Contralateral Suppression Of Otoacoustic Emissions Research Articles

Evaluation of the auditory findings of patients with obstructive sleep apnea syndrome

ObjectivesTo investigate the effects of hypoxia occurring in patients with Obstructive Sleep Apnea Syndrome (OSAS) on Auditory evoked late latency, Auditory brainstem response, and the contralateral suppression of otoacoustic emissions. Materials and methods46 patients diagnosed with OSAS were divided into groups as moderate and severe based on their Apnea Hipopnea Index (AHI) values. The control group consisted of 22 healthy individuals. All participants underwent an Auditory Brainstem Response (ABR) test, Auditory Evoked Late Latency Response (LLR), and Contralateral Suppression Otoacoustic Emission (CS-OAE). FindingsThere was no statistical difference between the OSAS group and the control group regarding P1 latency, N1 latency, and P1 and N1 wave amplitude (p > 0.05). In ABR, statistically significant differences were found between the control, moderate OSAS, and severe OSAS groups in wave I in the right and left ear (p < 0.05). In the analyses performed for the otoacoustic emission frequencies with and without contralateral suppression of the right and left ear, suppression was not observed at some frequencies, and this was regarded as statistically significant (p < 0.05). ConclusionIt is considered that OSAS does not have cortical effects but impacts the brainstem region and the cochlea. Bilateral impact, especially observed in wave I of ABR, is prominent on the auditory nerve. Considering that the medial olivo-cochlear (MOC) system is affected in patients with OSAS, it is thought that these patients are inadequate in suppressing noise, and this may cause various problems, particularly the inability to distinguish speech in noisy environments.

Contralateral Suppression of Transient-evoked Otoacoustic Emissions in Leisure Noise Exposed Individuals.

Leisure noise may have a significant impact on hearing thresholds and young adults are often exposed to loud music during leisure activities. This behavior puts them at risk of developing noise-induced hearing loss (NIHL). A frequent initial indication of NIHL is reduced hearing acuity at 4 kHz. The objective of the current study was to assess the role of the medial olivocochlear reflex (MOCR) in leisure noise-exposed individuals with and without a 4-kHz notch. Audiological evaluation, including pure-tone and immittance audiometry, was performed for 156 college-going, young adults between May 2019 to December 2019. All participants had averaged pure-tone audiometric thresholds within normal limits, bilaterally. Annual individual exposure to personal listening devices (PLDs) was calculated using the Noise Exposure Questionnaire. The participants were then categorized into exposed (with and without audiometric 4 kHz notch) and nonexposed groups. Transient-evoked otoacoustic emission amplitude and its contralateral suppression were measured using linear and nonlinear click stimuli to study the effect of leisure noise exposure on MOCR. A significantly reduced overall contralateral suppression effect in participants exposed to PLD usage (P = 0.01) in both linear and nonlinear modes. On the contrary, significantly increased suppression was observed in linear mode for the 4 kHz frequency band in the PLD-exposed group without an audiometric notch (P = 0.009), possibly suggesting an early biomarker of NIHL. Measuring contralateral suppression of otoacoustic emissions may be an effective tool to detect early NIHL in leisure noise-exposed individuals.

Does glutaric aciduria type 1 affect hearing function?

This study aimed to evaluate audiological findings among patients with glutaric aciduria type 1 (GA-1). We used a large test battery for the audiological evaluation of 17 individuals with GA-1 (the study group) and 20 healthy individuals (the control group). Conventional audiometry (0.125-8kHz), distortion product otoacoustic emissions (DPOAEs) (1, 1.5, 2, 3, 4, 6, and 8kHz), contralateral suppression of otoacoustic emissions, and auditory brainstem response (ABR) ( 30, 50, 70 and 90 dB nHL) were measured for all participants (n = 37). Mild sensorineural hearing loss was found in 77.47% (n = 13) of the patients with GA-1, and normal hearing thresholds were seen in 23.53% (n = 4). There were three asymptomatic patients at the time of diagnosis [two developed mild mental motor retardation (MMR) and one developed severe MMR during the follow-up], one with a normal hearing threshold and two with mild hearing loss), and 14 symptomatic patients (three with normal hearing thresholds and 11 with mild hearing loss). Seven of the symptomatic patients diagnosed following an encephalopathic crisis required intensive care and showed significantly worse hearing thresholds than those without symptoms [20.86 ± 4.47 vs. 15.44 ± 3.96 decibel hearing level (dB HL), p = 0.039*], while five had mild-to-moderate hearing loss. Acute encephalopathic crisis had a negative effect on hearing function in the symptomatic patients. The emission and contralateral suppression amplitude values of the study group were significantly lower compared to the control group (p < 0.05). The I-V interpeak latency and absolute latencies of ABR waves I, III, and V of the study group were observed to be significantly prolonged and morphologically distorted compared to those of the control group (p < 0.05). Five patients had MMR, and three had moderate MMR; all eight had mild-to-moderate hearing loss. In addition, of the eight patients with mild MMR, four had mild hearing loss. In particular, the morphological findings of ABR waves were significantly worse in the patients with severe and moderate MMR (p < 0.05). There was a significant correlation between a macrocephaly history (12 patients) and hearing loss (p = 0.041*). Magnetic resonance imaging findings were evaluated in all the 17 patients with GA-1, and typical fronto-temporal atrophy and sylvian fissure enlargement were observed. Our findings support that GA-1 is associated with auditory impairment, primarily in symptomatic patients. Adequate audiological test battery evaluation is essential in this context, particularly for symptomatic patients with a history of encephalopathic crises.

The Relationship between Contralateral Suppression of Transient Evoked Otoacoustic Emission and Unmasking of Speech Evoked Auditory Brainstem Response

Introduction Several studies have shown that efferent pathways of the auditory system improve perception of speech-in-noise. But, the majority of investigations assessing the role of efferent pathways on speech perception have used contralateral suppression of otoacoustic emissions as a measure of efferent activity. By studying the effect of efferent activity on the speech-evoked auditory brainstem response (ABR), some more light could be shed on the effect of efferent pathways on the encoding of speech in the auditory pathway. Objectives To investigate the relationship between contralateral suppression of transient evoked otoacoustic emission (CSTEOAE) and unmasking of speech ABR. Methods A total of 23 young adults participated in the study. The CSTEOAE was measured using linear clicks at 60 dB peSPL and white noise at 60 dB sound pressure level (SPL). The speech ABR was recorded using the syllable /da/ at 80 dB SPL in quiet, ipsilateral noise, and binaural noise conditions. In the ipsilateral noise condition, white noise was presented to the test ear at 60 dB SPL, and, in the binaural noise condition, two separate white noises were presented to both ears. Results The F0 amplitude of speech ABR was higher in quiet condition; however, the mean amplitude of F0 was not significantly different across conditions. Correlation analysis showed a significant positive correlation between the CSTEOAE and the magnitude of unmasking of F0 amplitude of speech ABR. Conclusions The findings of the present study suggests that the efferent pathways are involved in speech-in-noise processing.

The Reliability of Contralateral Suppression of Otoacoustic Emissions Is Greater in Women than in Men.

The aim of this study was to compare the reliability of the medial olivocochlear reflex (MOCR) between men and women. The strength of the MOCR was measured in terms of the suppression of transiently evoked otoacoustic emissions (TEOAEs) by contralateral acoustic stimulation (CAS). The difference between TEOAEs with and without CAS (white noise) was calculated as raw decibel TEOAE suppression as well as normalized TEOAE suppression expressed in percent. In each subject, sets of measurements were performed twice. Reliability was evaluated by calculating the intraclass correlation coefficient, the standard error of measurement, and the minimum detectable change (MDC). The study included 40 normally hearing subjects (20 men; 20 women). The estimates of MOCR for both genders were similar. Nevertheless, the reliability of the MOCR was poorer in men, with an MDC around twice that of women. This can be only partially attributed to slightly lower signal-to-noise ratios (SNRs) in men, since we used strict procedures calling for high SNRs (around 20 dB on average). Furthermore, even when we compared subgroups with similar SNRs, there was still lower MOCR reliability in men.

Controlled (re)evaluation of the relationship between speech perception in noise and contralateral suppression of otoacoustic emissions

In people with normal hearing (NH), speech perception in noise (SPIN) improves when the speech signal is presented not gated with noise but after a delay. The medial olivocochlear reflex (MOCR) was thought to be involved in the neural dynamic range adaptation (NDRA) responsible for this adaptive SPIN; however, some of the recent studies do not support this hypothesis and suggest that adaptive SPIN involves the NDRA to noise-level statistics, irrespective of MOCR activation. A plausible reason for this discrepancy could be the variations and limitations of the experimental designs used in different studies. Using a relatively controlled and comprehensive study design, this study attempts to verify whether a delay between the delivery of speech and the noise improves the SPIN and whether MOCR mediates such effects. The SPIN was estimated by measuring speech reception thresholds (SRT) in noise under simultaneous-onset and delayed-onset (noise precedes speech onset by 300 ms) conditions. The SPIN in both ears was independently examined for ipsilateral, contralateral, and bilateral noise in women with normal hearing (N = 18; age range, 18–25 years). Contralateral suppression of transient-evoked otoacoustic emissions (CSOAEs) was used to estimate the MOCR based cochlear gain reduction. Under all test conditions, SPIN was improved in delayed-onset than in simultaneous-onset conditions, and the mean improvement in the SRT ranged from 0.7±1.7 to 1.8±1.8 dB. No significant correlation was obtained between CSOAEs and the mean temporal improvement in SRT, suggesting that MOCR may not be a predominant mechanism for the temporal improvement in SPIN.

ELEKTROFIZJOLOGICZNA I ELEKTROAKUSTYCZNA OCENA SŁUCHU U OSÓB Z NEUROFIBROMATOZĄ TYPU 1

BackgroundType 1 neurofibromatosis occurs in 1 in every 3,000 individuals, representing 90% of cases of neurofibromatosis. Hearing impairments are not commonly described as an alteration resulting from the pathology; however, sensorineural hearing losses with retrocochlear characteristics may occur as a result of the presence of acoustic neurinomas.ObjectivesTo assess the electrophysiological and electroacoustic hearing characteristics of individuals with neurofibromatosis type 1.Material and methodsWe assessed 15 patients, 10 females and 5 males, aged between 9 and 31 years, using the following procedures: pure tone audiometry, transient evoked otoacoustic emissions, contralateral suppression of otoacoustic emissions, and brainstem auditory evoked potentials.ResultsAll individuals presented auditory thresholds within normal limits. The mean amplitude of the general responses of otoacoustic emissions in the right and left ears were 11.8 and 12.8 dB, respectively; the suppression effect of otoacoustic emissions was present in 73.3% for the right ear and 66.7% for the left. For brainstem auditory evoked potentials, we obtained mean wave latencies for the right and left ears respectively of wave I: 1.83 and 1.80 ms, III: 4.08 and 4.15 ms, and V: 5.96 and 6.09 ms.ConclusionsIndividuals with neurofibromatosis type 1 present auditory thresholds within normal limits, present transient otoacoustic emissions, the nonsystematic presence of the suppression effect of otoacoustic emissions and prolonged latencies in brainstem auditory evoked potentials.

Reliability of contralateral suppression of otoacoustic emissions in children

Objective The purpose of the study was to determine the reliability in children of the medial olivocochlear reflex when measured as decibels of suppression of transiently evoked otoacoustic emissions (TEOAEs) by contralateral acoustic stimulation (CAS). Design TEOAEs with and without CAS (white noise) were measured. In each subject, measurements were performed twice. Of particular interest was the suppression of TEOAEs by CAS and its reliability. Reliability was evaluated by calculating the standard error of measurement (SEM) and minimum detectable change (MDC). Study sample Fifty-one normally hearing girls aged 3–6 years. Results The average global TEOAE suppression was around 0.6 dB. The highest reliability was for global values, with SEM of 0.2 dB and MDC of ±0.55 dB for the standard 2.5–20 ms recording window and slightly higher values for an 8–18 ms window. The worst reliability in the studied group was for the 1 kHz half-octave frequency band. Additionally, ears without spontaneous otoacoustic emissions had higher suppression levels than those with, but they also had lower signal-to-noise ratios, which may limit their clinical utility. Conclusions The current study shows that, under the studied paradigm, TEOAE suppression does not have satisfactory reliability since MDC was similar to the level of suppression.

Contralateral suppression of otoacoustic emissions in pre-school children

BackgroundContralateral suppression of otoacoustic emissions (OAEs) may serve as an index of the medial olivocochlear (MOC) reflex. To date, this index has been studied in various populations but never in pre-school children. The purpose of this study was to fill this gap and describe how the MOC reflex affects the properties of transiently evoked OAEs (TEOAEs) in this age group. In addition, the influence of the presence of spontaneous OAEs (SOAEs) in the studied ear on the suppression of TEOAEs was also investigated. MethodsTEOAEs with and without contralateral acoustic stimulation (CAS) by white noise were measured in 126 normally hearing pre-school children aged 3–6 years. The values of response levels, suppression by CAS, and signal-to-noise ratios (SNRs) of TEOAEs were investigated for the whole signal (global) and for half-octave frequency bands from 1 to 4 kHz. Only ears with SNR >6 dB were used in the analyses. SOAEs were acquired using the so-called synchronized SOAEs (SSOAEs) technique. ResultsEars with SSOAEs had higher response levels and SNRs than ears without SSOAEs, and suppression was lower (0.58 dB compared to 0.85 dB). Only 22% of all studied ears had an SNR >20 dB, a level recommended in some studies for measuring suppression. There were no significant effects of age or gender on TEOAE suppression. ConclusionsSuppression levels for pre-school children did not differ appreciably from those of adults measured under similar conditions in other studies. Taken together with no effect of age in the data studied here, it seems that there is no effect of age on TEOAE suppression. However, we did find that the presence of SSOAEs had an effect on TEOAE suppression, a finding which has not been reported in earlier studies on different populations. We suggest that the presence of SSOAEs might be a crucial factor related to MOC function.

Contralateral suppression of otoacoustic emissions in a clinical sample of children with auditory processing disorder

Objective: The suppression of evoked otoacoustic emissions (EOAE) may serve as a clinical tool to evaluate the medial olivocochlear (MOC) reflex, which is thought to aid speech discrimination (particularly in noise) by selectively inhibiting cochlear amplification. The present study aimed to determine if contralateral transient evoked otoacoustic emission (TEOAE) suppression was present in a clinical sample of children with listening difficulties with and without auditory processing disorder (APD).Design: A three-group, repeated measure design was used.Study sample: Forty three children aged 8–14 years underwent an auditory processing assessment and were divided into three groups: children with reported listening difficulties with APD, children with reported listening difficulties without APD, and children with normal hearing. APD was defined as per British Society of Audiology.Results: TEOAE suppression was present in all three participant groups. No significant group, age or ear effects were observed for TEOAE suppression in dB or as a normalised index.Conclusion: Contralateral TEOAE suppression method could not be used as a clinical tool to identify APD in this study’s participating children and did not support the hypothesised link between reduced MOC function and general listening difficulties in background noise in children with or without APD.

The correlation between hair and eye colour and contralateral suppression of otoacoustic emissions.

Genetics and environmental factors frequently influence individual’s susceptibility to hearing loss. It is postulated that melanin in the inner ear is related to individual’s susceptibility to noise induced hearing loss (NIHL). General pigmentation in turn, suspected to be related to the amount of pigmentation in the inner ear. The amount of melanin in the inner ear is said to modulate the endocochlear potential and provide an otoprotective effect.Aim:The study aimed to determine the relationship between the contralateral suppression of otoacoustic emissions (CSOAE) in individuals with brown eyes and hair, and blue eyes and blond hair, and temporary emission shift (TES) after short-term noise exposure.Setting and Design:The research was conducted using a quantitative research design with a quasi-experimental repeated within the subject design to compare the CSOAE in subjects with different hair and eyes colour with TES after short-term noise exposure. Quantitative research was used to determine the relationship between the measurable variables to predict occurrence.Material and Method:The hearing sensitivity of young adults was determined by using pure tone audiometry followed by CSOAE’s and distortion product otoacoustic emissions (DPOAE) before listening to music for one hour individually. Pure tone audiometry and DPOAE’s were repeated after music exposure to determine the amount of TES and temporary threshold shift (TTS).Statistical Analysis used:One-way ANOVA was used during the analysis of the data obtained during this research study, in addition to, two-tailed Wilcoxon Sign Rank test and Friedman’s test. In all analyses, a 95% level of significance (P<0.05) was used.Results:No statistically significant difference between efferent suppression was measured by CSOAE’s between the participant groups. A larger TTS at 4000 Hz and TES at 2000 Hz was evident in the blue eyes and blond hair group after short-term music exposure. Conclusion: CSOAE’s were unable to predict which group of individuals were more susceptible to NIHL after short-term noise exposure.

Objective assessment of subjective tinnitus through contralateral suppression of otoacoustic emissions by white noise: effects of frequency, gender, tinnitus bilaterality and age.

Accumulating evidence seems to support an association between tinnitus and medial olivocochlear bundle (MOCB) dysfunction. Most studies use patient/control comparisons to support this correlation. The aim of this study was to investigate the hypothesis in a substantially different way and evaluate the roles of gender, age, frequency and tinnitus bilaterality as possible confounding factors. The population consisted of 78 normal hearing patients with chronic tinnitus, 28 normal hearing controls, 19 presbycousic tinnitus patients and 13 presbycousic controls (n = 276 ears). Mean suppression amplitudes of transient evoked otoacoustic emissions (TEOAEs) and distortion product OAEs (DPOAEs) by contralateral white noise (50 dB SPL) were computed. Mean suppression values < 1 dB SPL or < 2 dB SPL were validated as positive test results. Overall suppression (OS) values < 1 dB SPL were qualified as a diagnostic test of moderate positive predictive value for both DPOAEs and TEOAEs, while OS values < 2 dB SPL were found to be of large negative predictive value for DPOAEs and moderate for TEOAEs. Mean suppression values (for all frequencies, OS) are of higher diagnostic value than suppression values corresponding to either lower (1-2 kHz) or higher frequencies (2.8-4 kHz for TEOAEs and 2.8-6 kHz for DPOAEs). After excluding patients with unilateral tinnitus from the analysis, correlations were found to be stronger. Useful correlations were also attributed for all age groups < 61 years. In females, OAE suppression seems to have a stronger positive predictive value, while in males it seems to have a stronger negative predictive value. OAE-based assays of MOCB function as an objective diagnostic tool for subjective tinnitus might deserve further investigation. Tinnitus uni- or bi-laterality is a confounding factor, which probably confirms the observation that defective function of the MOCB usually applies to the contralateral ear as well. Gender is an additional confounding factor, while correlations can be verified for all age groups < 61 years old.

Functional Interplay Between the Putative Measures of Rostral and Caudal Efferent Regulation of Speech Perception in Noise.

Efferent modulation has been demonstrated to be very important for speech perception, especially in the presence of noise. We examined the functional relationship between two efferent systems: the rostral and caudal efferent pathways and their individual influences on speech perception in noise. Earlier studies have shown that these two efferent mechanisms were correlated with speech perception in noise. However, previously, these mechanisms were studied in isolation, and their functional relationship with each other was not investigated. We used a correlational design to study the relationship if any, between these two mechanisms in young and old normal hearing individuals. We recorded context-dependent brainstem encoding as an index of rostral efferent function and contralateral suppression of otoacoustic emissions as an index of caudal efferent function in groups with good and poor speech perception in noise. These efferent mechanisms were analysed for their relationship with each other and with speech perception in noise. We found that the two efferent mechanisms did not show any functional relationship. Interestingly, both the efferent mechanisms correlated with speech perception in noise and they even emerged as significant predictors. Based on the data, we posit that the two efferent mechanisms function relatively independently but with a common goal of fine-tuning the afferent input and refining auditory perception in degraded listening conditions.

Effect of practicing yoga on functioning of efferent auditory system

Introduction: The present study attempted to determine the effect of practicing Yoga on the functioning of the efferent auditory system using contralateral suppression of otoacoustic emissions (OAE). Method: The efferent suppression of transient evoked OAE (TEOAE), and distortion product OAE (DPOAE) was recorded from 40 participants (20 who practice Yoga regularly and 20 who do not practice yoga regularly). Results: The results of this study showed that there was an increase in the amount of suppression of both TEOAE and DPOAE in individuals who practice Yoga. The result suggests that Yoga enhances the sensory perception and improves auditory attention. The constant practice of Yoga could have led to the plasticity of the efferent auditory system. Conclusions: Thus, the practice of Yoga may be used to strengthen the efferent auditory system. However, further studies on a larger group of the population are essential for better clinical applicability of the results.

Assessment of rock musician's efferent system functioning using contralateral suppression of otoacoustic emissions.

ObjectiveContralateral suppression of oto acoustic emission (OAE) is referred as activation of efferent system. Previous literature mentioned about the importance of contralateral suppression of OAEs as a tool to assess efferent system in different groups of population. There is dearth of literature to explore the efferent system function in experienced musicians exposed to rock music using TEOAEs and DPOAEs.MethodsTwo groups of participant (14 rock musicians and 14 non-musicians) in the age range of 18–25 years were involved in the study. Contralateral suppression of TEOAEs and DPOAEs were measured using ILO (Version 6) in both groups.ResultsDescriptive statistics showed higher suppression of TEOAEs and DPOAEs in rock-musicians at most of the frequencies in comparison to non-musicians. For DPOAE measures, Mann Whitney U test results revealed significantly greater DPOAE suppression only at 1 kHz and 3 kHz in rock-musicians compared to non-musicians. For within group comparison, Kruskal Wallis test results revealed there were significant difference observed across most of the frequencies i.e. at 1 kHz, 3 kHz and 6 kHz. For TEOAE measures, Mann Whitney U test results revealed that only at 2 kHz, TEOAE suppression in rock-musician was significantly greater compared to non-musicians. Similarly, Kuskal Wallis test results revealed that within group there were no significant differences observed for most of the frequencies except 2 kHz.ConclusionsBased on the above finding, present study concludes that rock musicians are having better efferent system compared to non-musicians. No suppression effect at few frequencies probably indicates more vulnerability at those frequencies. Contralateral suppression of DPOAE shows more significant finding in comparison to contralateral suppression of TEOAEs in present study.

Objective assessment of subjective tinnitus through contralateral suppression of otoacoustic emissions by white noise; suggested cut-off points

Objective: Normative otoacoustic emission (OAE) suppression values are currently lacking and the role of cochlear efferent innervation in tinnitus is controversial. The aim of this study was to investigate the association between tinnitus and medial olivocochlear bundle (MOCB) malfunction. Potential suppression amplitude cut-off criteria that could differentiate participants with tinnitus from those without were sought. Design: Mean suppression amplitudes of transient evoked OAEs and distortion product OAEs by contralateral white noise (50 dBSL) were recorded. Six mean suppression amplitudes criteria were validated as possible cut-off points. Study sample: The population consisted of normal hearing (n = 78) or presbycusic adults (n = 19) with tinnitus or without (n = 28 and 13, respectively) chronic tinnitus (in total, n = 138 78 females/60males, aged 49 ± 14 years). Results: Participants with mean suppression values lower than 0.5–1 dBSPL seem to present a high probability to report tinnitus (specificity 88–97%). On the other hand, participants with mean suppression values larger than 2–2.5dBSPL seem to present a high probability of the absence of tinnitus (sensitivity 87–99%). Correlations were stronger among participants with bilateral presence or absence of tinnitus. Conclusions: This study seem to confirm an association between tinnitus and low suppression amplitudes (<1 dBSPL), which might evolve into an objective examination tool, supplementary to conventional audiological testing.

Concurrent measures of contralateral suppression of transient-evoked otoacoustic emissions and of auditory steady-state responses.

Contralateral suppression of otoacoustic emissions (OAEs) is frequently used to assess the medial olivocochlear (MOC) efferent system, and may have clinical utility. However, OAEs are weak or absent in hearing-impaired ears, so little is known about MOC function in the presence of hearing loss. A potential alternative measure is contralateral suppression of the auditory steady-state response (ASSR) because ASSRs are measurable in many hearing-impaired ears. This study compared contralateral suppression of both transient-evoked otoacoustic emissions (TEOAEs) and ASSRs in a group of ten primarily older adults with either normal hearing or mild sensorineural hearing loss. Responses were elicited using 75-dB peak sound pressure level clicks. The MOC was activated using contralateral broadband noise at 60 dB sound pressure level. Measurements were made concurrently to ensure a consistent attentional state between the two measures. The magnitude of contralateral suppression of ASSRs was significantly larger than contralateral suppression of TEOAEs. Both measures usually exhibited high test-retest reliability within a session. However, there was no significant correlation between the magnitude of contralateral suppression of TEOAEs and of ASSRs. Further work is needed to understand the role of the MOC in contralateral suppression of ASSRs.

Effect of musical training on masking paradigm

Background: Musicians outperform nonmusicians on brainstem and cortical level processing. However, there are limited literature comparing musicians and nonmusicians on the overall release of masking abilities and correlation across otoacoustic emissions (OAEs), masking level difference (MLD) and quick speech-in-noise (Quick-SIN). Aim: To investigate the physiological differences between musicians and nonmusicians by evaluating the effect of musical training on contralateral suppression (CAS) of OAE, MLD, and Quick-SIN. Materials and Methods: Distortion product OAEs (DPOAEs) recording with and without noise, MLD test using continuous (CMLD) and pulsating pure tones (PMLD) and Quick-SIN in Kannada were carried out on 15 musicians and 15 nonmusicians. Results: Musicians outperformed nonmusicians on Quick-SIN and CAS of OAEs. However, no significant difference was observed between two groups on CMLD and PMLD. There was a significant difference observed in CMLD, PMLD as well as suppression amplitude across frequencies tested in both groups. A significant difference between PMLD and CMLD was observed only for musicians at 2 kHz. In both groups, there was a significant level of correlation for CAS of DPOAE and Quick-SIN with CMLD and with PMLD between the parameters tested. Conclusion: The results of our finding suggest that CAS of DPOAE and Quick-SIN are sensitive tools to quantify the effect of musical training, compared to MLD. Musical training helps to strengthen afferent and efferent pathways, and hence it aids in speech perception abilities in noise. Hence, for the intervention of individuals with difficulties in speech perception in noise, musical training can be a choice to be considered. As well for appropriate diagnosis and interpretation, one needs to consider the musical experience of individual tested.

Efferent Auditory System Functioning and Speech Perception in Noise in Individuals with Type II Diabetes Mellitus

Objective: There could be efferent system damage in individuals with type II diabetes mellitus. The study attempts to determine the efferent auditory system functioning through contralateral suppression of otoacoustic emissions (OAE) and speech perception in noise (SPIN) in individuals with type II diabetes mellitus (DM). Method: The study was carried out on twenty five participants (50 ears) with type II DM patients who were diagnosed by an endocrinologist and twenty five healthy age matched controls (50 ears) were included in the study. Contralateral suppression of OAE and SPIN were administered on both the groups and they were compared and correlated. Results: The results of the study show that individuals with type II DM had statistically significant lower contralateral suppression values and had poorer speech perception in noise. In addition, there were significant correlations between SPIN scores and the amount of suppression in individuals with type II DM. Conclusion: The individuals with DM showed difficulty understanding speech in presence of noise and that can be attributed to efferent system damage. Thus, contralateral suppression can be a useful marker in early diagnosis of cochleopathy and auditory efferent disorder. The present study can provide important evidence for early diagnosis and early treatment of diabetic complications.

Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis.

Atypical medial olivocochlear (MOC) feedback from brain stem to cochlea has been proposed to play a role in tinnitus, but even well-constructed tests of this idea have yielded inconsistent results. In the present study, it was hypothesized that low sound tolerance (mild to moderate hyperacusis), which can accompany tinnitus or occur on its own, might contribute to the inconsistency. Sound-level tolerance (SLT) was assessed in subjects (all men) with clinically normal or near-normal thresholds to form threshold-, age-, and sex-matched groups: 1) no tinnitus/high SLT, 2) no tinnitus/low SLT, 3) tinnitus/high SLT, and 4) tinnitus/low SLT. MOC function was measured from the ear canal as the change in magnitude of distortion-product otoacoustic emissions (DPOAE) elicited by broadband noise presented to the contralateral ear. The noise reduced DPOAE magnitude in all groups ("contralateral suppression"), but significantly more reduction occurred in groups with tinnitus and/or low SLT, indicating hyperresponsiveness of the MOC system compared with the group with no tinnitus/high SLT. The results suggest hyperresponsiveness of the interneurons of the MOC system residing in the cochlear nucleus and/or MOC neurons themselves. The present data, combined with previous human and animal data, indicate that neural pathways involving every major division of the cochlear nucleus manifest hyperactivity and/or hyperresponsiveness in tinnitus and/or low SLT. The overactivation may develop in each pathway separately. However, a more parsimonious hypothesis is that top-down neuromodulation is the driving force behind ubiquitous overactivation of the auditory brain stem and may correspond to attentional spotlighting on the auditory domain in tinnitus and hyperacusis.