Middle and long latency auditory evoked potentials in cat. II. Component distributions and dependence on stimulus factors

The middle (10–50 ms) and long (50–600 ms) latency periods of the auditory evoked potential (AEP) were investigated in muscle-paralyzed, artificially respired cats with respect to two issues: (1) the distribution of components across the skull, and (2) the effects of changing stimulus intensity on component latencies and amplitudes. The distributional data were gathered during a behavioral study in which four behavioral tasks related to classical pupillary conditioning were used to vary attentional and arousal processes. The distributions across the skull surface (averaged across tasks) of 12 peaks and troughs (P10, N13. P17, N22, P31, N41, P55, N70, N100, N140. P260 and N520) and seven principal components derived from the set of waveforms collected during this experiment are reported. Both peak amplitudes and principal component scores were distributed differentially across the skull surface. In the second experiment, acoustic stimulus intensity was varied, and AEPs collected from a vertex and temporal electrode site. In general, increasing stimulus intensity had a stronger influence on the earlier portions of the AEP, where increased amplitude and decreased latency was the rule, than on later ones. The relationships between cat and human AEP components were discussed based on both the data presented in this paper and in previous papers.     

Temporal masking of auditory evoked brainstem responses in human newborns and adults

Temporal masking effects on brainstem evoked responses (BERs) were studied in normal human newborns and adults. Forward masking prolonged the latencies of the newborn BERs significantly longer than adult BERs. The effect of backward masking on BER latencies for both newborns and adults was small, suggesting that either backward masking effects for these stimuli are mediated by structures rostral to the brainstem or that backward masking does not affect the latency of the BER. Increasing the duration of the forward masker prolonged BER latencies more for newborns than adults. Increasing the intensity of the masker prolonged BER latencies for both newborns and adults, however, there were no significant age-intensity interactions.     

正常青年人多频稳态听觉诱发反应测试

目的 :测定正常青年人多频稳态听觉诱发反应 (ASSR)阈值 ,为临床诊断提供客观依据。方法 :选正常青年人 2 2例 (4 4耳 ) ,行ASSR阈值测试。结果 :在 0 .2 5～ 8.0kHz频区间 ,ASSR平均阈值约在 4 0～ 6 0dBHL之间 ,从低频到高频其阈值越来越高 ,0 .2 5kHz、0 .5kHz、1.0kHz处的ASSR平均阈值约为 4 0dBHL ,2 .0kHz处约为 4 5dBHL ,4 .0kHz处约为 5 0dBHL ,8.0kHz处约为 6 0dBHL。ASSR阈值与纯音听阈间差值多在2 5～ 5 5dBHL之间 ,从低频到高频其阈差值越来越高 ,0 .2 5kHz处的差值约为 2 5dBHL ,0 .5kHz处约30dBHL ,1.0kHz处约 35dBHL ,2 .0kHz处约 4 0dBHL ,4 .0kHz处约 5 0dBHL ,8.0kHz处约 5 5dBHL。结论 :正常青年人ASSR阈值与纯音听阈间有一定差值。利用这一差值 ,通过测试ASSR阈值可推断出被检查者纯音听阈的阈值     

Temporal integration of pure tones in the cat

A behavioral method for assessing auditory threshold in cats using food reward conditioning is described. The method requires that the cat press its nose against a touch panel in order to receive a stimulus and that it remove its nose when the stimulus is detected. Behavioral thresholds for pure tone stimuli of various durations are described for three laboratory-raised cats. For all frequencies tested, detection threshold varies as an exponential function of stimulus duration. For frequencies from 125 Hz to 8 kHz, integration time constant and stimulus frequency are inversely related. Response latencies are also affected by the duration of the stimulus. Results are considered in the light of similar measures obtained from human subjects.     

Altered auditory brainstem evoked responses in the ferret model for Reye's syndrome

The effects of influenza B, aspirin and hyperammonemia on the functional integrity of the cochlea were examined using the ferret model for Reye's syndrome. Auditory brainstem evoked responses (ABR) were recorded from treated ferrets and compared to those recorded from controls. Delayed latencies of all waves, as well as increased I-IV Interwave latencies were observed in recordings from treated ferrets. Importantly, the latencies of Wave I, nerve generator potential from the eighth nerve, and Wave IV, response potential from the brainstem nuclei, increased on Days 3 and 5 of the study. However, recorded ABR from treated ferrets on Day 10 showed that while the latencies of Wave IV were approximate to those of controls, Wave I remained delayed. These results suggest that systemic effects of influenza B, aspirin and hyperammonemia may lead acutely to both peripheral and central auditory dysfunction, and that the functional integrity of the central auditory system may recover more quickly than that of the peripheral system. Furthermore, these results suggest that such effects may lead to acute transient hearing impairment in patients with Reye's syndrome.     

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.     

双耳同侧记录的言语诱发听性脑干反应的对比研究

目的:比较左、右耳记录的言语诱发听性脑干反应(speech-ABR)在时域及频域上的差异,探讨脑干编码不同耳别来源的言语信息的差异及其可能原因。方法:以合成言语/da/为刺激声对健康成人进行双耳同侧记录的speech-ABR测试,分析反应的潜伏期、幅值及波形评分。对反应20～50ms部分进行快速傅立叶变换,计算基频及第一共振峰的幅值。结果:不同耳别记录的speech-ABR主波的潜伏期差异无统计学意义;右耳记录的A波幅值显著大于左耳记录,O波幅值则显著小于左耳记录,其他主波幅值的耳别差异均无统计学意义。右耳记录的波形评分大于左耳记录,两者差异有统计学意义。无论记录耳别,基频的幅值均大于第一共振峰的幅值,差异有统计学意义;无论是基频的幅值还是第一共振峰的幅值,耳别差异均无统计学意义。结论:speech-ABR在脑干的来源和分布无明显偏向性,与大脑半球言语功能的不对称性无明显对应性。听觉传导通路、功能性what-where通路以及大脑两侧半球不是简单的对应关系。     

Simultaneous recording of fast and slow auditory evoked potentials (Slow-Fast-Simultaneous-ERA,SFS-ERA)

Summary In order to reduce measurement time we have used part of the interstimulus interval of the slow cortical responses to record fast brain stem responses. For this purpose we reconstructed a programmable audiometer and preamplifier which are controlled by a computer. These, with 1/4 ms-click and tone-burst stimulation simultaneously gained fast and slow responses, not only give a frequency-related view of the threshold and the kind of hearing loss — because of amplitude and latency —, but also in some cases — because of differences between both responses — give ideas of the possible location of the hearing impairment through the auditory pathways. The audiological value of this new method is discussed and explained by giving examples of two interesting cases, one central-neural hearing loss and one questionable aggravation.     

Averaged evoked auditory responses in the chronically implanted cat

Averaged evoked auditory responses from chronically implanted dural electrodes over the midectosylvian gyrus were evaluated in eight cats. The effects of the distribution of electrodes and levels of alertness were observed for each animal and the entire group. Changes in duration, rise and decay times, and repetition rates were also analyzed. Data from these experiments suggested a large variability in the amplitude and latency of the response. On the other hand, they also suggested a stable reproducible threshold of detectability — a point where the response disappeared upon further reduction in sound pressure levels. This characteristic of the evoked system served as a reliable measurement of an evoked auditory threshold and appeared as a potential means for evaluating relative changes of auditory function within the same animal.     

The choice of distracting task can affect the quality of auditory evoked potentials recorded for clinical assessment

Auditory evoked potential (AEP) recordings often require subjects to ignore the stimuli and stay awake. In the present experiment, early (ABR), middle (MLR), and late latency (LLR) AEPs were recorded to compare the effect of five different distracting tasks: (1) doing nothing eyes open, (2) reading, (3) watching a movie, (4) solving a three-digit sum, and (5) doing nothing eyes closed (or counting the stimuli for LLR). Results showed that neither the amplitudes nor the latencies of the ABR, MLR, or LLR were affected by task. However, the amount of pre-stimulus activity (noise) or amplitude rejection was significantly and differently affected by the distracting task. For the ABR, the math task was the noisiest but, for the MLR, the amount of noise was greater when watching a movie. As for the LLR, reading and watching a movie yielded the lowest percentage of rejected traces. In conclusion, the choice of distracting task depends on the AEP being measured and should be chosen to improve the quality of the AEP traces and thus reduce recording time.     

Nonlinear functional modeling of scalp recorded auditory evoked responses to maximum length sequences

The purpose of this study was to model the adult human's scalp recorded evoked response to auditory pulses separated by varying inter pulse intervals (IPIs). The responses modeled probably reflect auditory nerve and brainstem generators. The subjects were 10 young adult humans with normal hearing. They were presented pseudo random sequences of pulses (maximum length sequences, MLSs) in order to characterize their system response. For the stimuli and the responses modeled accounting for temporal nonlinearities (interactions among the pulses) improved model performance only marginally. Nonlinear contributions to the models decreased with increasing interval between the input pulses. Increasing the memory of the model beyond 20 ms did not increase modeled performance dramatically. Model performance varied as a function of minimum IPI (MIPI) of the MLSs. At the shortest MIPI overall model performance deteriorated (due, in part, to a decrease in SNR), but nonlinear effects became relatively more important. At the longest MIPI performance also deteriorated, possibly due to the increasing influence of longer latency, more variable evoked potential components. Modeled performance generalized to responses recorded in the same recording session to the same and different MLSs. This study confirms the similarity between MLS linear kernels and conventionally averaged evoked responses- both are adapted responses reflecting the IPIs of the evoking stimuli.     

Intracranial pressure and auditory evoked responses of the cat

Auditory evoked responses (AERs) were recorded from the primary cortex, medial geniculate body (MG), inferior colliculus (IC) and cochlear nucleus (CN) of the cat anesthetized with sodium pentobarbitone to examine the effects of increased intracranial pressure (ICP) on neural activity in the different levels of auditory centres. ICP was increased by injecting saline solution into the intracranial space and a tone burst was used for activating the auditory centres. Cortical response (ACR) began to decrease in amplitude from about 30-40 mmHg of ICP. A decrease in amplitude of MG response and that of IC response followed in the order with a further increase in ICP. CN response was most resistant and usually remained even when ACR and MG responses were totally abolished. Recovery of the AERs followed a release of the increased pressure in the reversed order to the decrease in the AERs. When an increase was repeated with a short interval of pressure release such as 5 to 10 min, recovery of ACR became much slower and no recovery was sometimes observed 30-60 min after the release of ICP increased to a level below 100 mmHg. A discussion was conducted on the origin of the changes in AERs in response to increased ICP. We concluded from the results that the higher auditory centres are more susceptible to an increase in ICP to suppress the neural activities without apparent influence on the lower centres. A clinical test of ABR may be available to predict the prognosis of the auditory disorders.     

Frequency-dependence of early auditory evoked responses in the guinea pig

Summary Neural auditory responses in the guinea pig, monitored by surface electrodes (brain stem potentials and frequency-following responses) and by electrodes at the round window, were analyzed for evidence of frequency dependence in the range from 500 Hz to 15 kHz. The characteristics of the brain stem potentials and frequency-following responses with stimuli near threshold intensity for frequencies below 2 kHz indicate that this activity derives from the excitation of apical regions of the basilar membrane. The same interpretation applies to the potentials recorded at the round window. Comparison of the responses seen with surface electrodes and those appearing at the round window reveals that the broad potential P_I of the brain stem response to low-frequency stimuli corresponds to the compound action potential, while the frequency-following responses correspond to phase-locked responses in the acoustic nerve.     

Audiologic evaluation of neonates with severe hyperbilirubinemia using transiently evoked otoacoustic emissions and auditory brainstem responses

OBJECTIVES: To audiologically clarify the lesion site and to test the reliability of transiently evoked otoacoustic emissions (TEOAEs) in hearing screening of hyperbilirubinemic neonates. STUDY DESIGN: Eleven neonates with severe hyperbilirubinemia who had exchange transfusion in the neonatal intensive care unit of an academic hospital over a 3-year period were included in this study. They were tested with auditory brainstem response (ABR) and TEOAEs after exchange transfusion during hospitalization or at an immediate follow-up visit after discharge. Follow-up ABR tests were performed when infants showed significant hearing loss. METHODS: ABR and TEOAE tests were performed on the 11 neonates with severe hyperbilirubinemia after exchange transfusion. Follow-up ABR tests were carried out in 3-month intervals in the four neonates who showed abnormal or no response on initial ABR. RESULTS: Four neonates showed abnormal or no response and the other seven demonstrated normal response in ABR. All 11 neonates passed TEOAEs. Two neonates showed improvement in auditory function at 3- or 6-month follow-up ABR. CONCLUSION: The results of this study indicate that the site of lesion in hearing loss caused by hyperbilirubinemia may be at the retrocochlear location while the cochlea remains intact. TEOAEs may have limitations in evaluation of hearing in the neonates with hyperbilirubinemia.