粉红噪声掩蔽下的听性脑干反应诊断早期梅尼埃病

目的 研究正常人和临床确诊为梅尼埃病的患者在粉红噪声掩蔽下的听性脑干反应(ABR)测试结果,了解粉红噪声掩蔽下的ABR对耳蜗积水的诊断意义.方法 受试对象分为两组,15例健康成人作为对照组;28例临床确诊为单侧梅尼埃病患者为梅尼埃病组.首先生成满足条件的高通粉红噪声,比较两组对象在粉红噪声掩蔽下的ABR波V潜伏期的变化.结果 对照组ABR波V缺失或明显延迟,0.5 kHz掩蔽时波V潜伏期延长均值为2.66 ms;而梅尼埃病组掩蔽噪声不能掩蔽ABR波V,波V潜伏期延长均值为0.86 ms.结论 高通粉红噪声掩蔽的条件下,ABR波V潜伏期延长可用于判断是否存在耳蜗积水.     

The Effects of Salicylate on Auditory Evoked Potential Amplitwde from the Auditory Cortex and Auditory Brainstem

Tinnitus has often been studied using salicylate in animal models as they are capable of inducing tempo-rary hearing loss and tinnitus. Studies have recently observed enhancement of auditory evoked responses of the auditory cortex (AC) post salicylate treatment which is also shown to be related to tinnitus like behavior in rats. The aim of this study was to observe if enhancements of the AC post salicylate treatment are also present at structures in the brainstem. Four male Sprague Dawley rats with AC implanted electrodes were tested for both AC and auditory brainstem response (ABR) recordings pre and post 250 mg/kg intraperitone-al injections of salicylate. The responses were recorded as the peak to trough amplitudes of P1-N1 (AC), ABR wave V, and ABR waveⅡ. AC responses resulted in statistically significant enhancement of ampli-tude at 2 hours post salicylate with 90 dB stimuli tone bursts of 4, 8, 12, and 20 kHz. Wave V of ABR re-sponses at 90 dB resulted in a statistically significant reduction of amplitude 2 hours post salicylate and a mean decrease of amplitude of 31%for 16 kHz. WaveⅡamplitudes at 2 hours post treatment were signifi-cantly reduced for 4, 12, and 20 kHz stimuli at 90 dB SPL. Our results suggest that the enhancement chang-es of the AC related to salicylate induced tinnitus are generated superior to the level of the inferior colliculus and may originate in the AC.     

高频听力损失对豚鼠低频区时间分辨率的影响

目的 构建豚鼠高频听力损失模型,通过听觉惊跳反射前抑制方法观察高频听力损失后,低频区时间分辨率的变化.方法 采用简单随机法将豚鼠分为实验组(6只)和对照组(4只),实验组暴露于声压级110 dB的12 kHz纯音下30 h,建立8 kHz以上听力损失模型,对照组未作处理.于噪声暴露前、暴露后2周、4周、6周及8周等五个时间点进行听觉惊跳反射前抑制试验和听觉脑干反应(ABR)测试.在听觉惊跳反射前抑制试验中,选用0.5～2 kHz,0.5～4 kHz和0.5～8 kHz三种背景噪音频率(均在听敏度正常的低频段)来观察低频区时间分辨率的变化.结果 噪声暴露后2周,实验组动物呈现8 kHz以上频率陡降型高频听力损失,在16 kHz、32 kHz和48 kHz频率均有平均55 dB的阈移,与声暴露前相比差异均有统计学意义(P值均＜0.05),而1 kHz、2 kHz、4 kHz和8 kHz在噪音暴露前后差异均无统计学意义(P值均＞0.05).在8周的实验期内,实验组高频听力损失仍然存在.对照组豚鼠所有频率的听敏度在实验期内各个时间点差异均无统计学意义(P值均＞0.05).实验组在8 kHz的背景噪音下,声暴露后第2周抑制能力减弱,与暴露前相比差异具有统计学意义(P=0.036),其余时间点和暴露前相比差异无统计学意义(P值均＞0.05);在4 kHz的背景噪音下,声暴露后所有时间点的抑制能力与暴露前相比差异均无统计学意义(P值均＞0.05);在2 kHz的背景噪音下,声暴露后第6周、第8周抑制能力降低,与暴露前相比差异具有统计学意义(P值均＜0.05).结论 高频听力损失可降低正常低频区的时间分辨率.

Abstract：

Objective To constitute the animal model of high frequency hearing loss and observer the temporal processing abilities of low frequency regions using prepulse inhibition of auditory startle response (gap-PPI).Methods Ten guinea pigs were randomly grouped into two groups: the high frequency hearing loss group with six guinea pigs and the control group with four guinea pigs.The former group was exposed to 12 kHz tone at 110 dB SPL for 30 hours to establish the high frequency hearing loss above 8 kHz and the latter group received no stimuations.Before and two,four,six and eight weeks after noise exposure,gapPPI and auditory brainstem response (ABR) were recorded in both groups.In the gap-PPI experiment,three different background noises as 0.5-2 kHz,0.5-4 kHz and 0.5-8 kHz were applied to test the temporal gap.Results High frequency hearing loss above 8 kHz was shown two weeks after noise exposure.The averaged ABR thresholds of 16 kHz,32 kHz and 48 kHz were elevated about 55 dB and shown statistical significance compared to those before exposure (P ＜ 0.05＝.No significant difference of ABR thresholds were shown between 1 kHz,2 kHz,4 kHz and 8kHz before and after noise exposure(P ＞0.05).In the control group,the ABR thresholds remained stable during experiment.In the gap-PPI test,two weeks after noise exposure of 8 kHz,the experiment group showed attenuated inhibition ability and recovered gradually four weeks after noise exposure.No statistical differences of inhibition ability at time points of two,four,six and eight weeks after noise exposure of 4 kHz were detected when compared with that of pre-exposure.Under the background noise of 2 kHz,the inhibition ability attenuated and reached statistical significance at 6-8 weeks after noise exposure.Conclusion The high frequency hearing loss might induce an impairment of the temporal processing in the low frequency region.     

听力筛查转诊婴幼儿不同滤波条件短纯音诱发听性脑干反应的比较

目的 短纯音诱发听性脑干反应(ABR)是听力筛查转诊婴幼儿听力评估的重要方法,本研究比较滤波分别为30～1500 Hz与30～3000 Hz时不同频率短纯音ABR阈值之间的差异,总结两种滤波条件下ABR波形特点及对阈值判断的影响,以选择更优化的频率特异性ABR测试参数.方法 应用美国IHS公司SmartEP听觉诱发电位仪记录18例(22耳)2～33月龄婴幼儿短声、滤波为30～1500 Hz与30～3000 Hz短纯音ABR各频率反应阈.结果 0.5 kHz、1 kHz、2 kHz、4 kHz滤波为30～3000 Hz短纯音ABR反应阈比滤波为30～1500 Hz短纯音ABR反应阈高.0.5 kHz及2.0 kHz两种滤波条件下短纯音ABR反应阈之间差异具有统计学意义(t值分别为2.238及2.217,P值均＜0.05),其他频率两种滤波条件下反应阈之间差异无统计学意义(P值均＞0.05).同等刺激强度下,滤波为30～3000 Hz的ABR波形与30～1500 Hz相比不平滑,反应波曲线上会出现锯齿状细小的干扰波.结论 在用短纯音ABR反应阈评估婴幼儿听力时,30～1500 Hz可以作为更优化的滤波设置参数.

Abstract：

Objective Auditory brainstem responses (ABR) evoked by tone burst is an important method of hearing assessment in referral infants after hearing screening. The present study was to compare the thresholds of tone burst ABR with filter settings of 30 - 1500 Hz and 30 - 3000 Hz at each frequency,figure out the characteristics of ABR thresholds with the two filter settings and the effect of the waveform judgement, so as to select a more optimal frequency specific ABR test parameter. Methods Thresholds with filter settings of 30 - 1500 Hz and 30 -3000 Hz in children aged 2 -33 months were recorded by click,tone burst ABR. A total of 18 patients ( 8 male / 10 female), 22 ears were included. Results The thresholds of tone burst ABR with filter settings of 30 - 3000 Hz were higher than that with filter settings of 30 - 1500 Hz. Significant difference was detected for that at 0. 5 kHz and 2.0 kHz ( t values were 2.238 and 2. 217, P ＜ 0. 05 ), no significant difference between the two filter settings was detected at the rest frequencies tone evoked ABR thresholds. The waveform of ABR with filter settings of 30 - 1500 Hz was smoother than that with filter settings of 30 - 3000 Hz at the same stimulus intensity. Response curve of the latter appeared jagged small interfering wave. Conclusions The filter setting of 30 - 1500 Hz may be a more optimal parameter of frequency specific ABR to improve the accuracy of frequency specificity ABR for infants' hearing assessment.     

EFFECTS OF MODERATE NOISE EXPOSURE ON HEARING FUNCTION IN C57BL/6J MICE

Objective To study characteristics of hearing loss after exposure to moderate noise exposure in C57BL/6J mice. Methods Male C57BL/6J mice with normal hearing at age of 5-6 weeks were chosen for this study. The mice were randomly sclccted to be studied immediately after exposure （Group P0）, or 1 day （Group P1）, 3 days （Group P3）, 7 day （Group P7） or 14 days （P14） after exposure. Their before exposure condition served as the normal control. All mice were exposed to a broad-band white noise at 100 dB SPL for 2 hours, ABR thresholds were used to estimate hearing status at each time point. Results ABR threshold elevation was seen at every tested frequency at P0 （P〈0.01）. Elevation at high-frequencies （16 kHz and 32 kHz） was greater than at lower frequencies （4 kHz and 8 kHz, P〈0.05）. From P1 to P14, ABR thresholds continuously improved, and there was no significant difference between P14 and before exposure （P〉0.05）. Conclusion There is a frequency specific re- sponse to 100 dB SPL broad-band white noise in C57BL/6J mice, with the high-frequency being more susceptible. Hearing loss induced by moderate noise exposure appears reversible in C57BL/6J mice.     

不同病因引起的新生儿高胆红素血症听性脑干反应的特点

目的 探讨不同病因引起的新生儿高胆红素血症的听性脑干反应(ABR)特点及其与临床的关系.方法 将88例(176耳)高胆红素血症患儿按病因分为6组,同时选取15名(30耳)健康新生儿作为正常对照,均进行ABR测试,并比较各组间的差异,42 d后患儿复查ABR.结果 不同病因中,葡萄糖6-磷酸脱氢酶(glucose-6-phosphate dehydrogenase,G-6-PD)缺乏症所致的高胆红素血症ABR反应阈增高最明显,异常率最高.不同病因组之间及与对照组间ABR的Ⅲ波、Ⅴ波潜伏期及Ⅲ-Ⅴ、Ⅰ-Ⅴ波间期差异均具有统计学意义(P值均＜0.05).高胆红素血症患儿ABR各波潜伏期及波间期均较对照组延长,其中新生儿感染最容易引起ABR各波潜伏期及波间期延长,其次是ABO溶血与其他不明原因组,母乳性黄疸组潜伏期与波间期相对要短.多病因组ABR反应阈的异常率明显高于单病因组(P＜0.05);单种病因与多种病因引起的高胆红素血症组间比较,ABR各波潜伏期及波间期差异无统计学意义(P值均＞0.05).30例患儿进行了复查,复查前后除Ⅰ-Ⅲ波间期外,各波潜伏期及波间期差异均具有统计学意义(P值均＜0.05).结论 高胆红素血症对听觉系统的损害与病因的种类及数量有关.由G-6-PD缺乏、新生儿感染、ABO溶血、多病因以及不明原因引起的高胆红素血症与母乳性黄疸相比,更易导致听觉功能损害.高胆红素血症对听觉的损害存在一定的可逆性.

Abstract：

Objective To explore the characteristics of auditory brainstem response (ABR) in neonatal hyperbilirubinemia induced by different causes. Methods A total of 88 neonates ( 176 ears) with hyperbilirubinemia were divided into several groups according to the causes and followed up after 42 d, and 15 nomal neontes (30 ears) were measured ABR and analyzed the results. Results The thresholds of ABR in glucose-6-phosphate dehydrogenase were the highest in all the groups and had the lowdest incidence rate.The wave Ⅲ, Ⅴ latencies and Ⅲ-Ⅴ, Ⅰ -Ⅴ interwave intervals of the ABR were significantly difference and prolonged during test in comparison to the latencies in the control group ( P ＜ 0. 05 ). The neonatal infections group had the longest wave and interwave intervals, followed by ABO incompatibility hemolytic diseases and the unknown cause groups, while the breastfeeding jaundice were the shortest in the groups of neonatal hyperbilirubinemia. The thresholds of ABR in the hyperbilirubinemia caused by several etiologies were significant abnomality when compared with the single etiology. However, they were similar in the wave latencies and interwave intervals of ABR. During the follow up, the ABR wave latencies and interwave intervals except for interwave latency Ⅰ-Ⅲ were significantly shorter. Conclusions The toxicity of hyperbilirubinemia to the auditory nervous system are related to the species and number of etiologies. The neonate hyperbilirubinemia cuased by glucose-6-phosphate dehydrogenase, infections, ABO incompatibility hemolytic diseases and many etiologies are much more dangerous to the auditory system than the breastfeeding jaundice. The damages of hyperbilirubinemia to the auditory nervous system are reversible probably.     

Speech perception in noise: Masking and unmasking

Speech perception is essential for daily communication.Background noise or concurrent talkers,on the other hand,can make it challenging for listeners to track the target speech(i.e.,cocktail party problem).The present study reviews and compares existing findings on speech perception and unmasking in cocktail party listening environments in English and Mandarin Chinese.The review starts with an introduction section followed by related concepts of auditory masking.The next two sections review factors that release speech perception from masking in English and Mandarin Chinese,respectively.The last section presents an overall summary of the findings with comparisons between the two languages.Future research directions with respect to the difference in literature on the reviewed topic between the two languages are also discussed.     

压耳式及插入式耳机给声诱发听性脑干反应

目的比较以压耳式及插入式耳机给声诱发的听性脑干反应(ABR)的差异。方法以TDH-39P压耳式和ER-3A插入式耳机给声,通过真耳测试短声在外耳道的频谱图,对一组听力正常青年人(男30耳,女24耳)进行短声诱发ABR测试,并观察对侧给予白噪声掩蔽后ABR反应阈的改变。结果两种给声方式诱发出极为相似的ABR波形,两者反应阈及潜伏期均无显著性差异(P>0.05)。采用插入式耳机对侧加40～70dBSPL强度的白噪声对ABR的阈值及阈上10dB强度下波V潜伏期均无显著性影响(P>0.05)。真耳分析测试结果显示两种耳机给声方式下外耳道短声的频谱图极为相似,仅强度相差3dB(0.5～4kHz)。结论插入式和压耳式耳机给声方式的ABR测试结果之间无显著性差异。为此,建议临床中应准备两种给声方式并获取相应的正常值,以便使用时灵活选择。插入式耳机对侧给声的ABR掩蔽不存在中枢掩蔽现象。     

Contralateral Suppression of Distortion Product Otoacoustic Emission in Children with Auditory Processing Disorders

Previous research has demonstrated that the amplitude of evoked emissions decreases in human sub-jects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is be-lieved to control this phenomenon. Recent research has examined this effect in individuals with auditory pro-cessing disorders (APD), specifically with difficulty understanding speech in noise. Results showed tran-sient evoked otoacoustic emissions (TEOAEs) were not affected by contralateral stimulation in these sub-jects. Much clinical research has measured the function of the MOCB through TEOAEs.This study will use an alternative technique, distortion product otoacoustic emissions (DPOAEs), to examine this phenomenon and evaluate the function of the MOCB. DPOAEs of individuals in a control group with normal hearing and no significant auditory processing difficulties were compared to the DPOAEs of children with signifi-cant auditory processing difficulties.Results showed that the suppression effect was observed in the control group at 2 kHz with 3 kHz of narrowband noise. For the auditory processing disorders group, no significant suppression was observed.Overall, DPOAEs showed suppression with contralateral noise, while the APD group levels increased overall.These results provide further evidence that the MOCB may have reduced function in children with APD.     

3种不同条件短纯音诱发听性脑干反应频率特异性观察

目的 :观察比较线性窗短纯音、加宽频带噪声掩蔽的线性窗短纯音及Blackman窗门控短纯音对听性脑干反应 (ABR)频率特异性的影响。方法 :16例听力正常成年人分别接受 3种不同条件短纯音诱发的ABR测试 ,记录各自在 1、2、4kHz不同声强下的ABR波V潜伏期。结果与结论 :① 4、2kHz各刺激声强及 1kHz 70dBnHL以下声强时 ,3种不同条件短纯音有着相同的频率特异性 ;在低频 (1kHz)高声强 (≥ 70dBnHL)时 ,线性窗短纯音因有频谱播散现象而需加用掩蔽噪声来改善频率特异性或需直接采用Blackman窗门控短纯音。②宽频带噪声掩蔽短纯音及Blackman窗门控短纯音在 1、2、4kHz各刺激强度下可获得相同的频率特异性反应 ,但宽频带噪声掩蔽短纯音诱发的反应振幅相对较小 ,因此Blackman窗短纯音更为可取     

An alternative diagnostic test for active Ménière's disease and cochlear hydrops using high-pass noise masked responses: the complex amplitude ratio

We [Don et al.: Otol Neurotol 2005;26:711-722] previously demonstrated that patients diagnosed with an active case of Ménière's disease could be distinguished from non-Ménière's normal-hearing subjects by a special auditory brainstem response method involving clicks and ipsilateral high-pass masking pink noise. Specifically, auditory brainstem responses to clicks presented alone and clicks with masking noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz were recorded. It was shown that the level of masking noise sufficient to progressively mask the response to clicks in non-Ménière's normal-hearing subjects was insufficient to appropriately mask the responses in Ménière's disease subjects, resulting in an obvious undermasked component. A relative latency measure of wave V or the undermasked component in the response to clicks with 0.5 kHz high-pass masking noise and wave V in the response to clicks presented alone clearly distinguished these two groups on an individual level, thus making it a valuable clinical tool. However, determining the peak latency of wave V or the undermasked component can be difficult in some cases. In anticipation of this difficulty, we investigated and present in this paper several amplitude measures that may help in the evaluation of these cases. One amplitude measure, the 'complex amplitude ratio', appears to be a good alternative when the latency measure of the undermasked component is difficult to determine.     

Auditory brain stem response in newborn infants--masking effect on ipsi- and contralateral recording

Ipsilateral and contralateral auditory brain stem responses (ABR) were recorded in 10 full-term neonates. We investigated the effect of the masking level on the peak latency and amplitude on ipsi- and contralateral recordings. Clicks were presented at 85 dB HL to the ipsilateral ear and the masking white noise was presented at 75, 65, 55, 45 and 0 dB HL on the contralateral one, respectively. Masking had no significant effect on the ipsi- and contralateral recording in regard to latency and amplitude except for wave CVI (contralateral wave VI). In addition, ABR was recorded in an infant with total unilateral hearing loss. Crossover responses on both sides were observed with-out contralateral masking, but these responses were completely eliminated when 45 dB HL contralateral masking masked the 85 dB HL clicks to the dead ear. Therefore, it is suggested that such crossover responses will contribute to the ipsi- and contralaterally recorded ABR waveform when an ABR recording is carried out without contralateral masking. Our results indicate that contralateral masking is necessary and should be used in cases of unilateral hearing loss.     

A diagnostic test for Ménière's Disease and Cochlear Hydrops: impaired high-pass noise masking of auditory brainstem responses.

HYPOTHESIS: Endolymphatic hydrops in patients diagnosed with Ménière's disease causes changes in the response properties of the basilar membrane that lead to impaired high-pass noise masking of auditory brainstem responses to clicks. BACKGROUND: Ménière's disease is defined as the idiopathic syndrome of endolymphatic (cochlear) hydrops, which is an abnormal increase in the volume of cochlear fluid (endolymph) in the inner ear. Accurate detection and diagnosis are important but difficult because of the lack of sufficiently sensitive tests. METHODS: Two populations were compared: (1) 38 non-Ménière's normal-hearing subjects; and (2) 23 patients who, at the time of testing, continued to have at least three of the four hallmark symptoms (i.e., tinnitus, vertigo, fluctuating hearing loss, and fullness) used in the diagnosis of Ménière's disease. Auditory brainstem responses to clicks presented ipsilaterally with masking noise that was high-pass filtered at various frequencies were recorded. RESULTS: In the Ménière's patients, the masking noise is insufficient such that an undermasked Wave V is still present at a latency similar to that of Wave V in the response to the clicks alone. In the control non-Ménière's normal-hearing subjects, this undermasked component was either absent or significantly delayed because of the masking noise. The difference in the delays between these populations is such that the distributions do not overlap, resulting in 100% sensitivity and 100% specificity. CONCLUSION: This test is able to distinguish objectively active Ménière's disease in individuals and may show promise for tracking changes in the severity of the disease caused by progression or treatment.     

The selective effects of central masking on brain stem potentials

The effect of contralateral white noise stimulation on ipsilaterally presented click evoked brain stem potentials was examined. Continuous contralateral white noise does not influence the brain stem response components but pulsed white noise simultaneously presented with the clicks produced a central masking effect which was observed as an amplitude reduction confined to Wave V. Our findings confirm those of Zwislocki (1971) that pulsed noise is a more effective central masker than continuous noise. A computer addition of the responses to pulsed white noise and clicks recorded independently revealed no reduction in Wave V amplitude but the response to the two stimuli presented simultaneously showed a specific reduction in Wave V amplitude. No change in the latency of Wave V was observed to suggest any 'cross-over' masking of the click stimulus. Patients with total unilateral deafness did not exhibit this phenomenon. The effect of a time delay of the masker to one ear in relation to the click presented to the other ear reduced the amplitude of Wave V less than when the two stimuli were presented simultaneously. The reduction in the amplitude, being specific to Wave V, suggests that the effect is central and that the particular locus for this aspect of central masking is at the level of the inferior colliculus.     

Contribution of various frequency bands to ABR in dolphins

Auditory brainstem responses (ABR) to clicks and noise bursts of various frequency bands and intensities were recorded in two bottlenosed dolphins, Tursiops truncatus. The purpose was to assess contributions of various parts of the cochlear partition to ABR and travelling wave velocity in the cochlea. At band-pass filtered stimuli (1-0.25 oct wide), ABR amplitude increased with increasing stimulus frequency, thus indicating higher contribution of basal cochlear parts. At high-pass and low-pass filtered stimuli, ABR amplitude increased with passband widening. However, the sum of all narrow-band contributions was a waveform of higher amplitude than the real ABR evoked by the wide-band stimulus. Applying a correction based on an assumption that the 'internal spectrum' is about 0.4 oct wider than the nominal stimulus spectrum resulted in the sum of narrow-band contributions equal to the wide-band ABR. The travelling wave velocity was computed based on ABR latencies and assigned a frequency of 128 kHz to the basal end of the cochlea. The computation gave values from 38.2 oct/ms at the proximal end of the basilar membrane to 4.0 oct/ms at a distance of 3.25 oct (13.5 kHz).     

An analysis of auditory brainstem responses in infants

Acoustic brainstem responses (ABRs) were recorded from 148 infants from 4 to 60 weeks of age. 28 subjects returned to the laboratory 3 or more times for additional recordings. Filtered clicks of 1, 2, 4 and 8 kHz were presented at two intensities, 30 and 50 dB HL re the average threshold for a group of young adults. Responses to a broadband click, 50 dB nHL, were also recorded. The latencies of waves I, III and V were measured. Wave I latencies for the 8 kHz filtered click showed no change but those for lower frequencies decreased with age. The latency decreases with age were largest for wave V, and, among the filtered clicks, was largest for the responses to 1 kHz. Best-fitting curves were determined for latency vs. age for each filtered click and for the broadband click. Wave V —Wave I latency differences showed that the rostral conduction time for responses to the 8 kHz FC decreased with age and, for the 1 kHz filtered click (50 dB), remained constant. The early development of basal regions in the cochlea is viewed as insuring the delivery of a wide range of frequencies to rostral segments of the auditory system. The limiting feature of maturation is at rostral sites. The immature auditory system appears to be fully capable of transducing low frequency stimuli, but not high frequencies.     

正常成年Wistar大鼠短声及短纯音听性脑干反应波形分析

目的：分析正常 Wistar 大鼠短声（click）及短纯音（tone burst,TB）诱发听性脑干反应（cABR、tb-ABR）结果,标准化 Wistar大鼠ABR测试方法,为大鼠听觉研究提供参考。方法正常成年雄性 Wistar 大鼠15只,分别进行cABR和tbABR（4、8、12、16、24、32 kHz）测试,观察80、50、20 dB SPL 强度下各波的引出率,以引出率最高的波来判断阈值,同时量取该波的潜伏期和幅值,检测ABR波Ⅱ、Ⅳ振幅I／O曲线。结果①20 dB SPL强度下cABR和tbABR波Ⅱ和波Ⅳ最晚消失的比例几乎相同;②cABR 阈值为21．83±4．45 dB SPL,4～32 kHz 频率tbABR阈值分别为24．33±5．37、14．17±4．37、14．33±4．68、16．67±4．22、23．00±5．81、31．00±7．36 dB SPL;③80 dB SPL cABR波Ⅰa、Ⅰb、Ⅱ、Ⅲ、Ⅳ、Ⅴ潜伏期分别为1．76±0．12、2．13±0．11、2．67±0．16、3．49±0．28、4．39±0．29、5．45±0．41 ms,tbABR 4 kHz波Ⅰa、Ⅰb、Ⅱ、Ⅲ、Ⅳ、Ⅴ潜伏期分别为2．02±0．09、2．88±0．16、3．77±0．25、4．69±0．29、5．78±0．41 ms,8 kHz分别为1．76±0．07、2．28±0．10、2．63±0．16、3．49±0．21、4．44±0．28、5．48±0．43 ms,12 kHz分别为1．76±0．08、2．24±0．12、2．61±0．25、3．53±0．25、4．46±0．32、5．52±0．45 ms,16 kHz分别为1．79±0．10、2．25±0．12、2．70±0．18、3．62±0．27、4．52±0．37、5．61±0．49 ms,24 kHz分别为1．75±0．09、2．27±0．11、2．67±0．16、3．60±0．27、4．52±0．38、5．60±0．51 ms,32 kHz分别为1．77±0．10、2．24±0．12、2．64±0．20、3．59±0．34、4．52±0．40、5．61±0．52 ms;④I／O曲线示在高强度时波Ⅱ振幅明显高于波Ⅳ,但在低强度时,波Ⅱ振幅与波Ⅳ基本相同,甚至波Ⅳ振幅高于波Ⅱ。结论正常成年大鼠短声及短纯音诱发ABR波Ⅳ出现率最高,低强度声刺激时,波Ⅱ、Ⅳ振幅基本相同,甚至波Ⅳ振幅高于波Ⅱ,可以波Ⅳ最后消失的强度为阈值。     

Frequency specificity of the auditory brainstem response elicited by 1,000-Hz filtered clicks

In normal-hearing subjects and in subjects with a flat cochlear hearing loss, auditory brainstem responses (ABR) were recorded at various levels of a 1,000-Hz filtered click stimulus with and without high-pass filtered masking noise. The difference in latency of the major peak in the ABR for the masked and unmasked condition was zero at the ABR threshold. We regard this as proof of the frequency specificity of the 1,000-Hz filtered click-stimulated ABR threshold. The difference between ABR threshold and the subjective puretone threshold at 1,000 Hz amounted to 19 dB in normal-hearing subjects and to 10 dB in subjects with a flat cochlear hearing loss. This is probably related to loss of temporal integration and an abnormal loudness growth (recruitment).     

Contribution of click frequency bands to the human binaural interaction components

The purpose of this study was to determine the contribution of click frequency bands (broad-band, >2000 Hz, <2000 Hz and <1000 Hz) to binaural interaction components (BICs) of the human auditory brainstem evoked potentials (ABEPs). The human BICs were studied by subtracting the potentials to binaural clicks from the algebraic sum of monaurally evoked potentials to either ear. Effective frequency bands were derived using clicks alone or clicks with ipsilateral or binaural masking noise, high- or low-pass filtered at different cut-off frequencies. Analysis included single-channel vertex-cervical spinous process VII derivation of BIC and ABEP, as well as estimating the single, centrally located dipole equivalent of the surface activity from three orthogonally positioned electrode pairs, using the three-channel Lissajous' trajectory (3-CLT) analysis. All BIC 3-CLTs included three major components (labeled BdII, BeI, and BeII) approximately corresponding in latency to IIIn, V and VI ABEP peaks. All apex latencies of BIC 3-CLT, except BeI, were longer in response to <2000 Hz and <1000 Hz (low-frequency) effective clicks. Apex amplitude of components BeI and BeII of BIC 3-CLT were smaller with low-frequency effective clicks than with broad-band or high-frequency (>2000 Hz) clicks. We suggest that binaural interaction component BeI is mainly tuned to high frequencies, showing no frequency effect on latency, and decreasing in amplitude with decreasing click high frequency content. In contrast, BdII and BeII of the human BICs are evoked more synchronously by high-frequency binaural inputs, but are also sensitive to low frequencies, increasing in latency according to the cochleotopic activation pattern. These differences between BIC components may reflect their roles in sound localization.     

A comparison of the effects of broadband masking noise on the auditory brainstem response in young and older adults

We examined the effects of ipsilateral-direct, continuous, broadband noise on auditory brainstem response (ABR) wave I and V latencies and amplitudes in young adult versus older adult humans. It was hypothesized that age might influence the effects of masking noise on ABR peak latencies and/or amplitudes, given the frequent complaint of older persons' ability to process speech in background noise. Young adults had hearing thresholds of 20 dB HL or better for the octave frequencies from 250 to 8,000 Hz. A subset of older study participants had thresholds of 20 dB HL or better across frequency, but others had thresholds up to 45 dB HL. All data were collected and analyzed with a Nicolet Bravo. An electrode was placed on the tympanic membrane (as well as on high forehead and contralateral mastoid), and a click level of 115 dB pSPL was used to maximize wave I amplitude. Masker conditions included a no-noise control and noise levels ranging from 20 to 70 dB effective masking, in 10 dB steps. With increasing noise level, both age groups showed minimal changes in wave I latency, but substantial increases in wave V latency and I-V interval. Peak amplitudes decreased with increasing noise level. Mean amplitudes were smaller for the older group, most notably for wave I. Mean peak latencies were greater in the older group, but the I-V interval was similar across age groups, as was the change in peak latencies and I-V interval across noise level. ABR parameters for the older adults with hearing meeting the 20-dB HL criterion at all frequencies (older-better) were compared to those who didn't meet this criterion (older-worse). Mean wave I latency was greater and wave V latency and I-V interval were smaller for the older-worse group at all noise levels. Mean wave I and V amplitudes were similar for the older-better and older-worse groups. In participants with normal or near-normal hearing, ABR changes with increasing age included small latency increases and a substantial reduction in wave I amplitude. The effects of ipsilateral-direct masking noise on the click-evoked ABR are similar for young and older adults.