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OBJECTIVE: The objective of this study was to determine the gender-specific normative values of masking level difference (MLD) in healthy young adults for two different measurement conditions. METHODS: One hundred young adults between the ages of 19 and 25 were included. Tympanometry, pure tone audiometry, and MLD were performed. In the first MLD measurement condition, the threshold level where the signal was out of phase and the noise was in phase (SπNo) was subtracted from the threshold level where the signal and noise were in phase (SoNo). In the second MLD measurement condition, the threshold level where the signal was in phase and the noise was out of phase (SoNπ) was subtracted from the threshold level where the signal and noise were in phase (SoNo). The mean test scores were obtained in decibels. Comparisons were made in terms of gender and conditions. RESULTS: The mean MLD for SoNo-SπNo condition was 10.3 ± 1.99 dB. For SoNo-SoNπ condition, the mean MLD was 6.72 ± 2.38 dB. A significant difference was determined between the MLD under two different measurement conditions (p <.05). There was no significant difference in terms of gender (p >.05). CONCLUSION: Mean normative values of MLD test scores in gender-specific healthy young adults for two different measurement conditions are presented.

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Congenital or early-onset unilateral hearing loss (UHL) can disrupt the normal development of the auditory system. In extreme cases of UHL (i.e., single sided deafness), consistent cochlear implant use during sensitive periods resulted in cortical reorganization that partially reversed the detrimental effects of unilateral sensory deprivation. There is a gap in knowledge, however, regarding cortical plasticity i.e. the brain's capacity to adapt, reorganize, and develop binaural pathways in milder degrees of UHL rehabilitated by a hearing aid (HA). The current study was set to investigate early-stage cortical processing and electrophysiological manifestations of binaural processing by means of cortical auditory evoked potentials (CAEPs) to speech sounds, in children with moderate to severe-to-profound UHL using a HA. Fourteen children with UHL (CHwUHL), 6-14 years old consistently using a HA for 3.5 (±2.3) years participated in the study. CAEPs were elicited to the speech sounds /m/, /g/, and /t/ in three listening conditions: monaural [Normal hearing (NH), HA], and bilateral [BI (NH + HA)]. Results indicated age-appropriate CAEP morphology in the NH and BI listening conditions in all children. In the HA listening condition: (1) CAEPs showed similar morphology to that found in the NH listening condition, however, the mature morphology observed in older children in the NH listening condition was not evident; (2) P1 was elicited in all but two children with severe-to-profound hearing loss, to at least one speech stimuli, indicating effective audibility; (3) A significant mismatch in timing and synchrony between the NH and HA ear was found; (4) P1 was sensitive to the acoustic features of the eliciting stimulus and to the amplification characteristics of the HA. Finally, a cortical binaural interaction component (BIC) was derived in most children. In conclusion, the current study provides first-time evidence for cortical plasticity and partial reversal of the detrimental effects of moderate to severe-to-profound UHL rehabilitated by a HA. The derivation of a cortical biomarker of binaural processing implies that functional binaural pathways can develop when sufficient auditory input is provided to the affected ear. CAEPs may thus serve as a clinical tool for assessing, monitoring, and managing CHwUHL using a HA.

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The binaural interaction component (BIC) of the auditory evoked potential is the difference between the waveforms of the binaural response and the sum of left and right monaural responses. This investigation examined BICs of the auditory brainstem (ABR) and middle-latency (MLR) responses concerning three objectives: 1) the level of the auditory system at which low-frequency dominance in BIC amplitudes begins when the binaural temporal fine structure is more influential with lower- than higher-frequency content; 2) how BICs vary as a function of frequency and lateralization predictability, as could relate to the improved lateralization of high-frequency sounds; 3) how attention affects BICs. Sixteen right-handed participants were presented with either low-passed (< 1000 Hz) or high-passed (> 2000 Hz) clicks at 30 dB SL with a 38 dB (A) masking noise, at a stimulus onset asynchrony of 180 ms. Further, this repeated-measures design manipulated stimulus presentation (binaural, left monaural, right monaural), lateralization predictability (unpredictable, predictable), and attended modality (either auditory or visual). For the objectives, respectively, the results were: 1) whereas low-frequency dominance in BIC amplitudes began during, and continued after, the Na-BIC, binaural (center) as well as summed monaural (left and right) amplitudes revealed low-frequency dominance only after the Na wave; 2) with a predictable position that was fixed, no BIC exhibited equivalent amplitudes between low- and high-passed clicks; 3) whether clicks were low- or high-passed, selective attention affected the ABR-BIC yet not MLR-BICs. These findings indicate that low-frequency dominance in lateralization begins at the Na latency, being independent of the efferent cortico-collicular pathway's influence.

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Sound localization testing is key for comprehensive hearing evaluations, particularly in cases of suspected auditory processing disorders. However, sound localization is not commonly assessed in clinical practice, likely due to the complexity and size of conventional measurement systems, which require semicircular loudspeaker arrays in large and acoustically treated rooms. To address this issue, we investigated the feasibility of testing sound localization in virtual reality (VR). Previous research has shown that virtualization can lead to an increase in localization blur. To measure these effects, we conducted a study with a group of normal-hearing adults, comparing sound localization performance in different augmented reality and VR scenarios. We started with a conventional loudspeaker-based measurement setup and gradually moved to a virtual audiovisual environment, testing sound localization in each scenario using a within-participant design. The loudspeaker-based experiment yielded results comparable to those reported in the literature, and the results of the virtual localization test provided new insights into localization performance in state-of-the-art VR environments. By comparing localization performance between the loudspeaker-based and virtual conditions, we were able to estimate the increase in localization blur induced by virtualization relative to a conventional test setup. Notably, our study provides the first proxy normative cutoff values for sound localization testing in VR. As an outlook, we discuss the potential of a VR-based sound localization test as a suitable, accessible, and portable alternative to conventional setups and how it could serve as a time- and resource-saving prescreening tool to avoid unnecessarily extensive and complex laboratory testing.

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Objective assessment of spatial and binaural hearing deficits remains a major clinical challenge. The binaural interaction component (BIC) of the auditory brainstem response (ABR) holds promise as a non-invasive biomarker for diagnosing such deficits. However, while comparative studies have reported robust BIC in animal models, BIC in humans can sometimes be unreliably evoked even in subjects with normal hearing. Here we explore the hypothesis that the standard methodology for collecting monaural ABRs may not be ideal for electrophysiological assessment of binaural hearing. This study aims to improve ABR BIC measurements by determining more optimal stimuli to evoke it. Building on previous methodology demonstrated to enhance peak amplitude of monaural ABRs, we constructed a series of level-dependent chirp stimuli based on empirically derived latencies of monaural-evoked ABR waves I, IV and the binaural-evoked BIC DN1, the most prominent BIC peak, in a cohort of ten chinchillas. We hypothesized that chirps designed based on BIC DN1 latency would specifically enhance across-frequency temporal synchrony in the afferent inputs leading to the binaural circuits that produce the BIC and would thus produce a larger DN1 than either traditional clicks or chirps designed to optimize monaural ABRs. Compared to clicks, we found that level-specific chirp stimuli evoked significantly greater BIC DN1 amplitudes, and that this effect persisted across all stimulation levels tested. However, we found no significant differences between BICs resulting from chirps created using binaural-evoked BIC DN1 latencies and those using monaural-evoked ABR waves I or IV. These data indicate that existing level-specific, monaural-based chirp stimuli may improve BIC detectability and reduce variability in human BIC measurements.

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Background: Musical perception requires a host of skills. Instrumental musicians place greater emphasis on motor coordination, whereas vocal musicians rehearse vocal sounds. The study explored the differential advantages of musical background on binaural integration and interaction in musicians (instrumentalists, vocalists) and compared them with age-matched non-musicians. Methods: Eight six participants aged 20-40 y with normal hearing sensitivity were subjected to binaural tests using a standard group comparison research design. The participants were segregated into three groups - Group 1 included instrumentalists (n = 26, mean age: 17.73 ± 2.83 y), while Group 2 and Group 3 consisted of vocalists (n = 30, mean age: 19.30 ± 2.47 y) and non-musicians (n = 30, mean age: 18.20 ± 3.02 y) respectively. The binaural processes namely integration (Dichotic syllable test, DST; and virtual acoustic space identification - VASI) and interaction (Interaural difference thresholds for time and level: ITD & ILD), were administered on all the participants. Results: Statistical analyses showed the main effect of musicianship. Bonferroni pair-wise test revealed that the musicians (instrumentalists and vocalists) outperformed (p < 0.05) non-musicians in all the tests. The differential advantage of the musical background was seen on the binaural integration test with instrumentalists performing better in the VASI test compared to vocalists, and vice-versa for DST. No difference was observed in interaction tasks (ITD & ILD) between vocalists and instrumentalists (p > 0.05). Conclusion: Musical background-induced differential advantages can be reasonably noted in the binaural skills of instrumentalists and vocalists (compared to non-musicians).

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The binaural masking level difference (BMLD) is a psychoacoustic method to determine binaural interaction and central auditory processes. The BMLD is the difference in hearing thresholds in homophasic and antiphasic conditions. The duration, phase and frequency of the stimuli can affect the BMLD. The main aim of the study is to evaluate the BMLD for stimuli of different durations and frequencies which could also be used in future electrophysiological studies. To this end we developed a GUI to present different frequency signals of variable duration and determine the BMLD. Three different durations and five different frequencies are explored. The results of the study confirm that the hearing threshold for the antiphasic condition is lower than the hearing threshold for the homophasic condition and that differences are significant for signals of 18ms and 48ms duration. Future objective binaural processing studies will be based on 18ms and 48ms stimuli with the same frequencies as used in the current study.

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The binaural interaction component (BIC) of the auditory brainstem response (ABR) is the difference obtained after subtracting the sum of right and left ear ABRs from binaurally evoked ABRs. The BIC has attracted interest as a biomarker of binaural processing abilities. Best binaural processing is presumed to require spectrally-matched inputs at the two ears, but peripheral pathology and/or impacts of hearing devices can lead to mismatched inputs. Such mismatching can degrade behavioral sensitivity to interaural time difference (ITD) cues, but might be detected using the BIC. Here, we examine the effect of interaural frequency mismatch (IFM) on BIC and behavioral ITD sensitivity in audiometrically normal adult human subjects (both sexes). Binaural and monaural ABRs were recorded and BICs computed from subjects in response to narrowband tones. Left ear stimuli were fixed at 4000 Hz while right ear stimuli varied over a ∼2-octave range (re: 4000 Hz). Separately, subjects performed psychophysical lateralization tasks using the same stimuli to determine ITD discrimination thresholds jointly as a function of IFM and sound level. Results demonstrated significant effects of IFM on BIC amplitudes, with lower amplitudes in mismatched conditions than frequency-matched. Behavioral ITD discrimination thresholds were elevated at mismatched frequencies and lower sound levels, but also more sharply modulated by IFM at lower sound levels. Combinations of ITD, IFM and overall sound level that resulted in fused and lateralized percepts were bound by the empirically-measured BIC, and also by model predictions simulated using an established computational model of the brainstem circuit thought to generate the BIC.

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The Masking Level Difference (MLD) test is one of the main instruments for investigating binaural interaction. Studies with children aged 7-12 years still disagree about the influence of age on test performance and present discordant reference values. This study aimed to verify the effect of age on the performance of children aged 7-12 years in the MLD test and to establish reference values and cutoff criteria for this age group. Fifty-nine children with normal hearing were organized in three groups according to their age: 7-8 (n = 20), 9-10 (n = 20), and 11-12 (n = 19) years. The participants completed the MLD test by Auditec®. The Kruskal-Wallis statistical test was used to compare groups. Reference values were obtained by calculating mean, standard deviation, median, mode, and percentiles, while the cutoff criterion was obtained by subtracting two standard deviations from the mean. No statistically significant differences were observed between the groups regarding the MLD test measures. The mean MLD was 10.51 ± 1.84 dB and the cutoff point was set at 7 dB. Thus, reference values for the MLD test were established for children aged 7-12 years, who presented no effect of age on test performance.

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OBJECTIVE: To analyze binaural integration, we used a new stimulation mode of the electrically evoked auditory brainstem response (EABR), to reflect bilaterally implanted cochlear function. DESIGN: EABR was tested using the following procedure: First, both ears were evaluated separately, with the contralateral speech processor closed (C), followed by another measurement with both processors open (O). Subsequently, the eV latencies and amplitudes were assessed. The Speech, Spatial, and Qualities of Hearing Scale (SSQ), Categories of auditory performance (CAP) and speech intelligibility rating (SIR) scores were used to assess binaural hearing ability subjectively. STUDY SAMPLE: Fifteen subjects with bilateral CI from 1997 to 2018 were recruited, each diagnosed with severe to profound hearing loss. RESULTS: All SSQ scores, except for one, were greater than six (the exception scored 1.3/0.8/1.0). All CAP/SIR scores except one were greater than 6/4 (the exception scored 0/1). All patients exhibited good quality EABR measurements. The open contralateral processor significantly reduced the eV latency while enhancing the eV amplitude compared to monaural stimulation. The objective EABR results were consistent with subjective speech perception and auditory ability assessed using the SSQ scale. CONCLUSION: The EABR accurately reflected auditory pathway maturation and development after CI; thus, reflecting accordance with subjective speech and hearing performances. Furthermore, bilateral CI facilitates binaural integration and auditory brainstem plasticity.

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Differences in the timing and intensity of sounds arriving at the two ears provide fundamental binaural cues that help us localize and segregate sounds in the environment. Neural encoding of these cues is commonly represented asymmetrically in the cortex with stronger activation in the hemisphere contralateral to the perceived spatial location. Although advancing age is known to degrade the perception of binaural cues, less is known about how the neural representation of such cues is impacted by age. Here, we use electroencephalography (EEG) to investigate age-related changes in the hemispheric distribution of interaural time difference (ITD) encoding based on cortical auditory evoked potentials (CAEPs) and derived binaural interaction component (BIC) measures in ten younger and ten older normal-hearing adults. Sensor-level analyses of the CAEP and BIC showed age-related differences in global field power, where older listeners had significantly larger responses than younger for both binaural metrics. Source-level analyses showed hemispheric differences in auditory cortex activity for left and right lateralized stimuli in younger adults, consistent with a contralateral activation model for processing ITDs. Older adults, however, showed reduced hemispheric asymmetry across ITDs, despite having overall larger responses than younger adults. Further, when averaged across ITD condition to evaluate changes in cortical asymmetry over time, there was a significant shift in laterality corresponding to the peak components (P1, N1, P2) in the source waveform that also was affected by age. These novel results demonstrate across-hemisphere cortical dynamics during binaural temporal processing that are altered with advancing age.

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Binaural hearing is critically important for the perception of sound spatial locations. The primary auditory cortex (AI) has been demonstrated to be necessary for sound localization. However, after hearing onset, how the processing of binaural cues by AI neurons develops, and how the binaural processing of AI neurons is affected by reversible unilateral conductive hearing loss (RUCHL), are not fully elucidated. Here, we determined the binaural processing of AI neurons in four groups of rats: postnatal day (P) 14-18 rats, P19-30 rats, P57-70 adult rats, and RUCHL rats (P57-70) with RUCHL during P14-30. We recorded the responses of AI neurons to both monaural and binaural stimuli with variations in interaural level differences (ILDs) and average binaural levels. We found that the monaural response types, the binaural interaction types, and the distributions of the best ILDs of AI neurons in P14-18 rats are already adult-like. However, after hearing onset, there exist developmental refinements in the binaural processing of AI neurons, which are exhibited by the increase in the degree of binaural interaction, and the increase in the sensitivity and selectivity to ILDs. RUCHL during early hearing development affects monaural response types, decreases the degree of binaural interactions, and decreases both the selectivity and sensitivity to ILDs of AI neurons in adulthood. These new evidences help us to understand the refinements and plasticity in the binaural processing of AI neurons during hearing development, and might enhance our understanding in the neuronal mechanism of developmental changes in auditory spatial perception.

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The binaural interaction component (BIC) is a sound-evoked electrophysiological signature of binaural processing in the auditory brainstem that has received attention as a potential biomarker for spatial hearing deficits. Yet the number of trials necessary to evoke the BIC, or its measurability, seems to vary across species: while it is easily measured in small rodents, it has proven to be highly variable and less reliably measured in humans. This has hindered its potential use as a diagnostic tool. Further measurements of the BIC across a wide range of species could help us better understand its origin and the possible reasons for the variation in its measurability. Statistical analysis on the function relating BIC DN1 amplitude and the interaural time difference has been performed in only a few small rodent species, thus it remains to be shown how the results apply to more taxonomically diverse mammals, and those with larger heads. To fill this gap, we measured BICs in rhesus macaque. We show the overall behavior of the BIC is the same as in smaller rodents, suggesting that the brainstem circuit responsible for the BIC is conserved across a wider range of mammals. We suggest that differences in measurability are likely because of differences in head size.

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Subtracting the sum of left and right monaural auditory brainstem responses (ABRs) from the corresponding binaural ABR isolates the binaural interaction component (ABR-BIC). In a previous investigation (Ikeda, 2015), during auditory yet not visual tasks, tone-pips elicited a significant difference in amplitude between summed monaural and binaural ABRs. With click stimulation, this amplitude difference was task-independent. This self-critical reanalysis's purpose was to establish that a difference waveform (i.e., ABR-BIC DN1) reflected an auditory selective attention effect that was isolable from stimulus factors. Regardless of whether stimuli were tone-pips or clicks, effect sizes of the DN1 peak amplitudes relative to zero improved during auditory tasks over visual tasks. Auditory selective attention effects on the monaural and binaural ABR wave-V amplitudes were tone-pip specific. Those wave-V effects thus could not explain the stimulus-universal effect of auditory selective attention on DN1 detectability, which was thus entirely binaural. In a manner isolated from auditory selective attention, multiple mediation analyses indicated that the higher right monaural wave-V amplitudes mediated individual differences in how clicks, relative to tone-pips, augmented DN1 amplitudes. There are implications of these findings for advancing ABR-BIC measurement.

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The inferior colliculus (IC) receives inputs from the ascending auditory pathway and helps localize the sound source by shaping neurons' responses. However, the contributions of excitatory or inhibitory synaptic inputs evoked by paired binaural stimuli with different inter-stimulus intervals to auditory responses of IC neurons remain unclear. Here, we firstly investigated the IC neuronal response to the paired binaural stimuli with different inter-stimulus intervals using in vivo loose-patch recordings in anesthetized C57BL/6 mice. It was found that the total acoustic evoked spikes remained unchanged under microsecond interval conditions, but persistent suppression would be observed when the time intervals were extended. We further studied the paired binaural stimuli evoked excitatory/inhibitory inputs using in vivo whole-cell voltage-clamp techniques and blockage of the auditory nerve. The amplitudes of the contralateral excitatory inputs could be suppressed, unaffected or facilitated as the interaural delay varied. In contrast, contralateral inhibitory inputs and ipsilateral synaptic inputs remained almost unchanged. Most IC neurons exhibited the suppression of contralateral excitatory inputs over the interval range of dozens of milliseconds. The facilitative effect was generated by the summation of contralateral and ipsilateral excitation. Suppression and facilitation were completely abolished when ipsilateral auditory nerve was blocked pharmacologically, indicating that these effects were exerted by ipsilateral stimulation. These results suggested that the IC would inherit the binaural inputs integrated at the brainstem as well as within the IC and synaptic excitations, modulated by ipsilateral stimulation, underlie the binaural acoustic response.

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The ability to sense occasionally occurring sounds in an environment is critical for animals. To understand this ability, we studied responses to acoustic oddball paradigms in the rat's midbrain auditory neurons. An oddball paradigm is a random sequence of stimuli created using two tone bursts, with one presented at a high probability (standard stimulus) and the other at a low probability (oddball stimulus). The sounds were either colocalized at the ear contralateral to a neuron under investigation (c90° azimuth) or separated with one at c90° while the other at another azimuth. We found that most neurons generated stronger responses to a sound at c90° when it was presented as an oddball than as a standard stimulus. Relocating one sound from c90° to another azimuth changed both responses to the relocated sound and the sound that remained at c90°. Most notably, the response to an oddball stimulus at c90° was increased when a standard stimulus was relocated from c90° to a location that was in front of the animal or on the ipsilateral side of recording. The increase was particularly large in neurons that displayed transient firing under contralateral stimulation but no firing under ipsilateral stimulation. These neurons likely play a particularly important role in using spatial cues to detect occasionally occurring sounds. Results suggest that effects of spatial separation between two sounds of an oddball paradigm on responses to the sounds were dependent on changes in the level of adaptation and binaural inhibition.

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The auditory brainstem response (ABR) is a commonly used objective clinical measure for hearing evaluation. It can be also used to draw conclusions about the functioning of distinct stages of the auditory pathway including the binaural processing stages using the binaural interaction component (BIC) of the ABR. OBJECTIVE: To study binaural processing in normal hearing subjects complaining of tinnitus. METHODS: Sixty cases with bilateral normal peripheral hearing were included in this work, divided into 2 groups, i.e., group 1 (comprised of 30 healthy subjects representing the control group) and group 2 (comprised of 30 subjects with tinnitus representing the study group). All of the subjects were submitted to a basic audiological evaluation (including pure tone audiometry, speech audiometry, and immittancemetry) and ABR audiometry recorded in monaural and then binaural conditions. RESULTS: In monaural recording, the tinnitus group showed significantly delayed latencies of waves I, III, and V in addition to significantly reduced wave I and III amplitudes when compared with the controls. Similar significant findings were found when binaural ABR responses were compared between both groups. Comparing BIC between both groups showed significant earlier BIC for latencies of waves I and V in the control group, while the BIC for amplitudes showed similar results in both groups. CONCLUSIONS: These finding suggest the presence of binaural processing deficits in tinnitus patients at different levels along the ascending auditory pathway.

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INTRODUCTION: There is ample evidence that auditory dysfunction is a common feature of autism spectrum disorder (ASD). Binaural interaction component (BIC) manifests binaural interaction and is valid and proven response which reflects ongoing binaural processing. OBJECTIVES: To investigate the differences in binaural interaction component of auditory brainstem response (ABR-BIC) between children with autism spectrum disorder (ASD) and normal peers and to correlate between ABR-BIC amplitudes and the acquired communication skills in ASD children. METHODS: ASD was diagnosed according to the criteria of 5th edition of diagnostic and statistical manual of mental disorders (DSM-V) and all children with ASD underwent test of acquired communication skills (TACS). Click evoked ABRs were elicited by left monaural, right monaural and binaural stimulation at intensity of 65 dBnHL in all participants. ABR-BIC was then calculated as the difference between the binaurally evoked ABR waveform and a predicted binaural waveform created by algebraically summing the left and right monaurally evoked ABRs. The difference in amplitudes that gives rise to ABR-BIC is at IV-VI waves. RESULTS: ABR-BIC amplitudes were demonstrated to be significantly reduced in the ASD group compared to the control group. There was significant positive correlation between ABR-BIC amplitude and the language and social scores in TACS. CONCLUSION: This study provided an objective evidence of binaural processing disorder in children with ASD.

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Binaural processing disorder is an important deficit in children with (C)APD so binaural processing evaluations are crucial. There are subjective and objective tests for assessing binaural processing. Subjective tests require patient attention and active so objective evaluation of binaural processing is important. The aim of present study was investigating binaural interaction component (BIC) of middle latency response (MLR) in children suspected to (C)APD. Sixty 8-12 year-old children suspected to (C)APD and sixty normal children were selected based on inclusion criteria. Both groups were matched in terms of sex (40 boys and 20 girls) and age (9.05 ± 1.25 years old). MLR test (monaural right ear, monaural left ear and binaural) was performed in all the cases and BIC was calculated by subtracting binaural response from summed monaural responses. Independent t test showed that latency of Pa and Na (ms), Pa-Na amplitude (µv), BIC latency (ms) and amplitude (µv) were significantly different from normal subjects (p value ≤0.001). Present study showed that MLR and BIC of MLR are clinically available and objective tests that can be used to determining children suspected to (C)APD. These tests might have the potential to separating normal children from children with (C)APD objectively.

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The auditory brain stem response (ABR) is an evoked potential that indexes a cascade of neural events elicited by sound. In the present study we evaluated the influence of sound frequency on a derived component of the ABR known as the binaural interaction component (BIC). Specifically, we evaluated the effect of acoustic interaural (between-ear) frequency mismatch on BIC amplitude. Goals were to 1) increase basic understanding of sound features that influence this long-studied auditory potential and 2) gain insight about the persistence of the BIC with interaural electrode mismatch in human users of bilateral cochlear implants, presently a limitation on the prospective utility of the BIC in audiological settings. Data were collected in an animal model that is audiometrically similar to humans, the chinchilla (Chinchilla lanigera; 6 females). Frequency disparities and amplitudes of acoustic stimuli were varied over broad ranges, and associated variation of BIC amplitude was quantified. Subsequently, responses were simulated with the use of established models of the brain stem pathway thought to underlie the BIC. Collectively, the data demonstrate that at high sound intensities (≥85 dB SPL), the acoustically elicited BIC persisted with interaurally disparate stimulation (click frequencies ≥1.5 octaves apart). However, sharper tuning emerged at moderate sound intensities (65 dB SPL), with the largest BIC occurring for stimulus frequencies within ~0.8 octaves, equivalent to ±1 mm in cochlear place. Such responses were consistent with simulated responses of the presumed brain stem generator of the BIC, the lateral superior olive. The data suggest that leveraging focused electrical stimulation strategies could improve BIC-based bilateral cochlear implant fitting outcomes.NEW & NOTEWORTHY Traditional hearing tests evaluate each ear independently. Diagnosis and treatment of binaural hearing dysfunction remains a basic challenge for hearing clinicians. We demonstrate in an animal model that the prospective utility of a noninvasive electrophysiological signature of binaural function, the binaural interaction component (BIC), depends strongly on the intensity of auditory stimulation. Data suggest that more informative BIC measurements could be obtained with clinical protocols leveraging stimuli restricted in effective bandwidth.

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