Auditory Middle Latency Responses Research Articles

An Electrophysiological Measure of Binaural Hearing in Noise

A common complaint of patients with (central) auditory processing disorder is difficulty understanding speech in noise. Because binaural hearing improves speech understanding in compromised listening situations, quantifying this ability in different levels of noise may yield a measure with high clinical utility. To examine binaural enhancement (BE) and binaural interaction (BI) in different levels of noise for the auditory brainstem response (ABR) and middle latency response (MLR) in a normal hearing population. An experimental study in which subjects were exposed to a repeated measures design. Fifteen normal hearing female adults served as subjects. Normal hearing was assessed by pure-tone audiometry and otoacoustic emissions. All subjects were exposed to 0, 20, and 35 dB effective masking (EM) of white noise during monotic and diotic click stimulation. ABR and MLR responses were simultaneously acquired. Peak amplitudes and latencies were recorded and compared across conditions using a repeated measures analysis of variance (ANOVA). For BE, ABR results showed enhancement at 0 and 20 dB EM, but not at 35 dB EM. The MLR showed BE at all noise levels, but the degree of BE decreased with increasing noise level. For BI, both the ABR and MLR showed BI at all noise levels. However, the degree of BI again decreased with increasing noise level for the MLR. The results demonstrate the ability to measure BE simultaneously in the ABR and MLR in up to 20 dB of EM noise and BI in up to 35 dB EM of noise. Results also suggest that ABR neural generators may respond to noise differently than MLR generators.

Suppression of the Pb (P1) component of the auditory middle latency response with contralateral masking

ObjectiveIn this study, the effects of contralateral noise or speech on middle latency response (MLR) components Pa and Pb (P1 or P50) were studied using high rates clicks in normal hearing awake adult subjects. MethodsOne standard (4.88Hz) and four jittered click sequences (24.4, 39.1, 58.6, 78.1Hz) at different mean rates were monaurally presented to ten subjects. The contralateral ears were stimulated with continuous pink noise, recorded speech or no stimulus for control. Overlapping MLR responses to jittered click stimuli were deconvolved using the frequency domain continuous loop averaging deconvolution (CLAD). ResultsThe recordings show that contralateral noise or speech stimulation suppresses Pb component greatly at rates around 40Hz while earlier components (ABR and Pa) are not significantly affected. The suppression of the Pb component is about 50% with some latency reduction. ConclusionsThe results show that the Pb component of the MLR is significantly affected by contralateral stimulus at resonance rates at around 40Hz. It appears that the contralateral noise obliterates the amplitude enlargement due to resonance effect. SignificanceThese findings show that the Pb is generated very differently from the Pa component and strongly inhibited by the contralateral ear. These results also explain the previously observed masking of the 40Hz auditory steady-state responses (ASSR) with contralateral noise.

Effects of chronic and acute smoking on AMLRs in older and younger listeners

Chronic and acute smoking effects on the auditory middle latency response (AMLR) were studied in older (55–81 years) and younger (19–30 years) normal-hearing listeners. Forty healthy participants were selected for one of four groups: older smokers, older nonsmokers, younger smokers, or younger nonsmokers. Biochemical urine analyses confirmed participant categorization as smoker or nonsmoker. Click-evoked AMLRs were acquired once from nonsmokers and twice (chronic condition, acute condition) from smokers. Waveform latency (V, Na, Pa) and relative amplitude (V-Na, Na-Pa) were examined with two independent variables (age, smoking) using MANOVA. Results (n=40) revealed no chronic effect of smoking in the AMLR from smokers compared to nonsmokers. However, in both older and younger smokers (n=20), Na-Pa amplitude was significantly larger in the acute compared to the chronic smoking condition, indicating an acute smoking effect. There was no interaction of smoking and aging. This is a first study describing long-term, chronic and acute smoking effects on AMLRs in older compared to younger listeners. Results suggest that cigarette smoking is an important variable for AMLR research and clinical practice.

High Dosage Sildenafil Induces Hearing Impairment in Mice

Sildenafil is widely administered for the treatment of erectile dysfunction. Recently, sensorineural hearing loss following the ingestion of sildenafil was reported in one male patient. We examined hearing in mice that were administered high doses of sildenafil for up to 105 d. To assess hearing impairment, we evaluated auditory brainstem responses, auditory middle latency responses, and otoacoustic emissions. At high doses, sildenafil increased the hearing threshold shift of auditory brainstem responses. High-dose sildenafil treatment also resulted in delayed latency of both auditory brainstem responses and auditory middle responses. Otoacoustic emissions differed between control and high-dose sildenafil groups with long-term treatment. Collectively, these data demonstrate that high-dose and long-term sildenafil administration can induce hearing impairment in mice.

The Comparative Study of Aging and Auditory Evoked Potentials in the Mouse Model

Presbycusis is a progressive hearing impairment associated with aging, characterized by hearing loss and a degeneration of cochlear structures. The mouse has been a useful model of presbycusis, as it displays an accelerated age-related peripheral hearing loss. The purpose of this study is compared with aging and auditory evoked potentials in the mouse. Method：Adult male ICR mice 7, 10, 17, 23 and 27 weeks were used in this study. In order to assess age-related hearing loss (AHL), we evaluated auditory brainstem response (ABR) and auditory middle latency response (AMLR) for the evaluation of sensorineural function in peripheral auditory nerve. Results：Hearing thresholds was significantly increased 17, 23 and 27 weeks after birthing comparing with 7 weeks in the mouse. Pa latency of AMLR was no difference for 6 weeks from 23 weeks group, Absolute latency of wave IV and interpeak latency of wave I-IV were significantly delayed for 6 weeks from 23 weeks group. The result suggests that significant changes of auditory evoked potentials from 17 weeks have taken place, age-related hearing loss (AHL) could be evaluated by the shift of hearing threshold and the increasing of ABR latency in the mouse. KEY WORDS：Aging·Mouse model·Auditory evoked potential.

Auditory neuropathy in streptozotocin-induced diabetic mouse

An investigation of the mechanism of damage to the peripheral nervous system and central nervous system in diabetes mellitus (DM) is highly important in current neurological research. Auditory neuropathy is a hearing disorder in which the auditory brainstem evoked potential is absent or severely abnormal. This study investigated auditory neuropathy caused by streptozotocin in mouse model. In order to assess diabetic auditory neuropathy, we evaluated auditory brainstem response (ABR) for the evaluation of sensorineural function in peripheral auditory nerve. Auditory middle latency response (AMLR) was employed to assess the middle response in the midbrain. STZ groups significantly increased the absolute latencies IV and the interpeak latencies I–III and I–IV of ABR compared with STZ 0 group. Pa latency of AMLR also significantly increased in proportion to STZ dosage. Taken together, our results demonstrate that STZ-induced DM may impair the auditory pathway from peripheral auditory nerve to midbrain in the mouse model. We suggest that the STZ-induced diabetic mouse model may be useful for the evaluation of auditory pathway impairment by using ABR and AMLR tests.

A comparison study on latency and amplitude of auditory brainstem response and auditory middle latency response in patients with multiple sclerosis and in healthy control group aged between 20 to 50 years old

A comparison study on latency and amplitude of auditory brainstem response and auditory middle latency response in patients with multiple sclerosis and in healthy control group aged between 20 to 50 years old

Preservation of brainstem neurophysiological function in hydranencephaly

The preservation of central neurophysiological function was assessed in a 32-year-old woman with hydranencephaly using brainstem auditory evoked responses (BAER), auditory middle latency responses (MLR), cortical auditory evoked responses (CER), strobe electroretinograms (ERG), strobe-flash visual evoked responses (VER) and median and tibial nerve somatosensory evoked responses (SER). The BAER to the right ear stimulation revealed wave peaks I through VII with normal thresholds, morphology and latencies, while the BAER in the left ear was abnormal. The auditory MLR and CER were absent. Grossly normal strobe ERGs were acquired bilaterally with peak waves at 20 and 50 ms. Strobe VERs were poorly defined and abnormal bilaterally. Left and right median nerve SER revealed significant conduction defects in the large fiber sensory system caudal to the thalamus, above the lower pontine level. Bilateral tibial nerve stimulation revealed normal knee popliteal fossa potentials, but distinct conduction defects in the large fiber sensory system rostral to the lower spinal cord. Brainstem electrophysiological measures revealed functional auditory afferent tracts and nuclei, in the absence of cortical influence, suggesting intact unilateral auditory function, which would support clinical observations of behavioral auditory responses in hydranencephaly.

Middle-latency auditory responses in neurological diseases

SummaryThe presence of middle-latency evoked auditory potentials allows for integrity evaluation of both peripheral and the central auditory systems, and also, that of the nucleus and auditory pathways of sub-cortical region. They have also been used to study alterations of these structures in different neurological diseases.Aimsthe aim of this study is to verify the latency of the middle-latency evoked auditory potentials and detect the presence of any deflections in subjects with neurological diseases.Materials and MethodsIn a clinical and prospective trial, 20 patients having central neurological diseases of various etiologies were evaluated and, positive and negative deflections produced by the middle-latency evoked auditory potentials in these patients were analyzed.ResultsData was statistically analyzed and showed significant modifications in middle-latency evoked auditory potentials.ConclusionThe authors concluded that patients with neurological disorders have either wave suppression or enlarged latency periods in relation to normal subjects.

Auditory Middle Latency Responses: a study of healthy children

SummaryAim: To examine the components of auditory middle latency responses (AMLRs) in a sample of healthy children to establish their properties. Methods: Thirty-two children of both genders aged between 10 to 13 years, with no neurological disorders, were included in the study. Data were analyzed statistically by descriptive statistics (mean + SD) and by analysis of variance using the F test. AMLRs were investigated with toneburst stimuli at 50, 60 and 70 dB HL. Results and Conclusions: The mean latencies of the components were Na = 20.79 ms, Pa = 35.34 ms, Nb = 43.27 ms, and Pb = 53.36 ms, in 70 dB HL. The mean values for the NaPa amplitude ranged from 0.2 to 1.9 mV (M = 1.0 mV). The amplitude increased and latency decreased with increasing sound intensity. Inclination of the NaPa wave complex was present in some cases, which deserves attention in similar studies or in children with speech, language and auditory processing difficulties. Conclusion: This study provides additional information about AMLRs and may be a reference for others clinical and experimental studies in children.

P b(P 1) resonance at 40 Hz: Effects of high stimulus rate on auditory middle latency responses (MLRs) explored using deconvolution

Objective In this study, the effects of high stimulus rate on middle latency response (MLR) components P a and P b (P 1 or P50) were studied using high rate clicks in normal hearing awake subjects were investigated. Methods Five jittered click sequences at different mean rates (24.4, 39.1, 58.6, 78.1, 97.7 Hz) were presented to 10 subjects. Overlapping MLRs were deconvolved using the frequency domain continuous loop averaging deconvolution (CLAD) [Özdamar Ö., Bohórquez, J., Signal to noise ratio and frequency analysis of continuous loop averaging deconvolution (CLAD) of overlapping evoked potentials. J. Acoust. Soc. Am., 119:429–438, 2006]. In addition conventional auditory transient MLRs at 4.88 Hz were obtained using conventional averaging. Results P a amplitude, latency and waveshape remained fairly constant up to 78.1 Hz. P b component, however, showed a variable waveshape with latencies covering a wide range (50–70 ms) and N b–P b amplitudes increasing at 39.1 and 58.6 Hz and decreasing at other rates. Conclusions Recordings show that both P a and P b MLR components can be consistently recorded at all rates up to 100 Hz. P b amplitude shows an increase at around 40 Hz showing a resonance at that frequency. Significance The dramatic increase of the P b component at around 40 Hz may account for the high amplitude of the 40 Hz ASSR.

Estudo das latências e amplitudes dos potenciais evocados auditivos de média latência em indivíduos audiologicamente normais

Estudo de coorte contemporânea com corte transversal. O Potencial Evocado Auditivo de Média Latência (PEAML) é gerado entre 10 e 80ms e possui múltiplos geradores, com maior contribuição da região tálamo-cortical. O estabelecimento de critérios de normalidade para os valores de latência e amplitude é necessário para uso clínico. OBJETIVOS: Analisar a latência e amplitude do PEAML em indivíduos sem alterações audiológicas, e verificar a confiabilidade da amplitude Pa-Nb. MATERIAL E MÉTODO: Foram coletados os PEAML de 25 indivíduos durante o ano de 2005 e analisados os componentes Na, Pa, Nb para cada orelha testada (A1 e A2), e posicionamento de eletrodo (C3 e C4). RESULTADOS: Observou-se diferença estatisticamente significante entre os valores médios de latência para C3A1 e C4A1 com relação aos componentes Na e Pa, não sendo encontrada esta diferença para o componente Nb e valores médios das amplitudes Na-Pa e Pa-Nb. CONCLUSÃO: Foram estabelecidos os valores das médias e desvios padrão para os parâmetros latência e amplitude dos componentes Na, Pa, Nb, e Na-Pa e Pa-Nb, nas condições C3A1, C4A1, C3A2, C4A2, proporcionando os parâmetros para a análise e interpretação deste potencial.

Middle Latency Response Study of Auditory Evoked Potentials' Amplitudes and Lantencies Audiologically Normal Individuals

SummaryContemporary cohort cross-sectional study. Introduction: The auditory middle latency response (AMLR) is generated between 10 and 80 ms and has multiple generators, with a greater contribution from the thalamus-cortical pathways. The establishment of normality criteria for latency and amplitude values is necessary for clinical use.Aimto analyze the latency and amplitude of the AMLR in individuals without audiological disorders, and verify the reliability of Pa-Nb amplitude.Materials and MethodsThe AMLR of 25 individuals was collected during 2005 and the Na, Pa, Nb components were analyzed for each tested ear (A1 and A2), and electrode positioning (C3 and C4).ResultsA statistically significant difference was noticed among middle latency values for C3A1 and C4A1 regarding components Na and Pa, and no difference for component Nb and mean values for amplitudes Na-Pa and Pa-Nb. Conclusions: We established average and standard deviation values for latency and amplitude parameters for components Na, Pa, Nb and Na-Pa and Pa-Nb, under conditions C3A1, C4A1, C3A2, C4A2, providing a parameter for the analysis and interpretation of this potential.

Auditory evoked potentials in females with high and low acceptance of background noise when listening to speech

Acceptable noise level (ANL) is a measure of a listener's acceptance of background noise when listening to speech. A consistent finding in research on ANL is large intersubject variability in the acceptance of background noise. This variability is not related to age, gender, hearing sensitivity, type of background noise, speech perception in noise performance, cochlear responses, or efferent activity of the medial olivocochlear pathway. In the present study, auditory evoked potentials were examined in 21 young females with normal hearing with low and high acceptance of background noise to determine whether differences in judgments of background noise are related to differences measured in aggregate physiological responses from the auditory nervous system. Group differences in the auditory brainstem response, auditory middle latency response, and cortical, auditory late latency response indicate that differences in more central regions of the nervous system account for, at least in part, the variability in listeners' willingness to accept background noise when listening to speech.

The Auditory Middle Latency Response, Evoked Using Maximum Length Sequences and Chirps, as an Indicator of Adequacy of Anesthesia

The auditory evoked potential known as the middle latency response (MLR), evoked with regular click stimulation at around 5 Hz, has been suggested as an indicator of adequacy of anesthesia. The MLR is a very small signal embedded in high levels of background noise, so it can take a long time to acquire. However, using a stimulus paradigm of chirps presented in a maximum length sequence, the acquisition of the MLR can be improved compared to using conventional click stimulation. In this pilot study, we investigated this new technique in a clinical environment. Significant changes in MLR amplitude, but not latency, were measured for six of seven subjects in association with changes in responsiveness to command using the isolated forearm technique. The absence of any latency shift differs from other studies of the MLR during anesthesia and highlights the limited understanding of the relationship between anesthesia and the MLR.

Sensitivity of the auditory middle latency response of the guinea pig to interaural level and time differences

This study examines the extent to which the auditory middle latency response (MLR) of the guinea pig is sensitive to sound localization cues such as interaural level and time differences (ILD and ITD, respectively). The MLR was recorded with an epidural electrode placed over the auditory cortex of an anesthetized guinea pig. Click stimuli were presented monaurally or binaurally with various ILDs and ITDs. The MLR was much larger for contralateral stimulation than for ipsilateral stimulation, and its amplitude was intermediate for diotic stimulation. The MLR amplitude was sensitive to both ILD and ITD: it decreased as the ipsilateral stimulus increased in level or advanced in time relative to the contralateral stimulus. The steep slope of the amplitude-versus-ITD function fell within an ITD range of ±330 μs, namely the guinea pig’s physiological ITD range. The response reduction that resulted from increasing the relative level of the ipsilateral level could be cancelled out by advancing the contralateral onset time relative to the ipsilateral onset time. This parallels the “time-intensity trading” in sound lateralization exhibited in human psychophysics. The results imply that the binaural interaction in the guinea pig MLR reflects aspects of neural processes that are involved in sound localization.

Fast Wavelet Estimation of Weak Biosignals

Wavelet-based signal processing has become commonplace in the signal processing community over the past decade and wavelet-based software tools and integrated circuits are now commercially available. One of the most important applications of wavelets is in removal of noise from signals, called denoising, accomplished by thresholding wavelet coefficients in order to separate signal from noise. Substantial work in this area was summarized by Donoho and colleagues at Stanford University, who developed a variety of algorithms for conventional denoising. However, conventional denoising fails for signals with low signal-to-noise ratio (SNR). Electrical signals acquired from the human body, called biosignals, commonly have below 0 dB SNR. Synchronous linear averaging of a large number of acquired data frames is universally used to increase the SNR of weak biosignals. A novel wavelet-based estimator is presented for fast estimation of such signals. The new estimation algorithm provides a faster rate of convergence to the underlying signal than linear averaging. The algorithm is implemented for processing of auditory brainstem response (ABR) and of auditory middle latency response (AMLR) signals. Experimental results with both simulated data and human subjects demonstrate that the novel wavelet estimator achieves superior performance to that of linear averaging.

Estudo eletrofisiológico do sistema auditivo periférico e central em indivíduos afásicos

Electrophysiology of the auditory system. Electrophysiological evaluation of the peripheral and central auditory system of brain injured patients. Experimental group: eleven brain injured and aphasic subjects, both genders and with ages ranging from 43 to 75; control group: eleven individuals without hearing complaints, equalized as to gender and age. The subjects were evaluated through auditory brainstem response (ABR); auditory middle latency response (AMLR) and auditory P300 response. An increase in the V wave latency and I-V interpeak in both groups, due to the age factor. The presence of statistically significant hemispheric differences when compared to the Pa component in MLAEP research, registered in the C3 (left hemisphere) and the C4 (right hemisphere). In researching the P300 Cognitive Potential, there was an absence or increase in P300 latency and a decrease in P300 amplitude in the presence of the N2 component. The AMLR and auditory P300 response have proven to be effective instruments for evaluating aphasic individuals.

Auditory brainstem and middle latency responses to 1 kHz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80–90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.

Effects of speech-coding strategies on speech perception performance in Mandarin-speaking children with Nucleus 24 cochlear implants

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