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Biomedical subjects

A R Thornton

Publications and source records attributed to A R Thornton.

84 records · Page 5Linked to original sources
PubMed1976

Time-intensity trade for speech: a temporal speech-Stenger effect.

Time-intensity trade for selected spondaically stressed words was investigated using a centering method for interaural time delays of 0.00, 1.00, 2.00, 2.25, 2.50, and 2.75 msec at five levels of presentation: 0-, 25-, 40-, 55-, AND 70-DB HL (ANSI, 1969). Lateralization effects increased with level of presentation, with a maximum lateralization effect of between 22 and 30 dB occuring with an interaural time delay of 2.25 msec. Multiple images were perceived by all subjects with an interaural time delay of 2.75 msec and by some subjects with an interaural time delay of 2.50 msec at high levels of presentation. No "ear effect" was observed for any of the listeners. A potential clinical application is discussed for this temporal speech-Stenger effect.

Adult↗
PubMed1976

Neurological applications of surface-recorded electrocochleography.

A new outpatient technique, involving the recording of auditory-evoked responses from scalp electrodes, is described. Responses are obtained from the cochlea, cochlear nerve, and auditory brain stem nuclei. The effects of various disorders on these responses are illustrated and the procedure is assessed as a diagnostic technique.

Auditory Perception↗
PubMed1975

Distortion of averaged post-auricular muscle responses due to system bandwidth limits.

Substantially different waveform details have been reported in various studies of the post-auricular muscle (PAM) response. By examining the high frequency limits of the pass-bands used to record the response it would appear that the system bandwidth limits have affected the waveform. Recordings were made using a very wide bandwidth, and were used to obtain power spectra of these PAM responses. These determined the minimum bandwidth requirements to avoid distortion of the waveform. It seems clear that a substantial proportion of the differences reported have been due to the use of a recording bandwidth which has distorted the response.

Acoustic Stimulation↗
PubMed1975

The adaptation of cochlear and brainstem auditory evoked potentials in humans.

The adaptation of the responses from the cochlear nerve and the auditory brainstem nuclei was studied using a burst of four clicks as the stimulus. Nine experimental conditions were obtained from three stimulus levels (60, 70 and 80 dB SL) and from three intervals between click in the burst (15, 24 and 32.5 msec). Six subjects were each tested three times for each of the experimental conditions and the techniques used and results obtained are summarized. Various models of the adaptation of the brainstem responses are proposed which predict different results. The results for the adaptation of the N1 response are basically in agreement with previous work, and the more central brainstem responses showed less adaptation than the peripheral responses. These findings may be explained by postulating different adaptation mechanisms for the peripheral and central responses. The 60dB stimulus level condition gave rise to more adaptation than the 80dB level, and this is in agreement with studies of low and high threshold reception systems reported elsewhere.

Adaptation, Physiological↗
PubMedDate not supplied

Ultrastructural findings in a case of Menière's disease.

The temporal bones of an individual with documented unilateral Meniere's disease were prepared for light and electron microscopy. A morphometric analysis was performed on hair cells, spiral ganglion cells, dendritic fibers in the osseous spiral lamina, afferent and efferent endings, and afferent synaptic contacts. In the ear with Meniere's disease, we found hair cell damage, including disruption of the cuticular bodies and basalward displacement of some outer hair cells. There was no significant difference in the number of hair cells or spiral ganglion cells on the two sides. There was a significant decrease, however, in the number of afferent nerve endings and afferent synapses at the base of both inner and outer hair cells in the ear with Meniere's disease as compared to the contralateral ear.

Aged↗
PubMedDate not supplied

Electrophysiological studies of the auditory system.

Electrophysiological measures of cochlear function can be obtained using the techniques of transtympanic electrode and surface electrocochleography. These provide measures of the basic parameters of the cochlear microphonic, cochlear nerve and auditory brainstem nuclei action potentials, which enable the functional mechanisms of the cochlea and auditory pathway to be defined for normally hearing subjects and, by comparison, give diagnostic information about the pathologies involved in auditory disorders. Data are presented on the values and variability of the responses obtained from normally hearing subjects. The comparative values of each technique in estimating auditory threshold, cochlear function and in evaluating neurological conditions are discussed using data from clinical patients.

Acoustic Stimulation↗
PubMedDate not supplied

Contralateral and ipsilateral 'suppression' of evoked otoacoustic emissions at high stimulation rates.

A previous study has shown that the amplitude of otoacoustic emissions decreases with increase in stimulus rate. Furthermore, these changes are similar to the changes initiated by contralateral suppression of the click-evoked otoacoustic emission. Further studies have been carried out which showed that contralateral suppression, due to a 60 dB SL white-noise suppressor, has a magnitude of about 2.7 dB for the normal subjects used in this study. The equivalent ipsilateral 'suppression' is approximately 8 dB at a stimulus rate of 2000 clicks/s. The two effects have an equivalent magnitude at a stimulus rate of approximately 300 clicks/s. In acoustic neuroma patients, where the nerve pathway is impeded by the tumour, the ipsilateral 'suppression' effect is virtually absent. These findings suggest that an ipsilateral 'suppression' similar in form but larger in magnitude than the more usual contralateral suppression can be created by increasing the stimulus rate using maximum length sequence (MLS) techniques.

Acoustic Stimulation↗