The effect of handedness in tactile speech perception.

This study examined differential performance of normally hearing subjects using a tactile device on the dominant versus non-dominant hand. The study evaluated whether tactual sensitivity for non-speech stimuli was greater for the dominant hand as compared with the non-dominant hand, and secondly, whether there was an advantage for speech presented tactually to the dominant hand, resulting from a preferential pathway to the language processing area in the left cerebral hemisphere. Evaluations of threshold pulse width, dynamic ranges, paired electrode identification, and a closed-set tactual pattern discrimination test battery showed no difference in tactual sensitivity measures between the two hands. Speech perception was assessed with closed sets of vowels and consonants and with open-set Harvey Gardner (HG) words and Arthur Boothroyd (AB) words. Group mean scores were higher in each of the tactually aided conditions as compared with the unaided conditions for speech tests, with the exception of AB words in the tactile plus lip-reading plus audition/lip-reading plus audition condition on the right hand. Overall mean scores on the closed-set vowel test and on open-set HG and AB words were significantly higher for the tactually aided condition as compared with the unaided condition. Comparison of performance between the dominant and non-dominant hand showed a significant advantage for the dominant hand on the closed-set vowel test only. No significant differences between hands in either tactually aided or unaided conditions were evident for any of the other speech perception tests. Factors influencing this result could have been variations in degree of difficulty of the tests, the amount of training subjects received, or the training strategy employed. Although an advantage to presenting speech through the dominant hand may exist, it is unlikely to be great enough to outweigh possible restrictions on everyday use.

Relationships among speech perception, production, language, hearing loss, and age in children with impaired hearing.

Eighty-seven primary-school children with impaired hearing were evaluated using speech perception, production, and language measures over a 3-year period. Forty-seven children with a mean unaided pure-tone-average hearing loss of 106 dB HL used a 22-electrode cochlear implant, and 40 with a mean unaided pure-tone-average hearing loss of 78 dB HL were fitted with hearing aids. All children were enrolled in oral/aural habilitation programs, and most attended integrated classes with normally hearing children for part of the time at school. Multiple linear regression was used to describe the relationships among the speech perception, production, and language measures, and the trends over time. Little difference in the level of performance and trends was found for the two groups of children, so the perceptual effect of the implant is equivalent, on average, to an improvement of about 28 dB in hearing thresholds. Scores on the Peabody Picture Vocabulary Test (PPVT) and the Clinical Evaluation of Language Fundamentals showed an upward trend at about 60% of the rate for normally hearing children. Rates of improvement for individual children were not correlated significantly with degree of hearing loss. The children showed a wide scatter about the average speech production score of 40% of words correctly produced in spontaneous conversations, with no significant upward trend with age. Scores on the open-set Consonant-Nucleus-Consonant (CNC) monosyllabic word test and the Bench-Kowal-Bamford (BKB) sentence test were strongly related to language level (as measured by an equivalent age on the PPVT) and speech production scores for both auditory-visual and auditory test conditions. After allowing for differences in language, speech perception scores in the auditory test condition showed a slight downward trend over time, which is consistent with the known biological effects of hearing loss on the auditory periphery and brainstem. Speech perception scores in the auditory condition also decreased significantly by about 5% for every 10 dB of hearing loss in the hearing aid group. The regression analysis model allows separation of the effects of language, speech production, and hearing levels on speech perception scores so that the effects of habilitation and training in these areas can be observed and/or predicted. The model suggests that most of the children in the study will reach a level of over 90% sentence recognition in the auditory-visual condition when their language becomes equivalent to that of a normally hearing 7-year-old, but they will enter secondary school at age 12 with an average language delay of about 4 or 5 years unless they receive concentrated and effective language training.

Use of a multichannel electrotactile speech processor by profoundly hearing-impaired children in a total communication environment.

As part of a larger subject group, four profoundly hearing-impaired children enrolled in a total communication educational program were fitted with the University of Melbourne's multichannel electrotactile speech processor (Tickle Talker). Sound detection thresholds for pure tones were at lower levels with the tactile device than with hearing aids, especially for high frequency sounds above 2 kHz. Two of the children also detected all speech sounds of the Ling five-sound test at normal conversational levels using only the Tickle Talker. The children were able to use tactile input to achieve higher scores on three speech feature subtests of the PLOTT test when using the Tickle Talker plus hearing aids as compared to hearing aids alone. Mean improvements were 22.4 percent on vowel length, 28 percent on vowel identification, and 35 percent on consonant manner. Improvements were also shown by individual children on the closed-set WIPI and open-set PBK word tests, and on the open-set BKB sentence test, when the Tickle Talker was combined with hearing aids, and with hearing aids and lipreading. Comparisons of these results with those of children using the Tickle Talker in other educational settings show that children in a total communication environment can potentially benefit to a similar degree from use of tactual input. Anecdotal reports from the children and school staff members indicated that daily use of the Tickle Talker did not interfere with the signing aspects of total communication.

Improved electrotactile speech processor: Tickle Talker.

The Tickle Talker, an eight-channel electrotactile speech processor, has been developed from continuing research at the University of Melbourne. The development of the device has focused on production of reliable speech-processing hardware, design of cosmetically and ergonometrically acceptable electrode transducers, implementation of acute and chronic biomedical studies demonstrating device safety, design and testing of alternative speech-encoding strategies to provide benefit to speech perception and production, and design and testing of appropriate training methods for optimizing benefits. The Tickle Talker has been shown to provide benefits in supplementing lipreading or aided residual hearing for hearing-impaired adults and children. Improvements in speech processing have resulted in an increase in benefits to speech perception, and open the way for more flexible approaches to encoding speech input. Continuing development of the electrode circuitry has now produced a device that is robust and has an extended battery life. Safety studies have clearly demonstrated that there are no long-term contraindications to device use. The results suggest that the device has a role to play in rehabilitation programs for severely and profoundly hearing-impaired adults and children.

Speech perception in children using the advanced Speak speech-processing strategy.

The Speak speech-processing strategy, developed by the University of Melbourne and commercialized by Cochlear Pty Limited for use in the new Spectra 22 speech processor, has been shown to provide improved speech perception for adults in both quiet and noisy situations. The present study evaluated the ability of children experienced in the use of the Multipeak (Mpeak) speech-processing strategy (implemented in the Nucleus Minisystem-22 cochlear implant) to adapt to and benefit from the advanced Speak speech-processing strategy (implemented in the Nucleus Spectra 22 speech processor). Twelve children were assessed using Mpeak and Speak over a period of 8 months. All of the children had over 1 year's previous experience with Mpeak, and all were able to score significantly on open-set word and sentence tests using the cochlear implant alone. Children were assessed with both live-voice and recorded speech materials, including Consonant-Nucleus-Consonant monosyllabic words and Speech Intelligibility Test sentences. Assessments were made in both quiet and in noise. Assessments were made at 3-week intervals to investigate the ability of the children to adapt to the new speech-processing strategy. For most of the children, a significant advantage was evident when using the Speak strategy as compared with Mpeak. For 4 of the children, there was no decrement in speech perception scores immediately following fitting with Speak. Eight of the children showed a small (10% to 20%) decrement in speech perception scores for between 3 and 6 weeks following the changeover to Speak. After 24 weeks' experience with Speak, 11 of the children had shown a steady increase in speech perception scores, with final Speak scores higher than for Mpeak. Only 1 child showed a significant decrement in speech perception with Speak, which did not recover to original Mpeak levels.

Effects of articulation training on the production of trained and untrained phonemes in conversations and formal tests.

The aim of this study was to investigate the effectiveness of articulation training for specific phonemes on the production of phonemes in conversational language samples, the 108 Single Word Articulation Test (Paatsch, 1997), and the Phonetic Level Evaluation (Ling, 1976). Speech production skills of 12 hearing-impaired children were assessed using these evaluation tools pre- and posttraining. A total of six phonemes were selected for each child to be trained during 15-to 20-minute daily sessions throughout an 8-week speech production program. Three phonemes, with a particularly high error rate, were trained at a phonetic level (category 1) while three phonemes, with an intermediate error rate of 40% to 70%, were trained at a phonological level (category 2). Results showed improvements in the percentage of correctly articulated category 1 phonemes and category 2 phonemes. The improvements for category 2 phonemes were larger than for category 1 phonemes for all test materials. It may be that phonological level training is more effective than phonetic level training or that phonemes with an intermediate error rate are easier to train than phonemes with a high error rate. Untrained vowels and consonants also improved slightly after training. Phonological process analysis showed that many of the errors apparent in the trained phonemes also had occurred in the untrained phonemes. This may have resulted in the generalization and carryover of taught speech skills into other aspects of the child's spoken language.

The effect of language knowledge on speech perception: what are we really assessing?

OBJECTIVE: The authors examined whether open-set speech perception scores are limited by knowledge of vocabulary and syntax and further considered whether remediation of vocabulary and syntax will increase open-set speech perception scores. STUDY DESIGN: This was a repeated-measures study design in the setting of a primary (elementary) school for the hearing-impaired. PATIENTS: The study population was composed of three hearing-impaired children using Nucleus 22-channel cochlear implant. INTERVENTION: Intervention used was language remediation sessions. MAIN OUTCOME MEASURES: The main outcome measures were assessment of auditory-alone speech perception benefit using open-set words and sentences and assessment of syntactic knowledge using the Test of Syntactic Ability. Outcome measures were applied before and after remediation. RESULTS: Child 1 and child 2 showed a significant postremediation improvement in their overall scores on the Test of Syntactic Ability and in their ability to perceive words learned during remediation. Child 1 and child 2 also showed a significant improvement in their scores on a modified Bamford-Kowal-Bench open-set sentence test, which specifically targeted grammatical constructs trained in remediation sessions. CONCLUSIONS: Remediation of language knowledge deficits significantly improved open-set speech perception for two children, suggesting a need to include language remediation in cochlear implant habilitation programs.

Perception of sentences, words, and speech features by profoundly hearing-impaired children using a multichannel electrotactile speech processor.

Fourteen prelinguistically profoundly hearing-impaired children were fitted with the multichannel electrotactile speech processor (Tickle Talker) developed by Cochlear Pty. Ltd. and the University of Melbourne. Each child participated in an ongoing training and evaluation program, which included measures of speech perception and production. Results of speech perception testing demonstrate clear benefits for children fitted with the device. Thresholds for detection of pure tones were lower for the Tickle Talker than for hearing aids across the frequency range 250-4000 Hz, with the greatest tactual advantage in the high-frequency consonant range (above 2000 Hz). Individual and mean speech detection thresholds for the Ling 5-sound test confirmed that speech sounds were detected by the electrotactile device at levels consistent with normal conversational speech. Results for three speech feature tests showed significant improvement when the Tickle Talker was used in combination with hearing aids (TA) as compared with hearing aids along (A). Mean scores in the TA condition increased by 11% for vowel duration, 20% for vowel formant, and 25% for consonant manner as compared with hearing aids alone. Mean TA score on a closed-set word test (WIPI) was 48%, as compared with 32% for hearing aids alone. Similarly, mean WIPI score for the combination of Tickle Talker, lipreading, and hearing aids (TLA) increased by 6% as compared with combined lipreading and hearing aid (LA) scores. Mean scores on open-set sentences (BKB) showed a significant increase of 21% for the tactually aided condition (TLA) as compared with unaided (LA). These results indicate that, given sufficient training, children can utilize speech feature information provided through the Tickle Talker to improve discrimination of words and sentences. These results indicate that, given sufficient training, children can utilize speech feature information provided through the Tickle Talker to improve discrimination of words and sentences. These results are consistent with improvement in speech discrimination previously reported for normally hearing and hearing-impaired adults using the device. Anecdotal evidence also indicates some improvements in speech production for children fitted with the Tickle Talker.

Perception of amplitude envelope variations of pulsatile electrotactile stimuli.

Gross variations of the speech amplitude envelope, such as the duration of different segments and the gaps between them, carry information about prosody and some segmental features of vowels and consonants. The amplitude envelope is one parameter encoded by the Tickle Talker, an electrotactile speech processor for the hearing impaired which stimulates the digital nerve bundles with a pulsatile electric current. Psychophysical experiments measuring the duration discrimination and identification, gap detection, and integration times for pulsatile electrical stimulation are described and compared with similar auditory measures for normal and impaired hearing and electrical stimulation via a cochlear implant. The tactile duration limen of 15% for a 300-ms standard was similar to auditory measures. Tactile gap detection thresholds of 9 to 20 ms were larger than for normal-hearing but shorter than for some hearing-impaired listeners and cochlear implant users. The electrotactile integration time of about 250 ms was shorter than previously measured tactile values but longer than auditory integration times. The results indicate that the gross amplitude envelope variations should be conveyed well by the Tickle Talker. Short bursts of low amplitude are the features most likely to be poorly perceived.

Cochlear implants for congenitally deaf adolescents: is open-set speech perception a realistic expectation?

The prognosis for benefit from use of cochlear implants in congenitally deaf adolescents, who have a long duration of profound deafness prior to implantation, has typically been low. Speech perception results for two congenitally deaf patients implanted as adolescents at the University of Melbourne/Royal Victorian Eye and Ear Hospital Clinic show that, after 12 months of experience, both patients had significant open-set speech discrimination scores without lipreading. These results suggest that although benefits may in general be low for congenitally deaf adolescents, individuals may attain significant benefits to speech perception after a short period of experience. Prospective patients from this group should therefore be considered on an individual basis with regard to prognosis for benefit from cochlear implantation.

Variation in speech perception scores among children with cochlear implants.

OBJECTIVE: The objective of this study was to identify common factors affecting speech perception scores in children with cochlear implants. DESIGN: Speech perception data for 167 implanted children were collected at two cochlear implant centres in Melbourne and Sydney. The data comprised audition-alone scores on open-set word and sentence tests. Children were selected on the basis that they had a Nucleus 22-electrode cochlear implant. The average age of the children was 5 yr. Information was also collected about 12 factors that may have influenced speech perception scores for each child. Analysis of covariance was used to identify factors that significantly affected speech perception scores. Pearson pairwise correlation coefficients were also calculated for all factors analyzed. RESULTS: The analyses in this study identified factors that accounted for 51%, 34%, and 45% of the variance in phoneme, word and sentence perception scores. Scores decreased by 1.4 to 2.4% per year of profound deafness prior to implantation. Children who normally use oral communication scored significantly higher than children normally using sign or simultaneous oral and sign communication. Children implanted in Sydney scored higher on average than children implanted in Melbourne. CONCLUSIONS: The results show that a significant part of the variation in speech perception scores is systematically related to audiological and environmental factors for each child. The reasons for significant differences between children using different communication modes or from different clinics were not identified.

Perception of multiple electrode stimulus patterns: implications for design of an electrotactile speech processor.

Identification of multiple-electrode stimulus patterns was evaluated in nine adult subjects, to assess the feasibility of providing additional speech information through the tactual display of an electrotactile speech processor. Absolute identification scores decreased from 97.8% for single electrodes, to 61.9% for electrode pairs, and, to 31.8% for electrode triplets. Although input information increased with paired-and triple-electrode stimuli, information transmission scores were not significantly increased for either electrode pairs (2.99 bits) or triplets (2.84 bits) as compared with single electrodes (2.84 bits). These results suggest that speech coding strategies using stimulus patterns of electrode pairs or triplets would provide little improvement beyond that found for the present single-electrode scheme. However, higher absolute identification scores (73.6%), and an increase in information transmission to 3.88 bits, were recorded for test stimuli containing all combinations of paired and single electrodes. Based on this finding, two stimulus sets using a restricted number of combinations of paired and single electrodes were evaluated. The two stimulus sets simulated the spatial patterns of paired and single electrodes arising from use of alternative speech coding schemes to increase consonant voicing information. Results for the two stimulus sets showed higher electrode identification scores (79.7% and 90.4%), as compared with paired-electrode stimuli. Although electrode identification score was not as high as for single electrodes, information transmission was increased to 3.31 bits for the VF2 stimulus set. Analysis of the responses also showed that scores for identification of simulated voicing information conveyed by the two stimulus sets were 99.4 and 90.4% correct.(ABSTRACT TRUNCATED AT 250 WORDS)

Articulation accuracy of children using an electrotactile speech processor.

OBJECTIVE: Use of wearable tactile speech perception devices is suggested to help overcome the difficulties in speech production resulting from severe and profound hearing impairment in children. This suggestion is based on the assumption that subjects can use tactile input in isolation, or in combination with information from residual aided hearing, to monitor and modify their speech. The present study evaluated the benefits to articulation provided through use of a multichannel electrotactile device ("Tickle Talker"). DESIGN: Six profoundly hearing-impaired children were videotaped speaking with the Tickle Talker on and with the Tickle Talker off during conversations with their audiologist. Five of the subjects also wore their binaural hearing aids during all recorded conversations. The number of vowels, consonants, and overall phonemes correctly articulated by each child in the two conditions were compared. RESULTS: One subject improved articulation of initial consonants and initial phonemes; one subject improved articulation of total vowels, total consonants, initial consonants, total phonemes, and initial phonemes; and a third subject improved articulation of total vowels and medial phonemes. CONCLUSIONS: Use of on-line tactile feedback from the Tickle Talker may benefit the articulation accuracy of some children, and the device may therefore be suitable to use with children who have not responded to more traditional speech training techniques.

Factors in the development of a training program for use with tactile devices.

A review of the literature suggests that, in order to maximize the benefits available through a tactile device, it must be accompanied by an effective and adaptive training program. There are a number of factors to consider in the design of such a training program, including the type of tasks and response formats to include, the amount of training, subject motivation and device use, the characteristics of the potential user population, the specific device to be used and the type of information it provides, and the evaluation procedures to be followed. The type and saliency of the information provided by a particular tactile device are highlighted as the most important yet neglected consideration in designing a training program. The training program used with the University of Melbourne's multiple-channel electrotactile device is presented to show how these important factors may be addressed, to indicate the flexibility required in a training program, and to provide a general framework on which researchers may base the development of programs for other tactile devices.

Role of a multichannel electrotactile speech processor in a cochlear implant program for profoundly hearing-impaired adults.

Four profoundly hearing-impaired adults who did not meet current selection criteria for implantation at the University of Melbourne were each fitted with a wearable multichannel electrotactile speech processor (Tickle Talker). The subjects were evaluated with a test battery of speech discrimination tests subsequent to training in use of the device. Thresholds for detection of pure tones were lower for the Tickle Talker than for hearing aids across the frequency range 250 to 4000 Hz. Mean speech detection thresholds for the Ling 5-sound test showed that all sounds were detected by users of the electrotactile device at normal conversational speech intensity levels. Mean speech discrimination scores were significantly higher (p less than 0.05) in the tactually aided condition as compared with the tactually unaided for identification of vowels and consonants, on open-set words, open-set sentences, and on connected discourse tracking. Mean scores increased by 20% for vowels, 19% for consonants, 30% for open-set words, and 25% for open-set sentences when the Tickle Talker was used in a multimodal combination with lipreading or lipreading and hearing aids. Speechtracking rates for three subjects showed increases of from 18 to 28 wpm when the tactile device was used. Comparison of tactually aided versus unaided tracking rates for two subjects with long-term experience shows continuing improvement with additional experience with the device. These results demonstrate that hearing-impaired adults not meeting selection criteria for cochlear implantation may benefit from use of an electrotactile speech processor, and highlight the potential benefits from integration of such devices into cochlear implant programs for profoundly hearing-impaired patients.

Speech perception results for children with implants with different levels of preoperative residual hearing.

OBJECTIVE: Many reports have established that hearing-impaired children using the Nucleus 22-channel cochlear implant may show both significant benefits to lipreading and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised questions about whether severely or severely-to-profoundly deaf children should be candidates for cochlear implants. To study this question, postoperative results for implanted children with different levels of preoperative residual hearing were evaluated in terms of speech perception benefits. STUDY DESIGN/SETTING: A retrospective study of the first 117 children, sequentially, to undergo implantation in the Melbourne and Sydney Cochlear Implant Clinics was undertaken. All children had been assessed by and received their implants in a tertiary referral centre. MAIN OUTCOME MEASURES: To assess aided residual hearing, the children were grouped into four categories of hearing on the basis of their aided residual hearing thresholds measured preoperatively. To assess benefits, the scores of children on standard speech perception tests were reviewed. As different tests were used for children with different ages and language skills, children were grouped into categories according to the level of postoperative speech perception benefit. RESULTS: The results showed that children in the higher categories of aided preoperative residual hearing showed significant scores on open-set word and sentence perception tests using the implant alone. For children in lower categories of aided residual hearing, results were variable within the groups. More than 90% of children with implants with aided residual hearing thresholds in the speech range above 1 kHz achieved open-set understanding of words and sentences. CONCLUSION: While the results of this preliminary study confirm previous findings of differential outcomes for children with different levels of preoperative residual hearing, they suggest that children with severe to profound hearing impairments should be considered for cochlear implantation.