Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 10 of 86
-
ItemForward masking patterns produced by intracochlear electrical stimulation of one and two electrode pairs in the human cochlea( 1989)Abstract not available due to copyright.
-
ItemImplantation of the Melbourne/Cochlear multiple-electrode extracochlear prosthesis(Annals Publishing Co., 1989)The Melbourne/Cochlear multiple-electrode extracochlear implant is designed for deaf patients who are unsuited to multiple-electrode intracochlear implantation. The implant consists of a receiver-stimulator package connected via a lead wire assembly to six individual stimulating electrodes. There is a choice of two alternative surgical procedures, both of which are via a combined middle ear approach using anterior and posterior tympanotomies. Four active electrodes shaped into compressible platinum-iridium soft-balls are fed through the mastoid cavity and across the facial recess, and placed into cavities that are made over the cochlear turns that project to the medial wall of the middle ear. One hard-ball active electrode is placed into the round window niche. One hard-ball reference electrode is placed into the hypotympanum. An additional electrode wrapped around the lead wire assembly can be used as an alternative reference electrode. A specially designed insertion needle facilitates the placement and the fixation of the soft-ball electrodes.
-
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.
-
ItemThe biologic safety of the Cochlear Corporation multiple-electrode intracochlear implant( 1988)Studies have been undertaken to confirm the biologic safety of the Cochlear Corporation multi-electrode intracochlear implant. The materials used are biocompatible. The electrode array is flexible: it can be inserted with minimal or no trauma, providing the insertion is stopped when resistance is first felt. An atraumatic insertion is facilitated if a good view is obtained along the scala tympani of the basal turn of the cochlea by drilling through the crista fenestrae. The passage of the electrode around the cochlea can be facilitated if the electrode is rotated during insertion (clockwise for the left and anticlockwise for the right cochlea). The electrode can be explanted and another one reinserted with minimal or no trauma. A seal established around the electrode after an implantation period of 2 weeks can prevent infection extending from the middle to the inner ear. The electrical stimulus parameters produced by the Nucleus receiver-stimulator cause no loss of spiral ganglion cells or corrosion of the platinum band electrodes. Long-term stimulation has been carried out for up to 8 years in patients without affecting their clinical performance.
-
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 surgical anatomy for multiple-electrode extracochlear implant operations(Cambridge University Press, 1988)Direct access to the whole length of the cochlear turns via endaural middle ear approach for the placement of extracochlear electrodes is severely restricted. Approximately 10 mm. of the cochlear turns are accessible, being less than a third of their length. The middle cranial fossa, the facial nerve, the internal carotid artery and the temporomandibular joint restrict the access. A further restriction is caused by the position of the cochlea and the direction of its axis. The anterior part of the cochlea lies anterior to the tympanic membrane and medial to the temporomandibular joint, thus limiting an endaural approach to a posterolateral direction. Despite this limitation small sections of the basal, middle and apical turns of the cochlea can be reached.