Middle Latency Response Research Articles

Generation of the 40-Hz auditory steady-state response (ASSR) explained using convolution

Objective In this study, the superposition theory of the 40-Hz auditory steady-state response (ASSR) generation is investigated using auditory brainstem response (ABR) and middle latency responses (MLRs) obtained with 40 Hz jittered sequences with the continuous loop averaging deconvolution (CLAD) algorithm. Methods Click sequences at around 40 Hz with high (maximum length sequence), medium and low jitters were presented to normal hearing awake adult subjects monaurally. Overlapping MLR responses were deconvolved using the frequency domain CLAD method. In addition, conventional auditory MLRs at 4.88 Hz and ASSRs at 39.1 Hz were obtained in all subjects. Synthetic ASSRs were constructed using different rate and jitter MLRs as base recordings. Contributions of the primary components were investigated by wave elimination using phasors. Results Findings indicate that the generation of the 40-Hz ASSRs can be explained successfully by the superposition of the ABR and MLR waves generated at that stimulation rate. N a–P a and N b–P b components of the MLR contribute about equally (45% each), while the wave V of the ABR contributes a lesser amount (10%). Conclusions Forty-Hertz ASSRs are composite responses generated by the superposition of the major waves of the ABR and the MLR. Dramatic amplitude increase of the ASSR at 40 Hz is primarily due to the superposition of the resonating P b component to the P a wave. Significance Several unexplained properties of the 40-Hz ASSR can be explained by the stimulus and brain state dependent characteristics of the slow ABR, the P a and the P b components of the MLR.

Comparison of noise-induced changes of auditory brainstem and middle latency response amplitudes in rats

Auditory brainstem responses (ABRs) and middle latency responses (MLRs) were compared after noise exposure to elucidate the specific effects of a loud sound on the central auditory system in rats. Rats were exposed twice for 1 h to broad-band noise (BBN) of 118 dB SPL (first exposure) and 122 dB SPL (second exposure) with an interval between the exposures of three weeks. The first noise exposure produced threshold shifts (TSs) amounting to 5–45 dB, and the second exposure resulted in 40–70 dB TSs. The slope of MLR amplitude-intensity functions (AIFs) increased significantly in correlation with the TS, resembling loudness recruitment. However, maximal MLR amplitudes measured at 8 kHz increased after the first and second noise exposures to almost equal values in individual animals regardless of the TS. In addition, maximum MLR amplitude enhancement was dependent on pre-exposure MLR voltage, probably reflecting the level of metabolic activity or neurotransmitter processes in individual animals. In contrast to MLR amplitudes, ABR amplitudes were suppressed after noise exposure without changing the slope of ABR AIFs. The MLR changes reflect the specific effects of noise exposure on the central auditory system.

Effects of stimulus manipulation on electrophysiological responses in pediatric cochlear implant users. Part I: Duration effects

Discrepancies between electrophysiological and behavioral thresholds in cochlear implant users might be due to differences in stimuli such as the duration and rate of the electrical pulse train. In the present study, we asked: Is there an effect of stimulus duration on electrophysiological responses of the auditory brainstem, thalamo-cortex, and behavioral thresholds? In 5 pediatric cochlear implant users, behavioral thresholds in response to electrical pulse trains at 500 pulses per second (pps) were significantly lower for 40 ms than 2 ms duration pulse trains. Clear electrically evoked auditory brainstem responses (EABR) and electrically evoked middle latency responses (EMLR) were generated by single electrical pulses and 2, 6, and 10 ms pulse trains (500 pps) in 5 children. There was a linear decrease in the inter-wave latency between the eV of the EABR and the Na of the EMLR as duration increased. No significant effect of duration was found on eV latency relative to the last pulse in the train or Na latency relative to the onset of the stimuli. Behavioral threshold data is consistent with temporal integration of auditory activity. Electrophysiological data indicates that: (a) recognizable EABR and EMLR waveforms can be recorded in response to electrical pulse trains of up to 10 ms; and (b) pulse train stimuli have unique effects on the auditory brainstem compared to thalamo-cortical areas.

Auditory middle latency responses and P300 in mild developmental disorders with hearing problems

Auditory middle latency responses and P300 in mild developmental disorders with hearing problems

Coffee improves auditory neuropathy in diabetic mice

Coffee is a widely consumed beverage and has recently received considerable attention for its possible beneficial effects. Auditory neuropathy is a hearing disorder characterized by an abnormal auditory brainstem response. This study examined the auditory neuropathy induced by diabetes and investigated the action of coffee, trigonelline, and caffeine to determine whether they improved diabetic auditory neuropathy in mice. Auditory brainstem responses, auditory middle latency responses, and otoacoustic emissions were evaluated to assess auditory neuropathy. Coffee or trigonelline ameliorated the hearing threshold shift and delayed latency of the auditory evoked potential in diabetic neuropathy. These findings demonstrate that diabetes can produce a mouse model of auditory neuropathy and that coffee consumption potentially facilitates recovery from diabetes-induced auditory neuropathy. Furthermore, the active constituent in coffee may be trigonelline.

Evaluation of cochlear implant users’ performance using middle and late latency responses

Aim of the study was to investigate whether postoperative middle and late latency responses (MLR and LLR) give some clues of postoperative performance of cochlear implant (CI) users. The study was performed in ten prelingual and six postlingual-CI patients with the age ranging from 6 to 48 years (mean 19.7 +/- 15.7 years). The following criteria were sought for inclusion: (1) to have active 15 electrodes for a Nucleus implant and six electrodes for a Medel implant at least and (2) to be cooperative for the tests. Ten healthy subjects with no hearing and balance problem were also included into the study as a control group. All implanted patients had auditory perception and linguistic development tests pre- and postoperatively, MLR and LLR testing postoperatively. Latencies and amplitudes of MLR and LLR were measured. Patients were divided into groups based on the onset of hearing loss (pre- and postlingual), auditory performance (good and moderate), and also duration of postimplantation period. Latency and amplitude of potentials were compared among the pre- and postlingual-CI patients and the control group. The same parameters were compared among the patients with good and moderate auditory performance scores and the control group. Finally, the parameters were analyzed in patients implanted within last 12 months and those implanted earlier. Latency of MLR and LLR was found to be shorter in postlingually deaf implantees compared to prelingually deaf implantees. Amplitudes of MLR and LLR tended to be higher in postlingually deaf implantees compared to prelingually deaf implantees. The better postoperative performance was associated with shorter latency and higher amplitude of MLR and LLR. MLR and LLR latencies were very close to each other in patients implanted within last 12 months and those implanted earlier. MLR and LLR amplitudes were higher in patients implanted earlier than 13 months. However, mentioned comparisons failed to yield statistical strength. Based on these results, it would be reasonable to conclude that postoperative MLR and LLR might give some clues about postoperative performance of CI users.

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.

Cochlear Implantation Results in Patients With Kearns-Sayre Syndrome

To examine the evidence for a cochlear, retrocochlear, or central site of lesion for deafness in two cochlear implant recipients with Kearns-Sayre Syndrome (KSS). Speech perception data and electrically evoked Auditory Brainstem (eABR) and Middle Latency Responses were obtained in two patients with KSS and compared with a group of non-KSS implant recipients. Speech perception data and electrophysiological responses for the patients with KSS were similar to those obtained in non-KSS patients. Results are consistent with an initial cochlear site of lesion for deafness in KSS, and with relative sparing of the central auditory pathway early in the disease.

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.

Load‐related modulation of cutaneous reflexes in the tibialis anterior muscle during passive walking in humans

Although cutaneous reflexes are known to be strongly modulated in a phase-dependent manner during walking in both human and cat, it is not clear whether the movement-related or the load-sensitive afferent feedback plays a more important role in regulating this modulation. To address this issue in humans, we investigated modulation of the cutaneous reflex in the tibialis anterior muscles (TA) of 17 subjects during passive walking with a load (0%, 33%, 66% unloading of body weight) and without a load (100% unloading). These walking tasks were performed passively with a robotic gait trainer system. Cutaneous reflexes in TA, elicited by electrical stimulation to the distal tibial (Tib) and superficial peroneal (SP) nerves, were recorded during 10 different phases of the walking cycle, and the middle latency responses (MLR, 70-120 ms) were analysed. During loaded walking, the magnitudes of the MLR induced by Tib nerve stimulation were strongly increased during the late stance-to-early swing phase irrespective of the amount of load (phase modulation), a phenomenon that also occurred without background electromyogram in the TA. Predominant suppression of the MLR following SP nerve stimulation at the early stance phase changed to facilitation at the late stance. By contrast, the MLR following either Tib or SP nerve stimulation was not at all modulated by the stepping phase during both unloaded walking (100% unloading) and standing. These results suggest that phasic changes in the load-related afferent information in concert with rhythmic lower limb movement play a key role in modulating cutaneous reflexes during walking.

Does long-term unilateral deafness change auditory evoked potential asymmetries?

ObjectiveTo investigate the long-term cortical changes in auditory evoked potential (AEP) asymmetries associated with profound unilateral deafness. MethodsElectroencephalographic (EEG) recordings from 68 channels were used to measure auditory cortex responses to monaural stimulation from 7 unilaterally deaf patients and 7 audiogram-matched controls. Source localization of the AEP N100 response was carried out and regional source waveform amplitude and latency asymmetries were analysed for activity in the N100 latency range and for the middle latency response (MLR) range. ResultsAsymmetry indices (contralateral−ipsilateral)/(contralateral+ipsilateral) showed that matched control subjects, like normally hearing participants, produced activity in the N100 latency range that was more contralaterally dominant for left compared to right ear stimulation. Contrary to expectation, source waveforms and asymmetry indices in the MLR and N100 latency range were similar for unilaterally deaf patients, their matched controls and a group of normally hearing participants. ConclusionsRegional source waveform analysis revealed no evidence of systematic cortical changes in hemispheric asymmetries associated with long-term unilateral deafness. It is possible that a reorganization of cortical asymmetries to a ‘normal’ pattern had taken place in the years between deafness and testing. SignificanceElectrophysiological measures of auditory hemispheric asymmetries do not suggest long-term cortical reorganisation as a result of profound unilateral deafness.

Phase-dependent modulation of cutaneous reflexes in tibialis anterior muscle during passive stepping

The purpose of this study was to determine whether the cutaneous reflex elicited in the tibialis anterior (TA) muscle would be modulated in a phase-dependent manner while human subjects were passively stepping on a treadmill (treadmill stepping) or in the air (air stepping). The passive stepping was produced by a robotic gait trainer, Lokomat. The cutaneous reflexes following electric stimulation to the distal tibial nerve were recorded at ten different phases of a step cycle under the condition of tonic dorsiflexion [10% of maximum electromyography activity (EMGmax)]. Cutaneous reflex EMG responses with peak latencies of 70–120 ms [middle latency responses (MLR)] were then analysed. The results showed that there were no visible differences in the background EMG activities at the ten phases or two passive stepping conditions. During treadmill stepping, however, the magnitude of the facilitatory reflex responses between the late stance and the early swing phase was strongly enhanced, whereas no clear modulation of the MLR during air stepping was observed. These results suggest that the load-related afferent information plays a key role in the modulation of the cutaneous reflex during human walking.

Audiological findings in individuals exposed to organic solvents: Case studies

Millions of people around the world are exposed to industrial organic solvents such as toluene and xylene in the manufacturing sectors. Solvents are neurotoxic substances that are detrimental to the functioning of the nervous system, including the central auditory nervous system (CANS). This study investigated hearing and auditory processing in seven individuals with a history of exposure to industrial solvents. A battery of audiological tests was administered to all subjects: pure tone, speech, and impedance audiometry, otoacoustic emissions tests, auditory brainstem responses, middle latency responses, as well as the SCAN-A and R-SPIN tests with low predictability sentence lists. All individuals in this study exhibited findings consistent with retrocochlear and/or central abnormality. Two of the seven subjects in this study had normal pure tone thresholds at all frequencies bilaterally, yet showed abnormal retrocochlear/central results on one or more tests. The auditory test battery approach used in this study appears to be valuable in evaluating the pathological conditions of the CANS in solvent-exposed individuals.

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.

聴性定常反応聴力検査

This study describes the history, stimulus tones, detection techniques, source generators and clinical applications of auditory steady-state responses (ASSR). The most important benefit of ASSR in objective audiometry is that it can provide an accurate assessment of hearing at different audiometric frequencies in a frequency specific manner, if sinusoidally amplitude-modulated tones are used as tonal stimuli. Power spectrum analysis and phase coherence using fast Fourier transform are useful for the automatic detection of threshold because of the sinusoidal response waveform configuration. Because the detectability of ASSR changes under different arousal states, 40-Hz ASSR is suitable for waking adults and 80-Hz ASSR for sleeping children in the assessment of hearing. Regarding the sources of those responses, 40-Hz ASSR is considered the steady-state version of the middle latency response and 80-Hz ASSR is considered the steady-state version of auditory brainstem response (ABR). Bone conduction stimuli are also useful in the assessment of conductive hearing loss, though the responses are not reliable at the intensity level of 60dB or higher. The difficulty in predicting a hearing level of 500Hz or less using the 80-Hz ASSR threshold can be explained by auditory filter. Its advantage is that the thresholds at 4 different frequencies in both ears can be predicted more rapidly than ABR using the multiple simultaneous stimulation technique. In addition, the ASSR to clicks may provide a rapid screening technique. Finally, it may be helpful in assessing suprathreshold hearing to use ASSRs to sounds that sweep their intensity (sweep technique) or actual speech sounds. In this respect, ASSRs may contribute to the objective fitting of hearing aids in young children.

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.

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.