Middle latency response: frequency and intensity effects

Auditory middle latency responses (MLR) and auditory brainstem responses (ABR) were measured with epidural electrodes in unanesthetized gerbils. Response thresholds of simultaneously recorded MLRs and ABRs, and latencies and amplitudes of MLR peaks were analyzed with respect to stimulus intensity (10-80 dB SPL) and frequency (0.5, 1, 2, 4, 8 and 16 kHz). Only minor changes in the latencies of the MLR were associated with increases in stimulus intensity. Changes in latencies were more apparent for waves A and B as compared to wave C, and were significant only at low intensities. Latencies did not change significantly as a function of stimulus frequency. Amplitudes of the MLR were highly variable between animals, particularly waves B and C, and showed complex changes with intensity. In general, wave amplitudes were inversely related to stimulus frequency. The gerbil MLR resembles MLRs recorded under similar conditions in guinea pig, cat, and rat. Some qualitative similarities between gerbil and human MLRs are apparent. Results indicate that the MLR is a less sensitive measure of hearing threshold relative to the fast waves of the ABR at frequencies above 1 kHz. However, clearly defined MLRs are elicited with a wide range of stimulus frequencies. Because the surface recorded MLR reflects activation of central auditory pathways, including the cortex, it may provide an electrophysiological measure which can be utilized to study central components of normal and pathological auditory function.     

Auditory brainstem and middle latency responses in non-human primates

Auditory brainstem (ABR) and middle latency responses (MLR) were obtained from each ear in 8 crab-eating macaques, 4 white-handed gibbons, 4 siamangs and 2 orangutans. Macaques ranged in age from 5 days to 15 years with the 6 older animals in age-matched, male-female pairs. From each animal, latency-intensity functions were obtained and multiple MLR recordings were measured at 60 and 70 dB. Latency-intensity functions, interwave intervals, thresholds and percent detectability were calculated for ABR waveforms. Waves II and IV were largest in amplitude and were most consistently detected at low stimulus intensities in all species tested. Waves I and II had adult latencies in the youngest animal tested (5-day-old macaque), while waves III and IV were prolonged in comparison to the 15-month-old macaque, in whom latencies had reached adult values. There were no apparent sex differences in evoked potentials in the age-matched, male-female pairs. A broad, negative MLR at 7-13 ms was observed in all animals. Longer latency MLRs varied among animals of the same species, but were replicable in some individuals, including the youngest macaque (5 days) and orangutan (7 months). These data were compared to responses obtained in humans, other primates and other vertebrates.     

Development of the middle latency response in an animal model and its relation to the human response

Although the clinical use of the middle latency response (MLR) in adults is fairly straightforward, its use is complicated by maturational changes that continue throughout the first decade of life. In order to telescope the time period of this long developmental course, we have approached the study of MLR maturation using the gerbil as an animal model. The course of MLR obtained over the temporal lobe development was characterized in the Mongolian gerbil ranging in age from 10 days to 3 months of life. The adult gerbil MLR consists of two positive peaks (A and C) at 11 and 25 ms, respectively, and a negative component (B) at 16 ms. These components emerge in a systematic fashion as a function of age. The present work supports a strong age effect of increased MLR detectability in the gerbil, similar to findings reported for humans. Wave A was infrequently detected in young animals, but when present, it occurred at adult latencies. The latency of waves B and C decreased systematically with age. The amplitude of all components increased with age, similar to findings in humans. The fact that adult-like thresholds were obtained shortly after birth indicates that when present, MLRs may be a good index of hearing threshold. Effects of stimulating across a wide range of intensities were described. The gerbil model appears appropriate for the study of development of the central auditory system function.     

Effect of caffeine on central auditory pathways: an evoked potential study

Caffeine is consumed in various forms like tea, coffee, chocolates and colas. The present study evaluated the effect of caffeine on auditory brainstem response (ABR), mid latency response (MLR) and slow vertex response (SVR) in 40 male volunteers. The recordings were done using a computerized evoked potential recorder by 10–20 electrode placement system. The subjects consumed 3 mg/kg body weight of caffeine after 12 h abstinence from caffeine in any form. The data obtained revealed that latencies of waves IV and V along with I–V interpeak interval of ABR decreased significantly. This was accompanied with significant increase in amplitude of wave V. MLR latencies and latency of P1 wave of SVR was significantly decreased following caffeine ingestion. The results indicated that caffeine improves transmission in the peripheral and central brain auditory pathways.     

Maturation of auditory evoked potentials in young guinea pigs with binaural conductive hearing loss

Summary A reversible conductive hearing loss produced during the first 4 weeks post partum caused marked alterations in the development of click-evoked auditory brainstem (ABR) and middle latency (MLR) responses in guinea pigs. The early component PI in the ABR in controls showed adult-like latencies at the time of birth, while the later ABR components P_III and P_V and all components investigated in the MLR showed postnatal development characterized by a shortened latency that persisted for the whole period of investigation. The course of the ABR latencies showed the sharpest decrease during the first 2–3 weeks of life, while that for the MLR took place during the first 5 weeks. In addition to the increased ABR thresholds and lengthened ABR latencies due to the conductive hearing loss, development of the ABR inter-peak latencies (IPL) and MLR latencies was retarded. The IPL reached control values 1 week after the end of the deprivation phase, while the delay in MLR started later (4th week) and lasted longer than did that in the ABR. These findings showed that a long-lasting postnatal conductive hearing loss does not generate sustained impairment at the level of the brainstem but can evoke longer-lasting deficiencies at higher stations of the auditory pathway.     

Frequency selectivity of the middle latency response

A forward masking paradigm was used to assess the frequency selectivity of the middle latency response (MLR). Tuning curves of the MLR were obtained in unanesthetized gerbils. Changes in the amplitudes of MLR waves A, B, and C with latency values of 10 to 13 ms, 14 to 17 ms, and 20 to 25 ms, respectively, were analyzed as a function of masker frequency and intensity. Tuning curves of the MLR were also compared to tuning curves of the auditory brainstem response (ABR), which was recorded simultaneously with the MLR. The MLR and ABR differed in their response to forward masking. The MLR was reduced in amplitude or eliminated by masker stimuli that had minimal or no effect on the ABR. Forward masking often caused variable and non-monotonic changes in the amplitude of the MLR. Tuning curves of the MLR indicate that the MLR is less frequency selective than the ABR. The MLR is an electrophysiological measure of auditory function central to the auditory brainstem. Therefore, it may provide information concerning central components of normal and pathological auditory function. However, because of the variability of MLR amplitudes with forward masking, tuning curves of the MLR are difficult to obtain and are not efficient for routine measurements of frequency selectivity.     

Computer-assisted ABR interpretation using the automatic construction of the latency-intensity curve

In this paper, we present a new computerised technique for the automatic construction of the latency intensity curve (LI curve). We take a pattern recognition approach determined by a priori information. We use knowledge gained from the audiogram and from physiological considerations. Therefore, we consider all recordings at different intensities as well as results from the extraction of a single auditory brainstem response (ABR) at a given stimulus intensity. We tested our method successfully: it allows us to prevent misrecognition errors in response detection or in latency measurements. Automatic recognition of the waves and recognition by the ear, nose and throat (ENT) specialist coincided in at least 90 per cent of cases. For wave V, the average deviation between the response thresholds given by our automatic recognition algorithm and those given by the ENT specialist was 5 dB, and the average deviation of the latencies was 0.05 ms.     

The normative basis for click and frequency-specific BERA in high-risk infants

The use of brainstem electric response audiometry (BERA) for early detection of hearing loss is predicated upon large-sample normative data. Auditory brainstem response (ABR) thresholds for click and notch-masked tonepip stimuli were examined in 230 normal infants with no risk factors for hearing loss, tested under audiometrically ideal conditions at between 48 and 56 weeks post-conception. The ABR threshold distributions for clicks and tonepips differed considerably. Almost all infants had click thresholds consistent with normal hearing on adult criteria, whereas many appeared to have hearing loss at 500 Hz. ABR latencies for 70 dBnHL clicks were more variable than expected, even in infants with click thresholds of 30 dB or better. In males, wave V latency was about 0.2 ms larger than in females, but there was no such difference for wave I. For both sexes, there was a linear decrease in wave V latency with age at approximately 0.1 ms per month, but wave I latency was constant.     

Gender effects in auditory brainstem responses to air- and bone-conducted clicks in neonates.

Examinations of gender differences in auditory brainstem response (ABR) wave V latencies and thresholds to air- and bone-conducted clicks were undertaken with neonates. Two hundred and two full-term neonates participated (i.e., 103 males and 99 females). Wave V latency measures for air- and bone-conducted click stimuli of 30, 45, and 60 dB nHL and 15 and 30 dB nHL, respectively, and thresholds to air- and bone-conducted clicks were determined. Female newborns displayed statistically significant shorter wave V latencies than male newborns for air-conducted click stimuli (i.e., approximately 0.2-0.3 ms; P=.0016). There were no significant gender differences in wave V latencies to bone-conducted click stimuli (P=.11). With respect to ABR thresholds, no statistically significant differences were observed for either air-conducted clicks (P=.054) or bone-conducted clicks (P=.18). Educational objectives: As a result of this activity, the participant will be able to (1) describe gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates and (2) summarize possible explanations for observed gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates.     

正常气骨导听性脑干反应及其应用

［摘要］目的：研究骨导听性脑干反应(ABR)的波形特点及正常的气、骨导ABR Ⅴ波潜伏期-强度曲线及相应的反应阈值,为临床气导ABR（AC ABR）和骨导ABR(BC ABR)的联合应用提供参考依据。方法：利用Nicolet spirit型诱发电位仪、EAR 3A插入式耳机和Radioear B 71骨振动器对一组听力正常年轻人（男32耳、女24耳）进行短声气骨导ABR测试,并观察对侧给予白噪声掩蔽对BC ABR阈值及潜伏期的影响。结果：气骨导ABR相应强度下波形相似波Ⅴ潜伏期－强度曲线表明,随着刺激强度逐渐减低,潜伏期逐渐延长。骨导Click的潜伏期要比气导Click潜伏期延长的程度大,BC ABR反应阈比气导ABR高。对侧70?dBSPL以下强度宽带噪声的使用对BC ABR阈值及阈上10?dB强度下波Ⅴ潜伏期均无显著影响（P＞0.05）。结论：(1) BC ABR波形特点与相应刺激强度的AC ABR极为相似。BC ABR与AC ABR潜伏期-强度函数曲线可望联合用于传导障碍及其程度的评估;(2) 骨导行为的听阈水平超过40?dBHL时,BC ABR难以引出,对其结果的解释应持慎重态度;(3) 骨导ABR测试时常规加对侧噪声掩蔽,但掩蔽声强度不应超过60?dB。     

Comparisons of the development of auditory brainstem response latencies between cats and humans.

Developmental changes in the peak latencies of auditory brainstem responses (ABR) recorded from humans and kittens were compared to test the hypothesis that developmental time courses among mammals are the same when appropriately normalized. Response latencies were computed as the difference from adult latency and conceptional ages were represented as percentages relative to the age that ABR wave latencies achieved a criterion value within 0.2 ms of asymptotic latency (i.e., adulthood). An underlying assumption of this exercise is that far-field response latency is an appropriate index of overall 'auditory development'. Results of this analysis suggest that developmental changes in latency of responses arising within the auditory periphery are similar between humans and cats, when appropriately normalized, and that more central changes show less correspondence. Consequently, absolute time course differences for specific developmental parameters must be considered and caution should be exercised when extrapolating results acquired from one species to the other.     

Functional development of the auditory brainstem in the tammar wallaby (Macropus eugenii): the superior olivary complex and its relationship with the auditory brainstem response (ABR)

Twenty pouch-young tammar wallabies (Macropus eugenii) were used to determine the generator of the auditory brainstem response (ABR) during development through ABR and focal superior olivary complex (SO) recordings. A click response from the SO in the wallaby was recorded from postnatal day (PND) 112 when the ABR was only a positive-negative deflection. Before PND 120, the SO response did not contribute to the ABR as it occurred outside the ABR time-span. After PND 140, the SO response was correlated with multiple waves of the ABR with its dominant component corresponding to the ABR P3 wave. The latency, threshold, and amplitude of the SO response developed to the adult-like level at PND 140, while the rate-following ability in the SO response reached the adult level at PND 160. Presumably this was due to more complicated mechanisms underlying the auditory adaptation. The adaptation of the SO response was directly proportional to the stimulus rate and intensity as well as developmental status. Developmental comparison between the ABR and the focal responses from four auditory brainstem nuclei indicated that each ABR component may have a dominant contributor from the auditory brainstem, but there was no simple and exclusive association between the ABR component and the auditory brainstem nuclei.     

Auditory brainstem responses in young children with Down's syndrome

Auditory brainstem evoked responses (ABRs) were studied in 37 Japanese infants and children with Down's syndrome to determine the level of the lesion causing their unresponsiveness to sound stimuli. ABR thresholds, peak latencies of waves I and the peak interval latency of wave I-V were measured. For comparison with ABR thresholds, behavioral audiometry was performed. Thirty-two percent of the patients (12 cases) with Down's syndrome showed no responses by ABR as well as behavioral audiometry. The other ABR abnormalities with respect to age-matched controls were classified into 6 types: shorter wave I latencies (2 cases, 5%), shorter wave V latencies (7 cases, 19%), shorter wave I-V intervals (8 cases, 22%), wave I prolongation (13 cases, 35%), wave V prolongation (5 cases, 14%) and prolongation of wave I-V peak interval (no case, 0%). Our results demonstrate a high incidence of hearing loss at middle and inner ear levels, and suggest some anomaly within the auditory brainstem in Japanese cases of Down's syndrome.     

Estrogen treatment and age effects on auditory brainstem responses in the post-breeding Long-Evans rat

The auditory brainstem response (ABR) was recorded from 20-month-old Long Evans hooded female rats to determine if latency reductions occur from estrogen replacement. The ABR in these post-breeding age rats was also examined for reductions in response latencies as a function of adult age. Tone pip stimuli (8 and 40 kHz) were presented at 21, 51, or 81 s(-1). Aging control and ovariectomized animals showed slower response latencies for waves Ib-VI than young adults for 8 and 40 kHz stimulation at 21 s(-1). Increased stimulus rate resulted in longer latencies for all waves at 20 months. In contrast to hormone treatment effects in young adults, ABR latencies in post-breeding age estrogen-treated animals were not reduced, consistent with a general decrease in CNS responsiveness to estrogen steroids associated with age. The results also suggest that sensorineural modifications in the auditory system which prolong ABR latencies can occur early in the aging process of adult female subjects.     

Auditory brain stem responses of kernicterus infants

Auditory brainstem evoked responses (ABRs) and behavioral audiometry in 25 infants with kernicterus were studied to determine the level of the lesion causing their hearing disorders. ABR thresholds, peak latencies of wave I and V, and interwave latency of wave V-I were measured; behavioral audiometric thresholds were determined through conditioned orientation reflex audiometry (COR).Eighty-eight per cent of infants with kernicterus who showed ABR threshold elevation with respect to age-matched normals, were found to show ABR abnormalities associated with peripheral hearing loss, and 84% of these were found to have COR threshold elevation.The ABR abnormalities were threshold elevation of wave V, prolonged latency of wave I and V, and the absence of ABRs. However, no brainstem lesion pattern was found in our cases.Our results suggested that at least some lesions which produce hearing disorders in kernicterus occur in the cochlea or auditory nerve.     

脑干肿瘤切除术中的听性脑干反应分析

目的 探索脑干肿瘤手术中听性脑干反应（ＡＢＲ）变化规律及其监护作用。方法 对５例脑干肿瘤手术患者,从术前、术中至术后进行了ＡＢＲ的动态观察,对术中监护记录的４００余份ＡＢＲ的潜伏期、振幅和波形分化的资料进行分析和统计学处理。结果 术中牵拉、分离、挤压均可引起ＡＢＲⅠ、Ⅲ和Ｖ波潜伏期延长,振幅降低,波形分化差等改变,其中３例动态变化指标好,呈可逆性变化,均康复出院。另２例术后潜伏期持续延长、波形分化     

Einfluß monauraler Deprivation auf die Reifung der Hörbahn bei der mongolischen Wüstenrennmaus (Meriones unguiculatus)

Several investigations prove that monaural acoustic deprivation induces detrimental changes in the auditory pathway. So far the major interest focused on degenerative processes on the deprived side, while effects on the contralateral untreated side were not taken into consideration. This ontogenetic study investigates effects of early monaural acoustic deprivation on the functional development of the acoustically evoked auditory brainstem response (ABR) in the Mongolian gerbil. Young gerbils were deafened by a single intracochlear application of neomycin sulfate. The ABR development on the contralateral side differed in a late developmental period from that of normally hearing animals. These changes persisted until adulthood. Between day 55 and day 90 a significant 5 dB decrease of the ABR thresholds and a significant shortening of the interpeak latency II-V occurred. The results confirm that a complete monaural deprivation during the sensible or critical period leads on the contralateral side to plastic or compensatory changes in the auditory brainstem.     

正常新生儿和婴儿的短音听性脑干反应和听觉稳态反应

目的 建立听力正常婴儿短音听性脑干反应(tone-pip ABR)和听觉稳态反应(auditorysteady state response,ASSR)反应阈的正常参考值,研究其听觉发育的生物学规律,并比较两种听力检测技术的频率特性.方法 选取0～6月龄听力正常婴儿80例(160耳),按月龄分为四组:新生儿组、42 d组、3月龄组和6月龄组,每组20例(40耳),男女例数均等,分别记录其短声ABR的潜伏期及在0.25、0.5、1、2、4、8 kHz频率范围内tone-pip ABR和ASSR的反应阈.结果 在70 dB正常听力级短声刺激下,短声ABRⅠ、Ⅲ、Ⅴ波潜伏期、Ⅰ～Ⅲ、Ⅲ～Ⅴ、Ⅰ～Ⅴ波间期随月龄增加逐渐缩短,波Ⅰ于42 d前、波Ⅲ于3个月前发育变化显著.tone-pip ABR波形与短声ABR相似,Ⅰ、Ⅲ、Ⅴ波潜伏期随频率增加逐渐缩短,波形分化逐渐清晰.不同频率、不同月龄tone-pip ABR和ASSR反应阈差异具有统计学意义(P值均＜0.05).除0.25 kHz外,其余频率tone-pip ABR反应阈均低于ASSR.不同月龄tone-pip ABR和ASSR听力曲线形状相似.结论 0～6月正常婴儿tone-pip ABR的潜伏期和波间期随月龄增加逐渐缩短,而反应阈无明显变化.tone-pip ABR和ASSR均有稳定的频率特异性,tone-pip ABR反应阈低于ASSR,可能更接近主观纯音听阈.     

不同品系正常成年小鼠听性脑干反应特点

目的 研究正常成年CBA、C57BL、昆明系和129系四种品系小鼠的听性脑干反应(auditory brainstem response,ABR),分析其ABR反应阈和潜伏期,得到正常值范围,标准化测试流程,为小鼠的听觉相关研究提供参考.方法 对6周龄正常CBA、C57BL、昆明系和129系四种品系小鼠各20只(20耳),完全麻醉后,进行短声(click)和短纯音(tone burst,tb) ABR测试,观察四种品系小鼠ABR各波的引出率,记录引出率最高的波反应阈值及各波潜伏期.结果 ①在80 dB SPL强度下,CBA、C57BL、昆明系和129系四种品系小鼠ABR各波引出率均为100％,CBA小鼠ABR波形分化最好;在30 dB SPL强度下,除129小鼠外,其余3种小鼠波Ⅱ引出率最高,129小鼠在阈值附近50 dB SPL强度下也是波Ⅱ引出率最高;129小鼠ABR反应阈明显高于其它三种小鼠,差异均有统计学意义(P均＜0.05);②四种品系小鼠的短纯音听觉敏感频率为8、12、16 kHz,其中对12 kHz的短纯音最敏感;③麻醉情况下,ABR各波潜伏期随着测试时间延长而延长,尤其波Ⅲ以后各波潜伏期延长更明显.80 dB SPL强度下CBA、C57BL、昆明系、129系四种小鼠ABR波形在波工前均可分化出SP(summating potential,SP)波,引出率分别为100％、90％、80％、50％,相同刺激条件下,SP波出现率高的小鼠其ABR反应阈相对较低.结论 麻醉状态下,CBA、C57BL、昆明系和129系四种品系小鼠短声及短纯音ABR波Ⅱ引出率最高,故以波Ⅱ刚刚出现的刺激声强度确定为反应阈值;C57BL、昆明系和129系三种品系小鼠的ABR结果均没有CBA小鼠稳定,四种品系小鼠中CBA小鼠更适合用来建立听觉功能相关研究的动物模型;SP波可间接反映毛细胞功能.     

The relative importance of head size, gender and age on the auditory brainstem response

Correlations between the ABR (auditory brainstem response) and subject characteristics of gender, age, and head diameter were established in simple and multiple regression analyses of normal hearing individuals. The simple regression tests demonstrated that head diameter and gender were significantly correlated with the latencies and amplitudes of waves I, III, and V and the I-V and III-V interpeak intervals. In nearly all cases, head diameter correlated more highly with the ABR waves than did gender. Males had longer latencies than females with comparable head diameter, suggesting that factors other than head size are differentiating them. Age was significantly correlated only with the latency of wave III. All significant subject variables also were compared simultaneously in a multiple regression analysis to determine their order of significance and relative contributions to the ABR wave latencies. This permitted the establishment of regression equations for each wave latency to predict the ABR with measurable subject characteristics.