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Biomedical subjects

A J Fourcin

Publications and source records attributed to A J Fourcin.

8 recordsLinked to original sources
PubMed1990

Psychoacoustic aspects of speech pattern coding for the deaf.

The SiVo aid, which provides a sinusoidal signal indicating voice fundamental frequency and voicing information, was compared as an aid to lipreading to a conventional hearing aid having extended low-frequency output. Speech perceptual measures of consonant confusions in lipreading and the identification of a simple intonation contrast were collected from a group of 8 profoundly deaf adults. Audiometric and psychoacoustic measures were also collected. In the intonation task, 6 of the 7 patients tested performed better with the SiVo aid and the seventh scored perfectly with both aids. Four patients (out of 8) preferred to use the SiVo aid rather than the conventional aid, and 2 of these showed a significant advantage with the SiVo aid in the aided lipreading of consonants. The remaining 4 patients preferred the conventional aid, although none of these patients showed a significant advantage with the conventional aid in the lipreading of consonants. The 4 patients who preferred the SiVo aid over the conventional aid had very profound hearing loss and minimal dynamic range at 500 Hz and above, and those receiving the greatest benefit showed no measurable frequency selectivity. In the 2 patients who preferred the SiVo aid, yet showed no significant advantage for the SiVo aid in consonant lipreading, consonant confusions were also measured for aided lipreading, using a prototype aid providing both voice fundamental frequency and voiceless excitation patterns. Both patients showed additional and significant benefit from inclusion of the voiceless pattern element.

Audiometry, Pure-Tone↗
PubMed1987

Structural effects of short term and chronic extracochlear electrical stimulation on the guinea pig spiral organ.

To assess the effects of extracochlear electrical stimulation on cochlear structure, guinea pigs were implanted and stimulated with single middle ear electrodes either at round window or promontory sites, and their cochleae examined by transmission electron microscopy. Implanted but unstimulated, or unimplanted control animals were examined in the same way. Alternating current stimulation at the promontory for 2 h at 150 Hz, 500 microA, caused outer hair cell efferent endings to become dense and vacuolated, but no hair cells were damaged. With direct current stimulation at 500 microA for 2 h the basal regions of the stimulated cochlea were badly damaged and many outer hair cells lysed. Long term (up to 1200 h) round window stimulation at 100 or 141 Hz, 15-91 microA rms, did not cause cell death or inner hair cell damage, but basal outer hair cells and their efferent endings were badly affected in both ipsilateral and contralateral cochleae. The compound action potential of the auditory evoked response to broad band click stimuli was not altered by chronic electrical stimulation. It is concluded that chronic stimulation with the parameters used does not threaten cochlear survival, and it is proposed that the bilateral structural changes induced by chronic stimulation are caused by excessive activation of the cochlear efferent pathways.

Animals↗
PubMed1985

Microprocessor-controlled speech pattern audiometry. Preliminary results.

Interactive microprocessor-controlled speech pattern tests making use of high-quality synthetic speech have been used to assess the development of subjects' ability to process speech contrasts of increasing complexity, from prosodic contrasts to a 'date-gate' place contrast. These tests have been particularly useful in mapping the development or recovery of subjects functioning at the very first stages of processing ability. Some results obtained with profoundly hearing-impaired children and with adults suffering from brain stem disorders are reported, and further applications of speech pattern audiometric techniques are briefly discussed.

Adolescent↗
PubMed1985

Audiological rehabilitation of patients with brainstem disorders.

A brief account is given of the course of rehabilitation of three patients with severe brainstem injuries. Particular use has been made of synthetic speech pattern assessment procedures which have been integrated into the management model of Goldstein and Stephens (1981). The use of speech stimuli of controllable simplicity has two main clinical benefits: the early course of re-acquisition can be examined analytically, second, aspects of speech receptive and productive rehabilitation can be facilitated. Re-acquisition of perceptive ability in some of these patients may follow a progression from simple to complex acoustic pattern contrasts and this may provide an effective basis for future techniques of rehabilitation.

Adult↗
PubMed1979

External electrical stimulation of the cochlea: clinical, psychophysical, speech-perceptual and histological findings.

Our progress towards the development of a particular form of cochlear implant for the totally deaf is described. A single channel stimulation at the round window or promontory is used. This involves a minimum of surgical intervention and infective risk, preserves the possibility of remission and allows the application of later developments. The signal used for stimulation is designed to be matched both to the deaf lip-reader's needs and to his new, restricted, auditory ability. This is done by concentrating on the acoustic pattern components of speech which carry intonation and voiced-voiceless information. Surgical electrophysical, psychoacoustic and speech perceptual aspects of our work with twelve patients are described. The tests involve responses, for example, relating to: threshold for sinusoids; frequency difference limens; periodic -aperiodic discrimination; stress placement; and consonant labelling using combined visual and electrical inputs. Relatively extensive measurements were made with six patients. Significant individual differences were found and the sets of responses provide an essential basis for an appraisal of the potential usefulness of our work to the individual patient. Possible reasons for the individual differences are discussed. A brief indication is given of the techniques which we have developed for the future speech training and speech production evaluation of patients with electro-cochlear voice monitoring. The final section of our paper mentions our histological investigation of the effects of this type of stimulation in the guinea pig.

Acoustic Impedance Tests↗