Effects of a Nucleus Multichannel Cochlear Implant Upon Speech Production in Children Emily A. Tobey, PhD; M. Suzanne Hasenstab, PhD Department of Communication Disorders, Louisiana State University Medical Center, New Orleans, Louisiana (E. A. T.) and Department of Otolaryngology, Medical College of Virginia, Richmond, Virginia (M.S. H.)
ABSTRACT The purpose of this report is to describe the speech production of children participating in the Food and Drug Administration’s approved clinical trials for the Nucleus multichannel cochlear implant. A significant increase in the ability to imitate nonsegmentalaspects of speech was noted after using the implant; however, nonsegmental performance did not appear to increase significantly between 12, 18, or 24 mo postimplantation. Significant increases occurred in imitative and elicited segmental performance after implantation at all measurement points. Speech intelligibility was significantly higher postimplant than preimplant; however, no significant change in mean length of utterance was observed. Data from these studies suggest a multichannel cochlear implant may provide information that is useful for assisting in the development or refinement of some aspects of spoken communication.
POOR SPOKEN COMMUNICATION is often a consequence of profound hearing impairment in children. Reduced speech intelligibility is commonly reported and seems related to segmental and nonsegmental errors (see for a review, Osberger & McGarr, 1982; Smith, 1975). Previous examinations of consonant production in profoundly hearing-impaired children reveal articulatory error patterns incorporating substitutions, omissions, and distortions (Brannon, 1966; Geffner, 1980; Gold, 1978; Markides, 1970; Nober, 1967; Osberger & McGarr, 1982; Smith, 1975). Voicing errors appear frequently, although the direction of the error (voiced for voiceless or voiceless for voiced consonants) differs across studies (Hudgins & Numbers, 1942; Mangan, 196 1;Nober, 1967; Smith, 1975). Manner and place of articulation errors also are observed. Such errors include nasal-oral substitutions (Markides, 1970; Smith, 1975) and glottal-stop substitutions (Smith, 1975). 48s
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Place of articulation errors often reveals the substitution of a more visible, anterior placement for other less visible placements (Gold, 1978). Segmental errors also are noted during vowel production. Several investigators (Boone, 1966; Nober, 1967: Smith, 1975) report that front vowels are produced with more errors than back vowels, suggesting difficulty with tongue positioning. Other investigators observe a greater number of errors with vowels requiring high- or mid-tongue heights than vowels with low-tongue heights (Geffner, 1980: Smith, 1975). Thus, the poor speech of profoundly hearing-impaired children appears to be due, in part, to segmental errors associated with consonant and vowel production. Profoundly hearing-impaired children who receive single-channel cochlear implants appear to approve their abilities to imitate segmental aspects of speech (Kirk & Hill-Brown, 1985). Significant increases in production of vowels, diphthongs, and simple consonants are noted after 1 yr of use with the House/3M single-channel cochlear implant. Increased use of correctly produced vowels and consonants also is evident in the spontaneous speech of children receiving singlechannel implants (Kirk & Hill-Brown, 1985). Similar observations occur for profoundly hearingimpaired children receiving multichannel cochlear implants. After I yr of use with the Nucleus multichannel cochlear implant, 85% of the vocalizations produced in a spontaneous language sample were judged to be either speech or speechlike and 67% were identified as English phonemes (Osberger, Robbins, Berry, Todd, Hesketh, & Sedey, 1990). Tobey and colleagues report significant improvement in children’s ability to imitate segmental aspects of speech (Tobey, Angelette, Murchison, Nicosia, Sprague, Staller, Brimacombe, & Beiter, 1991) and increased consonant repertoires (Tobey, Pancamo, Staller, Brimacombe, & Beiter, 199 1) in profoundly hearing-impaired children after using a multichannel cochlear implant for a year. Rapid changes in vowel formant frequencies, fundamental frequencies, and durations also are evident in trials contrasting speech produced with a multichannel cochlear implant turned on versus off (Tobey et al, 1991). Improvement in the ability to imitate nonsegmental aspects of speech also are reported for profoundly hearing-impaired children after a year’s use with either a single-channel (Kirk &
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Hill-Brown, 1985) or a multichannel device (Tobey et al, 199 1). Although these studies differ considerably in the type of speech tokens examined and dependent variables measured, it seems that auditory information delivered via a cochlear implant may be useful for enhancing t h e development of some speech sounds. T h e purpose of this report is t o update data obtained from four speech production protocols collected on children participating in the pediatric clinical trials for the Nucleus multichannel cochlear implant. T h e four speech production protocols included assessment of nonsegmental performance, segmental abilities in imitative and elicited conditions, speech intelligibility, and mean length of utterances. This report extends earlier observations (Tobey et al, 199 1) by reviewing long-term postoperative data from the subjects collected longitudinally and by analyzing subsets of paired comparisons across time. T h e speech production measures described were the minimum protocol suggested by a committee of speechlanguage pathologists for tracking speech production performance over time (Tobey. 1986). In addition, the committee suggested that an independent evaluation center for speech-language analyses be formed as part of the clinical trials to, in part, provide statistical updates on the speech production measures. A center was established a t the Communication Sciences Laboratories of t h e Department of Communication Disorders, Louisiana State University Medical Center as a response to this suggestion. METHODS AND PROCEDURES
Subjects Seventy-eight children participated in the speech production protocols, which were acquired over 24 mo. The mean age of the subjects was 8.5 yr, with a range from 2.3 yr to 17.7 yr. The average age at onset of profound hearing impairment was 1.43 yr and the mean length of profound hearing impairment was 6.07 yr. Fifty-five percent of the subjects were female and 53% of the population was implanted in the left ear. The most prevalent etiology was meningitis (46.1%). The etiology of deafness was unknown in 42. I % of the subjects. The majority of the children were in self-contained hearingimpaired classes (53.2%), mainstreamed with either an interpreter or resource teacher (24.2%), in a day school (14.5%) or residential school (8. I %). Total communication was used by 57.1% and auditory-oral communication was used by 30.2% of the subjects. All subjects participating in the speech production protocols used the Nucleus Wearable Speech Processor (WSP) with an FO-FI-F2 coding strategy. Speech Production Protocols Speech production protocols were administered by 29 investigative centers participating in the Food and Drug Administration's (FDA) clinical trials. The type and number of speech measures administered varied as a function of the age of the child, the length of deafness, and speech/language skills at the time of testing. Protocols were completed by a member of the clinical team at each center. The speech protocols were designed to assess fundamental skills underlying expressive communication, such as the imiEar and Hearing, Vol. 12, No. 4, 1991
tation of prosodic features and sounds, and also to assess more complex aspects, such as overall speech intelligibility. Nonsegmental and segmental portions of the Phonetic Level Speech Evaluation (PLE) (Ling, 1976) were administered before implantation. and at 6, 12, 18. and 24 mo postimplantation. The nonsegmental protocol examined children's ability to imitate a clinician modeling variations in loudness, pitch. and duration. Segmental assessment investigated childrens' ability to imitate syllables in isolation. repeat multiple syllables. alternate repetition of two different syllables. and imitate syllables varying in pitch. Following the techniques discussed by Ling ( 1976). responses were rated as consistently correct. inconsistently correct, or consistently in error. A numeric value system developed by Kirk and Hill-Brown (1985) was applied to the samples. As shown in Table I , incorrect imitation of nonsegmental stimuli was assigned a 0, inconsistently correct trials were assigned a I , and consistently correct sounds were assigned a 2. Sounds produced in isolation in the segmental subtest were assigned a 0 for error trials, a 1 for inconsistently correct trials. and a 2 for consistently correct trials. Imitations of repeated syllables were assigned a 3 for inconsistently correct trials and a 4 for consistently correct trials. Imitations of alternating syllables were assigned a 5 for inconsistently correct trials and a 6 for consistently correct trials. The imitation of syllables varying in pitch received a 7 for inconsistently correct trials and an 8 for consistently correct trials. The highest score achieved on an individual trial was used and all items on the test were included in the analysis. Nonsegmental and segmental scores were acquired by totaling the numeric values for all items administered. Mean scores for the entire population of children administered this protocol were calculated. In addition, three additional paired comparison analyses were completed. In the first analysis, data were compared for three time periods: preimplant. 1 yr postoperatively and 2 yr postoperatively. One yr postoperative scores were obtained either at 6 or 12 mo postimplant and 2 yr postoperative scores were obtained either at 18 or 24 mo postimplant. In the event a child received the protocol at both
Table 1. Numeric scoring system used for quantifying performance on the Phonetic Level Speech Evaluation (PLE) and Phonologic Level Speech Evaluation (Phonologic) developed by Kirk and Hill-Brown (1 985).
Test Measures PLE Nonsegmental Subtest and Phonologic Test Consistent Error Productions Inconsistently Correct Productions Consistently Correct Productions PLE Segmental Subtests Consistent Error Productions Isolated Syllables Inconsistently Correct Productions Consistently Correct Productions Repeat Multiple Syllables Inconsistently Correct Productions Consistently Correct Productions Alternating Syllables Inconsistently Correct Productions Consistently Correct Productions Pitch Varying Syllables Inconsistently Correct Productions Consistently Correct Productions
Speech in Cochlear-ImplantedChildren
Scores
0 1 2 0 1 2
3 4 5
6 7 8
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time periods (i.e., at 6 and 12 mo), the earliest time period score was used as a means of conservatively estimating performance changes. Two additional analyses were performed with a subset of children who received the protocol on four (preimplant and 6. 12. and 18 mo postoperatively) or five (preimplant and 6 . 12. 18, and 24 mo postoperatively) different test periods. Data were examined using analysis of variance for repeated measures. Phonological measures were assessed using Ling's ( 1976) PLE. In this protocol, a clinician engages a child in play situations or in spontaneous conversation in order to acquire a language sample. The resulting samples were examined to determine which sounds a given child produced under elicited, nonimitative circumstances. As shown in Table I , sounds were rated as consistently correct, inconsistently correct, or error productions. Ratings were converted to numeric values using a system similar to the one described by Kirk and HillBrown ( 1985). Consistently correct productions were assigned a 2 , inconsistently correct productions were assigned a I , and error productions received a 0. Scores were achieved by summing the total number of scores. Data were analyzed with paired comparisons in two ways. First, comparisons were made between preimplant performance and performance recorded at 6 and 12 mo postimplant. Second. comparisons were made of a subset of children who received the protocol before implantation, 1 yr postimplantation and 2 yr postimplantation. Data were analyzed using a repeated measures analysis of variance. A third protocol examined speech intelligibility. Materials assessing speech intelligibility were adopted from McGarr ( 1 983). Target stimuli were 36 monosyllabic words embedded in sentences varying in overall length. The monosyllabic words were selected from a previously described corpus of words produced by deaf children (Smith, 1975) and represented the 18 words ranked highest and lowest in speech intelligibility by listeners. Half of the sentences contained high contextual information (i.e., the flag is red, white, and blue) and half contained low contextual information (i.e., is the fat baby crying?). Samples were scored by determining the number of target words that were correctly identified by judges. Overall intelligibility was calculated by converting the total number of correctly identified target words to a percent correct score. Pre- and postimplant performance was compared using a I-test. A fourth measure, mean length of utterances (MLU), was determined by engaging the children in conversation using pictures or age-appropriate toys. Five min samples of speech were transcribed and the total number of words within each utterance calculated. Mean length was determined by dividing the total number of words by the number of utterances spoken in the time period. Pre- and postimplant performance was statistically analyzed using a t-test.
to increase with increasing length of implant use. In order to examine the significance of this trend, data were collapsed to contrast performance after 1 and 2 yr postoperative experience to preoperative performance for the 37 children who had data at the three intervals. Figure 2 depicts nonsegmental performance preimplant and at the two postoperative intervals. Nonsegmental performance is significantly higher postimplant than preimplant [ F ( 2 , 72) = 27.1, p < 0.00011: however, post hoc analyses revealed no significant differences between the two postoperative nonsegmental performances. In order to ensure that this procedure for collapsing the data across time intervals accurately represented postoperative performance at the data collection points, we conducted two additional analyses on a smaller subset of children who received nonsegmental testing at 6 mo postoperative intervals. The mean age at implantation of the children included in the paired comparisons was 6.8 yr. The average length of deafness was 4.9 yr, and mean age of deafness onset was 2.0 yr. The demographics of this sample were similar to the total
36
" I
[li
PRE 6 N=
12 18 2 4
( 7 8 ) ( 7 3 ) (70) (43) (18)
Figure 1. Mean performance of children receiving the nonsegmental subtest of the PLE before implantation and at 6 mo intervals postimplantation is shown.
N=37 27
RESULTS
Figure 1 illustrates the mean performance of all children receiving the nonsegmental subtest of the PLE. As the figure indicates, the number of children receiving this measure differed across the various test sessions, with fewer children administered the measure at 18 and 24 mo postoperatively. This is due, in part, to the smaller number of children who had worn devices for this length of time and to a reduction in the number of tests required by the FDA after the premarket approval. Performance of nonsegmental aspects of the PLE seems 50s
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PRE
1 YR
2YR
POST
POST
Figure 2. Paired comparisons of the mean performance of children receiving the nonsegmental subtests of the PLE before implantation and at two times postimplantation is depicted.
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number of children receiving the nonsegmental protocol (mean age 7.6 yr, average length of deafness 6.07 yr, and average age of deafness onset 1.43 yr). These data are shown in Figure 3. Significantly higher nonsegmental performance was found postimplant than preimplant for the subset of children who were tested at four 6 month intervals [F(3, 81) = 7.30. p < 0.0002].Similarly, children tested across five 6 mo intervals also demonstrated significantly higher postoperative than preoperative performance on the nonsegmental measure [F(4,40) = 11.60.p < 0.0011. However, post hoc analyses revealed no significant changes in performance between 12, 18. or 24 mo. Figure 4 illustrates the mean performance of all children receiving the segmental subtest of the PLE. The number of children receiving this measure differs across the various test sessions, with fewer children receiving the measure at 18 and 24 mo postoperatively. Once again, data were collapsed to allow paired comparison analyses and significantly lower segmental performance was observed preimplant relative to 1 and 2 yr postoperative performance [F(2,78)= 25.99,p < O.OOGl](see Fig. 5). Segmental performance continues to improve with additional implant experience and is significantly higher in the later postimplant session ( p < 0.0 1). As in the nonsegmental analyses, we examined performance in a smaller subset of subjects receiving segmental assessments at four or five 6 mo intervals to ensure that collapsing of the data into 1 and 2 yr postoperative intervals accurately reflected perform-
w
---4
I
I
cz 3 0 0 - 0 0 v, Z O O - -
3 Q 100.cz 0-
PRE 6 N=
12 18 2 4
(81) (74) (74) (43) (18)
Figure 4. Mean performance on the segmental subtest of the PLE is shown for children receiving the measure before implantation and at 6 mo intervals.
N=40
w [y: 300
0
zooLdi
Q 100
cz
0
PRE
1 YR
2 YR
POST POST N=28
CK 27
Figure 5. Paired comparisons of the mean performance of children receiving the segmental subtest of the PLE before implantation and at two times postimplantationare depicted.
0
P
6
12
18 N=ll
27
P
6 12 18 24
Figure 3. Paired comparisons of the mean performance of two subsets of children receiving the nonsegmental subtest of the PLE are shown. In the upper panel, Performance of children receiving the measure preimplant and across four 6 mo intervals is depicted. Similar data for children receiving the measure preimplant and across five 6 mo intervals are depicted in the lower panel.
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ance changes. Demographic information regarding the average age and length of deafness of the children is described in the section discussing the nonsegmental performances. Figure 6 portrays the mean segmental performance for these subsets of subjects. Significantly higher segmental performance occurred postimplant than preimplant for children who received testing on four 6 mo intervals [F(3, 84) = 16.6,p < 0.0011 and five 6 mo intervals [F(4,52) = 20.37,p < 0.00011. In both instances, post hoc analyses revealed that segmental performance continued to significantly improve over time postimplant ( p < 0.0 1). Performance on the PLE is shown in Figure 7 for the 3 1 children receiving this protocol before implantation and postoperatively at 6 mo and 1 yr after implantation. Significantly higher phonological performance was found after implantation than before implantation [F(2,60) = 12.21,p < 0.00011. Post hoc analyses indicated no significant differences in phonological performance at 6 and 12 mo postimplantation. Data were available on a smaller subset of children receiving this protocol preoperatively and postoperatively at 1 and 2 yr intervals. The average age at the time of implant, Speech in Cochlear-Implanted Children
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average length of deafness, and mean age at onset of deafness for the subset of children was 6.9 yr. 5.1 yr. and 1.9 yr. respectively. These demographics are representative of the total group of children receiving this protocol (mean age at implant was 7.0 yr. average length of deafness was 5.4 yr, and mean age at onset of deafness was 1.7 yr). As shown in Figure 8, significantly higher performance was noted postimplant than preimplant [F(2, 22) = 12.16, p < 0.011 and performance at the 2 yr postoperative interval was higher than the first annual postoperative session ( p < 0.0 I). Mean speech intelligibility scores obtained pre- and postimplant are shown in Figure 9. Speech intelligibility also was significantly higher postimplant than preimplant ( t = -1.04, df = 18, p < 0.01). Figure 10 depicts the mean length of utterances reported preimplant and 800
PRE
1 YR
2 YR
POST
POST
Figure 8. Mean performance on the PLE is depicted for children preimplant and at two times postimplant.
N=27
W
CK 3001 A
PRE
P
12
6
POST
18
800
I
IN=''
W Df 300-
1 YR
Figure 9. Mean speech intelligibility scores are shown for children receiving this protocol before implantation and postimplantation. The postimplantation scores represent performance acquired at 6 or 12 mo.
0
u If) ZOO-.
3 Q: 100Df
n -J
P
6 12 18 24
Figure 6. Paired comparisons of the mean performance of two subsets of children receiving the segmental subtest of the PLE are shown. In the upper panel, performance of children receiving the measure preimplant and across four 6 mo intervals are depicted. Similar data for children receiving the measure preimplant and across five 6 mo intervals are depicted in the lower panel. 262 1
PRE
POST
Figure 10. Mean length of utterance is shown for children receiving this protocol before implantation and after 12 mo of use with an implant.
1 yr postoperatively. No significant change in mean length of utterances was found postimplantation ( t = -0.70, p < 0.49, df = 54). Further analysis contrasting performance at later dates was not possible due to the small number of subjects receiving this protocol at later dates. DISCUSSION
PRE
6
12
Figure 7. Mean performance on the PLE is depicted for children preimplant and postimplant. The postimplantationscores are derived by collapsing Performance acquired at 6 and 12 mo postimplant.
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Although it is difficult to separate contributions directly attributable to the multichannel cochlear implant from those associated with maturation or training, data from the speech production protocols suggest some aspects of speech production may be influenced by Ear and Hearing, Vol. 12, No. 4, Supplement, 1991
experience with the implant. Significantly higher imitative abilities are observed for nonsegmental aspects of speech using a multichannel cochlear implant similar to that previously reported for single-channel implant users (Kirk & Hill-Brown, 1985). Nonsegmental performance, however, appears to plateau after implantation, and no significant change in performance is noted between measures acquired early (6 or 12 mo) or late (18 or 24 mo) postimplant. These findings may be influenced by a reduction in the number of children receiving the protocol. As mentioned earlier, the reduced numbers are related to the fewer number of children who had devices for this length of time and to a reduction in the number of tests required by the FDA for long-term follow-up. Although it also is possible that the plateau effect observed might be due to a ceiling effect on this task, inasmuch as the maximum score possible is 36, a review of the data presented in Figures 1 to 3 indicates mean performances postimplant fall within the range of 19 to 21. Auditory cues for prosodic, nonsegmental imitation may be coded by a multichannel implant in several ways. Alterations in loudness are coded by the implant as changes in current level and fundamental frequency variations are coded by the stimulation rate delivered to a given channel. These preliminary data suggest the greatest impact a multichannel cochlear implant may have upon imitative nonsegmental performance occurs within the first year after receiving the device. It may be possible that nonsegmental aspects change more rapidly within the first year because the prosodic features coded by the implant may be more salient to children as they learn to pair vocalizations with intents in order to develop more effective pragmatic communication skills. A plateau in nonsegmental performance may occur as children shift their attention to more advanced communication skills such as accurate sound production. An additional factor which may influence nonsegmental performance is the content of a child’s habilitation program. Typically (re)habilitation programs stress segmental performance via the correct pronunciation of sounds rather than prosodic variations, per se. Abilities of children to imitate segmental aspects of the PLE seem to continue to increase with experience with the implant. Segmental performance is significantly higher at each subsequent postimplant test period, suggesting this may be a more robust finding, relying less upon the number of subjects than the previously discussed nonsegmental performances. Continued improvement in the ability to imitate segmental aspects of speech, as experience with an implant lengthens, also is evident in the performance of children using single-channel cochlear implants (Kirk & Hill-Brown, 1985). Acoustic studies contrasting formant frequencies in the word “head” indicate more centralized values when an implant is turned off versus on, and provide further support for better segmental production with auditory feedback delivered by a multichannel cochlear implant (Tobey et al, 1991; Svirsky & Tobey, 1991). Ear and Hearing, Vol. 12, No. 4, 1991
Steady progress over time in segmental performance may reflect the children’s increasing ability to use information coded by single- or multichannel implants to guide or refine their speech production. Both the envelope information coded by single-channel implants and the spectral information coded by multichannel implants appear to be used by children to develop more accurate consonant and vowel production. In addition. increased use of segmental speech sounds are observed postimplant using elicited procedures in the PLE. Increased usage of segmental aspects during the elicited procedures of the PLE postimplant suggest that speech skills developed in conjunction with multichannel implant use may be generalized to situations using a prompt rather than direct imitation to elicit the responses. A variety of vowels and consonants is more accurately produced postimplant. Increased evidence of more accurately produced vowels and consonants may be related to several factors. A multichannel cochlear implant is capable of providing spectral and timing information regarding most of the vowels and many of the consonants. This information, in conjunction with the aural rehabilitation procedures, may aid many children in defining meaningful phonemic categories which may be further accentuated with speech production training. Changes in the ability to produce segmental aspects of speech also appear to interact in a positive fashion with overall speech intelligibility. In the measures contrasting speech intelligibility before and 1 yr after implantation, significant increases in intelligibility are found. Before implantation, speech intelligibility resembles that previously reported by Smith (1975) for other populations of profoundly hearing-impaired children. Intelligibility, however, nearly doubles after a year’s experience with the multichannel implant. These observations suggest the higher intelligibility scores noted postimplant are not necessarily indicative of the intelligibility associated with profoundly hearing-impaired populations, but rather may reflect contributions associated with the auditory feedback provided by an implant. Although segmental and intelligibility performance increases after implantation, the mean length of utterances produced by children wearing the implants does not significantly change. It is possible that longer use with an implant is needed in order to directly influence utterance length. The greatest increases in performance after experience with an implant seem to be in the fundamental skills underlying more advanced aspects of spoken communication. It is tempting to speculate what the long-term effects of cochlear implants (and the rehabilitation techniques accompanying the implants) might have upon spoken communication in profoundly hearing-impaired children. Continued acquisition of fundamental skills underlying prosody and sound production may lead to more sophisticated language skills. It is possible that children using cochlear implants may experience longterm benefits associated with learning to use the spectral and temporal auditory information provided by the Speech in Cochlear-ImplantedChildren
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speech processor to enhance phonologic. syntactic, morphologic, and semantic aspects of language. It also is possible that increases in linguistic capabilities may positively influence the long-term academic performance of the children. Taken overall, data from this study suggest increases in some fundamental, underlying skills of spoken communication are observed in profoundly heanng-impaired children who receive multichannel cochlear implants. Alterations in the ability to imitate prosodic aspects associated with the melody of speech are observed within the first year of use with an implant. Improved abilities to imitate segmental aspects associated with consonant and vowel production are observed through the first 2 yr of implant use. Some generalization of these skills are evident in the increased accuracy of sounds produced under elicited, rather than imitative conditions. However, only minimal changes in speech intelligibility or mean length of utterances is evident. REFERENCES Boone D. Modification of the voices of deaf children. Volta Rev 1966:686-692. Brannon J. Visual feedback of glossal motions and its influence on the speech of deaf children (PhD dissertation). Northwestern University, Chicago, IL, 1966. Geffner D. Feature characteristics of spontaneous speech production in young deaf children. J Commun Disord 1980:12:443-454. Gold T. Speech and hearing skills: A comparison between hard-ofhearing and deaf children (PhD dissertation). City University of New York, New York, NY, 1978. Hudgins C and Numbers F. An investigation of the intelligibility of the speech of the deaf. Genet Psycho1 Monograph 1942;28:289302. Kirk K and Hill-Brown C. Speech and language results in children with a cochlear implant. Ear Hear 3985:6:36S-47S.
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Ling D. Speech and the Hearing Impaired Child: Theory and Practice. Washington. D.C.: Alexander Graham Bell Association. 1976. Mangan K. Speech improvement through articulation testing. Am Ann Deaf 1961:7:391-395. Markides A. The speech of deaf and partially hearing children with special reference to factors affecting intelligibility. Br J Commun Disord 1970:5:124-140. Nober H. Articulation of the deaf. Exceptional children. 1967:l 1:61 1-621. Osbereer M and McGarr N. beech and Language: Advances in Basic Research and Practice. New York: AcadekcPress. 1982. Osberger M. Robbins A. Berry S. Todd S, Hesketh L. and Sedey A. Analysis of the spontaneous speech samples of children with a cochlear implant or tactile aid. Am J Otol I99 I :(Suppl): 173-1 8 1. Smith C. Residual hearing and speech production in deaf children. J Speech Hear Res 1975: 18:795-8 I 1. Svirsky M and Tobey E. Effects of different types of auditory stimulation on vowel formant frequencies in multichannel cochler implant users. J Acoust SOCAm 199 1:89:2895-2904. Tobey E. Speech production considerations in the management of children receiving cochlear implants. Sernin Hear 1986:7:407-422. Tobey E, Angelette S, Murchison C. Nicosia J. Sprague S. Staller S, Brimacombe J, and Beiter A. Speech production in children receiving a multichannel cochlear implant. Am J Otol 1991:(S~ppl):164-172. Tobey E. Pancamo S. Staller S. Brimacombe J. and Beiter A. Consonant production in children receiving a multichannel cochlear implant. Ear Hear 1991;12:23-31.
Acknowledgments: Portions of the analysis of this data were completed using equipment purchased from a Deafness Research Foundation grant and research funds from Cochlear Corporation. Preparation of the manuscript was partially supported by an NIH Academic Research Enhancement Award awarded to the first author. We wish to express our appreciation to all the clinical centers for their participation and especially to thank the children and their parents for their cooperation on this project. Address reprint requests to Dr. Emily A. Tobey, Department of Curnmunication Disorders, LSU Medical Center, 1900 Gravier Street, New Orleans, La 701 12.
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ABSTRACT The purpose of this report is to describe the speech production of children participating in the Food and Drug Administration’s approved clinical trials for the Nucleus multichannel cochlear implant. A significant increase in the ability to imitate nonsegmentalaspects of speech was noted after using the implant; however, nonsegmental performance did not appear to increase significantly between 12, 18, or 24 mo postimplantation. Significant increases occurred in imitative and elicited segmental performance after implantation at all measurement points. Speech intelligibility was significantly higher postimplant than preimplant; however, no significant change in mean length of utterance was observed. Data from these studies suggest a multichannel cochlear implant may provide information that is useful for assisting in the development or refinement of some aspects of spoken communication.
POOR SPOKEN COMMUNICATION is often a consequence of profound hearing impairment in children. Reduced speech intelligibility is commonly reported and seems related to segmental and nonsegmental errors (see for a review, Osberger & McGarr, 1982; Smith, 1975). Previous examinations of consonant production in profoundly hearing-impaired children reveal articulatory error patterns incorporating substitutions, omissions, and distortions (Brannon, 1966; Geffner, 1980; Gold, 1978; Markides, 1970; Nober, 1967; Osberger & McGarr, 1982; Smith, 1975). Voicing errors appear frequently, although the direction of the error (voiced for voiceless or voiceless for voiced consonants) differs across studies (Hudgins & Numbers, 1942; Mangan, 196 1;Nober, 1967; Smith, 1975). Manner and place of articulation errors also are observed. Such errors include nasal-oral substitutions (Markides, 1970; Smith, 1975) and glottal-stop substitutions (Smith, 1975). 48s
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Place of articulation errors often reveals the substitution of a more visible, anterior placement for other less visible placements (Gold, 1978). Segmental errors also are noted during vowel production. Several investigators (Boone, 1966; Nober, 1967: Smith, 1975) report that front vowels are produced with more errors than back vowels, suggesting difficulty with tongue positioning. Other investigators observe a greater number of errors with vowels requiring high- or mid-tongue heights than vowels with low-tongue heights (Geffner, 1980: Smith, 1975). Thus, the poor speech of profoundly hearing-impaired children appears to be due, in part, to segmental errors associated with consonant and vowel production. Profoundly hearing-impaired children who receive single-channel cochlear implants appear to approve their abilities to imitate segmental aspects of speech (Kirk & Hill-Brown, 1985). Significant increases in production of vowels, diphthongs, and simple consonants are noted after 1 yr of use with the House/3M single-channel cochlear implant. Increased use of correctly produced vowels and consonants also is evident in the spontaneous speech of children receiving singlechannel implants (Kirk & Hill-Brown, 1985). Similar observations occur for profoundly hearingimpaired children receiving multichannel cochlear implants. After I yr of use with the Nucleus multichannel cochlear implant, 85% of the vocalizations produced in a spontaneous language sample were judged to be either speech or speechlike and 67% were identified as English phonemes (Osberger, Robbins, Berry, Todd, Hesketh, & Sedey, 1990). Tobey and colleagues report significant improvement in children’s ability to imitate segmental aspects of speech (Tobey, Angelette, Murchison, Nicosia, Sprague, Staller, Brimacombe, & Beiter, 1991) and increased consonant repertoires (Tobey, Pancamo, Staller, Brimacombe, & Beiter, 199 1) in profoundly hearing-impaired children after using a multichannel cochlear implant for a year. Rapid changes in vowel formant frequencies, fundamental frequencies, and durations also are evident in trials contrasting speech produced with a multichannel cochlear implant turned on versus off (Tobey et al, 1991). Improvement in the ability to imitate nonsegmental aspects of speech also are reported for profoundly hearing-impaired children after a year’s use with either a single-channel (Kirk &
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0196/0202/91/1204-0048S$03.00/0EARAND HEARING Copyright 0 1991 by Williams 8 Wilkins Printed in the U S A .
Ear and Hearing, Vol. 12, No. 4, Supplement, 1991
Hill-Brown, 1985) or a multichannel device (Tobey et al, 199 1). Although these studies differ considerably in the type of speech tokens examined and dependent variables measured, it seems that auditory information delivered via a cochlear implant may be useful for enhancing t h e development of some speech sounds. T h e purpose of this report is t o update data obtained from four speech production protocols collected on children participating in the pediatric clinical trials for the Nucleus multichannel cochlear implant. T h e four speech production protocols included assessment of nonsegmental performance, segmental abilities in imitative and elicited conditions, speech intelligibility, and mean length of utterances. This report extends earlier observations (Tobey et al, 199 1) by reviewing long-term postoperative data from the subjects collected longitudinally and by analyzing subsets of paired comparisons across time. T h e speech production measures described were the minimum protocol suggested by a committee of speechlanguage pathologists for tracking speech production performance over time (Tobey. 1986). In addition, the committee suggested that an independent evaluation center for speech-language analyses be formed as part of the clinical trials to, in part, provide statistical updates on the speech production measures. A center was established a t the Communication Sciences Laboratories of t h e Department of Communication Disorders, Louisiana State University Medical Center as a response to this suggestion. METHODS AND PROCEDURES
Subjects Seventy-eight children participated in the speech production protocols, which were acquired over 24 mo. The mean age of the subjects was 8.5 yr, with a range from 2.3 yr to 17.7 yr. The average age at onset of profound hearing impairment was 1.43 yr and the mean length of profound hearing impairment was 6.07 yr. Fifty-five percent of the subjects were female and 53% of the population was implanted in the left ear. The most prevalent etiology was meningitis (46.1%). The etiology of deafness was unknown in 42. I % of the subjects. The majority of the children were in self-contained hearingimpaired classes (53.2%), mainstreamed with either an interpreter or resource teacher (24.2%), in a day school (14.5%) or residential school (8. I %). Total communication was used by 57.1% and auditory-oral communication was used by 30.2% of the subjects. All subjects participating in the speech production protocols used the Nucleus Wearable Speech Processor (WSP) with an FO-FI-F2 coding strategy. Speech Production Protocols Speech production protocols were administered by 29 investigative centers participating in the Food and Drug Administration's (FDA) clinical trials. The type and number of speech measures administered varied as a function of the age of the child, the length of deafness, and speech/language skills at the time of testing. Protocols were completed by a member of the clinical team at each center. The speech protocols were designed to assess fundamental skills underlying expressive communication, such as the imiEar and Hearing, Vol. 12, No. 4, 1991
tation of prosodic features and sounds, and also to assess more complex aspects, such as overall speech intelligibility. Nonsegmental and segmental portions of the Phonetic Level Speech Evaluation (PLE) (Ling, 1976) were administered before implantation. and at 6, 12, 18. and 24 mo postimplantation. The nonsegmental protocol examined children's ability to imitate a clinician modeling variations in loudness, pitch. and duration. Segmental assessment investigated childrens' ability to imitate syllables in isolation. repeat multiple syllables. alternate repetition of two different syllables. and imitate syllables varying in pitch. Following the techniques discussed by Ling ( 1976). responses were rated as consistently correct. inconsistently correct, or consistently in error. A numeric value system developed by Kirk and Hill-Brown (1985) was applied to the samples. As shown in Table I , incorrect imitation of nonsegmental stimuli was assigned a 0, inconsistently correct trials were assigned a I , and consistently correct sounds were assigned a 2. Sounds produced in isolation in the segmental subtest were assigned a 0 for error trials, a 1 for inconsistently correct trials. and a 2 for consistently correct trials. Imitations of repeated syllables were assigned a 3 for inconsistently correct trials and a 4 for consistently correct trials. Imitations of alternating syllables were assigned a 5 for inconsistently correct trials and a 6 for consistently correct trials. The imitation of syllables varying in pitch received a 7 for inconsistently correct trials and an 8 for consistently correct trials. The highest score achieved on an individual trial was used and all items on the test were included in the analysis. Nonsegmental and segmental scores were acquired by totaling the numeric values for all items administered. Mean scores for the entire population of children administered this protocol were calculated. In addition, three additional paired comparison analyses were completed. In the first analysis, data were compared for three time periods: preimplant. 1 yr postoperatively and 2 yr postoperatively. One yr postoperative scores were obtained either at 6 or 12 mo postimplant and 2 yr postoperative scores were obtained either at 18 or 24 mo postimplant. In the event a child received the protocol at both
Table 1. Numeric scoring system used for quantifying performance on the Phonetic Level Speech Evaluation (PLE) and Phonologic Level Speech Evaluation (Phonologic) developed by Kirk and Hill-Brown (1 985).
Test Measures PLE Nonsegmental Subtest and Phonologic Test Consistent Error Productions Inconsistently Correct Productions Consistently Correct Productions PLE Segmental Subtests Consistent Error Productions Isolated Syllables Inconsistently Correct Productions Consistently Correct Productions Repeat Multiple Syllables Inconsistently Correct Productions Consistently Correct Productions Alternating Syllables Inconsistently Correct Productions Consistently Correct Productions Pitch Varying Syllables Inconsistently Correct Productions Consistently Correct Productions
Speech in Cochlear-ImplantedChildren
Scores
0 1 2 0 1 2
3 4 5
6 7 8
49s
time periods (i.e., at 6 and 12 mo), the earliest time period score was used as a means of conservatively estimating performance changes. Two additional analyses were performed with a subset of children who received the protocol on four (preimplant and 6. 12. and 18 mo postoperatively) or five (preimplant and 6 . 12. 18, and 24 mo postoperatively) different test periods. Data were examined using analysis of variance for repeated measures. Phonological measures were assessed using Ling's ( 1976) PLE. In this protocol, a clinician engages a child in play situations or in spontaneous conversation in order to acquire a language sample. The resulting samples were examined to determine which sounds a given child produced under elicited, nonimitative circumstances. As shown in Table I , sounds were rated as consistently correct, inconsistently correct, or error productions. Ratings were converted to numeric values using a system similar to the one described by Kirk and HillBrown ( 1985). Consistently correct productions were assigned a 2 , inconsistently correct productions were assigned a I , and error productions received a 0. Scores were achieved by summing the total number of scores. Data were analyzed with paired comparisons in two ways. First, comparisons were made between preimplant performance and performance recorded at 6 and 12 mo postimplant. Second. comparisons were made of a subset of children who received the protocol before implantation, 1 yr postimplantation and 2 yr postimplantation. Data were analyzed using a repeated measures analysis of variance. A third protocol examined speech intelligibility. Materials assessing speech intelligibility were adopted from McGarr ( 1 983). Target stimuli were 36 monosyllabic words embedded in sentences varying in overall length. The monosyllabic words were selected from a previously described corpus of words produced by deaf children (Smith, 1975) and represented the 18 words ranked highest and lowest in speech intelligibility by listeners. Half of the sentences contained high contextual information (i.e., the flag is red, white, and blue) and half contained low contextual information (i.e., is the fat baby crying?). Samples were scored by determining the number of target words that were correctly identified by judges. Overall intelligibility was calculated by converting the total number of correctly identified target words to a percent correct score. Pre- and postimplant performance was compared using a I-test. A fourth measure, mean length of utterances (MLU), was determined by engaging the children in conversation using pictures or age-appropriate toys. Five min samples of speech were transcribed and the total number of words within each utterance calculated. Mean length was determined by dividing the total number of words by the number of utterances spoken in the time period. Pre- and postimplant performance was statistically analyzed using a t-test.
to increase with increasing length of implant use. In order to examine the significance of this trend, data were collapsed to contrast performance after 1 and 2 yr postoperative experience to preoperative performance for the 37 children who had data at the three intervals. Figure 2 depicts nonsegmental performance preimplant and at the two postoperative intervals. Nonsegmental performance is significantly higher postimplant than preimplant [ F ( 2 , 72) = 27.1, p < 0.00011: however, post hoc analyses revealed no significant differences between the two postoperative nonsegmental performances. In order to ensure that this procedure for collapsing the data across time intervals accurately represented postoperative performance at the data collection points, we conducted two additional analyses on a smaller subset of children who received nonsegmental testing at 6 mo postoperative intervals. The mean age at implantation of the children included in the paired comparisons was 6.8 yr. The average length of deafness was 4.9 yr, and mean age of deafness onset was 2.0 yr. The demographics of this sample were similar to the total
36
" I
[li
PRE 6 N=
12 18 2 4
( 7 8 ) ( 7 3 ) (70) (43) (18)
Figure 1. Mean performance of children receiving the nonsegmental subtest of the PLE before implantation and at 6 mo intervals postimplantation is shown.
N=37 27
RESULTS
Figure 1 illustrates the mean performance of all children receiving the nonsegmental subtest of the PLE. As the figure indicates, the number of children receiving this measure differed across the various test sessions, with fewer children administered the measure at 18 and 24 mo postoperatively. This is due, in part, to the smaller number of children who had worn devices for this length of time and to a reduction in the number of tests required by the FDA after the premarket approval. Performance of nonsegmental aspects of the PLE seems 50s
Tobey and Hasenstab
PRE
1 YR
2YR
POST
POST
Figure 2. Paired comparisons of the mean performance of children receiving the nonsegmental subtests of the PLE before implantation and at two times postimplantation is depicted.
Ear and Hearing, Vol. 12, No. 4, Supplement, 1991
number of children receiving the nonsegmental protocol (mean age 7.6 yr, average length of deafness 6.07 yr, and average age of deafness onset 1.43 yr). These data are shown in Figure 3. Significantly higher nonsegmental performance was found postimplant than preimplant for the subset of children who were tested at four 6 month intervals [F(3, 81) = 7.30. p < 0.0002].Similarly, children tested across five 6 mo intervals also demonstrated significantly higher postoperative than preoperative performance on the nonsegmental measure [F(4,40) = 11.60.p < 0.0011. However, post hoc analyses revealed no significant changes in performance between 12, 18. or 24 mo. Figure 4 illustrates the mean performance of all children receiving the segmental subtest of the PLE. The number of children receiving this measure differs across the various test sessions, with fewer children receiving the measure at 18 and 24 mo postoperatively. Once again, data were collapsed to allow paired comparison analyses and significantly lower segmental performance was observed preimplant relative to 1 and 2 yr postoperative performance [F(2,78)= 25.99,p < O.OOGl](see Fig. 5). Segmental performance continues to improve with additional implant experience and is significantly higher in the later postimplant session ( p < 0.0 1). As in the nonsegmental analyses, we examined performance in a smaller subset of subjects receiving segmental assessments at four or five 6 mo intervals to ensure that collapsing of the data into 1 and 2 yr postoperative intervals accurately reflected perform-
w
---4
I
I
cz 3 0 0 - 0 0 v, Z O O - -
3 Q 100.cz 0-
PRE 6 N=
12 18 2 4
(81) (74) (74) (43) (18)
Figure 4. Mean performance on the segmental subtest of the PLE is shown for children receiving the measure before implantation and at 6 mo intervals.
N=40
w [y: 300
0
zooLdi
Q 100
cz
0
PRE
1 YR
2 YR
POST POST N=28
CK 27
Figure 5. Paired comparisons of the mean performance of children receiving the segmental subtest of the PLE before implantation and at two times postimplantationare depicted.
0
P
6
12
18 N=ll
27
P
6 12 18 24
Figure 3. Paired comparisons of the mean performance of two subsets of children receiving the nonsegmental subtest of the PLE are shown. In the upper panel, Performance of children receiving the measure preimplant and across four 6 mo intervals is depicted. Similar data for children receiving the measure preimplant and across five 6 mo intervals are depicted in the lower panel.
Ear and Hearing, Vol. 12, No. 4, 1991
ance changes. Demographic information regarding the average age and length of deafness of the children is described in the section discussing the nonsegmental performances. Figure 6 portrays the mean segmental performance for these subsets of subjects. Significantly higher segmental performance occurred postimplant than preimplant for children who received testing on four 6 mo intervals [F(3, 84) = 16.6,p < 0.0011 and five 6 mo intervals [F(4,52) = 20.37,p < 0.00011. In both instances, post hoc analyses revealed that segmental performance continued to significantly improve over time postimplant ( p < 0.0 1). Performance on the PLE is shown in Figure 7 for the 3 1 children receiving this protocol before implantation and postoperatively at 6 mo and 1 yr after implantation. Significantly higher phonological performance was found after implantation than before implantation [F(2,60) = 12.21,p < 0.00011. Post hoc analyses indicated no significant differences in phonological performance at 6 and 12 mo postimplantation. Data were available on a smaller subset of children receiving this protocol preoperatively and postoperatively at 1 and 2 yr intervals. The average age at the time of implant, Speech in Cochlear-Implanted Children
51s
average length of deafness, and mean age at onset of deafness for the subset of children was 6.9 yr. 5.1 yr. and 1.9 yr. respectively. These demographics are representative of the total group of children receiving this protocol (mean age at implant was 7.0 yr. average length of deafness was 5.4 yr, and mean age at onset of deafness was 1.7 yr). As shown in Figure 8, significantly higher performance was noted postimplant than preimplant [F(2, 22) = 12.16, p < 0.011 and performance at the 2 yr postoperative interval was higher than the first annual postoperative session ( p < 0.0 I). Mean speech intelligibility scores obtained pre- and postimplant are shown in Figure 9. Speech intelligibility also was significantly higher postimplant than preimplant ( t = -1.04, df = 18, p < 0.01). Figure 10 depicts the mean length of utterances reported preimplant and 800
PRE
1 YR
2 YR
POST
POST
Figure 8. Mean performance on the PLE is depicted for children preimplant and at two times postimplant.
N=27
W
CK 3001 A
PRE
P
12
6
POST
18
800
I
IN=''
W Df 300-
1 YR
Figure 9. Mean speech intelligibility scores are shown for children receiving this protocol before implantation and postimplantation. The postimplantation scores represent performance acquired at 6 or 12 mo.
0
u If) ZOO-.
3 Q: 100Df
n -J
P
6 12 18 24
Figure 6. Paired comparisons of the mean performance of two subsets of children receiving the segmental subtest of the PLE are shown. In the upper panel, performance of children receiving the measure preimplant and across four 6 mo intervals are depicted. Similar data for children receiving the measure preimplant and across five 6 mo intervals are depicted in the lower panel. 262 1
PRE
POST
Figure 10. Mean length of utterance is shown for children receiving this protocol before implantation and after 12 mo of use with an implant.
1 yr postoperatively. No significant change in mean length of utterances was found postimplantation ( t = -0.70, p < 0.49, df = 54). Further analysis contrasting performance at later dates was not possible due to the small number of subjects receiving this protocol at later dates. DISCUSSION
PRE
6
12
Figure 7. Mean performance on the PLE is depicted for children preimplant and postimplant. The postimplantationscores are derived by collapsing Performance acquired at 6 and 12 mo postimplant.
52s
Tobey and Hasenstab
Although it is difficult to separate contributions directly attributable to the multichannel cochlear implant from those associated with maturation or training, data from the speech production protocols suggest some aspects of speech production may be influenced by Ear and Hearing, Vol. 12, No. 4, Supplement, 1991
experience with the implant. Significantly higher imitative abilities are observed for nonsegmental aspects of speech using a multichannel cochlear implant similar to that previously reported for single-channel implant users (Kirk & Hill-Brown, 1985). Nonsegmental performance, however, appears to plateau after implantation, and no significant change in performance is noted between measures acquired early (6 or 12 mo) or late (18 or 24 mo) postimplant. These findings may be influenced by a reduction in the number of children receiving the protocol. As mentioned earlier, the reduced numbers are related to the fewer number of children who had devices for this length of time and to a reduction in the number of tests required by the FDA for long-term follow-up. Although it also is possible that the plateau effect observed might be due to a ceiling effect on this task, inasmuch as the maximum score possible is 36, a review of the data presented in Figures 1 to 3 indicates mean performances postimplant fall within the range of 19 to 21. Auditory cues for prosodic, nonsegmental imitation may be coded by a multichannel implant in several ways. Alterations in loudness are coded by the implant as changes in current level and fundamental frequency variations are coded by the stimulation rate delivered to a given channel. These preliminary data suggest the greatest impact a multichannel cochlear implant may have upon imitative nonsegmental performance occurs within the first year after receiving the device. It may be possible that nonsegmental aspects change more rapidly within the first year because the prosodic features coded by the implant may be more salient to children as they learn to pair vocalizations with intents in order to develop more effective pragmatic communication skills. A plateau in nonsegmental performance may occur as children shift their attention to more advanced communication skills such as accurate sound production. An additional factor which may influence nonsegmental performance is the content of a child’s habilitation program. Typically (re)habilitation programs stress segmental performance via the correct pronunciation of sounds rather than prosodic variations, per se. Abilities of children to imitate segmental aspects of the PLE seem to continue to increase with experience with the implant. Segmental performance is significantly higher at each subsequent postimplant test period, suggesting this may be a more robust finding, relying less upon the number of subjects than the previously discussed nonsegmental performances. Continued improvement in the ability to imitate segmental aspects of speech, as experience with an implant lengthens, also is evident in the performance of children using single-channel cochlear implants (Kirk & Hill-Brown, 1985). Acoustic studies contrasting formant frequencies in the word “head” indicate more centralized values when an implant is turned off versus on, and provide further support for better segmental production with auditory feedback delivered by a multichannel cochlear implant (Tobey et al, 1991; Svirsky & Tobey, 1991). Ear and Hearing, Vol. 12, No. 4, 1991
Steady progress over time in segmental performance may reflect the children’s increasing ability to use information coded by single- or multichannel implants to guide or refine their speech production. Both the envelope information coded by single-channel implants and the spectral information coded by multichannel implants appear to be used by children to develop more accurate consonant and vowel production. In addition. increased use of segmental speech sounds are observed postimplant using elicited procedures in the PLE. Increased usage of segmental aspects during the elicited procedures of the PLE postimplant suggest that speech skills developed in conjunction with multichannel implant use may be generalized to situations using a prompt rather than direct imitation to elicit the responses. A variety of vowels and consonants is more accurately produced postimplant. Increased evidence of more accurately produced vowels and consonants may be related to several factors. A multichannel cochlear implant is capable of providing spectral and timing information regarding most of the vowels and many of the consonants. This information, in conjunction with the aural rehabilitation procedures, may aid many children in defining meaningful phonemic categories which may be further accentuated with speech production training. Changes in the ability to produce segmental aspects of speech also appear to interact in a positive fashion with overall speech intelligibility. In the measures contrasting speech intelligibility before and 1 yr after implantation, significant increases in intelligibility are found. Before implantation, speech intelligibility resembles that previously reported by Smith (1975) for other populations of profoundly hearing-impaired children. Intelligibility, however, nearly doubles after a year’s experience with the multichannel implant. These observations suggest the higher intelligibility scores noted postimplant are not necessarily indicative of the intelligibility associated with profoundly hearing-impaired populations, but rather may reflect contributions associated with the auditory feedback provided by an implant. Although segmental and intelligibility performance increases after implantation, the mean length of utterances produced by children wearing the implants does not significantly change. It is possible that longer use with an implant is needed in order to directly influence utterance length. The greatest increases in performance after experience with an implant seem to be in the fundamental skills underlying more advanced aspects of spoken communication. It is tempting to speculate what the long-term effects of cochlear implants (and the rehabilitation techniques accompanying the implants) might have upon spoken communication in profoundly hearing-impaired children. Continued acquisition of fundamental skills underlying prosody and sound production may lead to more sophisticated language skills. It is possible that children using cochlear implants may experience longterm benefits associated with learning to use the spectral and temporal auditory information provided by the Speech in Cochlear-ImplantedChildren
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speech processor to enhance phonologic. syntactic, morphologic, and semantic aspects of language. It also is possible that increases in linguistic capabilities may positively influence the long-term academic performance of the children. Taken overall, data from this study suggest increases in some fundamental, underlying skills of spoken communication are observed in profoundly heanng-impaired children who receive multichannel cochlear implants. Alterations in the ability to imitate prosodic aspects associated with the melody of speech are observed within the first year of use with an implant. Improved abilities to imitate segmental aspects associated with consonant and vowel production are observed through the first 2 yr of implant use. Some generalization of these skills are evident in the increased accuracy of sounds produced under elicited, rather than imitative conditions. However, only minimal changes in speech intelligibility or mean length of utterances is evident. REFERENCES Boone D. Modification of the voices of deaf children. Volta Rev 1966:686-692. Brannon J. Visual feedback of glossal motions and its influence on the speech of deaf children (PhD dissertation). Northwestern University, Chicago, IL, 1966. Geffner D. Feature characteristics of spontaneous speech production in young deaf children. J Commun Disord 1980:12:443-454. Gold T. Speech and hearing skills: A comparison between hard-ofhearing and deaf children (PhD dissertation). City University of New York, New York, NY, 1978. Hudgins C and Numbers F. An investigation of the intelligibility of the speech of the deaf. Genet Psycho1 Monograph 1942;28:289302. Kirk K and Hill-Brown C. Speech and language results in children with a cochlear implant. Ear Hear 3985:6:36S-47S.
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Ling D. Speech and the Hearing Impaired Child: Theory and Practice. Washington. D.C.: Alexander Graham Bell Association. 1976. Mangan K. Speech improvement through articulation testing. Am Ann Deaf 1961:7:391-395. Markides A. The speech of deaf and partially hearing children with special reference to factors affecting intelligibility. Br J Commun Disord 1970:5:124-140. Nober H. Articulation of the deaf. Exceptional children. 1967:l 1:61 1-621. Osbereer M and McGarr N. beech and Language: Advances in Basic Research and Practice. New York: AcadekcPress. 1982. Osberger M. Robbins A. Berry S. Todd S, Hesketh L. and Sedey A. Analysis of the spontaneous speech samples of children with a cochlear implant or tactile aid. Am J Otol I99 I :(Suppl): 173-1 8 1. Smith C. Residual hearing and speech production in deaf children. J Speech Hear Res 1975: 18:795-8 I 1. Svirsky M and Tobey E. Effects of different types of auditory stimulation on vowel formant frequencies in multichannel cochler implant users. J Acoust SOCAm 199 1:89:2895-2904. Tobey E. Speech production considerations in the management of children receiving cochlear implants. Sernin Hear 1986:7:407-422. Tobey E, Angelette S, Murchison C. Nicosia J. Sprague S. Staller S, Brimacombe J, and Beiter A. Speech production in children receiving a multichannel cochlear implant. Am J Otol 1991:(S~ppl):164-172. Tobey E. Pancamo S. Staller S. Brimacombe J. and Beiter A. Consonant production in children receiving a multichannel cochlear implant. Ear Hear 1991;12:23-31.
Acknowledgments: Portions of the analysis of this data were completed using equipment purchased from a Deafness Research Foundation grant and research funds from Cochlear Corporation. Preparation of the manuscript was partially supported by an NIH Academic Research Enhancement Award awarded to the first author. We wish to express our appreciation to all the clinical centers for their participation and especially to thank the children and their parents for their cooperation on this project. Address reprint requests to Dr. Emily A. Tobey, Department of Curnmunication Disorders, LSU Medical Center, 1900 Gravier Street, New Orleans, La 701 12.
Ear and Hearing, Vol. 12, No. 4, Supplement, 1991
