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H A Beagley

Publications and source records attributed to H A Beagley.

14 recordsLinked to original sources
PubMed1979

Temporary threshold shift, loudness, and auditory evoked potentials.

TTS2 of 20dB was produced in a group of subjects using a 1000 Hz pure tone. All TTS and related measurements were made at 1500 Hz. The recovery of TTS, and of TLS or 'temporary loudness shift' (measured against a reference tone at 20db, 40dB and 60dB SL in the opposite ear), as well as N1-P2 amplitude of the Vertex potential, were plotted. There was an orderly recovery of both TLS and TTS although the rate of recovery of the latter was noticeably more rapid. Recovery of N1-P2 amplitude was much less orderly, although it did recover in much the same way. When the amplitudes were measured at 40dB SL the recovery was more orderly and followed the course of TTS more closely. It was concluded that any relation between N1-P2 amplitude and growth of loudness was indirect.

Acoustic Stimulation↗
PubMed1978

Differences in brainstem response latency with age and sex.

Brainstem evoked potentials in response to clicks at 60dB, 70dB and 80dB were recorded from a group of 70 normally hearing subjects. There were 10 subjects (5 male, 5 female) for each of the decades from the second to the eighth. The youngest subject was 14 years, the oldest 79 years. The possibility of there being increased latencies as a function of age was examined. The results indicated that there was, for practical purposes, no such increase. On the other hand there was very strong evidence that in females latenceis are shorter than in males. In addition, amplitudes were reduced in the case of older subjects. Condifidence limits for latency were calculated. These may be helpful in deciding whether or not a particular latency is outside the normal range.

Acoustic Stimulation↗
PubMed1977

Electrocochleographic changes in acoustic neuroma: some experimental findings.

Reversible experimental lesions were produced in the central end of the cochlear nerve at the IAM of guinea pigs by various procedures, including the instillation of KCl (0.1 or 0.01 M). As a result the usual diphasic AP waveforms seen in guinea pigs (when click stimuli are used) were transformed into monophasic, widened negative waves. This change, attributed to a neural block, was reversible, e.g. when the instilled KCl was dispersed by irrigation with normal saline. It is suggested that the widened monophasic negative AP's observed at ECochG in cases of acoustic neuroma or similar lesions, are produced in this way.

Action Potentials↗
PubMed1976

Transtympanic electrocochleography in the diagnosis of retrocochlear tumours.

Transtympanic electrocochleography has been used as a diagnostic procedure in over 250 adult patients with sensorineural deafness. No complications have been encountered. Among these patients vestibulocochlear Schwannoma (acoustic neuroma) has been confirmed in 56 ears while 11 other ears have been found to be affected by other space-occupying lesions. As a result of our observations in these patients, we would like to propose that there are at least three separate criteria to be considered in reaching or strongly suspecting a diagnosis of such pathology. These are broadening of the action potential (loss of P1), observation of a clear microphonic response, and preservation of the action potential even when using stimulus intensities which are not audible in the patients' affected ears. The merits of each of these criteria are discussed and compared with other clinical and operative findings. With the electrocochleographic techniques now employed in searching for acoustic neuromas, false negative results are rare though false positive results are still obtained.

Acoustic Stimulation↗
PubMedDate not supplied

Survey of the clinical use of electrocochleography.

A questionnaire on the clinical use of electrocochleography (ECochG) was distributed to clinics throughout the world which use this method. The 26 replies comprised 3696 cases with a median age of 22.5 years. The majority (57.1%) were tested with a transtympanic promontory electrode. The risk of any undesirable effect from this electrode placement was negligible (less than 0.1%), but a greater probability (less than 1.0%) of serious complication from general anesthetics was revealed. On the benefit side, ECochG added significant information to the diagnoses of 87.8% of the children and 34.2% of the adults, and in 48.2% of the children and 2.0% of the adults this information was a primary factor in the hearing evaluation and decision on management. The cases for which ECochG was most helpful were predominantly children and neonates with complex neurological or psychiatric problems which interfered with reliable testing by other methods. Comparisons of ECochG with other methods were reported in 63.2% of the cases. The respondents judged 97.4% of those comparisons to reflect favorably on the validity of ECochG.

Action Potentials↗
PubMedDate not supplied

Relation between the waveform of the cochlear whole nerve action potential and its intensity function.

The whole-nerve action potential (AP) was recorded by intracochlear electrodes in the guinea-pig. As is well known, in normal conditions, the AP elicited by tone bursts displays negative and positive deflections. Inactivation of the central end of the nerve at the internal auditory meatus (IAM), by introduction of a few drops of KC1 solution, or by mechanical pressure, produces a change in the wave shape of AP which is transformed into a single negative deflection. The relation of the amplitude of the monophasic AP to the intensity of the tone burst is monotonic, in contrast to the classical two-slope variation observed in normal conditions. These results are interpreted by the disappearance of a positive component of the response produced at the IAM. The convolution of the monophasic unit AP would explain the monotonic intensity function.

Acoustic Stimulation↗
PubMedDate not supplied

Fully objective ERA by phase spectral analysis.

A method of ERA using the Vertex potential is presented which is entirely objective. The result is given by means of a statistical evaluation which is derived automatically. The method is based on pattern analysis of the V-potential, the technique relying essentially on analysis of the phase spectrum of the appropriate Fourier components.

Acoustic Stimulation↗
PubMedDate not supplied

Pattern analysis of auditory-evoked EEG potentials.

A pattern analysis approach to the detection of auditory evoked potentials in the EEG is reported. Pattern aspects of individual post-stimulus responses have been examined first through their correlation coefficients using the suprathreshold average evoked potential as a reference pattern, and second by the ensemble distribution of phase values of Fourier spectral components, employed to characterise signal pattern. The correlation study indicated that suprathreshold stimuli act to increase the reference pattern similarity of individual records. Individual harmonic phase values are distributed approximately uniformly for unstimulated EEG, but were demonstrated to be increasingly aggregated for increasingly suprathreshold stimuli. It is proposed that a fully objective audiometric technique can be based on a phase-spectral technique.

Acoustic Stimulation↗