Biomedical subjects
Richard T Miyamoto
Publications and source records attributed to Richard T Miyamoto.
Cochlear implantation for tinnitus suppression.
A high prevalence of tinnitus in cochlear implant users has been demonstrated, but fortunately a large percentage of patients do report some degree of tinnitus suppression postoperatively. Improvements in the duration and intensity and the annoyance level and loudness of the perceived tinnitus postimplant have been demonstrated. The risk of worsening of the tinnitus percept after cochlear implantation is small.
Speech perception skills of deaf infants following cochlear implantation: a first report.
OBJECTIVE: We adapted a behavioral procedure that has been used extensively with normal-hearing (NH) infants, the visual habituation (VH) procedure, to assess deaf infants' discrimination and attention to speech. METHODS: Twenty-four NH 6-month-olds, 24 NH 9-month-olds, and 16 deaf infants at various ages before and following cochlear implantation (CI) were tested in a sound booth on their caregiver's lap in front of a TV monitor. During the habituation phase, each infant was presented with a repeating speech sound (e.g. 'hop hop hop') paired with a visual display of a checkerboard pattern on half of the trials ('sound trials') and only the visual display on the other half ('silent trials'). When the infant's looking time decreased and reached a habituation criterion, a test phase began. This consisted of two trials: an 'old trial' that was identical to the 'sound trials' and a 'novel trial' that consisted of a different repeating speech sound (e.g. 'ahhh') paired with the same checkerboard pattern. RESULTS: During the habituation phase, NH infants looked significantly longer during the sound trials than during the silent trials. However, deaf infants who had received cochlear implants (CIs) displayed a much weaker preference for the sound trials. On the other hand, both NH infants and deaf infants with CIs attended significantly longer to the visual display during the novel trial than during the old trial, suggesting that they were able to discriminate the speech patterns. Before receiving CIs, deaf infants did not show any preferences. CONCLUSIONS: Taken together, the findings suggest that deaf infants who receive CIs are able to detect and discriminate some speech patterns. However, their overall attention to speech sounds may be less than NH infants'. Attention to speech may impact other aspects of speech perception and spoken language development, such as segmenting words from fluent speech and learning novel words. Implications of the effects of early auditory deprivation and age at CI on speech perception and language development are discussed.
Language development in deaf infants following cochlear implantation.
OBJECTIVE: To evaluate the benefits of cochlear implantation in infancy and compare them to those obtained in children implanted at a slightly older age. MATERIAL AND METHODS: Using standard language measurement tools, including the Grammatical Analysis of Elicited Language--Presentence Level (GAEL-P) and the Reynell Developmental Language Scales, progress was documented in a child who received a cochlear implant in infancy and compared to that achieved in children implanted at older ages. A new measurement tool, the Visual Habituation Procedure, was used to document early skills and the results were compared to those obtained in normal-hearing infants. RESULTS: By the age of 2 years the subject implanted in infancy achieved scores on the GAEL-P which were nearly equivalent to those achieved at the age of 5 1/2 years by children implanted at later ages. Age-equivalent scores on the Reynell Developmental Language Scales were achieved by the subject implanted in infancy and the ability to discriminate speech patterns was demonstrated using the Visual Habituation Procedure. CONCLUSION: This report demonstrates enhanced language development in an infant who received a cochlear implant at the age of 6 months.
Modeling open-set spoken word recognition in postlingually deafened adults after cochlear implantation: some preliminary results with the neighborhood activation model.
HYPOTHESES: Do cochlear implants provide enough information to allow adult cochlear implant users to understand words in ways that are similar to listeners with acoustic hearing? Can we use a computational model to gain insight into the underlying mechanisms used by cochlear implant users to recognize spoken words? BACKGROUND: The Neighborhood Activation Model has been shown to be a reasonable model of word recognition for listeners with normal hearing. The Neighborhood Activation Model assumes that words are recognized in relation to other similar-sounding words in a listener's lexicon. The probability of correctly identifying a word is based on the phoneme perception probabilities from a listener's closed-set consonant and vowel confusion matrices modified by the relative frequency of occurrence of the target word compared with similar-sounding words (neighbors). Common words with few similar-sounding neighbors are more likely to be selected as responses than less common words with many similar-sounding neighbors. Recent studies have shown that several of the assumptions of the Neighborhood Activation Model also hold true for cochlear implant users. METHODS: Closed-set consonant and vowel confusion matrices were obtained from 26 postlingually deafened adults who use cochlear implants. Confusion matrices were used to represent input errors to the Neighborhood Activation Model. Responses to the different stimuli were then generated by the Neighborhood Activation Model after incorporating the frequency of occurrence counts of the stimuli and their neighbors. Model outputs were compared with obtained performance measures on the Consonant-Vowel Nucleus-Consonant word test. Information transmission analysis was used to assess whether the Neighborhood Activation Model was able to successfully generate and predict word and individual phoneme recognition by cochlear implant users. RESULTS: The Neighborhood Activation Model predicted Consonant-Vowel Nucleus-Consonant test words at levels similar to those correctly identified by the cochlear implant users. The Neighborhood Activation Model also predicted phoneme feature information well. CONCLUSION: The results obtained suggest that the Neighborhood Activation Model provides a reasonable explanation of word recognition by postlingually deafened adults after cochlear implantation. It appears that multichannel cochlear implants give cochlear implant users access to their mental lexicons in a manner that is similar to listeners with acoustic hearing. The lexical properties of the test stimuli used to assess performance are important to spoken-word recognition and should be included in further models of the word recognition process.
PET imaging of differential cortical activation by monaural speech and nonspeech stimuli.
Positron emission tomography imaging was used to investigate the brain activation patterns of listeners presented monaurally (right ear) with speech and nonspeech stimuli. The major objectives were to identify regions involved with speech and nonspeech processing, and to develop a stimulus paradigm suitable for studies of cochlear-implant subjects. Scans were acquired under a silent condition and stimulus conditions that required listeners to press a response button to repeated words, sentences, time-reversed (TR) words, or TR sentences. Group-averaged data showed activated foci in the posterior superior temporal gyrus (STG) bilaterally and in or near the anterior insula/frontal operculum across all stimulus conditions compared to silence. The anterior STG was activated bilaterally for speech signals, but only on the right side for TR sentences. Only nonspeech conditions showed frontal-lobe activation in both the left inferior frontal gyrus [Brodmann's area (BA) 47] and ventromedial prefrontal areas (BA 10/11). An STG focus near the superior temporal sulcus was observed for sentence compared to word. The present findings show that both speech and nonspeech engaged a distributed network in temporal cortex for early acoustic and prelexical phonological analysis. Yet backward speech, though lacking semantic content, is perceived as speechlike by engaging prefrontal regions implicated in lexico-semantic processing.
Cochlear implantation with large vestibular aqueduct syndrome.
OBJECTIVES: In this investigation, we report the outcomes of 14 adults (age >18 y) and 9 children (age <18 y) with radiographically proven large vestibular aqueduct syndrome (LVAS) who received cochlear implants at Indiana University School of Medicine. STUDY DESIGN: This is a retrospective case-control study detailing the outcomes of 23 patients with LVAS and 46 control patients implanted with Nucleus (Cochlear Corp., Englewood, CO), Clarion (Advanced Bionics Corp., Sylmar, CA), or Med-El (MED-EL Corp., Innsbruck, Austria) cochlear implants. METHODS: Performance data on pure-tone averages, speech detection thresholds, and a variety of auditory and speech recognition tasks from these patients with LVAS were compared with performance data obtained from a matched group of 46 cochlear implant users who did not have LVAS. Specific patient characteristics used in matching included the age of the patient, the age at implant of the patient, and whether the patient was pre- or postlingually deafened. Data for the adult group was analyzed using the Student t test, and data for the pediatric patient group was compared using a chi2 test. RESULTS: The results indicated positive outcomes for both pediatric and adult groups. With both adult and pediatric groups, auditory and speech recognition performance did not differ significantly between those patients with LVAS and control subjects. CONCLUSIONS: This study adds further support for the use of cochlear implantation in patients with LVAS. Cochlear implantation is beneficial and can be offered as an eventual treatment of LVAS if hearing loss progresses to profound levels in these patients.
Changes in quality of life and the cost-utility associated with cochlear implantation in patients with large vestibular aqueduct syndrome.
OBJECTIVE: A group of 20 patients with large vestibular aqueduct syndrome was identified at the Indiana University School of Medicine. The major objective of this study was to explore the improvements in quality of life associated with cochlear implantation in patients with large vestibular aqueduct syndrome, as well as the cost-utility of cochlear implantation in this group. SETTING: A total of 70 patients were identified with large vestibular aqueduct syndrome through analysis of thin-section computed tomography of the temporal bone over the past 6 years at this medical center. Data collected from the medical records for each patient included demographic data, hearing-related statistics, implantation data, and audiometric data. Sixteen children and adults with large vestibular aqueduct syndrome had undergone cochlear implantation before the beginning of this study, and the remaining 54 children and adults were identified as undergoing treatment of progressive or fluctuant sensorineural hearing loss. Health utility indexes used in this analysis were taken through the use of the Ontario Health Utility Index, Mark III. The range of costs used for cost-utility analysis was derived from the costs of cochlear implantation at this medical center, as well as from costs associated with implantation published in the medical literature. METHODS: Participants were selected from the total population of patients with large vestibular aqueduct syndrome at this center who were postlingually deafened and who currently had severe hearing loss. Two groups were formed. These groups comprised either cochlear implant patients with large vestibular aqueduct syndrome or patients with large vestibular aqueduct syndrome currently using hearing aids. Ten of the 16 cochlear implant patients and 10 of the remaining 54 patients with large vestibular aqueduct syndrome met these criteria. Mark III health utility indexes were distributed to patients in each group and scored. Those health utility indexes not completed by the patients were scored by proxy, using the audiologist at this center who was the most familiar with the patient. Changes in quality of life associated with cochlear implantation were derived by comparison of the health utility index results of the two groups. Cost-utility measures were then made using discounted costs per quality-of-life years (QALYs) (5%), and a sensitivity analysis was performed that evaluated changes in scoring done by proxy. The cost-utility results were then compared with the cost-utilities derived from similar studies and associated with other disease states. RESULTS: Although both groups of patients had significant hearing loss, the hearing aid group had a better mean pure-tone average. The mean pure-tone average for the hearing aid group was 70.8 dB (SD 24.4), and the mean pure-tone average for the cochlear implant group was 107.0 dB (SD 21.7). Seven of the 20 health utility indexes were scored by proxy. Results from the base case indicate a 0.20 gain in health utility from cochlear implantation (hearing aid = 0.62, cochlear implant = 0.82, p = 0.037), resulting in a discounted cost per QALY of $12,774. Sensitivity analysis of the proxy scoring indicated that decreasing the hearing score one level on the health utility index resulted in a gain in health utility with cochlear implantation of 0.15, resulting in a discounted cost per QALY of $17,832. A decrease of the hearing score by two levels on the health utility survey resulted in no significant gain in quality of life with cochlear implantation. CONCLUSION: This study found an improvement in quality of life associated with cochlear implantation in postlingually deafened patients with large vestibular aqueduct syndrome. By weighing this improvement in quality of life against the significant difference noted between the pure-tone averages of each group, further strength can be given to this conclusion. This gain in quality of life, as well as the results derived for the cost-utility of cochlear implantation, was similar to that in previous published studies of cochlear implantation in all types of patients. These results also indicate a favorable cost-utility when compared with published data about other disease states. As patients with large vestibular aqueduct syndrome progress to profound levels of hearing loss, these results indicate that cochlear implantation can be offered as a beneficial, life-improving therapy.
Effects of age at implantation in young children.
This study examined the effects of age at implantation on the development of communication abilities in children with early implantation. The 73 participants were prelingually deafened, received a cochlear implant before 5 years of age, and used current cochlear implant technology. The children were administered a battery of speech and language outcome measures before implantation and again at successive 6-month postimplant intervals. A mixed model analysis was used to examine the rate of growth in word recognition and language skills as a function of age at time of implantation. The results revealed significant improvements in communication skills over time. Spoken word recognition improved at a faster rate in the oral children with early implantation. However, the children who underwent implantation before 3 years of age had significantly faster rates of language development than did the children with later implantation. The oral children demonstrated more rapid gains in communication abilities than did the children who used total communication.