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Results for “Evoked Potentials, Auditory”

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At least 19 recordsLinked to original sources

PubMed1981

Visual evoked potentials, auditory evoked potentials and EEG in shunted hydrocephalic children.

Visual evoked potentials (VEP) and auditory evoked potentials (AEP) were studied together with the EEG, in 15 hydrocephalic children who had been shunted previously, and in a control group of 10 normal children. From the control group normal VEP's, AEP's and EEG's were obtained. In all 15 hydrocephalic children the EEG was abnormal. AEP's were normal in 9 and abnormal in 6 cases. VEP's were normal in 7 and abnormal in 8 cases. Only 4 patients showed both abnormal VEP's and AEP's. No relation could be demonstrated between the severity of EEG disturbances and evoked response abnormalities.

Auditory Pathways↗

PubMed1991

Auditory evoked potentials.

Auditory evoked potentials (AEPs) have become an integral part of the current otologic/audiologic test battery. With these techniques, synchronous neural activity can be examined from the peripheral end organ of hearing up to the cortical structures responsible for audition. The clinical applications of AEPs range from their use as an indicator of auditory sensitivity in patients who either cannot or will not respond in a conventional behavioral test situation to their use in the diagnosis and monitoring of various otologic and neurologic disorders. As such, measurement of AEPs allows the clinician a unique glimpse of the auditory system.

Audiometry, Evoked Response↗

PubMed1994

Motor signs of wakefulness during general anaesthesia with propofol, isoflurane and flunitrazepam/fentanyl and midlatency auditory evoked potentials.

Auditory evoked potentials have been used as an indicator of awareness. In the present study we combined epidural analgesia with three techniques of general anaesthesia. Motor signs of intra-operative wakefulness were documented and assessed along with cardiovascular changes and with midlatency auditory evoked potentials. Thirty patients undergoing elective laparotomy were studied as follows: first continuous epidural analgesia was used in all patients to block painful sensation to the level of T5. Intravenous general anaesthesia was induced with propofol (2.5 mg.kg-1 b.w., group 1, n = 10), thiopentone (5 mg.kg-1 b.w., group 2, n = 10) or etomidate (0.2 mg.kg-1 b.w., group 3, n = 10) and maintained with a propofol (3-5 mg.kg-1, group 1), isoflurane (0.4-0.8 Vol%, group 2), flunitrazepam and fentanyl (0.005 mg.kg-1 b.w.) bolus injection every 20 to 30 s (group 3). Heart rate and arterial pressure were recorded continuously. Purposeful movements of the limbs, eye-opening or other movements as well as coughing were documented as motor signs of intra-operative wakefulness. Auditory evoked potentials were recorded in the awake state, after induction and during maintenance of general anaesthesia. Motor signs of intra-operative wakefulness occurred statistically significantly more often in the patients of the flunitrazepam/fentanyl group than in those of the propofol and isoflurane group. There was no correlation between wakefulness and cardiocirculatory parameters. In the awake patients midlatency auditory evoked potentials had high peak to peak amplitudes and a periodic waveform.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

The augmenting/reducing phenomenon in the auditory evoked potential.

Auditory evoked potentials (AEPs) were recorded to 4 intensities of tones (70, 80, 90, 100 dB) in 22 normal subjects. Augmenting (generally increasing amplitude with increasing stimulus intensity) and reducing (a levelling off or decrease in amplitude with increasing stimulus intensity) were found to occur at both central (Cz, C3, C4) and temporal (T3, T4) placements, regardless of which peak or peak-through measure was examined. There were generally low levels of agreement between central amplitude/intensity response patterns and those at temporal placements. An individual was seldom classified the same way (i.e. augmenter or reducer) when the augmenting or reducing was assessed using different AEP measures. These results suggest that in the AEP the suitability of the conventional definition and the validity of certain interpretations of augmenting/reducing are questionable.

Adult↗

PubMed1993

Infant malnutrition affects cortical auditory evoked potentials.

Auditory evoked potentials (AEPs) to click and name stimuli were recorded for 23 malnourished infants on admission to and 17 on discharge from hospital, together with those from age-matched controls. The number of peaks on the AEPs and the amplitude were examined. The malnourished infants' AEPs to click stimuli differed from the controls' on admission but not on discharge. The malnourished infants had smaller AEP amplitudes to name than to click stimuli on discharge while the controls did not. The data show that cortical AEPs in infants are affected by malnutrition.

Acoustic Stimulation↗

PubMed1977

Influence of succinylcholine on middle component auditory evoked potentials.

Auditory evoked potentials in the middle component time domain (post-stimulus, 8 to 50 msec) were recorded in response to 1,000-Hz tone pips in a normal-hearing adult subject. Electromyographic (EMG) responses in response to ulnar nerve shocks were recorded from the ipsilateral hypothenar muscles. With the assistance of an anesthesiologist, data were collected during a normal resting state, a state of light sedation, and a state of complete skeletal muscle paralysis from succinylcholine administration. During the paralyzed state, there was abolition of the normal EMG responses seen in the resting and sedated states. The auditory evoked potentials, however, appeared unchanged during the paralyzed state, indicating that they were not of myogenic origin.

Acoustic Stimulation↗

PubMed1998

Differences between congenitally blind and normally sighted subjects in the P1 component of middle latency auditory evoked potentials.

Auditory evoked potentials (0 to 100 msec. range) were recorded two times for 9 congenitally blind children (age = 14.1 yr. +/- 1.4 yr) and 9 age-matched children with normal vision. The groups' peak latency and amplitude of the P1 wave were compared. The peak latency was significantly lower for the congenitally blind than for the normally sighted on a two-factor analysis of variance. Since the P1 wave is thought to correspond to either the ascending reticular activating system or the primary auditory cortex, these results suggest that information processing at these neural levels may occur more efficiently in the blind.

Analysis of Variance↗

PubMedDate not supplied

[Age and features of cortical auditory evoked potentials].

Auditory evoked potentials (AEP) elicited by acoustic stimuli of various frequencies and intensities were studied in children aged from three to sixteen years. With age, peak latencies of the AEP components decrease on the average (taking into account the differences of such changes depending on the frequency and intensity of the stimuli presented) by 67.6 +/- +/- 13; 82.0 +/- 7.5; 65.6 +/- 7.2; 32.3 +/- 6.7 ms for components P1, N1, P2, N2 respectively. In 90% of the cases the thresholds of auditory sensations coincided with AEP thresholds; in 10% of the cases the thresholds of electrocortical reactions were by 5 dB lower than those of the auditory sensations. Enhancement of the stimulus to 80 dB lead to an increase of the AEP amplitude, while further augmentation of stimulus intensity in most cases resulted in a decrease of the AEP amplitude which was accompanied by unpleasant sensations or preceded their appearance. The frequency of this phenomenon drops with the age from 90% in 3-4 years old children, down to 30% in juveniles 15-16 years old.

Adolescent↗

PubMed1982

Logarithmic display of auditory evoked potentials.

Auditory evoked potentials (AEP) can be simultaneously recorded on-line as a succession of 11 waves, through a single input channel of a mini-computer. Since the response waves differ widely in frequency, a computing routine has been developed to display the whole response pattern in a single picture. Based upon a non-linear samples reduction of the digitized response, this routine allows a logarithmic transformation of the time axis. The method improves the identification of the AEP components and provides an objective estimate of the central auditory pathway for both neurophysiological and neuroclinical studies.

Computers↗

PubMed1976

Parameters of temporal recovery of the human auditory evoked potential.

Auditory evoked potentials (AEPs) to tone pips at three monopolar scalters were systematically varied: tone intensity (3.0, 1.5 and 0.75 sec), and direction of attention. Interstimulus intervals were computed separately for the 9 different combinations of the three possible first prior intervals (intervals between the test stimulus and the stimulus immediately preceding it) and the three possible second prior intervals (intervals between the stimulus preceding the test stimulus and the stimulus prior to that). Our results show that temporal amplitude recovery of N1 and P2 can be based solely on the first prior interval had not effect on amplitude. Furthermore, they show that it is inadvisable to use combined N1-P2 amplitude measures since the two peaks appear to be governed by separate processes. Recovery for N1 was different from that of P2, N1 showed no intensity effects while P2 did, and N1 and P2 had different topographic distributions. Directing attention to the tones did not affect N1 or P2 amplitudes but caused a highly significant increase in both N1 and P2 latency. Attention to the tones also produced a frontal negative baseline shift following them.

Adult↗

PubMed1990

The effect of low-frequency whole-body vibration under different visual conditions on auditory evoked potentials.

Auditory evoked brain potentials (AEP) were recorded from 9 healthy males during sinusoidal whole-body vibration (WBV) in the longitudinal (+/- az) direction with 0.6 Hz, 1.85 ms-2rms (F1), 1.01 Hz, 4.27 ms-2rms (F2) and without WBV (F3) under 3 visual conditions--homogeneous bright visual field (B), normal vision (N), and complete darkness (D). The sequences of the different experimental conditions were arranged according to a 9 X 9 Latin Square design. A subtraction technique was used to eliminate vibration-synchronous activity from the EEG. The N1 and N1P2 amplitudes decreased during F1 and F2, compared to F3. The latencies of N1 and P2 increased during F1 and F2. The effects of F1 and F2 did not differ. The visual conditions exhibited no systematic effect on the AEP. The results suggest (1) F1 and F2 to be equivalent exposure conditions and (2) the dominance of vestibular-auditory interactions, compared with visual-auditory ones.

Acoustic Stimulation↗

PubMedDate not supplied

Visual evoked potentials, brainstem auditory evoked potentials, and quantitative EEG in Baltic progressive myoclonus epilepsy.

Visual and brainstem auditory evoked potentials (VEP and BAEP, respectively) and quantitative EEG were studied in 16 patients with Baltic progressive myoclonus epilepsy (PME). The study demonstrated significantly delayed VEP latencies but normal amplitudes in Baltic PME. BAEPs showed slight but significant prolongation in central conduction time. Quantitative EEG revealed diminution of beta and alpha activity and accentuation of theta and delta activity. The slowing in VEP latencies is suggested to be due to impaired synaptic transmission and to reflect dopaminergic dysfunction in Baltic PME. We conclude that there is a multimodal disturbance in sensory projections to cortical areas in Baltic PME. The results give further evidence that nondemyelinating disorders--but with synaptic transmission defects--can produce changes in evoked potentials. The changes in epileptic brain are not confined to hyperexcitable epileptic neurons, but more widespread electrophysiological phenomena are produced.

Adolescent↗

PubMed1997

Differential changes of laser evoked potentials, late auditory evoked potentials and P300 under morphine in chronic pain patients.

The present study investigates the differential behavior of laser evoked brain potentials (LEPs), late auditory evoked potentials (AEP) and the endogenous P300 in response to morphine treatment, examined in 6 chronic pain patients. The main result was that in parallel with marked clinical pain relief, amplitudes of the long latency LEP positivity (P400) were significantly reduced under morphine. One patient suffering from extremely painful osteoporosis for 20 years exhibited a large middle latency component (N170) which was prominently attenuated by morphine. In contrast to LEP amplitude reductions, auditory N1 and P2 potentials appeared either unchanged or even enlarged during morphine treatment. Also P300 amplitude was slightly increased under morphine. Reaction time and mood scales also failed to indicate any sedation. Obviously, LEPs reflected specifically the analgesic morphine effect in this study, while stability or enhancement of AEPs and P300 during morphine treatment indicated lack of sedation or even improved perception and concentration due to the removal of persistent pain as a disruptive perceptual-cognitive stressor.

Adult↗

PubMed1985

Schizophrenia, psychoticism, neuroleptics, and auditory evoked potentials.

Auditory cortical evoked potentials of 20 schizophrenic patients with an acute exacerbation of the illness were investigated before neuroleptic medication and after remission of the acute symptoms, and compared with healthy controls matched for sex and age. Additionally, tests were conducted in 40 healthy volunteers to ascertain whether psychoticism or other personality factors were correlated with evoked potentials. The aim of the study was to test the overarousal hypothesis of schizophrenia and to control the effects of clinical state, neuroleptic medication and personality factors. Acutely ill schizophrenic patients had a shorter evoked potential N1 latency (Table 1). After remission of the symptoms under haloperidol N1 latency of the patients was no longer different from that of the controls. Patients after remission and on medication, however, had longer P2 and N2 latencies and a greater P2-N2 amplitude (Table 2). Psychoticism and extraversion were correlated negatively with amplitude data of components N1 and P2 in healthy volunteers. The results favor the overarousal hypothesis of schizophrenia. Haloperidol normalizes N1 latency in acutely ill patients. It's effect on later components of the evoked potentials seems comparable to a reduction in vigilance. Auditory evoked potentials might allow to follow up the effect of neuroleptics in acute schizophrenia. It seems necessary to consider personality factors when comparing patients with healthy controls in evoked potential studies.

Adult↗

PubMed1993

Magnetic fields normalize visual evoked potentials and brainstem auditory evoked potentials in multiple sclerosis.

The present communication concerns a 46 year old woman with a 10 year history of chronic progressive multiple sclerosis (MS) in whom external application of magnetic fields (MF) (7.5 picoTesla; 5 Hz) during a period of remission resulted in a rapid and dramatic improvement in symptoms including vision, cerebellar symptomatology (ataxia and dysarthria), mood, sleep, bowel and bladder functions as well as fatigue. Improvement in the patient's symptoms was associated with normalization of the pretreatment latencies of the visual evoked potentials and brainstem auditory evoked potential responses within a week after initiation of magnetic treatment. This report demonstrates that treatment with picoTesla MF is an effective, nonpharmacological modality in the management of MS and for the first time documents reversal of abnormal evoked potential responses by this treatment. The pineal gland is a magnetosensor. As MF affect the release of the pineal gland's principal hormone, melatonin, it is hypothesized that the effects of picoTesla MF in MS are partly mediated by the pineal gland which has recently been implicated in the pathogenesis of MS (Sandyk, 1992 a; b).

Electromagnetic Fields↗

PubMed1985

Visual evoked potentials and brainstem auditory evoked potentials in migraine and transient ischemic attacks.

A study of brainstem auditory evoked potentials (BAEPs) and pattern reversal visual evoked potentials (VEPs), recorded in intercritical phase, was carried out in 20 subjects (10 suffering from common migraine and 10 suffering from vertebrobasilar TIA) in order to obtain a comparative evaluation of cortical-subcortical functions. The data we obtained demonstrate the presence of BAEPs alterations in patients with previous vertebrobasilar TIA: no abnormalities were found in the migraine group. VEPs parameters are normal in both groups. Our data show that the study of the so-called "stimulus-related" potentials, such as BAEPs and pattern reversal VEPs, is useful in evaluating the damage produced by any noxa, while it cannot clearly emphasize individual factors predisposing to a specific pathology, as the absence of specific alterations in migraine patients demonstrates.

Adult↗

PubMed1992

A possible collicular component of the auditory evoked potential and its relationship to brainstem and cerebellar auditory potentials.

Auditory evoked potentials were recorded from the rat using skull screw electrodes inserted over the inferior colliculus and the cerebellum. In addition, brainstem auditory evoked potentials (BAEPs) were also recorded. The response recorded from over the inferior colliculus consisted of a slow positive potential with one of two possible peak latencies. The mean latency of the earlier potential was 5.6 ms and that of the later potential was 6.4 ms. A hypothetical generator for the first collicular potential is the termination of the lateral lemniscus in the ventrolateral inferior colliculus, while the later collicular potential could have its origins within the brachium of the inferior colliculus. None of the principal nor minor BAEP waves corresponded to either of the collicular responses. Nor did the trough of negativity between BAEP waves IV and V which is often thought to reflect activity generated within the midbrain. The potential recorded over the cerebellum also consisted of a slow positivity but with a slightly sharper contour than that of the collicular response. The mean latency of the cerebellar potential was 4.9 ms. As there was no temporal relationship between collicular and cerebellar potentials, the present study provided no support for the theory that cerebellar auditory potentials are artefactual and simply far field reflections of activity generated in the inferior colliculus. Judging by the timing of the BAEP waves, it is also concluded that the afferent volley most likely projects to the cerebellum via a collateral pathway branching off the caudal part of the lateral lemniscus.

Acoustics↗

PubMed1998

Contribution of initial median-nerve somatosensory evoked potentials and brainstem auditory evoked potentials to prediction of clinical outcome in cerebrovascular critical care patients: a statistical evaluation.

In a prospective study of 200 patients with cerebrovascular disease (48 intracerebral hemorrhages, [ICH]; 64 subarachnoid hemorrhages, [SAH]; 48 supratentorial and 40 infratentorial ischemic strokes), we assessed the individual and combined prognostic value of median-nerve somatosensory evoked potentials (SEP) and brainstem auditory evoked potentials (BAEP) within 72 hours of admission. Clinical outcome was graded in three ranked categories according to a modified Glasgow Outcome Scale. Likewise, the initial SEP and BAEP findings were graded in a three-class score. In all groups, the SEP were significantly correlated with outcome (P < 0.01). Likewise, after partialling out the prognostic effect of SEP, the contingency between BAEP and outcome was statistically significant, except in ICH (P = 0.07). The contingencies of SEP and outcome in ICH and supratentorial infarcts were higher than the corresponding partial contingencies for BAEP, while the latter were higher in infratentorial infarction and SAH. Therefore, in all disease groups except for SAH, the multiple contingency coefficients ranging from 0.67 to 0.75 were statistically significant and greater than either simple or partial contingencies alone. The results of the two evoked potential modalities combined permit statistically significant superior prognostication in most cerebrovascular diseases when compared to those of either of the modalities alone.

Cerebrovascular Disorders↗