Use Of Auditory Evoked Potentials Research Articles

Auditory evoked potential: a proposal for further evaluation in children with learning disabilities.

The information presented in this paper demonstrates the author’s experience in previews cross-sectional studies conducted in Brazil, in comparison with the current literature. Over the last 10 years, auditory evoked potential (AEP) has been used in children with learning disabilities. This method is critical to analyze the quality of the processing in time and indicates the specific neural demands and circuits of the sensorial and cognitive process in this clinical population. Some studies with children with dyslexia and learning disabilities were shown here to illustrate the use of AEP in this population.

Objective threshold estimation and measurement of the residual background noise in auditory evoked potentials of goldfish

A survey of papers using auditory evoked potentials (AEPs) published over the last 10 years (Table I) demonstrates that most AEP studies in animals have used subjective methods for auditory threshold determination. Subjective methods greatly reduce the value of statistical hypothesis testing and jeopardize tests of hypothetical experimental group differences in hearing sensitivity. Correspondingly, many attempts have been made to develop objective threshold determination methods, but these have not been used widely. Further, they seldom include an appreciation of the effects of residual noise in the AEP. In this study, AEPs evoked by tonal and noise stimuli in goldfish (Carassius auratus) were recorded and the residual background noise was measured and analyzed in detail. High variability was found in residual noise, but can be effectively controlled with a simple modification of averaging routines. Considerable interobserver disagreements were found using subjective threshold estimation. An objective method of threshold determination was developed based on comparison between AEP amplitude and controlled residual noise, using a signal detection theory approach to set specific threshold criteria. The usefulness of AEP in hypothesis testing for auditory function requires more control over residual background noise amplitudes and the use of objective threshold determination techniques.

Total Intravenous Anesthesia/Target-Controlled Infusion and Auditory-Evoked Potentials in Day Surgery Mammoplasty

Total intravenous anesthesia and the new parameter for administering the most recent drugs, target-controlled infusion, as well as the introduction of new short half-life molecules that do not accumulate have made anesthesia in day surgery safer. In this study, the use of auditory-evoked potentials monitoring made it possible to determine the target plasma concentration of propofol that induces a narcosis sufficiently deep and strictly necessary for effectiveness, thus minimizing the anesthesiologic risk linked to the use and the dosing of the drug, reducing the hospitalization time, and decreasing the side effects for patients undergoing day surgery mammoplasty.

Clinical use of AEVP‐ and AERP‐measures in childhood speech disorders

It has long been recognized that from the first months of life auditory perception plays a crucial role in speech and language development. Only in recent years, however, is the precise mechanism of auditory development and its interaction with the acquisition of speech and language beginning to be systematically revealed. This paper presents the results of a series of studies exploring the relevance of electrophysiological measurements for the objective diagnosis of children with language and speech disorders. In the first, retrospective, study, an inventory was made of clinical neurological, neuropsychological, logopedic and neurophysiological findings obtained from 43 children referred to the Paediatric Neurology Centre for the diagnosis of their speech and language deficits. Neurophysiological abnormalities were found in 95% of these children, among these deviant auditory evoked potentials (AEVPs). The second study demonstrated developmental trends in the waveform of the cortical AEVPs up to age 6 years; the implications for longitudinal studies are discussed. Preliminary results from the third study show emerging differences in auditory event‐related potentials (AERPs) for young children who are at risk for developmental dyslexia based on their family history. These findings underscore the clinical usefulness of neurophysiological measures for the diagnosis of speech‐language disorders. Clinical protocols are further developed and tested.

Excitatory effects of fentanyl upon the rat electroencephalogram and auditory-evoked potential responses during anaesthesia.

Previous studies have shown existence of inconsistent data concerning the use of auditory-evoked potential (AEP) and electroencephalogram (EEG) changes to measure the depth of anaesthesia in regimens involving the use of opioids. The present studies characterize the effects of fentanyl on those responses in rats. The effects of a bolus of fentanyl (6-10 microg kg(-1) intravenously) alone or following naloxone (100 microg kg(-1) intravenously) were examined using brain responses in rats during light anaesthesia with either propofol (20-30 mg kg(-1) h(-1)) or isoflurane (0.8%). Electrophysiological data were recorded using silver ball electrodes. The rats' tracheas were intubated and a femoral artery cannula was inserted to monitor blood pressure. Body temperature, respiratory and pulse rate, and pedal withdrawal data were also collected. Parameters measured before and following administration of naloxone and fentanyl or of fentanyl alone were compared using repeated-measures ANOVA. Fentanyl significantly increased the latency of the major peak from the AEP during propofol and isoflurane anaesthesia (F = 13.2 and 13.5, respectively; P < 0.05) and the amplitude differential between two waveform complexes, and the second differential index (F = 28.3 and 57.2, respectively; P < 0.01). The spectral edge frequency and median frequency from the EEG tended to increase. These effects were abolished by the prior administration of naloxone. These excitatory effects were inconsistent with the classical concept of brain activity depression indicating a deepening of anaesthesia.

Excitatory effects of fentanyl upon the rat electroencephalogram and auditory-evoked potential responses during anaesthesia

Background and objective: Previous studies have shown existence of inconsistent data concerning the use of auditory-evoked potential (AEP) and electroencephalogram (EEG) changes to measure the depth of anaesthesia in regimens involving the use of opioids. The present studies characterize the effects of fentanyl on those responses in rats. Methods: The effects of a bolus of fentanyl (6-10 μg kg−1 intravenously) alone or following naloxone (100 μg kg−1 intravenously) were examined using brain responses in rats during light anaesthesia with either propofol (20-30 mg kg−1 h−1) or isoflurane (0.8%). Electrophysiological data were recorded using silver ball electrodes. The rats' tracheas were intubated and a femoral artery cannula was inserted to monitor blood pressure. Body temperature, respiratory and pulse rate, and pedal withdrawal data were also collected. Parameters measured before and following administration of naloxone and fentanyl or of fentanyl alone were compared using repeated-measures ANOVA. Results: Fentanyl significantly increased the latency of the major peak from the AEP during propofol and isoflurane anaesthesia (F = 13.2 and 13.5, respectively; P < 0.05) and the amplitude differential between two waveform complexes, and the second differential index (F = 28.3 and 57.2, respectively; P < 0.01). The spectral edge frequency and median frequency from the EEG tended to increase. These effects were abolished by the prior administration of naloxone. Conclusions: These excitatory effects were inconsistent with the classical concept of brain activity depression indicating a deepening of anaesthesia.

Auditory nonlinearities measured with auditory-evoked potentials

This article describes the use of auditory-evoked potentials (AEPs) as a tool to assess nonlinear processes in the auditory system. Two-tone signals were used as stimuli to obtain AEPs in both animal and human subjects. Frequency analysis of the physiologic waveforms revealed frequencies in the evoked potential that were not present in the acoustic signal. The largest distortion product in the evoked potential corresponded to the difference between the two primary frequencies (f2-f1). This distortion product was present in all subjects tested. Other distortion products at frequencies defined by n(f2-f1), where n less than 5, were also present in some individuals. These frequencies represent distortion components generated from an even-order nonlinear system. Extensive acoustic and electric calibration procedures provided substantial evidence that the distortion products recorded in the AEP were biologic in origin and not the result of acoustic or recording artifact.