Middle Latency Auditory Evoked Responses Research Articles

Effects of odor on the vigilance (V) level : An investigation by topographical mapping (TM) of middle latency auditory evoked responses (MLR)( Effect of Aromas on Psycho-Physiology,The 21st Symposium on Life Information Science)

Effects of odor on the vigilance (V) level : An investigation by topographical mapping (TM) of middle latency auditory evoked responses (MLR)( Effect of Aromas on Psycho-Physiology,The 21st Symposium on Life Information Science)

無症候性脳梗塞における聴性中間反応(MLRs)と神経心理機能との相関性

無症候性脳梗塞における聴性中間反応(MLRs)と神経心理機能との相関性

P03-22 - Perturbations in p50 auditory evoked potential and hallucinatory behavior in schizophrenia

Earlier findings suggested auditory evoked potentials as diagnostic measure in schizophrenia. However, the relationship between different components of middle latency auditory evoked response (MLAER) and clinical symptoms of schizophrenia is unclear. In this study we explored the relationship between the amplitude of P50 potential and hallucinatory behavior in medicated schizophrenic patients. MLAER from thirty seven outpatient, clinically stable medicated schizophrenic patients (mean age 43.5 years, SD = 11.7), twenty six males, were measured. The evoked potentials were elicited in a paired click paradigm. The amplitude of P50, measured from pre-stimulus baseline, was studied. The bandpass filter was 1-50 Hz. Twenty seven (20 males) patients experienced hallucinatory behavior. Schizophrenic patients with hallucinatory behavior had significantly (p< 0.05) smaller P50 amplitude, elicited by both first and second clicks in the pair. No significant differences were found for P50 amplitudes, measured from preceding negative deflection. Preliminary analysis suggests that the amplitude of the P50 auditory potential, measured from the pre-stimulus baseline in a paired click paradigm is related to hallucinatory behavior in schizophrenic patients.

Pure word deafness due to left subcortical lesion: Neurophysiological studies of two patients

Objective This study investigated the auditory processing in two patients with pure word deafness (PWD) using neurophysiological experimental methods. Methods We recorded the auditory brainstem response (ABR), the middle latency auditory-evoked response (MLR) and the auditory-evoked event-related potentials (ERPs) in two patients with PWD after subcortical hemorrhage in the left temporal lobe. Results Both patients showed normal response in ABR and abnormality in MLR. The latency of P300 evoked by right-ear stimulation was 51 ms longer in one patient and 26 ms longer in the other patient than that evoked by left-ear stimulation. Conclusions Our results suggested that the prolongation of P300 latency could be caused by the deterioration of auditory stimulus processing and supported the hypothesis that the defect in auditory temporal resolution was an important factor in the development of PWD. Significance This study demonstrated that recordings of ERP with auditory-evoked response such as ABR and MLR are useful to elucidate the deterioration of auditory stimulus processing in patients with PWD.

Prediction of movement following noxious stimulation during 1 minimum alveolar anesthetic concentration isoflurane/nitrous oxide anesthesia by means of middle latency auditory evoked responses

This paper investigates the applicability of generalized dynamic neural networks for the design of a two-valued anesthetic depth indicator during isoflurane/nitrous oxide anesthesia. The indicator construction is based on the processing of middle latency auditory evoked responses (MLAER) in combination with the observation of the patient's movement reaction to skin incision. The framework of generalized dynamic neural networks does not require any data preprocessing, visual data inspection or subjective feature extraction. The study is based on a data set of 106 patients scheduled for elective surgery under isoflurane/nitrous oxide anesthesia. The processing of the measured MLAER is performed by a recurrent neural network that transforms the MLAER signals into signals having a very uncomplex structure. The evaluation of these signals is self-evident, and yields to a simple threshold classifier. Using only evoked potentials before the pain stimulus, the patient's reaction could be predicted with a probability of 81.5%. The MLAER is closely associated to the patient's reaction to skin incision following noxious stimulation during 1 minimum alveolar anesthetic concentration isoflurane/nitrous oxide anesthesia. In combination with other parameters, MLAER could contribute to an objective and trustworthy movement prediction to noxious stimulation.

Middle Latency Auditory Evoked Responses and Electroencephalographic Derived Variables Do Not Predict Movement to Noxious Stimulation During 1 Minimum Alveolar Anesthetic Concentration Isoflurane/Nitrous Oxide Anesthesia

The electroencephalogram (EEG) and middle latency auditory evoked responses (MLAER) have been proposed for assessment of the depth of anesthesia.However, a reliable monitor of the adequacy of anesthesia has not yet been defined. In a multicenter study, we tested whether changes in the EEG and MLAER after a tetanic stimulus applied to the wrist could be used to predict subsequent movement in response to skin incision in patients anesthetized with 1 minimum alveolar anesthetic concentration (MAC) isoflurane in N2 O. We also investigated whether the absolute values of any of these variables before skin incision was able to predict subsequent movement. After the induction of anesthesia with propofol and facilitation of tracheal intubation with succinylcholine, 82 patients received 1 MAC isoflurane (0.6%) in N2 O 50% without an opioid or muscle relaxant. Spontaneous EEG and MLAER to auditory click-stimulation were recorded from a single frontoparietal electrode pair. MLAER were severely depressed at 1 MAC isoflurane. At least 20 min before skin incision, a 5-s tetanic stimulus was applied at the wrist, and the changes in EEG and MLAER were recorded. EEG and MLAER values were evaluated before and after skin incision for patients who did not move in response to tetanic stimulation. Twenty patients (24%) moved after tetanic stimulation. The changes in the EEG or MLAER variables were unable to predict which patients would move in response to skin incision. Preincision values were not different between patients who did and did not move in response to skin incision for any of the variables. MLAER amplitude increased after skin incision. We conclude that it is unlikely that linear EEG measures or MLAER variables can be of practical use in titrating isoflurane anesthesia to prevent movement in response to noxious stimulation. Implications: Reliable estimation of anesthetic adequacy remains a challenge. Changes in spontaneous or auditory evoked brain activity after a brief electrical stimulus at the wrist could not be used to predict whether anesthetized patients would subsequently move at the time of surgical incision. (Anesth Analg 1999;88:1412-7)

Individual differences in auditory middle latency responses in elderly adults and patients with Alzheimer's disease

Previous research has suggested that the Pb component of the middle-latency auditory evoked response (MLAER) is differentially abnormal in patients with Alzheimer's disease relative to control subjects. In the present study, this putative abnormality was examined in vertex-recorded MLAERs elicited by monaural stimulation in 14 patients with Alzheimer's disease (six females) and 22 age-matched control subjects (10 females). A sex difference in Pb elicitation was revealed in control subjects; Pb area was twice as large in females than males ( P<0.05). Pb and Pa amplitudes and latencies did not differ between male and female control subjects. Comparisons of Pb between patients and controls were conducted within each sex. There was no main effect of group on Pb area, amplitude, or latency. Pa amplitude was significantly larger in patients than control subjects; there was no group difference in Pa latency. This study did not replicate previous reports of differences in Pb between patients with Alzheimer's disease and elderly control subjects. We demonstrated that Pb elicitation may be unreliable in elderly control subjects and found evidence of a possible sex difference. The effects of inter-subject variables (e.g. age, sex) must be understood more fully before MLAERs can be exploited as meaningful markers of brain dysfunction. © 1997 Elsevier Science B.V.

Source localization of middle latency auditory evoked magnetic fields

The magnetic counterparts of middle latency auditory evoked responses (MLR) were measured for seven normal subjects with a 7-channel do superconducting quantum interference device (SQUID). The source of each component (Na, Pa, Nb and Pb) was estimated and plotted onto the individual magnetic resonance images (MRI). The source of Na, as well as those of Pa, Nb and Pb, was estimated to be in the supratemporal auditory cortex. The positions of Pa, Nb and Pb sources were compared with one another. No significant difference was observed between the positions of Pa and Nb sources. On the other hand, the source of Pb was found to be anterior to the sources of both Pa and Nb. It was suggested that there are more than two separate areas activated in the human auditory cortex during MLR.

Effects of sevoflurane on the middle latency auditory evoked response and the electroencephalographic power spectrum.

We investigated the effects of sevoflurane on the middle latency auditory evoked response (MLR) and the power spectrum of the electroencephalogram (EEG) in 10 elective surgical patients. The MLR and the EEG power spectrum were recorded with a surface electrode placed at the central (Cz) scalp location. End-tidal sevoflurane concentrations of 0%, 0.25%, 0.5%, 0.75%, 1.0%, and 1.5% in 50% nitrous oxide and oxygen were studied. The Na, Pa, and Nb components of the MLR increased in latency and decreased in amplitude in a dose-dependent manner at increasing concentrations of sevoflurane. The latencies for Na, Pa, and Nb increased in a linear fashion (correlation coefficients: r = 0.81, r = 0.81, and r = 0.89, respectively). The EEG delta power was dominant with increasing sevoflurane concentration, and was significantly increased at sevoflurane concentrations of 1.0%-1.5%. The beta power, median power frequency (MPF), and 95% spectral edge frequency (SEF) decreased significantly according to the increases by 0.5% sevoflurane. Regarding the changes evoked by 0.25% sevoflurane, the Nb latency of the MLR responded significantly under 0.75% of sevoflurane. At these low concentrations of sevoflurane, the MLR seemed to be more sensitive to changes in anesthetic concentration than the various EEG variables.

Effects of Sevoflurane on the Middle Latency Auditory Evoked Response and the Electroencephalographic Power Spectrum

We investigated the effects of sevoflurane on the middle latency auditory evoked response (MLR) and the power spectrum of the electroencephalogram (EEG) in 10 elective surgical patients.The MLR and the EEG power spectrum were recorded with a surface electrode placed at the central (Cz) scalp location. End-tidal sevoflurane concentrations of 0%, 0.25%, 0.5%, 0.75%, 1.0%, and 1.5% in 50% nitrous oxide and oxygen were studied. The Na, Pa, and Nb components of the MLR increased in latency and decreased in amplitude in a dose-dependent manner at increasing concentrations of sevoflurane. The latencies for Na, Pa, and Nb increased in a linear fashion (correlation coefficients: r = 0.81, r = 0.81, and r = 0.89, respectively). The EEG delta power was dominant with increasing sevoflurane concentration, and was significantly increased at sevoflurane concentrations of 1.0%-1.5%. The beta power, median power frequency (MPF), and 95% spectral edge frequency (SEF) decreased significantly according to the increases by 0.5% sevoflurane. Regarding the changes evoked by 0.25% sevoflurane, the Nb latency of the MLR responded significantly under 0.75% of sevoflurane. At these low concentrations of sevoflurane, the MLR seemed to be more sensitive to changes in anesthetic concentration than the various EEG variables. (Anesth Analg 1995;80:940-3)

Effects of stimulation side on human middle latency auditory evoked magnetic fields

We investigated the effects of the stimulation side on middle latency auditory evoked responses (MLR) with neuromagnetic methods. Middle latency auditory evoked magnetic fields elicited by 1.0 ms clicks presented at ipsilateral and contralateral ear were recorded with a 7-channel DC SQUID. The amplitudes and latencies of the magnetic equivalents of Pa and Pb responses, which are the two main peaks of MLR, were measured. The amplitude of the contralateral Pa response was found to be significantly larger than the ipsilateral Pa response. On the other hand, no significant difference was observed in the latencies of Pa and Pb between the ipsi- and contralateral responses.

Measurement of auditory evoked brain responses elicited by ipsilateral and contralateral ear stimulation with a high-sensitivity SQUID system

The effects of the stimulation side on human middle latency auditory evoked responses (MLR) were investigated with a high-sensitivity 7-channel DC SQUID system. We recorded middle latency auditory evoked magnetic fields elicited by ipsilateral and contralateral ear stimuli, and compared the amplitudes and latencies of the magnetic equivalents of Pa and Pb responses, which are the two main components of MLR. The amplitude of the contralateral Pa response was found to be significantly larger than the ipsilateral Pa response. On the other hand, no significant difference was observed in the latencies of Pa and Pb between the ipsi- and contralateral responses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Middle latency auditory evoked response (MLR): A study of comparison between dementia of the Alzheimer's type (DAT) and multi-infarct dementia (MID)

Middle latency auditory evoked response (MLR): A study of comparison between dementia of the Alzheimer's type (DAT) and multi-infarct dementia (MID)

The effect of preterm birth on brainstem, middle latency and cortical auditory evoked responses (BMC AERS)

Recent studies on the maturation of auditory brainstem evoked responses (ABRs) present conflicting results, whereas only sparse reports exist with respect to the maturation of middle latency auditory evoked responses (MLRs) and auditory cortical evoked responses (ACRs). The present study reports the effect of preterm birth on the maturation of auditory evoked responses in low risk preterm infants (27–34 weeks conceptional age). The ABRs indicate a consistent trend towards longer latencies for all individual ABR components and towards longer interpeak latencies in preterm infants. The MLR shows longer latencies for early component PO in preterm infants. The ACRs show a remarkable difference between preterm and term infants. At 40 weeks CA the latencies of ACR components Na and P2 are significantly longer in term infants, whereas at 52 weeks CA the latencies of the same ACR components are shorter in term infants. The results support the hypothesis that retarded myelination of the central auditory pathway is partially responsible for differences found between preterm infants and term infants with respect to late ABR components and early MLR component PO. Furthermore, mild conductive hearing loss in preterm infants may also play its role. A more complex mechanism is implicated to account for the findings noted with respect to MLR component Na and ACR components Na and P2.

Auditory evoked responses (ABR, MLR, SVR) and brain mapping in the elderly

The influence of age on evoked auditory brainstem responses (ABRs) is still a matter of controversy. It is well known that in the elderly the ABRs show a progressive latency shift of the principal components. While many authors have reported a I-V internal latency shift, others claim that there is not a delay in the central conduction time (CCT) with ageing. Middle latency auditory evoked responses (MLRs) are also reported to be impaired in the elderly, but the few results published need further investigations. This study investigates some of the controversial aspects of electrophysiological assessment of the auditory system in the elderly. 36 healthy subjects (18 males and 18 females), mean age 67.2 years +/- 5.8, underwent ABRs, MLRs and SVRs and SVRs brain mapping evaluation. All the data were compared with our normative data for young adults. Our results confirm previous reports of a latency shift of all principal components of ABR, but do not demonstrate a significant CCT impairment in the elderly. The MLRs, SVRs and brain mapping analysis also support this conclusion.

Middle latency auditory evoked responses in normal term infants: a longitudinal study.

Middle latency auditory evoked responses (MLAERs) were measured in 21 normal term infants, three to five days after birth and then at 6 weeks, 7 months and 1 year of age. A polyphasic waveform was elicited during natural sleep in all infants at each recording session by monaural click stimulation at a rate of 9 per second. A 70 dBHL stimulus was found to be optimal as the MLAER became less well defined when the stimulus intensity approached the threshold hearing level. The first 60 to 70 msec of the waveform was found to be most stable, with decreasing detectability of peaks at longer latencies. There was no change in wave latency or reproducibility of MLAERs recorded during different sleep states. Waves Po and Na showed a significant decrease in latency with increasing stimulus intensity at term and/or 6 weeks of age. This was not evident for the remainder of the waveform. Waves Po, Na, Pa, Nb, Pb and Nc exhibited significant decreases in latency with age, attaining values indistinguishable from adults by 7 months of age.

Effects of cortical lesions on middle-latency auditory evoked responses (MLR)

Middle-latency auditory evoked responses (MLRs) were recorded simultaneously at 3 or 4 electrode locations in the coronal plane in 5 normal subjects, 11 patients with temporal lobe lesions and in 5 patients with cortical lesions not involving the temporal lobes. In patients with unilateral temporal lobe lesions, the amplitude of Pa and hence that of the Na-Pa complex was reduced over the involved hemisphere but remained intact over the contralateral hemisphere. No MLR asymmetries were demonstrated in patients with cortical lesions that did not affect the temporal lobes or in 2 cases with unilateral anterior temporal lobectomy. The latency of wave V of the auditory brain-stem response was within normal limits in the majority of the patients studied regardless of the site of their cortical lesion.

The maturation of the central auditory conduction in preteram infants until three months post term. III. The middle latency auditory evoked response (MLR)

Middle latency auditory evoked responses (MLRs) were recorded in 64 premature infants; serially in 54 of them. The last recording sessions occurred at 50–52 weeks conceptional age (CA), defined as the gestational age (GA) added to the chronological age. The MLRs were analyzed for the components PO, Na and Pa, and the interpeak latency difference (IPLD) Na-PO. The detectability rate of PO and Na reached 80–90% at about 30 weeks CA. Pa reached the highest rate of about 60% at 52 weeks CA. The degree of prematurity did not result in clear differences with respect to the parameter values. Also, the side of stimulation did not influence the MLR parameter values. The latency values of the MLR components are strongly age dependent. Topographic differences were found between the sides ipsi- and contralateral to stimulation. They are, however, different for PO, Na and Pa. The influence of the state of vigilance on the parameter values could generally only be ebstablished at CA levels of about 32 and 52 weeks CA. The amplitude values at 52 weeks CA are especially sensitive for sleep or awake state. The particular pattern of age dependency of the different components and their topographic differences are consistent with a differential generation of bilateral nature. The early appearance of the response supports the generation of an early functioning subcortical structure in the auditory pathway.

Analog filtering of the middle latency auditory evoked response

There has been confusion on the origin of wave P0 of the middle latency auditory evoked response (MLR). It has been suggested wave P0 is a residual of the effects of restrictive filtering of wave V of the auditory brainstem response (ABR). Twelve subjects were used to study the effects of analog filtering on wave V of the ABR, and waves N0 through Nc. Monaural clicks were presented at 70 dBnHL. Two series of 1024 averages were collected for a 100-ms sample for nine filter conditions. High-pass filtering caused greater distortion of the waveforms than did changes in low-pass filtering. When high-pass filtering was at or above 150 Hz, P0 could not be consistently identified. It was observed that filtering of both the MLR and ABR had differential effects on ipsilateral versus contralateral recordings. The later MLR waveforms showed greater variability than either the earlier MLR waves, or the ABR wave V for changes in high-pass filtering, especially above 150 Hz. This study is in agreement with the concept of simultaneous recording of the ABR and MLR reported by Scherg [M. Scherg, Electroenceph. Clin. Neuro. 54, 339–341 (1982)] although that study did not directly address the question of filtering effects.

Middle-latency auditory evoked responses during open-heart surgery with hypothermia

Middle-latency auditory evoked responses (MLRs) were recorded from infants and adults before and during open heart surgery. Hypothermia was induced through perfusion cooling by cardiopulmonary bypass. In infants deep hypothermia (to 15°C nasopharyngeal temp.) was often followed by the induction of total circulatory arrest. In adults nasopharyngeal temperatures of 25°C were reached. The MLRs were elicited by unfiltered clicks presented through an insert type earphone and recorded with a vertex to ipsilateral earlobr electrode configuration. The MLRs proved to be resistant to muscle relaxation induced by pancuronium and to anesthesia induced and maintained in most cases by fentanyl. In most cases MLR peak latencies were progressively delayed as temperature decreased. Hypotension resulted in decreased MLR (Pa) amplitude.