Contralateral Suppression Of Otoacoustic Emissions Research Articles

Age related changes to the dynamics of contralateral DPOAE suppression in human subjects

BackgroundThe two ears are linked with a neural pathway such that stimulation of one ear has a modulating effect on the contralateral cochlea. This is mediated by cochlear afferent neurons connecting with olivo-cochlear efferents. The monitoring of this pathway is easily achieved by measuring contralateral suppression of otoacoustic emissions, and there is some clinical value in the ability to assess the integrity of this pathway. An important step in an evaluation of clinical utility is to assess any age-related changes. Accordingly, in the present study we measure the dynamics of contralateral DPOAE suppression in a population of normal hearing subjects of different ages.MethodsUsing a real-time DPOAE recording method we assessed contralateral DPOAE suppression in 95 ears from 51 subjects (age range 2–52 years). DPOAE (2f1-f2; f2 = 4.4 kHz; f2/f1 = 1.22) input–output functions were measured. In response to contralateral broadband noise, dynamic aspects of DPOAE suppression were measured, specifically suppression onset latency and time constants.ResultsAn age-related reduction in DPOAE amplitudes was observed. Both the detectability and the degree of contralateral DPOAE suppression were decreased in older age groups. We find an age-related increase in the latency of onset of DPOAE suppression to contralateral stimulation, but no significant change in suppression time-constants.ConclusionOlivo-cochlear function as revealed by contralateral suppression of DPOAEs shows some important age-related changes. In addition to reduced emissions (outer haircell suppression) we find an increased latency that may reflect deterioration in auditory brainstem function. Regarding clinical utility, it is possible that the changes observed may reflect an aspect of age-related hearing loss that has not been previously considered.

Contralateral Suppression of Transient Otoacoustic Emissions and Sentence Recognition in Noise in Young Adults

One purported role of the medial olivocochlear (MOC) efferent system is to reduce the effects of masking noise. MOC system functioning can be evaluated noninvasively in humans through contralateral suppression of otoacoustic emissions. It has been suggested that the strength of the MOC efferent activity should be positively associated with listening performance in noise. The objective of the study was to further explore this notion by examining contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) and sentence recognition in two noises with normal hearing young adults. A repeated measures multivariate quasi-experimental design was employed. Thirty-two normal hearing young adult females participated. Reception thresholds for sentences (RTSs) were determined monaurally and binaurally in quiet and in competing continuous and interrupted noises. Both noises had an identical power spectrum and differed only in their temporal continuity. "Release from masking" was computed by subtracting RTS signal-to-noise ratios in interrupted from continuous noise. TEOAEs were evoked with 80 dB peSPL click stimuli. To examine contralateral suppression, TEOAEs were evaluated with 60 dB peSPL click stimuli with and without a contralateral 65 dB SPL white noise suppressor. A binaural advantage was observed for RTSs in quiet and noise (p < .0001) while there was no difference between ears (p >.05). In noise, performance was superior in the interrupted noise (i.e., RTSs were lower vs. continuous noise; p < .0001). There were no statistically significant differences in TEOAE levels between ears (p >.05). There was also no significant difference in the amount of suppression between ears (p = .41). There were no significant correlations or predictive linear relations between the amount of TEOAE suppression and any indices of sentence recognition in noise (i.e., RTS signal-to-noise ratios and release from masking; p > .05). The findings are not consistent with the notion that increased medial olivocochlear efferent feedback, as assessed via contralateral suppression of TEOAEs, is associated with improved speech perception in continuous and interrupted noise.

Wavelet analysis demonstrates no abnormality in contralateral suppression of otoacoustic emissions in tinnitus patients

The efferent auditory system is thought to play a role in the origin of tinnitus. Part of this system can be tested in humans with contralateral suppression of otoacoustic emissions. Stimulation of the medial olivocochlear efferent system is responsible for this reduction of otoacoustic emissions after contralateral acoustic stimulation. Previous research on patients with tinnitus showed inconclusive results. With wavelet analysis both time and frequency information of the emission can be analysed and compared. Contralateral suppression of otoacoustic emissions was therefore measured in tinnitus patients (n = 26) and normal subjects (n = 37) and analysed using wavelets. No significant difference in suppression was found between the tinnitus patients and the control group.

What is the role of the medial olivocochlear system in speech-in-noise processing?

The medial olivocochlear (MOC) bundle reduces the gain of the cochlear amplifier through reflexive activation by sound. Physiological results indicate that MOC-induced reduction in cochlear gain can enhance the response to signals when presented in masking noise. Some previous studies suggest that this "antimasking" effect of the MOC system plays a role in speech-in-noise perception. The present study set out to reinvestigate this hypothesis by correlating measures of MOC activity and speech-in-noise processing across a group of normal-hearing participants. MOC activity was measured using contralateral suppression of otoacoustic emissions (OAEs), and speech-in-noise processing was measured by measuring the effect of noise masking on performance in a consonant-vowel (CV) discrimination task and on auditory brain stem responses evoked by a CV syllable. Whereas there was a significant correlation between OAE suppression and both measures of speech-in-noise processing, the direction of this correlation was opposite to that predicted by the antimasking hypothesis, in that individuals with stronger OAE suppression tended to show greater noise-masking effects on CV processing. The current results indicate that reflexive MOC activation is not always beneficial to speech-in-noise processing. We propose an alternative to the antimasking hypothesis, whereby the MOC system benefits speech-in-noise processing through dynamic (e.g., attention- and experience-dependent), rather than reflexive, control of cochlear gain.

Auditory efferent feedback system deficits precede age‐related hearing loss: Contralateral suppression of otoacoustic emissions in mice

The C57BL/6J mouse has been a useful model of presbycusis, as it displays an accelerated age-related peripheral hearing loss. The medial olivocochlear efferent feedback (MOC) system plays a role in suppressing cochlear outer hair cell (OHC) responses, particularly for background noise. Neurons of the MOC system are located in the superior olivary complex, particularly in the dorsomedial periolivary nucleus (DMPO) and in the ventral nucleus of the trapezoid body (VNTB). We previously discovered that the function of the MOC system declines with age prior to OHC degeneration, as measured by contralateral suppression (CS) of distortion product otoacoustic emissions (DPOAEs) in humans and CBA mice. The present study aimed to determine the time course of age changes in MOC function in C57s. DPOAE amplitudes and CS of DPOAEs were collected for C57s from 6 to 40 weeks of age. MOC responses were observed at 6 weeks but were gone at middle (15-30 kHz) and high (30-45 kHz) frequencies by 8 weeks. Quantitative stereological analyses of Nissl sections revealed smaller neurons in the DMPO and VNTB of young adult C57s compared with CBAs. These findings suggest that reduced neuron size may underlie part of the noteworthy rapid decline of the C57 efferent system. In conclusion, the C57 mouse has MOC function at 6 weeks, but it declines quickly, preceding the progression of peripheral age-related sensitivity deficits and hearing loss in this mouse strain.

Contralateral suppression of linear and nonlinear transient evoked otoacoustic emissions in neonates at risk for hearing loss

To investigate the transient evoked otoacoustic emissions (TEOAE) contralateral suppression in neonates at risk for hearing loss, 55 neonates at risk for hearing loss (risk group) and 72 full-term neonates not at such risk (control group) were bilaterally tested. In all neonates, the TEOAE were recorded in two stimulation modes (linear and nonlinear clicks), with and without contralateral acoustic stimulation. Findings revealed significant contralateral suppression of otoacoustic emissions in both groups, but the amount of TEOAE contralateral suppression was reduced for at risk group ( p = 0.001), supporting the hypothesis that medial olivocochlear bundle function is reduced in neonates at risk for hearing loss. The combination of contralateral acoustic stimulation and TEOAE enables easy and noninvasive study of auditory efferent function. However it should be emphasized that the reduction in TEOAE contralateral suppression in the risk group, statistically identified as a group effect, might not be detectable in individual cases. Further studies are needed in order to determine whether the lower amount of TEOAE contralateral suppression in neonates at risk for hearing loss represents a risk for developing auditory processing disorders. Learning outcomes: The reader will be introduced to the study using auditory efferent pathway activation by contralateral acoustic stimulation (CAS), resulting in the TEOAE suppression effect. The characteristics of TEOAE suppression in the neonatal population, in which it provides evidence of the reduced medial olivocochlear system function in those at risk for hearing loss, will also be addressed.

Contralateral Suppression of Otoacoustic Emissions in Children with Specific Language Impairment

The purpose of the investigation was to determine whether a group of children with specific language impairments (SLI) have reduced peripheral auditory processes thought to be associated with speech-in-noise intelligibility. Transient evoked otoacoustic emissions (TEOAE) and their suppression by the efferent activity of the medial olivocochlear system (MOCS) in response to contralateral acoustic stimulation were used to compare these processes in 18 children with SLI and 21 controls. The results revealed no group difference in TEOAE suppression effect or left/right asymmetry of TEOAE suppression effect. These results suggest that children with SLI do not have auditory processing problems at this peripheral level casting doubt on a hypothesized relationship between strength of MOCS activity and language impairment.

Mudanças das emissões otoacústicas por transientes na supressão contralateral em lactentes

It has been suggested that the function of the medial olivocochlear system (MOCS) can be evaluated by the suppression effect of the transient evoked otoacoustic emission (TEOAE). The competitive noise has an inhibitory effect on the functioning of the outer hair-cell, reducing the level of otoacoustic emissions. Despite the fact that there is no postnatal growth of the cochlea, middle ear growth and auditory processing development continue after birth. To analyze age-related changes of MOCS using the TEOAE suppression in healthy infants. 25 full-term infants with no risk factors for hearing loss were evaluated in two moments: at birth and at the age of six months. At both ages TEOAE were recorded in the "Quickscreen" mode, nonlinear stimulation at 78dB peSPL, for both ears, with and without contralateral noise presented at 60dB SPL. The data analyses, using ANOVA, revealed significant contralateral suppression of otoacoustic emissions in both groups, but the TEOAE levels and the amount of TEOAE contralateral suppression were smaller at six-month of age when compared to the neonatal period (p < 0.01). The TEOAE suppression effect for neonatals was 2.81dB (+/- 0.19dB) and at the age of six months was 1.41dB (+/- 0.29dB). The amount of TEOAE suppression decreased from birth to six months of age. The association between contralateral acoustic stimulation and a commercially available rapid TEOAE measurement system enables a non-invasive monitoring of the auditory efferent mechanism and seems to be clinically feasible to evaluate cochlear status and auditory efferent function development in infants at risk.

Distortion product otoacoustic emission suppression in subjects with auditory neuropathy.

The objective of this experiment was to address: 1) whether normal efferent system function is required for normal cochlear tuning as measured by distortion product otoacoustic emission (DPOAE) suppression in humans and 2) whether cochlear function, assessed by DPOAE suppression tuning, is normal in a small group of patients with auditory neuropathy. DPOAE suppression tuning curves (STCs) are similar to other physiologic measures of tuning. They are generated by evoking a DPOAE with two simultaneously presented pure tones and then suppressing the distortion product with a third tone of varying frequency and level. In this study, DPOAE STCs were generated with f2 frequencies of 1500, 3000, and 6000 Hz in 15 normal-hearing adults and four subjects with documented auditory neuropathy. Tuning curve width, slope and tip characteristics, as well as rate of suppression growth were measured in each group. Contralateral suppression of otoacoustic emissions (OAEs) was also recorded as an index of medial efferent function. Results show that the four subjects with auditory neuropathy lacked efferent suppression of OAEs. However, these four subjects showed normal estimates of cochlear tuning as measured by DPOAE suppression results. This finding suggests that normal efferent system function is not required at the time of test for normal DPOAE suppression tuning. It also suggests that cochlear function as evaluated by detailed measures of DPOAE suppression, is normal in these "typical" patients with auditory neuropathy.

Acoustically and electrically evoked contralateral suppression of otoacoustic emissions in guinea pigs

It is generally accepted that stimulation of the efferent auditory system results in changes of cochlear activity. A simple method of activating the olivocochlear pathway by contralateral electrical stimulation of the round window (ES-RW) was used in this study with the aim of comparing the efficacy of acoustically and/or electrically evoked contralateral suppression. The suppression of transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) was elicited by contralateral acoustic stimulation (AS) (61 dB SPL continuous white noise), and/or by electrical stimulation of an electrode implanted at the contralateral round window (monopolar rectangular pulses 0.1 ms, repetition rate 300 Hz, intensity 50–100 μA) in 12 guinea pigs. The average value of contralateral suppression of TEOAEs amounted to 1.04±0.48 dB for acoustic stimulation and 0.97±0.53 dB for round window electrical stimulation. The simultaneous presentation of both acoustic and electrical stimulation had only a slight additive effect and resulted in 1.27±0.79 dB diminution of TEOAEs. The suppression of DPOAEs during contralateral acoustic and electrical stimulation was evident mainly at low and middle frequencies (1–4 kHz). In two guinea pigs the maximum DPOAE suppression was present at high frequencies. The average values of contralateral suppression measured at individual f2 frequencies of DPOAEs were similar to those calculated from 1/4 octave power spectrum analysis of the TEOAEs in half of the animals. The results demonstrated that contralateral ES-RW had a similar suppressive effect on TEOAEs and DPOAEs as did contralateral AS and simultaneous AS+(ES-RW). The results of spectral analysis suggested that both modes of contralateral stimulation excited similar sensory cochlear elements and induce comparable suppression of both TEOAEs and DPOAEs.

Stronger bilateral efferent influences on cochlear biomechanical activity in musicians than in non-musicians

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.

556 Influence of handedness on peripheral auditory asymmetry

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.

Auditory efferents involved in speech-in-noise intelligibility.

Following studies proposing that medial olivocochlear efferents might be involved in the processing of complex signals in noise, we tested the involvement of efferent feedback in speech-in-noise intelligibility. Two approaches were used: measures of speech-in-noise intelligibility in vestibular neurotomized patients with cut efferents and comparison with normal hearing subjects; and correlations between effectiveness of olivocochlear feedback, assessed by contralateral suppression of otoacoustic emissions and speech-in-noise intelligibility in normal subjects. Contralateral noise improved speech-in-noise intelligibility in normal ears. This improvement, which was almost absent in de-efferented ears of vestibular neurotomized patients, was correlated with the strength of the olivocochlear feedback. Together, these results suggest that olivocochlear efferents play an antimasking role in speech perception in noisy environments.

Evidence of a medial olivocochlear involvement in contralateral suppression of otoacoustic emissions in humans

Otoacoustic emissions (OAEs) evoked by click stimuli were recorded in both ears of 20 normal human subjects, in the presence and absence of a contralateral masking broad band noise. No difference in the amplitude of OAE suppression was noted between the first tested ear and the second one. In addition, 20 pathological subjects were tested according to the same protocol. Ten of them belonged to a group of patients whose vestibular nerve was sectioned on one side to relieve incapacitating vertigo and thus represented a group in whom olivocochlear efferents were severed. A great reduction of suppression observed in the operated ear suggested that olivocochlear efferent fibers are necessary to obtain a full suppressive effect. Three of the pathological subjects were patients who had undergone a decompression of the facial nerve which necessitated the same surgical approach as vestibular neurotomy, but without any section of vestibular fibers. This surgical control group demonstrated that the surgical act by itself cannot explain the difference observed in the neurotomized group. Finally, seven of the pathological subjects were patients with Bell's palsy, which paralyses the facial nerve and abolishes the stapedial reflex. No suppression difference was observed between healthy ears and ears without stapedial reflex. Therefore, it appeared that the stapedial reflex was not involved in the contralateral suppression of EOAEs. However, as the tensor tympani muscle remained functional in these patients, its involvement in the suppressive effect cannot be excluded.