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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↗
PubMed2000

Different generators in human temporal-parasylvian cortex account for subdural laser-evoked potentials, auditory-evoked potentials, and event-related potentials.

In order to localize cortical areas mediating pain we now report subdural cortical potentials evoked by auditory stimulation (auditory-evoked potentials - AEPs) and by cutaneous stimulation with a laser (laser-evoked potentials - LEPs). Stimulation with the laser evokes a pure pain sensation by selective activation of nociceptors. LEPs were maximal over the inferior aspect of the central sulcus and had the same polarity on either side of the sylvian fissure. AEPs were maximal posterior to the LEP maximum and had opposite polarity on opposite sides of the sylvian fissure, consistent with the location of a known generator in the temporal operculum. Auditory P3 (event-related) potentials were maximal over the temporal base. These findings demonstrate that the LEP generator is not in secondary somatosensory cortex on the parietal operculum and is different from the P3 generator.

Adult↗
PubMed2006

[Auditory evoked potentials].

Auditory evoked potentials (AEPs) are an electrical manifestation of the brain response to an auditory stimulus. The waveform represents the passage of electrical activity provoked by auditory stimuli from the cochlea to cortex. The waves represented by I-VII are generated mainly in the brainstem. These waves are called the brain stem auditory evoked potentials (BAEPs) or the auditory brain stem response (ABR). The middle latency AEPs (MLAEP) are generated from the medial geniculate and primary auditory cortex. The long latency AEPs (LLAEP) are generated from the frontal cortex and association areas. The BAEPs appear to be an exquisitely sensitive monitor for pathological events during surgery. Anesthetics and mild hypothermia have minimum effect, if any, on the BAEPs. The BAEPs are useful during the microvascular decompression of the fifth or seventh cranial nerve, resection of acoustic neuroma and posterior fossa operations. Because the auditory pathway occupies a small area in the brainstem, combined use of other evoked potentials such as short latency sensory evoked potentials is recommended. The MLAEPs are most promising evoked responses for monitoring awareness or depth of anesthesia. When the concentration of anesthetics is increased, the amplitudes of the MLAEP's peaks are decreased and their latencies are elongated. Commercially developed A-line AEP monitor or aepEX can extract the AEPs waveform in a short period and automatically analyze the changes in the MLAEPs. These AEP based monitors may be superior to bispectral index (BIS) in detecting the transition from unconsciousness to consciousness.

Anesthesia↗
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↗
PubMed2004

Auditory evoked potentials.

Auditory evoked potentials (AEPs) are an electrical manifestation of the brain response to an auditory stimulus. Mid-latency auditory evoked potentials (MLAEPs) and the coherent frequency of the AEP are the most promising for monitoring depth of anaesthesia. MLAEPs show graded changes with increasing anaesthetic concentration over the clinical concentration range. The latencies of Pa and Nb lengthen and their amplitudes reduce. These changes in features of waveform are similar with both inhaled and intravenous anaesthetics. Changes in latency of Pa and Nb waves are highly correlated to a transition from awake to loss of consciousness. MLAEPs recording may also provide information about cerebral processing of the auditory input, probably because it reflects activity in the temporal lobe/primary cortex, sites involved in sounds elaboration and in a complex mechanism of implicit (non declarative) memory processing. The coherent frequency has found to be disrupted by the anaesthetics as well as to be implicated in attentional mechanism. These results support the concept that the AEPs reflects the balance between the arousal effects of surgical stimulation and the depressant effects of anaesthetics. However, AEPs aren't a perfect measure of anaesthesia depth. They can't predict patients movements during surgery and the signal may be affected by muscle artefacts, diathermy and other electrical operating theatre interferences. In conclusion, once reliability of the AEPs recording became proved and the signal acquisition improved it is likely to became a routine feature of clinical anaesthetic practice.

Anesthesia↗
PubMed2004

Effects of chronic olanzapine and haloperidol differ on the mouse N1 auditory evoked potential.

Auditory evoked potentials have been used in a variety of animal models to assess information-processing impairments in schizophrenia. Previous mouse models have primarily employed a paired click paradigm to assess the transient measures of auditory gating. The current study uses stimulus trains at varied interstimulus intervals (ISI) between 0.25 and 8 s in mice to assess the effects of chronic olanzapine and haloperidol on auditory processing. Data indicate that olanzapine increases the amplitude of the N40, P80, and P20/N40 components of the auditory evoked potential, whereas haloperidol had no such effect. The ISI paradigm also allowed for an evaluation of several components of the mouse evoked potential to assess those that display response properties similar to the human P50 and N100. Data suggest that the mouse N40 displays an ISI response relationship that shares characteristics with the human N100, whereas the P20 appears more consistent with the human P50 across the ISI range evaluated in this task. This study suggests that olanzapine may help improve N100 impairments seen in schizophrenia, while haloperidol does not.

Acoustic Stimulation↗
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↗
PubMed1999

Effect-site modelling of propofol using auditory evoked potentials.

Auditory evoked potentials (AEP) were used to monitor central nervous system effects during induction and recovery from anaesthesia produced by infusion of propofol 30 mg kg-1 h-1 in 22 healthy male patients. Non-parametric and parametric modelling techniques were used successfully to calculate the parameter keo which linked pharmacokinetic with pharmacodynamic aspects of drug action in only 15 of the study patients. In the non-parametric analysis, keo was found to have a mean value of 0.2 (range 0.1-0.36) min-1. Estimation of keo allowed calculation of the effect-site concentration (Ce50) associated with 50% of AEP effect for the population (2.08 micrograms ml-1; 95% confidence limits 1.7-2.45). There were no significant differences between keo values calculated by non-parametric and individual parametric modelling techniques. During recovery, 50% of patients demonstrated evidence of waking at an effect-site concentration of 2.28 micrograms ml-1.

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↗
PubMed2001

Real time mapping of rat midbrain neural circuitry using auditory evoked potentials.

Auditory evoked potentials were recorded in 360 homogeneously spaced sites, in a volume encapsulating the lateral lemniscus-inferior colliculus transition of anaesthetized rats, in order to calculate the electric field vector distribution with each moment in time referenced to the onset of sound presentation. Software, to conduct calculations and graphical representation, and hardware, to minimize neural damage upon recording, were developed in our laboratory. Our results indicate a smooth transition of both amplitude and direction of vectors, suggestive of sequentially activated sites with outward and inward ionic currents coherent with what is known of this part of the primary auditory pathway. That is, anatomical sites (neural generators) and latency for activation matches previous research of the auditory pathway, while adding a real time perspective to the anatomical substrates recruited during the auditory evoked response. An algorithm for calculating the divergent of the vector field, an estimate of the current source density inside the three-dimensional control volume, was used to infer the possible current sinks and sources generating the field potentials. This technique allowed a clear visualization of two distinct discharges arising from the lateral lemniscus towards the inferior colliculus, thus recording signal propagation, as a movie file, with 0.06 ms time resolution.

Algorithms↗
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↗