Interaural Time Difference Perception with a Cochlear Implant and a Normal Ear

Currently there is a growing population of cochlear-implant (CI) users with (near) normal hearing in the non-implanted ear. This configuration is often called SSD (single-sided deafness) CI. The goal of the CI is often to improve spatial perception, so the question raises to what extent SSD CI listeners are sensitive to interaural time differences (ITDs). In a controlled lab setup, sensitivity to ITDs was investigated in 11 SSD CI listeners. The stimuli were 100-pps pulse trains on the CI side and band-limited click trains on the acoustic side. After determining level balance and the delay needed to achieve synchronous stimulation of the two ears, the just noticeable difference in ITD was measured using an adaptive procedure. Seven out of 11 listeners were sensitive to ITDs, with a median just noticeable difference of 438 μs. Out of the four listeners who were not sensitive to ITD, one listener reported binaural fusion, and three listeners reported no binaural fusion. To enable ITD sensitivity, a frequency-dependent delay of the electrical stimulus was required to synchronize the electric and acoustic signals at the level of the auditory nerve. Using subjective fusion measures and refined by ITD sensitivity, it was possible to match a CI electrode to an acoustic frequency range. This shows the feasibility of these measures for the allocation of acoustic frequency ranges to electrodes when fitting a CI to a subject with (near) normal hearing in the contralateral ear.     

Bone-Conducted Sound Lateralization of Interaural Time Difference and Interaural Intensity Difference in Children and a Young Adult with Bilateral Microtia and Atresia of the Ears

Objective—We used multi-slice helical computerized tomography (MSHCT) to evaluate the 3D characteristics of the laryngeal structures in patients with unilateral vocal fold paralysis (UVFP) during phonation, and compared the results with those obtained using an aerodynamic vocal function test. Material and methods—The subjects were 37 patients with UVFP. The region over the larynx was scanned during quiet phonation and again during inspiration using MSHCT, and 3D endoscopic and coronal reconstruction images were produced. Maximum phonation time (MPT) and mean airflow rate (MFR) during phonation were measured. Results—During phonation, the affected fold was thinner than the healthy fold in 30 subjects and located at a higher position than the healthy fold in 21 subjects. Abduction or thinning of the affected fold during phonation (paradoxical movement) was seen in seven subjects. MFR was significantly greater when the affected fold was thinner than the healthy fold during phonation, and MPT was significantly shorter when the affected fold showed paradoxical movement. Over-adduction of the healthy fold during phonation was present in 15 subjects. There were no significant differences in MPT or MFR between subjects with and without over-adduction. Conclusion—The combination of MSHCT endoscopic and coronal reconstruction images enables the 3D characteristics of the unilaterally paralyzed larynx to be visualized during phonation, and some of these characteristics are significantly correlated with vocal function in patients with UVFP.     

Improving Interaural Time Difference Sensitivity Using Short Inter-pulse Intervals with Amplitude-Modulated Pulse Trains in Bilateral Cochlear Implants

Journal of the Association for Research in Otolaryngology - Interaural time differences (ITDs) at low frequencies are important for sound localization and spatial speech unmasking. These ITD cues...     

The Interaural Time Difference Pathway: a Comparison of Spectral Bandwidth and Correlation Sensitivity at Three Anatomical Levels

Temporal differences between the two ears are critical for spatial hearing. They can be described along axes of interaural time difference (ITD) and interaural correlation, and their processing starts in the brainstem with the convergence of monaural pathways which are tuned in frequency and which carry temporal information. In previous studies, we examined the bandwidth (BW) of frequency tuning at two stages: the auditory nerve (AN) and inferior colliculus (IC), and showed that BW depends on characteristic frequency (CF) but that there is no difference in the mean BW of these two structures when measured in a binaural, temporal framework. This suggested that there is little frequency convergence in the ITD pathway between AN and IC and that frequency selectivity determined by the cochlear filter is preserved up to the IC. Unexpectedly, we found that AN and IC neurons can be similar in CF and BW, yet responses to changes in interaural correlation in the IC were different than expected from coincidence patterns (“pseudo-binaural” responses) in the AN. To better understand this, we here examine the responses of bushy cells, which provide monaural inputs to binaural neurons. Using broadband noise, we measured BW and correlation sensitivity in the cat trapezoid body (TB), which contains the axons of bushy cells. This allowed us to compare these two metrics at three stages in the ITD pathway. We found that BWs in the TB are similar to those in the AN and IC. However, TB neurons were found to be more sensitive to changes in stimulus correlation than AN or IC neurons. This is consistent with findings that show that TB fibers are more temporally precise than AN fibers, but is surprising because it suggests that the temporal information available monaurally is not fully exploited binaurally.     

Modulation Enhancement in the Electrical Signal Improves Perception of Interaural Time Differences with Bimodal Stimulation

Interaural timing cues are important for sound source localization and for binaural unmasking of speech that is spatially separated from interfering sounds. Users of a cochlear implant (CI) with residual hearing in the non-implanted ear (bimodal listeners) can only make very limited use of interaural timing cues with their clinical devices. Previous studies showed that bimodal listeners can be sensitive to interaural time differences (ITDs) for simple single- and three-channel stimuli. The modulation enhancement strategy (MEnS) was developed to improve the ITD perception of bimodal listeners. It enhances temporal modulations on all stimulated electrodes, synchronously with modulations in the acoustic signal presented to the non-implanted ear, based on measurement of the amplitude peaks occurring at the rate of the fundamental frequency in voiced phonemes. In the first experiment, ITD detection thresholds were measured using the method of constant stimuli for five bimodal listeners for an artificial vowel, processed with either the advanced combination encoder (ACE) strategy or with MEnS. With MEnS, detection thresholds were significantly lower, and for four subjects well within the physically relevant range. In the second experiment, the extent of lateralization was measured in three subjects with both strategies, and ITD sensitivity was determined using an adaptive procedure. All subjects could lateralize sounds based on ITD and sensitivity was significantly better with MEnS than with ACE. The current results indicate that ITD cues can be provided to bimodal listeners with modified sound processing.     

The Role of Interaural Intensity Differences and Time Delay for Signal Detection in Noise

Résumé

Des expériences psycho-acoustiques ont démontré que l'audition binaurale non seulement rend possible la localisation de la source du son mais qu'elle améliore aussi considérablement la relation effective du signal au bruit. Les effets, qui sont écrits en détail, se produisent par des différences interaurales de l'intensité du signal ou par des différences interaurales du temps d'arrivée du signal. L'effet produit par l'un de ces deux paramètres de l'audition binaurale ne se superpose pas sur l'effet de l'autre. Ces effets sont liés à la condition que le signal et le bruit soient cohérents.     

Sensitivity to Interaural Time Differences Conveyed in the Stimulus Envelope: Estimating Inputs of Binaural Neurons Through the Temporal Analysis of Spike Trains

Sound-source localization in the horizontal plane relies on detecting small differences in the timing and level of the sound at the two ears, including differences in the timing of the modulated envelopes of high-frequency sounds (envelope interaural time differences (ITDs)). We investigated responses of single neurons in the inferior colliculus (IC) to a wide range of envelope ITDs and stimulus envelope shapes. By a novel means of visualizing neural activity relative to different portions of the periodic stimulus envelope at each ear, we demonstrate the role of neuron-specific excitatory and inhibitory inputs in creating ITD sensitivity (or the lack of it) depending on the specific shape of the stimulus envelope. The underlying binaural brain circuitry and synaptic parameters were modeled individually for each neuron to account for neuron-specific activity patterns. The model explains the effects of envelope shapes on sensitivity to envelope ITDs observed in both normal-hearing listeners and in neural data, and has consequences for understanding how ITD information in stimulus envelopes might be maximized in users of bilateral cochlear implants—for whom ITDs conveyed in the stimulus envelope are the only ITD cues available.     

Two Experiments on Subtle Mid-Frequency Hearing Loss and Its Influence on Word Discrimination in Noise-Exposed Listeners

The present study consisted of two experiments. Experiment I was directed toward the detection of subtle mid-frequency cochlear dysfunction and the determination of word discrimination in noise for persons with noise-induced hearing loss. The presence of significantly elevated aural-overload thresholds, consistent with the presence of cochlear pathology in regions of normal pure-tone sensitivity, confirmed previous findings obtained with this subject population by other investigators. In addition, a marked reduction in word discrimination was observed in the presence of a background of competing noise.

For experiment II, normal hearers listened to consonant-nucleus-consonant monosyllables filtered to match the mean audiometric configuration of the noise-exposed subjects in experiment I. Results showed significantly better performance with these filtered words by the normally hearing subjects than that by the noise-exposed group for unfiltered materials. The results of the second experiment were interpreted as providing further support for the presence of subtle auditory dysfunction in the mid-frequencies despite normal threshold sensitivity in this same frequency region.

Dans une première expérience, nous avons utilisé des sujets présentant une baisse de l'acuité auditive à la suite de traumatismes sonores. Nous avons tout d'abord cherché a connaiˇtre l'importance de l'atteinte cochléaire au niveau des fréquences moyennes et nous avons déterminé pour cela les seuils de surcharge auditive (test harmonique); comme certains auteurs précédents, nous nous sommes apençus que ces seuils étaient nettement élevés, témoignant d'une atteinte cochléaire dans une région dont la sensibilité aux sons purs était pourtant normale. Nous avons ensuite noté une baisse importante de la discrimination de mots en présence de bruit.

Dans une seconde expérience, nous avons utilisé des sujets à audition normale. Nous leur avons fait écouter des monosyllabes CNC filtrées de façon à se rapprocher de la configuration audiométrique moyenne des sujets précédents. Leur performance pour ces mots filtrés fut bien meilleure que celle des sujets ayant été exposés au bruit pour les mots non filtrés. Cette deuxième expérience nous semble encore meilleure pour mettre en évidence la présence d'un dysfonctionnement de la cochlée au niveau des fréquences moyennes alors que les seuils de sensation sont normaux pour ces měmes fréquences.     

豚鼠外淋巴间隙阻断术对前庭和耳蜗的影响

对１８只白色豚鼠施行单侧外半规管外淋巴间隙阻断术。术前、后观察ＡＢＲ、旋转试验，并作火棉胶连续切片光镜检查。结果提示：手术前、后ＡＢＲ阈值经统计学处理差异无显著性，而限震持续时间差异有显著性（术后缩短），初步表明本手术可致豚鼠前庭功能降低而未明显损伤耳蜗功能。     

Interaural cross correlation of event-related potentials and diffusion tensor imaging in the evaluation of auditory processing disorder: a case study

In a previous publication (Jerger et al, 2002), we presented event-related potential (ERP) data on a pair of 10-year-old twin girls (Twins C and E), one of whom (Twin E) showed strong evidence of auditory processing disorder. For the present paper, we analyzed cross-correlation functions of ERP waveforms generated in response to the presentation of target stimuli to either the right or left ears in a dichotic paradigm. There were four conditions; three involved the processing of real words for either phonemic, semantic, or spectral targets; one involved the processing of a nonword acoustic signal. Marked differences in the cross-correlation functions were observed. In the case of Twin C, cross-correlation functions were uniformly normal across both hemispheres. The functions for Twin E, however, suggest poorly correlated neural activity over the left parietal region during the three word processing conditions, and over the right parietal area in the nonword acoustic condition. Differences between the twins' brains were evaluated using diffusion tensor magnetic resonance imaging (DTI). For Twin E, results showed reduced anisotropy over the length of the midline corpus callosum and adjacent lateral structures, implying reduced myelin integrity. Taken together, these findings suggest that failure to achieve appropriate temporally correlated bihemispheric brain activity in response to auditory stimulation, perhaps as a result of faulty interhemispheric communication via corpus callosum, may be a factor in at least some children with auditory processing disorder.     

Human Long-Latency Potentials Evoked by Monaural Interruptions of a Binaural Click Train: Connection to Sound Lateralization Based on Interaural Intensity Differences

In 9 subjects with normal hearing, monaural offset (MO) responses in the long-latency range were recorded with and without an ongoing sound (click train at a rate of 250/s) at the opposite ear. In the latter case MOs were perceived simply as termination of a sound. In the former case, however, the abrupt transition from binaural to monaural (BM) stimulation was perceived as a shift of the fused image from the center to either side. Therefore, the fairly large difference potential obtained by subtracting the MO response from the BM response was evaluated as the cortical response to stimulation of the sound lateralization mechanism based on interaural intensity differences. These center-to-side responses, which could be characterized by an N1-P2 wave sequence at latencies of 120 and 220 ms, respectively, were compared with the auditory onset responses also recorded from the same subjects by means of a sequential stimulation paradigm. The scalp topography of the N1 components in all these responses recorded simultaneously from frontocentral, parietocentral and two superior temporal electrodes with a neck reference is discussed.     

前庭神经炎患者虚拟现实辅助主观垂直水平视觉研究

目的 通过观察前庭神经炎患者主观垂直、水平视觉测试结果,为临床诊断提供依据.方法 45名无眩晕的健康自愿者作为健康对照组,46名单侧前庭神经炎患者作为VN组,均佩戴VR眼镜,分别完成头正中位的主观垂直视觉和主观水平视觉试验.结果 健康对照组主观视觉水平线、主观视觉垂直线的偏斜角度为-2°～2°.以此为判定阳性与阴性的标...     

Influence of Canal Paresis and Compensation on Gain and Time Constant of Nystagmus Slow-phase Velocity to Yaw-axis Rotation

In order to assess the influence of canal paresis and compensation on the yaw-axis rotatory chair test parameters gain and time constant, a study was conducted in 435 patients diagnosed with unilateral peripheral vestibulopathy. Patients were grouped according to the amount of canal paresis found in the caloric test and by the result of a bedside examination of the vestibulo-ocular reflex (VOR). The time constant of the VOR diminishes as canal paresis increases and, when using a high-velocity sinusoidal test, there is a similar reduction in gain. Mean time constant was reduced when rotations were to the side of the lesion (ipsilesional) and to the normal (contralesional) and differences between both rotations were found for 21-80% canal paresis. Ipsilesional gain was significantly less than contralesional gain, which had a normal result independent of the amount of canal paresis; differences between them were significant when canal paresis was > 41%. Spontaneous nystagmus significantly influenced the appearance of asymmetries in gain and time constant in the tests performed while, with high-velocity sinusoidal rotation, gain was found to be significantly different for ipsilesional and contralesional rotations in non-acute symptomatic patients.     

Difference in maxillary sinus volumes of patients with cleft lip and palate

Background and objectiveSinus disease is noted to be common in patients with cleft lip and palate. Many have wondered if anatomic differences are a cause or at least a contributor of this. In this sense, comparisons of sinus volumes of patients with different craniofacial clefts may be helpful to determine possible differences from normal. Thus, the present study aimed to evaluate and compare the maxillary sinus volume of patients with unilateral (UCLP) and bilateral (BCLP) cleft lip and palate to control, i.e. non-cleft patients, using cone beam computed tomography (CBCT) images.MethodsThe sample consisted of 30 subjects with UCLP, 15 with BCLP and 15 control individuals (non-cleft). Each maxillary sinus was assessed three-dimensionally, segmented and its volume was calculated. The comparison between right and left sinus was performed by Student t-test, and the differences between the control and cleft groups were calculated using ANOVA.ResultsNo statistical differences were found when the sides were compared (p > 0.05). In relation to the assessment among groups, all comparisons had statistically significant differences (p < 0.05), with the UCLP group presenting the lowest sinus volume.ConclusionUCLP individuals present maxillary sinuses with smaller volumes, without differences found between the cleft and non-cleft side. BCLP subjects also present a reduction in the volume when compared to a control sample, but the average sinus volume is larger than in UCLP patients.     

Influence of speech-language therapy on P300 outcome in patients with language disorders: a meta-analysis

IntroductionThe patient's evolution in the audiology and speech-language clinic acts as a motivator of the therapeutic process, contributing to patient adherence to the treatment and allowing the therapist to review and/or maintain their clinical therapeutic conducts. Electrophysiological measures, such as the P300 evoked potential, help in the evaluation, understanding and monitoring of human communication disorders, thus facilitating the prognosis definition in each case.ObjectiveTo determine whether the audiology and speech-language therapy influences the variation of P300 latency and amplitude in patients with speech disorders undergoing speech therapy.MethodsThis is a systematic review with meta-analysis, in which the following databases were searched: Pubmed, ScienceDirect, SCOPUS, Web of Science, SciELO and LILACS, in addition to the gray literature bases: OpenGrey.eu and DissOnline. The inclusion criteria were randomized or non-randomized clinical trials, without language or date restriction, which evaluated children with language disorders undergoing speech therapy, monitored by P300, compared to children without intervention.ResultsThe mean difference between the latencies in the group submitted to therapy and the control group was −20.12 ms with a 95% confidence interval of −43.98 to 3.74 ms (p = 0.08, I² = 25% and p value = 0.26). The mean difference between the amplitudes of the group submitted to therapy and the control group was 0.73 uV with a 95% confidence interval of −1.77 to 3.23 uV (p = 0.57, I² = 0% and p value = 0.47).ConclusionThe present meta-analysis demonstrates that speech therapy does not influence the latency and amplitude results of the P300 evoked potential in children undergoing speech therapy intervention.     

阻塞性睡眠呼吸暂停低通气综合征患者及正常成人呼吸运动周期中上气道形态变化的研究

目的：通过观察呼吸运动周期中阻塞性睡眠呼吸暂停低通气综合征（OSAHS）患者与正常人上呼吸道形态变化的差别,探讨OSAHS的发病机制。方法：选取经PSG确诊的OSAHS患者20例和均无睡眠疾病方面主诉的正常对照组16例。利用PSG中呼吸监测系统记录其呼吸周期曲线,同时采用纤维内镜观察受检者在平静呼吸的呼吸周期中咽腔形态学的改变,将纤维内镜观察过程同步录制于PSG同一计算机内。后期根据呼吸曲线,分别于呼吸周期各个不同时相所对应的咽腔录像利用图像软件剪接为照片,分别测量各解剖区不同呼吸周期下上呼吸道的横截面积、左右径和前后径。结果：对照组与OSAHS组均表现为上呼吸道形态随呼吸运动而变化。吸气时面积开始减小,吸气中期呼吸道面积减至最小,持续到吸气末期,呼气时面积开始增大,呼气中期面积增至最大,持续到呼气末期,吸气相再次开始。对照组与OSAHS组在腭咽区和舌咽区的前后径、左右径及横截面积在呼吸运动中有明显变化。OSAHS组在腭咽区及舌咽区左右径、前后径及横截面积变化幅度均大于对照组。OSAHS组与对照组呼吸周期内腭咽区左右径及面积变化幅度均明显大于舌咽区及喉咽区。OSAHS组腭咽区前后径变化幅度也大于舌咽区及喉咽区。结论：呼吸运动周期中上呼吸道的形态存在周期性的变化,OSAHS患者的变化幅度明显大于对照组,这种较大的变化幅度是OSAHS患者睡眠中发生上呼吸道阻塞的基础。     

Artificial restoration of voice. I: Experiments in phonatory control of the reinnervated canine larynx

Coordinated electronic pacing of implanted nerve pedicles into paralyzed laryngeal muscles has allowed selective dynamic control of abduction, adduction, and elongation of the vocal cords. Modifications of the original circuit in a cervical muscle model has added fine tuning to basic "all-or-none" pacing. Rehabilitation of phonation illustrated the sophisticated nature of voice and the need for restoration of fine tuning. Five mongrel dogs received nerve-muscle pedicles into the thyroarytenoideus, cricothyroideus, and posterior cricothyroideus after denervation of one hemilarynx. Following appropriate reinnervation time, pedicles and intact recurrent laryngeal nerves were injected with currents of variable amplitudes and pulse widths to achieve graded vocal fold control while air was blown intratracheally towards the glottic chink. Videoscopic and spectral analyses indicated that artificial phonation could be restored to frequencies measured in the normal state. These experiments suggested that rehabilitation of the impaired voice by servocontrol might eventually be feasible.     

Biofilm Formation on Voice Prostheses: Influence of Dairy Products in vitro

Laryngectomized patients use silicone rubber voice prostheses to regain their speech; however, the lifetime of these devices is limited due to biofilm formation. Following anecdotal evidence, the influence of various dairy products on biofilm formation on voice prostheses was studied, using the artificial throat-model. Biofilms were grown on Groningen and Provox®2 voice prostheses by inoculating two artificial throats with the total microflora isolated from an explanted Groningen voice prosthesis. After 3 days, one throat was perfused three times daily with 650 ml dairy product; the other was perfused with phosphate buffered saline, used as a control. After 12 days the microflora on each voice prosthesis was determined. Perfusion of the artificial throat with buttermilk three times daily for 9 days reduced the amount of bacteria and yeasts in the biofilm on Groningen voice prostheses to 3% and 15% of the control, respectively. These effects were not observed with a pasteurized conservable buttermilk product. Yakult fermented milk drink, Mona mild yoghurt, Mona vifit yoghurt, semi-skimmed milk and low-fat yoghurt reduced the amount of bacteria by various degrees, ranging from 12% (Yakult) to 88% (Mona mild) of the control, but these products did not inhibit, and sometimes even stimulated, yeast growth. A combination of buttermilk and Yakult did not show a synergistic effect, as expected. Effects for the Provox®2 voice prosthesis were less pronounced. These in vitro experiments in the artificial throat demonstrated that the formation of the biofilm on voice prostheses can be lessened by the daily use of certain dairy products, of which buttermilk had the strongest inhibitory effect, followed by Yakult.