中枢听觉处理障碍

听觉活动并不仅仅是对声刺激的察觉．更重要的是要对听觉输入的信息进行正确的编码、感受、认识和理解等处理。     

单侧听觉剥夺后听觉中枢的重塑研究进展

单侧听觉剥夺后,听力正常耳主导听力,随着时间的延长,这种双耳信息输入的不对称,造成听觉中枢发育不对称(偏侧性改变),涉及听觉皮层及脑干听觉核团的不同区域,引起对应听觉通路发生一系列改变,包括结构、神经递质及受体等的改变,进而改变了两侧通路兴奋与抑制的平衡,损害了两耳信号的整合处理,导致声源定位能力及言语识别率降低,甚至影响患者的认知功能。这种偏侧化的改变可能会影响后续的听觉康复,因此,明确单侧听觉剥夺之后听觉中枢重塑的机制至关重要。本文就单侧听觉剥夺后听觉中枢的重塑研究进展做一回顾。     

中枢听觉处理障碍

中枢听觉处理障碍（central auditory processing disorders,CAPD）是指中枢听觉神经系统的功能受损而致的听功能缺陷,本文首先综述了CAPD的临床症状、特点及可能之病因.之后阐述了听觉内外余力对听觉言语测试的影响以及降低外余力的方法;听力损失、认知能力、药物、测试程式对CAPD测试的影响;言语测试和非言语测试的优缺点;不同测试模式的影响.最后阐述了CAPD的一些具体测试方法以及对测试结果进行测试时要注意的因素.     

电子耳蜗植入患儿中枢听觉系统发育的敏感期：耳蜗植入年龄的探讨

对先天性聋儿来说,耳蜗植入的关键是植入年龄的选择。尽管动物研究已经表明中枢听觉系统在缺乏声刺激时仍可以建立有效的神经联系,但长期听觉阻隔还是会引起中枢听觉系统广泛的退变,这些变化包     

人工耳蜗植入后听觉中枢可塑性改变

我国有听力残疾人2780万,其中0～6岁听障儿童约13.7万,且每年新出生聋儿约2.3万[1].如果听障儿童不能在听觉中枢发育的关键期内接受适宜的听觉刺激,可导致一生的语言残疾和交流障碍,给家庭和社会带来沉重负担.人工耳蜗植入(CI)通过刺激听神经,替代受损的毛细胞,将声音转为电信号传入中枢神经系统,可使患者重获听觉,是重度或极重度感音性聋的有效康复方法.至2008年底,全世界范围内已有1 2万重度感音神经性聋患者接受了人工耳蜗植入.     

AP-2蛋白调控网格蛋白介导突触囊泡胞吞的研究进展

神经元间的信息传递依赖于神经递质的释放,这一过程离不开正常有效的囊泡循环机制,突触囊泡循环是调控突触囊泡水平和维持神经递质释放的基础。囊泡回收则是循环过程中保证囊泡从突触前膜回收至胞内,参与新一轮囊泡形成和再生的重要保障。网格蛋白介导的内吞是突触囊泡回收的主要途径,衔接蛋白AP-2(adaptin-2)是参与这一内吞过程不同时期的关键蛋白,其通过绑定不同蛋白分子分别从结构和动力的层面参与了囊泡回收过程,AP-2对网格蛋白介导的突触囊泡胞吞过程具有重要意义。本文结合国内外最新研究报道,简要综述了AP-2的结构特点、分子基础、AP-2蛋白调控网格蛋白介导突触囊泡的胞吞及其与听力的关系。     

C—fos癌基因表达法及其在听觉中枢研究中的应用

C—fos癌基因表达法是利用神经元受到兴奋性刺激后C—fos基因的表达剧增和FOS蛋白在胞核内迅速堆积的特点，应用原位杂交或免疫组化的手段对中枢神经系统形态和生理进行研究的方法。本根据国外有关献对其方法的建立加以综述，并着重阐述它在听觉中枢系统(主要是耳蜗核和下丘核)研究中取得的进展。     

突发性聋患者听觉中枢在功能性核磁的表现

目的 利用血氧水平依赖性的功能性磁共振成像（blood oxygen level dependent functional MRI,BOLD～fMRD技术,观察突发性聋患者在接受纯音刺激时听觉中枢的变化。方法研究对象分为两组,突发性聋患者13例（均为左耳患病）为试验组,12例双耳听力正常的健康成年志愿者作为对照组。通过CoolEditPr02软件编辑1000Hz、127dB纯音,刺激模式采用ON／OFF组块设计,通过耳机分别给予右耳及双耳音频刺激,采用荷兰Philips Achieva3．0T磁共振成像系统,采集脑部的BOLD—fMRI数据,最后通过SPM2软件对数据进行统计学分析（组分析）,得到脑功能活动的图像。结果右耳接受纯音刺激时听力正常组主要中枢激活区在双侧颞上回、左枕叶、左额上回,此外还有左小脑、双侧海马及双侧旁中央小叶激活,听觉中枢表现为右侧优势偏向;突聋组见双侧颞上回,以及左侧海马、右枕叶和左侧距状裂区激活,听觉中枢表现为左侧优势偏向,突聋组听中枢激活容积小于正常组。双耳同时刺激时,听力正常组激活区主要在双侧颞中回,右侧扣带回和左胼胝体亦明显激活;突聋组双侧颞中回,以及右侧颞上回、右小脑、右侧额下回及右楔前叶激活,两组听觉中枢均表现为右侧优势偏向。听力正常组与突聋组比较,正常组左小脑、左胼胝体区明显激活,突聋组出现新的激活区右侧颞上回、右侧额下回及右小脑区：突聋组听中枢激活容积小于正常组。结论突聋患者在单耳刺激时听觉中枢出现优势偏向的改变,提示单侧耳聋的病人听觉皮质存在着结构重组;听觉中枢具有可塑性。突聋患者在双侧刺激时通过听觉重组使双耳对外界声音的感知尽量达到正常水平;突聋患者听觉中枢不仅本身存在重组现象,且同视觉皮质之间也发生了感觉交互作用。     

听觉传出神经系统研究进展

听觉传出神经在维持听觉高敏感度及分辨力、听觉调控及听觉防护等各方面起着十分重要的作用。听觉传出神经通路作为听觉系统重要的投射体系之一,橄榄耳蜗束是乞今为止已被证实存在的唯一的听觉传出神经通路;最近有学者提出,可能存在中缝背核-迷路听觉传出神经通路。     

中等强度噪声暴露对幼年豚鼠听觉中枢的影响

目的 探讨中等强度白噪声暴露对幼年豚鼠听觉中枢及听觉行为的影响,为研究噪声的隐匿性危害提供参考。方法 选取10只3周龄豚鼠,随机分成实验组和对照组,每组5只,实验组进行每日12小时85 dB SPL白噪声暴露,连续4周,于暴露结束当日和暴露结束后2周进行畸变产物耳声发射(DPOAE)、听性脑干反应(ABR)、噪声间隙听性脑干反应(GIN-ABR)和听觉惊跳反射(ASR)测试;对照组在安静环境下饲养至7周龄进行上述测试,比较两组结果。结果 暴露结束当日,实验组在16 kHz的DPOAE幅值显著降低(P<0.01),暴露结束后2周恢复。暴露结束当日,实验组12 kHz(P<0.05)、16 kHz(P<0.01)的ABR阈值显著升高,暴露结束后2周恢复;未发生阈移的6 kHz(P<0.05)、8 kHz(P<0.01)波Ⅳ幅值显著降低,且2周后未恢复(P<0.05)。暴露结束后2周,实验组4 ms间隙的GIN-ABR波Ⅳ幅值仍显著小于对照组(P<0.05),且实验组100 dB SPL刺激声的ASR幅值有减小趋势。结论 85 dB SPL白噪声暴露...     

The correlation between central auditory processing in autistic children and their language processing abilities

AimTo study the auditory profile at different levels of the auditory system in children with ASD and to verify the role of (Central) auditory processing disorder as an essential pathology of the autistic disorder or as an associated co-morbidity, and to establish the correlation between CAP findings and the language delay in these cases.PatientsThe study included 30 children with definite autistic disorder according to DSM-IV-TR criteria and ADI-R among those attending the outpatient neuropsychiatry clinic of Alexandria University Children Hospital at El Shatby. An informed consent was taken from all patients in this part of the study. Confidentiality of the records was maintained.MethodsAll cases were subjected to complete history taking and examination; special assessment to language skills and evoked potentials were done.ResultsThe results concluded that (central) auditory processing disorder is an essential pathology of the autistic disorder. Autistic children possess a dysfunctioning or an immature central auditory nervous system at both the brainstem and cortical levels.     

Assessment of central auditory processing in a group of workers exposed to solvents

Conclusion. Despite having normal hearing thresholds and speech recognition thresholds, results for central auditory tests were abnormal in a group of workers exposed to solvents. Workers exposed to solvents may have difficulties in everyday listening situations that are not related to a decrement in hearing thresholds. A central auditory processing disorder may underlie these difficulties. Objective. To study central auditory processing abilities in a group of workers occupationally exposed to a mix of organic solvents. Materials and methods. Ten workers exposed to a mix of organic solvents and 10 matched non-exposed workers were studied. The test battery comprised pure-tone audiometry, tympanometry, acoustic reflex measurement, acoustic reflex decay, dichotic digit, pitch pattern sequence, masking level difference, filtered speech, random gap detection and hearing-in-noise tests. Results. All the workers presented normal hearing thresholds and no signs of middle ear abnormalities. Workers exposed to solvents had lower results in comparison with the control group and previously reported normative data, in the majority of the tests.     

Evidence for increased NADPH-diaphorase-positive neurons in the central auditory system of the aged rat

Conclusions: The age-related increase in the production of nitric oxide (NO) suggests that this increase was related to neuron aging. Additional studies may provide information regarding aging-related changes in the central auditory system. Objectives: Although NO has been associated with aging, it is unclear whether specific areas of the central auditory system are involved. We therefore assayed aging-related changes in NADPH-diaphorase (NADPH-d), a selective histochemical marker for NO, in the neurons of the central auditory system and other brain regions. Materials and methods: The numbers of NADPH-d-stained neurons and the area and staining density of cell bodies were examined in aged (24 months old) and younger (4 months old) Wistar rats. Results: The number of NADPH-d-positive neurons in the inferior colliculus was significantly increased in aged rats (p<0.05), whereas the area of NADPH-d-positive neurons in all areas did not differ significantly between aged and younger rats (p>0.05). The staining densities of NADPH-d-positive neurons in the inferior colliculus, the auditory cortex, and the visual cortex were significantly greater in aged compared with younger rats (p<0.05).     

Comparison of two tests of auditory temporal resolution in children with central auditory processing disorder,adults with psychosis,and adult professional musicians

Abstract

Objective: Evaluate auditory temporal resolution threshold outcomes across three different populations. Design: Two commercially available tests of auditory gap detection (Random gap detection (RGDT) test, and Gaps-in-noise (GIN) test) were administered to all participants. Study sample: Adult professional musicians (APM) (N = 11, age range 28–61 years); children with central auditory processing disorder (CAPD) (N = 22, age range 7.5–17 years); and first episode psychosis patients (FEP) (N = 17, age range 18–48 years). Results: It was not possible to calculate a threshold for the RGDT for 13 of 22 children with CAPD and for 7 of 17 adults with FEP due to response inconsistency. Analysis of variance (ANOVA) excluding cases that produced inconsistent RGDT results showed that only RGDT thresholds differed across groups (F = 8.73, p = 0.001). Three t-tests comparing test means within group revealed statistically significant differences between the gap detection thresholds obtained with the RGDT vs. the GIN for each group. No significant correlations were seen between RGDT and GIN. Conclusion: Lower/better gap detection thresholds and smaller standard deviations were obtained using the GIN in all three groups. Lack of correlation between the two tests suggests that they may measure different processes.     

Coding of amplitude-modulated tones in the central auditory system of catfish

In the catfish central acoustic system information is coded by two subsets of units. Type I units show little or no adaptation, type II units adapt rapidly, and some units are transitional, showing moderate adaptation. The two groups of units also respond differently when exposed to sinusoidal amplitude modulation of the signal's carrier frequency. The tonic, less readily adapting type I units code over an intensity range of about 30 dB, are fairly insensitive to intensity changes, and follow stimulus envelopes of 60 Hz and less. They apparently discharge in response to the actual intensity of the signal rather than in response to something in its temporal pattern. The onset-sensitive, fast-adapting type II units on the other hand are restricted to an intensity range of only 10 dB, show greater sensitivity to intensity changes, and are capable of following the temporal pattern of amplitude-modulated stimuli exceeding 100 Hz. These units appear to code the temporal changes in the stimulus intensity irrespective of the absolute intensity of the signal.     

A time-frequency feature extraction scheme for the automated detection of binaural interaction in auditory brainstem responses

The binaural interaction component (BIC), the difference between the summed monaurally evoked potentials of each ear and the binaurally evoked brainstem potentials, has been shown to be related to directional hearing. However, the detection of the ß-peak as the most consistent part of the BIC is often difficult. Furthermore, there is no clearly defined signal feature characterizing the difference between the monaurally and the binaurally evoked brainstem responses. A closer look at the signals shows that amplitude differences as well as latency differences and variations in wave V slopes could be the reason for the formation of a ß-peak. Using a time-scale feature extraction scheme, we were able to define a signal feature (morphological local discriminant bases ( MLDB) coefficient 1) that accounts for the difference between the sum of the monaurally and binaurally evoked brainstem potentials. With use of this signal feature, reliable automated detection of differences between monaurally and binaurally evoked potentials is possible. As coefficient 1 replicates the behaviour of subjective measurements as well as of the BIC measurements, it can also be seen as a correlate of binaural interaction. With use of this signal feature, it is possible to judge from a given binaurally evoked potential whether it contains information on binaural interaction or not, without comparing it to the sum of the monaurally evoked brainstem responses. Consequently, binaural interaction can be assessed by one, instead of three, measurements by using the method described in this paper.     

The role of the efferent auditory system in developmental dyslexia

Objective

To assess the role of the efferent auditory system by inhibition of contralateral otoacoustic emission in dyslexic children with auditory processing disorders.

Methods

The study sample was 34 children: 17 with dyslexia and 17 age-matched controls. Sensitive speech tests (low-pass filtered, time-compressed, distorted and dichotic) were performed to assess coexisting auditory processing disorder. Distortion-product otoacoustic emission (DPOAE) values were measured in basal condition and with contralateral broadband noise signal delivered via an earphone transducer at 60 dB SPL.

Results

The lower scores at sensitive speech testing confirmed the association of an auditory processing disorder in the dyslexic children. DPOAE values were significantly attenuated by contralateral inhibition only in the control group (p = 0.001; dyslexics, p = 0.19); attenuation was not significant at any frequency in the dyslexic group.

Conclusions

The differences in DPOAE attenuation between the groups, although not statistically significant, suggest alterations in the auditory efferent system in the dyslexic population. These alterations may affect language perception. If confirmed in further studies with larger samples, these results could provide insight into a possible pathophysiological background of dyslexia.