Brain-stem Potentials Research Articles

The Changes of Auditory Brainstem Response (ABR) in Monaural and Binaural Stimulation

Simultaneous bilateral recordings of ABR in cats were performed using binaural and monaural stimulation following the section of the eighth nerve and the auditory ascending cross pathway (cochlear nucleus-superior olivary nucleus level).The results were as follows:1) Waves 1 and 2 seem to represent the potentials of the ipsilateral cochlear nerve and cochlear nucleus.2) Waves 3, 4 and 5 seem to represent the potentials of the contralateral brainstem evoked potentials.3) Wave 3 is related to the contralateral superior olivary nucleus, wave 4 to the contralateral superior olivary ascending pathway and wave 5 to the contralateral inferior colliculus.4) In order to locate the lesions, ABR should be evaluated whether there is the response to binaural or monaural stimulation or not.

The Role of Efferent Inhibition in Human Auditory Attention: An Examination of the Auditory Brainstem Potentials

This study examined whether the efferent olivocochlear bundle (OCB) functions to attenuate irrelevant auditory stimuli during visual attention. Subjects either counted 8000 Hz, 50 dB SL target tone pips, or target letters flashed rapidly on a visual display. The target stimuli were randomly interspersed among nontarget stimuli to prevent ther subjects anticipating their occurrence (Naatanen, 1975). The auditory brainstem potentials were tape recorded for separate analyses of the target and nontarget tone pips. The nontarget tone pips were not significantly affected suggesting they were attenuated in the auditory task (intramodal effect) as well as during the visual task. During focused visual attention, the auditory nerve component to the target tone pips was significantly reduced in amplitude by 37.4% and increased in latency by 90 musec. Wave V generated partially from the inferior colliculus was also reduced in amplitude by 12.9%; however, this decrement, was not statistically significant. The use of 8000 Hz tone pips and random target presentation precluded middle ear muscle contractions producing these results. It was concluded that the efferent OCB which synapses on and inhibits the hair cells and axons within the cochlea may function during visual attention by attenuating irrelevant acoustic stimuli.

Frequenzfolgepotentiale unter dem Aspekt der objektiven Geh�rdiagnostik im Tieftonbereich

Click evoked brainstem potentials have proved to be a reliable tool in testing the integrity of the high frequency channels of hearing (≥2 kHz). Evaluation of low frequency hearing loss (≤1 kHz), however, has shown to be much more difficult. Tackling this task we investigated the value of frequency following potentials (FFP) in case of subjects with known tone audiometric hearing loss. We find no good correlation between FFP threshold and tone audiogram when using 500 Hz transient stimulation and averaging technique. This fact cannot be explained only by recruitment effects. Threshold detection is possibly complicated by interference of different FFP generators. To establish rapid and sensitive on-line FFP analysis and to obtain reliable phase (i.e., latency) information we employed lock-in technique in recording frequency following responses on continuous, sweeping frequency stimulation (100–600 Hz). Results suggest a cochlear microphonic component generated in the basal turn and a neural one from low frequency tuned fibres, whereas inferior colliculus seems not to be involved as FFP generator.

Altersabh�ngige Analyse der Reizantworten der Hirnstammpotentiale beim Meerschweinchen

In completion to electrophysiological studies in man auditory evoked brain stem potentials of the guinea pig were recorded by way of the far-field technique. Two age groups of albino and pigmented guinea pigs were compared with regard to several parameters of the response. The four groups showed significant differences in auditory threshold. Albinos exhibited lower thresholds and a minor hearing loss in age. Changes in response pattern could not be found as components of the aging process. Beside higher thresholds old guinea pigs showed reduced amplitudes to high-frequency stimuli. The effect of age at the peripheral stations of the auditory pathway is discussed in the lights of these results.

Analysis of the click-evoked brainstem potentials in humans using high-pass noise masking. II. Effect of click intensity.

Derived narrow-band brainstem responses were obtained for click levels of 10--60 dB SL in normal hearing subjects. The amplitudes and latencies of the wave I, wave III, and wave V components in the derived BSER were studied as a function of click intensity. Characteristic differences were found between the input-output behavior of waves I and III on one hand and wave V on the other hand, especially for the low-frequency narrow bands (center frequencies of 0.5 and 1.0 kHz). While the wave I and wave III (peak-to-succeeding trough) amplitude showed a small (20--30 dB) dynamic range with saturation effects, the wave V amplitude continued to increase across the intensity range studied. At the high-frequency end (narrow-band center frequencies of 4 and 8 kHz), wave V also showed saturation. It is suggested that this difference across center frequency (place of origin along the cochlear partition) is responsible for the dominance of wave V at low-frequency stimulation (e.g., with tonebursts). The latencies of the three waves studied maintained their constant interwave delays across the observed intensity range in each narrow band. Quite large (up to 3.5 ms) increases in the narrow-band latencies were found for decreasing click levels; this is comparable in value with those for the unmasked BSER although the mechanism seems to be different. The major contribution to the BSER which determines its latencies, originates at 60 dB SL from the 8-kHz region but at low SL (10 and 20 dB) from the 2-kHz region. At these low intensity levels, the contribution from the apical part of the cochlea, however, is still of the same size as that from the high-frequency end.

Differential development of brainstem potentials in healty and high-risk infants.

Maturation along the brainstem acoustic pathway, as well as the integrity of these structures, has been shown to be reflected in brainstem evoked potential recordings. Trajectories formed from repeated sequential measurements of several brainstem response variables reveal distinct developmental curves for healthy and high-risk infants. Longitudinal analysis offers a means of determining temporary or permanent maturational effects on the central nervous system in early life.

Abnormal brain stem potentials in infants with threatened sudden infant death syndrome.

Fifteen infants at risk for sudden infant death syndrome by clinical criteria were tested using brain stem auditory evoked potential (BAEP) techniques. All infants demonstrated abnormalities on two or more of the seven criteria employed to assess results. The data indicate that BAEP testing may play a significant role in the identification and monitoring of these children.

Human auditory attention: the olivocochlear bundle may function as a peripheral filter.

ABSTRACTTwo experiments examined whether focused attention toward a visual display would alter the sensory transmission properties of the human auditory nerve and brainstem centers to irrelevant auditory tone pips. In the first experiment, 16 subjects either listened to 1000 Hz, 50dB SL tone pips presented binaurally at 10/sec (“Listen”), or mentally counted letters flashed rapidly on a screen (“Look”). The auditory brainstem potentials recorded from the vertex were averaged on‐line in groups of 500 with a 10‐msec sweep and a bandpass of 150–1500 Hz. Results indicated that during the “Look” trials, Wave 5 generated from the inferior colliculus (7.322 msec latency) was significantly reduced in amplitude by 16.4% and increased in latency by 27 μsec. A second experiment with 8 subjects demonstrated that the effects of attention are limited to the auditory nerve component when using 8000 Hz stimuli but are significant for both the auditory nerve and collicular components when a mid‐frequency (2000 Hz) tone pip is used. These results suggest that during concentrated attention toward visual stimuli, irrelevant auditory stimuli may be attenuated at a peripheral level possibly through the action of the efferent olivocochlear bundle.

Computer identification of waves in the auditory brain stem evoked potentials

The high reliability with which the waves I through V can be identified in auditory brain stem potential (BAEP) recordings suggests the possibility of using the computer to identify the peaks. This paper examines the application of a smoothing algorithm in which detection of zero crossings in the derivative array of the averaged potentials is used to identify waves I–V in clinical BAEP recordings. A comparison of computer wave identification with human evaluation is presented. The results suggest that computer evaluation cannot entirely replace ‘manualrs evaluation of the waves, but can expedite analysis and alert the clinician to potentially abnormal responses.

Brain stem auditory evoked potentials are related to interaural time discrimination in patients with multiple sclerosis

In a combined psychophysical-electrophysiological study on 29 patients with multiple sclerosis (MS), a compromised ability to make interaural time discriminations was nearly always found to be associated with ‘abnormal’ brain stem potentials evoked by clicks to at least one ear. However, no obvious relationships were found between evoked brain stem potentials and several other auditory behavioral measures such as interaural intensity discrimination, pure-tone thresholds and speech discrimination.

Problematik einer frequenzspezifischen Schwellenmessung mit den Hirnstammpotentialen unter Verwendung des otometrischen Signals (DWT)

This study aimes at investigating if the damped wavetrain stimulus (Victoreen) may be used in the evaluation of frequency specific thresholds using brainstem potentials. Stimulus frequencies were 1, 4, and 8 kHz. Starting with a control group (10 persons) latency curves for the brainstem potentials were established. The test group included patients with various forms of sensorineural hearing loss in the audiogram. Threshold measurements at the three stimulus frequencies were done with these patients using the potential IV (Jewet V). The latency curves of the normal hearing control group reveal a frequency-specific information being present in the brainstem potentials. This can be derived from latency shifts at different stimulus frequencies. However, investigating patients with a steep slope or a notch in the pure-tone audiogram introduces some difficulties in the ERA-threshold evaluation.

Les potentiels évoqués auditifs du tronc cérébral chez le sujet agé corrélation avec l'E.E.G.

Auditory brainstem potentials were recorded in 54 old adult subjects ranging in age from 61 to 89 years. Attention was paid to interwave latencies in order to assess the effects of aging on central conduction time. The data were compared to those obtained in 41 young adult subjects. Advancing age resulted in a slight-prolongation of I-III, III-V and I-V interpeak latencies when compared to young adult subjects (about 0.2 ms); nevertheless there were no statistical differences between the mean values of old and young subjects. Abnormalities of brainstem potentials were found in 30% of the old patients; i.e. interpeak latency prolongation and desynchronisation. Brainstem abnormalities were more likely to be found in patients with delta E.E.G. activity and criteria of deterioration at the psychometric tests. Lesser degrees of abnormalities (7%) were seen in old patients without any vascular or neurologic disorder, than in patients with one of those pathological processes (77%). The results suggest that brainstem potentials abnormalities observed in old subjects are not related to age as such, but to associated vascular or degenerative disorders, the frequency of which increases with age.

The location by early auditory evoked potentials (EAEP) of acoustic nerve and brainstem demyelination in multiple sclerosis (MS).

Tone pips of suprathreshold intensities elicit an acoustic nerve response (I) and six low amplitude brainstem potentials (II-VII) during the initial 10 ms. Seven waves were studied in 40 control subjects and 5 waves (I-V) in 47 patients with MS. The results suggest involvement of the auditory pathway of 24 of 27 patients in the clinically "definite", of 5 of 9 cases in the "probable" and in none of 5 patients in the "possible" MS groups. EAEPs were normal in 6 cases with a spinal form with one exception where changes of potential were indicative of a midbrain lesion. Dysfunction within the acoustic pathway was observed at the level of the acoustic nerve and in the medulla oblongata, pons and midbrain. The significance of the bilateral EAEP abnormalities found in some patients at different levels is discussed with regard to a polytopic location of the underlying lesion.

Auditory function in newborn intensive care unit patients revealed by auditory brain-stem potentials

The relations between clinical illness and auditory response (as revealed by auditory brain-stem potentials) were prospectively studied in a neonatal intensive care unit. Forty-nine tests were performed on 29 infants with gestational age 24 to 43 weeks and birth weight 530 to 3,380 gm. Auditory test results were classified as pass or fail, depending on the presence or absence of wave V at a latency of 7 to 11 ms in response to clicks 60 dB above the normal adult threshold. Six patients failed and 23 patients passed. The failures were not correlated with excessive noise exposure or ototoxic medication. Five of the patients who failed had intracranial hemorrhage. Routine screening of infants in the NICU for auditory impairment is a clinically feasible and useful procedure.

Sex differences in the amplitudes and latencies of the human auditory brain stem potential

Sex differences in the amplitudes and latencies of the auditory brain stem potential (BAEP) were investigated using 3 levels of intensity and 3 stimulus presentation rates. The females displayed consistently larger BAEPs for waves IV, V, VI, VII than the males. The only latency differences which reached significance over all the intensities and rates occurred for wave V. The females showed significantly shorter wave V latencies than the males. Since hearing losses and individually determined click thresholds were comparable between the two groups tested, the exact sources of the uneven distribution of amplitude and latency effects are in question. Differences in the relative distances of the anatomical generators are considered in accounting for the sex differences. Because the precise origin of the sex differences cannot be stated with certainty at this time, attempts to develop normative data for the BAEP should consider the possible influences of sex differences.

Clinical applications of evoked responses: A survey

Evoked responses were first described in the late forties. In the late fifties, technology had so far advanced that the method became practically useful in clinical applications. Descriptions of the normal response and the influence of age and the effect of attention were extensively studied. There are marked interindividual and interlaboratory differences, partly explained by differences in test set-up. This is why it is still necessary that every laboratory, using its own test set-up, should determine its own standard values in normal test subjects. The value of EK studies in clinical diagnosis may be summarized as follows: • ophthalmology, organic psychiatry, neuropaediatrics, multiple sclerosis, uraemia: ER studies often supply important diagnostic information; • local lesions of the cerebral hemispheres, peripheral nerves and spinal cord, coma: ER studies can be useful as source of supplemental diagnostic information; • non-organic psychiatry and psychology: ER studies are still of minor practical value in individual clinical diagnosis. Research into applications of spinal evoked potentials and brain stem potentials is still in its initial phase.

Auditory potentials of cochlear nerve and brain stem in multiple sclerosis.

Auditory evoked potentials of the cochlear nerve and the brain stem were recorded in ten patients with multiple sclerosis (MS) and four patients thought to possibly have MS. A characteristic pattern materialized, with a prolonged N1-P4 conduction time and absent or small N2 and/or N5 waves. We discuss possible clinical implications.

Electrical stimulation of the auditory nerve in cats. Long term electrophysiological and histological results.

Each of five cats (one congenitally deaf) had Pt-Ir electrodes placed in the modiolus. Some electrodes were stimulated with a 100 micronamp, 0.25 msec balanced biphasic 50/sec pulse for 2 hours for a total of 20 to 40 hours each over periods of several months. Pre- and poststimulation measures of click-evoked N1 responses, averaged brain stem potentials, and impedances showed no long-term effects of damage to the nerves. Light microscopy showed very acceptable tissue tolerance and no evidence of damage caused by electrical stimulation. The deaf cat had about 10% residual nerve fibers which responded to stimulation.

Interaural time discrimination and brain stem potentials in patients with multiple sclerosis

Twenty-nine patients with multiple sclerosis who had normal audiograms and good speech discrimination were studied. A two-alternative forced choice paradigm was used to determine interaural time and intensity JNDs for white noise bursts. Short-latency (< l0 ms) click evoked potentials were recorded between the vertex and earlobe. The subjects with normal interaural time JNDs usually had normal responses even if the interaural intensity JNDs were abnormally large. Those with abnormally long time JNDs usually had abnormal evoked responses; those with the longest time JNDs often exhibited no waves beyond the compound action potential of the auditory nerve. Patients with abnormal time JNDs and different evoked potentials on stimulating each ear showed a lateralization bias: whenever the interaural time of the stimulus was less than the subject's time JND the stimulus was localized towards the side for which potentials were more normal. [Supported by NIH and the Hôpital Cantonal of Geneva, Switzerland.]

Étude des potentiels évoqués du tronc cérébral dans les comas traumatiques : intérêt pour la détermination des niveaux de dysfonctionnement du tronc cérébral

Auditory brainstem potentials were recorded in 22 comatose patients in whom the level of brainstem dysfunction was defined by the clinical assessment of brainstem reflexes and posture. The patients with cortico-subcortical or diencephalic levels showed normal brainstem potentials. The other patients showed a relationship between the abnormalities of the different components of the brainstem potentials and the clinical levels of brainstem dysfunction caused by the rostro-caudal evolution. Alteration of wave V seemed to be related to a midbrain dysfunction, alteration of wave III to a pontine dysfunction and alteration of waves I and II to a lower brainstem dysfunction.