-impaired listeners regarding two fundamental aspects of intensity perception: loudness integration and loudness summation. Loudness functions for three different stimuli were measured using categorical loudness scaling in 8 normal-hearing and 12 hearing-impaired subjects. The results indicated that temporal loudness integration, defined as the difference in SPL between 16.25-ms and 300-ms noise bursts of equal loudness, was larger in the hearing-impaired than in the normal-hearing listeners. Loudness summation, defined as the difference in SPL between a 300-ms, 1,600-Hz tone pip and a white noise burst of the same duration and loudness, did not differ between the two groups. Implications of these results for hearing aid fitting strategies based on loudness normalization are discussed.

Electrically evoked auditory brainstem responses (EABRs) and loudness functions were measured in 14 subjects equipped with an MXM Digisonic cochlear implant. EABRs were evoked by 75-Hz pulse trains presented on the apical electrode. Loudness functions at the same rate and at a rate more conventional for psychoacoustic measurements (300 Hz) were measured using a categorical loudness-scaling procedure. The results revealed a significant difference in the loudness functions measured at 75 and 300 Hz, loudness increasing more steeply with stimulus intensity for the latter rate. Significant correlations between EABR wave V thresholds and perceptual thresholds measured at both 75 and 300 Hz were observed. Furthermore, in 8 out of the 14 patients, EABR wave V saturated at a stimulus level corresponding precisely to the loudest bearable, i.e. "Too loud" level for the 300-Hz stimulation rate; this same level corresponded to the "Comfortable" loudness level for the 75-Hz stimulation rate. On average, an almost linear relationship was observed over the first half of the loudness range between the stimulus intensity, expressed as a pulse duration in log units, and wave V amplitude in dB. Although further investigation is required before maximum comfort levels can be predicted reliably from EABR measures in individual subjects, these results indicate new directions regarding the estimation of perceptual dynamic range limits on the basis of EABR measures in cochlear implantees.