Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 10 of 13
-
ItemSpeech feature recognition with an electrotactile speech processor( 1989)The performance of eight subjects was assessed on a closed-set tactual test battery to evaluate efficiency of the speech feature encoding strategy currently used in the University of Melbourne multichannel electrotactile speech processor. The test battery included twelve subtests of suprasegmental and segmental speech feature contrasts. Results showed that all subjects scored significantly above chance on suprasegmental features such as syllable number, stress and vowel length. In addition, seven of the eight subjects scored significantly above chance for vowel formant frequency discrimination. Scores for manner of articulation contrasts were more variable, with better performance for the higher frequency, longer duration fricatives and affricates. Scores for voicing contrasts suggested that improvements to the tactual coding of this feature could be achieved. The second study examined the contribution of the tactual input to consonant feature identification for subjects using the electrotactile aid in combination with either a low-pass filtered auditory input or different levels of aided residual hearing and lipreading. Results for four normally-hearing subjects showed increased voicing and manner identification scores with the addition of tactual input. Similar results were found for two hearing-impaired subjects, one using the tactual input in combination with lipreading and one using the tactual input in combination with aided residual hearing.
-
ItemSpeech perception studies using a multichannel electrotactile speech processor, residual hearing, and lipreading( 1989)Abstract not available due to copyright.
-
ItemSpeech perception using combinations of auditory, visual, and tactile information( 1989)Four normally-hearing subjects were trained and tested with all combinations of a highly-degraded auditory input, a visual input via lipreading, and a tactile input using a multichannel electrotactile speech processor. The speech perception of the subjects was assessed with closed sets of vowels, consonants, and multisyllabic words; with open sets of words and sentences, and with speech tracking. When the visual input was added to any combination of other inputs, a significant improvement occurred for every test. Similarly, the auditory input produced a significant improvement for all tests except closed-set vowel recognition. The tactile input produced scores that were significantly greater than chance in isolation, but combined less effectively with the other modalities. The addition of the tactile input did produce significant improvements for vowel recognition in the auditory-tactile condition, for consonant recognition in the auditory-tactile and visual-tactile conditions, and in open-set word recognition in the visual-tactile condition. Information transmission analysis of the features of vowels and consonants indicated that the information from auditory and visual inputs were integrated much more effectively than information from the tactile input. The less effective combination might be due to lack of training with the tactile input, or to more fundamental limitations in the processing of multimodal stimuli.
-
ItemResults for two children using a multiple-electrode intracochlear implant( 1989)Abstract not available due to copyright.
-
ItemSynthetic vowel studies on cochlear implant patients( 1988)Abstract not available due to copyright.
-
ItemPerceptual studies on cochlear implant patients with early onset of profound hearing impairment prior to normal development of auditory, speech, and language skills( 1988)Abstract not available due to copyright.
-
ItemThe histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient: correlation with psychophysics and speech perception results( 1988)Cochlear implantation has become a recognised surgical procedure for the management of a profound-total hearing loss, especially in patients who have previously had hearing before going deaf (postlingual deafness). Nevertheless, it is important for progress in the field that patients who have had a cochlear implant, bequeath their temporal bones for research. This will then make it possible to further assess the safety of the procedure, and the factors that are important for its effectiveness. Biological safety has been assessed in a number of studies on animals, in particular, the biocompatibility of the materials used (1,2), the histopathological effects of long-term implantation on the cochlea (3, 4, 5, 6, 7, 8), and the effects of chronic electrical stimulation on the viability of spiral ganglion cells (9, 10, 11, 12). In studying the temporal bones of deceased cochlear implant patients it is possible to help establish that the animal experimental results are applicable to Man. Surgical trauma has been most frequently evaluated by inserting electrodes into cadaver temporal bones. It is important, however, to examine bones that have been previously implanted surgically to ensure that the cadaver findings are applicable to operations on patients. The effectiveness of cochlear implantation can be studied by correlating the histopathological findings, the dendrite and spiral ganglion cell densities, in particular, with the psychophysical and speech perception results. Other benefits also accrue, for example, establishing the accuracy of preoperative X-rays and electrical stimulation of the promontory in predicting cochlear pathology and spiral ganglion cell numbers. For the above reasons it has been especially interesting to examine both the temporal bones and central nervous system from one of our patients (patient 13) who participated in the initial clinical trial of the Cochlear Proprietary Limited (a member of the Nucleus group) multiple-electrode cochlear prosthesis, and who died due to a myocardial infarction following coronary bypass surgery.
-
ItemThe University of Melbourne/Cochlear Corporation (Nucleus) Program( 1986)Over the last two decades many have contributed to the understanding of how to help profoundly and totally deaf patients understand speech through electrical stimulation of the auditory nerve. We have referred to some of the work in a review of speech processing for cochlear implant prostheses.
-
ItemThe clinical trial of a multi-channel cochlear prosthesis( 1983)The results of a multiple-electrode cochlear implant carried out on 1st August, 1978 on a totally deaf patient (post-lingual hearing loss) showed that he could perceive sounds of different pitches depending on the electrode stimulated, and this finding was consistent with the place theory of frequency coding. Furthermore, stimulating individual electrodes produced percepts which the patient described as vowel-like in quality. The patient could also perceive different pitches which varied with the rate of stimulation up to 200 pulses/second, but at higher rates he had difficulties perceiving pitch changes (Clark et al. 1978; Tong et al, 1979). As a result of the psychophysical studies a speech processor was developed. The speech processor extracted: firstly, the voicing frequency to help the patient hear the rhythm of speech and know whether a speech sound was voiced or unvoiced (e.g., /b/ versus /p/); and, secondly, the second formant to enable the patient to recognize vowels and consonants and so hear words. In order to maximize speech intelligibility, the second formant stimulated an appropriate electrode, and the rate of stimulation on that electrode was related to the voicing frequency.
-
ItemPreoperative hearing aid evaluations for cochlear implant patients: a preliminary report using a minimal auditory capabilities battery( 1983)Two profoundly deaf patients were evaluated using the Minimal Auditory Capabilities (MAC) battery of speech discrimination tests. One patient was a multiple-channel cochlear implant patient (MC1) using a wearable speech-processor, the other a prospective cochlear implant patient using a hearing aid (HA). Results from the MAC battery showed that MC1 received significantly more auditory information via the speech-processor than was provided by the hearing aid to HA. These results indicated that the cochlear implant could be a suitable alternative for HA. However, the results indicated that HA gained some minimal benefit from the hearing aid and these results should be taken into consideration when deciding which ear should be implanted.