Treatment efficacy: hearing loss in children.

This article provides a review of the topic of treatment efficacy for children with hearing loss. Efficacy is related to a wide range of treatment goals in the areas of sensory and perceptual skill development, language development (regardless of communication modality), speech-production skill development, academic performance, and social-emotional growth. Topics addressed in this article include (a) the definition of hearing loss in children; (b) incidence and prevalence data; (c) the effects of childhood hearing loss on daily life, including language and literacy, speech perception and production, socialization and family dynamics; (d) the role of audiologists and speech-language pathologists in managing children with hearing loss; and (e) a summary of pertinent efficacy research for children with hearing loss. The analysis of the available research suggests that (a) early intervention for children who are deaf or hard of hearing has long-term positive effects on overall development; (b) a variety of communication modalities exist for this population, and research to date has been more descriptive than prognostic on the choice of modality; (c) sensory aids (hearing aids, tactile aids, and cochlear implants) provide different degrees of benefit for children in the areas of speech perception, production, and language development, depending upon the extent of their hearing loss; (d) few studies have addressed rates of learning and long-term outcomes, but existing data suggest that enriched programs provide some children with hearing loss with the ability to overcome developmental lags in language and academic skills.

Effect of relative amplitude and formant transitions on perception of place of articulation by adult listeners with cochlear implants.

Previous studies have shown that manipulation of a particular frequency region of the consonantal portion of a syllable relative to the amplitude of the same frequency region in an adjacent vowel influences the perception of place of articulation. This manipulation has been called the relative amplitude cue. Earlier studies have examined the effect of relative amplitude and formant transition manipulations upon labeling place of articulation for fricatives and stop consonants in listeners with normal hearing. The current study sought to determine if (a) the relative amplitude cue is used by adult listeners wearing a cochlear implant to label place of articulation, and (b) adult listeners wearing a cochlear implant integrated the relative amplitude and formant transition information differently than listeners with normal hearing. Sixteen listeners participated in the study, 12 with normal hearing and 4 postlingually deafened adults wearing the Nucleus 22 electrode Mini Speech Processor implant with the multipeak processing strategy. The stimuli used were synthetic consonant-vowel (CV) syllables in which relative amplitude and formant transitions were manipulated. The two speech contrasts examined were the voiceless fricative contrast /s/-"sh" and the voiceless stop consonant contrast /p/-/t/. For each contrast, listeners were asked to label the consonant sound in the syllable from the two response alternatives. Results showed that (a) listeners wearing this implant could use relative amplitude to consistently label place of articulation, and (b) listeners with normal hearing integrated the relative amplitude and formant transition information more than listeners wearing a cochlear implant, who weighted the relative amplitude information as much as 13 times that of the transition information.

Negative intraoral air pressures of deaf children with cochlear implants: physiology, phonology, and treatment.

The primary purpose of this investigation was to examine deaf children's use of negative intraoral air pressures (-Po's) from a physiological and a phonological perspective, with the hope of gathering insight into the strategies these children use to produce speech. A secondary purpose was to compare the effectiveness of two methods of treating these deviant productions. Subjects were four profoundly deaf children, age 6:6-9:2, who used cochlear implants and had demonstrated persistent use of -Po's. Po's were collected during production of CV syllables with initial [p] and [b] and a variety of vowel contexts. Two of the children used -PO's more often before low than high vowels. We suggest that this vowel-based pattern may result when deaf children learn to lower their larynges in response to visible jaw lowering cues. Another child presented with a pattern of more frequent -Po's before front than back vowels, suggesting that she may have expanded her pharynx anteriorly as she attempted to achieve an anterior tongue placement. Two children also clearly used -Po's more frequently for voiced than voiceless stops, possibly resulting from a tendency to use the degree rather than the timing of vocal fold adduction to distinguish voiceless and voiced phonemes. Two of the children were enrolled in a single-subject multiple baseline study to compare the effectiveness of traditional articulation treatment and visual-feedback treatment. The child who was a far less proficient talker demonstrated rapid and sustained change, whereas the better talker demonstrated minimal change with treatment. This study provides evidence that (a) deaf children use speech production strategies quite unlike those of normally hearing children and (b) deviant speech behaviors of deaf children should be treated before they become part of functional phonological systems. This work highlights the need to consider the unique speech behaviors of deaf children, and their reliance on alternate feedback mechanisms, when developing assessment and treatment procedures.

Variables affecting implant performance in children.

This study examined the variables that contribute to the large individual differences in the speech perception skills of children with the Nucleus multichannel cochlear implant. Sixty-one children were tested on four measures of speech perception: two tests of closed-set word recognition, one test of open-set recognition of phrases, and one open-set monosyllabic word test, scored on the basis of the percentage of phonemes as well as words identified correctly. The results of a series of multiple regression analyses revealed that the variables of processor type, duration of deafness, communication mode, age at onset of deafness, length of implant use, and age implanted accounted for roughly 35% of the variance on two tests of closed-set word recognition, and 40% of the variance on measures that assessed recognition of words or phonemes in an open set. Length of implant use accounted for the most variance on all of the speech perception measures.

Physiological assessment of speech and voice production of adults with hearing loss.

The purpose of this investigation was to study the impact of hearing loss on phonatory, velopharyngeal, and articulatory functioning using a comprehensive physiological approach. Electroglottograph (EGG), nasal/oral air flow, and intraoral air pressure signals were recorded simultaneously from adults with impaired and normal hearing as they produced syllables and words of varying physiological difficulty. The individuals with moderate-to-profound hearing loss had good to excellent oral communication skills. Intraoral pressure, nasal air flow, durations of lip, velum, and vocal fold articulations, estimated subglottal pressure, mean phonatory air flow, fundamental frequency, and EGG abduction quotient were compared between the two subject groups. Data from the subjects with hearing loss also were compared across aided and unaided conditions to investigate the influence of auditory feedback on speech motor control. The speakers with hearing loss had significantly higher intraoral pressures, subglottal pressures, laryngeal resistances, and fundamental frequencies than those with normal hearing. There was notable between-subject variability. All of the individuals with profound hearing loss had at least one speech/voice physiology measure that fell outside of the normal range, and most of the subjects demonstrated unique clusters of abnormal behaviors. Abnormal behaviors were more evident in the phonatory than articulatory or velopharyngeal systems and were generally consistent with vocal fold hyperconstriction. There was evidence from individual data that vocal fold posturing influenced articulatory timing. The results did not support the idea that the speech production skills of adults with moderate-to-profound hearing loss who are good oral communicators deteriorate when there are increased motoric demands on the velopharyngeal and phonatory mechanism. Although no significant differences were found between the aided and unaided conditions, 7 of 10 subjects showed the same direction of change for subglottal pressure, intraoral pressure, nasal air flow, and the duration of lip and vocal fold articulations. We conclude that physiological assessments provide important information about the speech/voice production abilities of individuals with moderate-to-profound hearing loss and are a valuable addition to standard assessment batteries.

A comparison of speech discrimination with cochlear implants and tactile aids.

This study investigates patterns of speech discrimination in profoundly hearing-impaired children who have received cochlear implants or tactile aids. The change/no change procedure was used to assess speech discrimination in these children. Three groups of subjects were tested: the first group used 3M/House single-channel cochlear implants; the second group used Nucleus 22-channel cochlear implants; and the third group used two-channel Tactaid II+ vibrotactile aids. Nine contrasts were constructed that assessed discrimination of suprasegmental and segmental speech features. Subjects were presented with stimulus trials in which stimuli changed during the trial or in which stimuli remained the same. Hits, misses, false alarms, and correct rejections were tallied and d' values were calculated for individual subjects for each contrast. Results indicated that different patterns of speech discrimination are provided by the three sensory prosthetic devices. For all contrasts, mean discrimination performance with the Nucleus device was better than that observed for the other two devices, despite the shorter duration of subject experience with this cochlear implant. In addition, interactions between device and speech contrast were not observed. Examination of individual subject performance revealed that each device group had a distribution of good to poor performers. The results suggest that the change/no change procedure is able to provide information regarding speech perception through sensory prosthetic devices despite existing differences in vocabulary and language skills of subjects.

Assessment of speech perception in children with cochlear implants and tactile aids: what should the future hold?

The purpose of this paper is to propose a rationale for the future development of speech perception evaluation materials for children using either cochlear implants or vibrotactile aids as sensory prosthetic devices. It is suggested that future evaluation tools extend beyond the assessment of device efficacy. In particular, they should address issues of normal perceptual development in children, as well as the results of intervention with children using these sensory prosthetic devices.

Speech perception with a single-channel cochlear implant: a comparison with a single-channel tactile device.

Suprasegmental and segmental speech perception tasks were administered to 8 patients with single-channel cochlear implants. Suprasegmental tasks included the recognition of syllable number, syllabic stress, and intonation. Segmental tasks included the recognition of vowels and consonants in three modalities: visual only, implant only, and visual + implant. Results were compared to those obtained from artificially deafened adults using a single-channel vibrotactile device. The patterns of responses for both suprasegmental and segmental tasks were highly similar for both groups of subjects, despite differences between the characteristics of the subject samples. These results suggest that single-channel sensory devices, whether they be cochlear implants or vibrotactile aids, produce similar patterns of speech perception errors, even when differences are observed in overall performance level.

Effects of transition length on the perception of stop consonants by children and adults.

The purpose of this investigation was to determine whether children with normal linguistic skills demonstrate increasing developmental changes in their perception of place of articulation for stop consonants with short- and long-duration formant transitions. Three experimental paradigms were used with children and adults: discrimination, labeling, and selective adaptation. Two sets of synthetic CV syllables, varying along a seven-step, bilabial-to-alveolar dimension, were used as stimuli. These two synthetic continua differed in the length of the second and third formant transitions. Results showed that children's discrimination abilities gradually approximated those of adults, but did not reach adult levels even at 10 years of age. Differences were not observed in the labeling task. Further, results of the selective adaptation task indicated that only the adult subjects showed a significant boundary shift for any adapting stimuli. The absence of selective adaptation in children was interpreted as a possible reflection of their poorer auditory abilities. Thus, the pattern of speech perception development for children for place of articulation is a complex one with a strong auditory developmental component.

A modified speech tracking procedure as a communicative performance measure.

A modified speech tracking procedure was investigated to determine the effects of controlling connected discourse materials and of specific prompting techniques on tracking rate and subjects' responses. In addition, comprehension was tested after subjects completed the tracking task. Two experiments were conducted with normally hearing subjects, one in which subjects tracked in an auditory plus noise condition and the second in which they tracked in a visual-alone condition. The results of these two experiments showed significant differences between tracking rates for controlled versus uncontrolled materials for both modalities, with higher tracking rates observed for the controlled materials. The use of specific prompting techniques reduced intertester variability in both modalities. Further, results indicated that comprehension ability and tracking skill are not perfectly related.

Vibrotactile perception of segmental features of speech: a comparison of single-channel and multichannel instruments.

This experiment compared the recognition performance of artificially deafened listeners for segmental stimuli presented through a single-channel tactile device and through a 24-channel vocoder. Both consonant and vowel stimuli were tested under visual only, tactile only, and visual + tactile conditions. Each subject received a pretest, eight 2-hr training sessions, and a posttest. Results indicated no significant differences between subject's overall recognition performance with two different tactile devices. Analysis of consonant confusions showed that both devices transmit the features of voicing, manner, and place of articulation in a similar fashion. In contrast to an earlier study on suprasegmental features by Carney and Beachler (1986), these results do not support the notion that preservation of the waveform envelope of speech is necessary for the transmission of segmental features of speech. These results also suggest that tactile perception of segmental features may not be altered significantly by the tactile array chosen.

Vibrotactile perception of suprasegmental features of speech: a comparison of single-channel and multichannel instruments.

The recognition of three suprasegmental aspects of speech--the number of syllables in a word, the stress pattern of a word, and rising or falling intonation patterns--through a single-channel tactile device and through a 24-channel tactile vocoder, using two groups of normal-hearing subjects, was compared. All subjects received an initial pretest on three recognition tasks, one for each prosodic feature. Half the subjects from each group then received 12 h of training with feedback on the tasks and stimuli used in the pretest. All subjects received a post-test which contained physically different stimuli from those previously tested. Performance was significantly better on the syllable-number and syllabic stress tasks with the single-channel than with the multichannel device on both the pre- and post-tests; no difference was found for the intonation task. Performance on the post-test was poorer for all trained subjects compared to their final training results, suggesting that cues learned in training were not readily transferable to new stimuli, even those with similar prosodic characteristics. Overall, the results provide support for the notion that certain prosodic features of speech may be conveyed more readily when the waveform envelope is preserved.

Perceived contrastive stress production in hearing-impaired and normal-hearing children.

Contrastive stress production patterns of 20 moderate-to-severely hearing-impaired children, aged 4:5-18:2 (years:months), were compared with those of 20 normal-hearing children, aged 3:7-6:7. The groups were matched on the basis of a linguistic measure, mean length of utterance. Analyses of judges' responses to the speakers' audiotapes recorded during a conversation-based task yielded evidence of similar production patterns for the groups although considerable individual performance variation was noted. This finding supports the view that language-matched normal and hearing-impaired children may not be very different in their production of this prosodic cue. Results of this study further support the idea that prosodic features of the speech signal enhance intelligibility, a factor which merits consideration in the intelligibility assessment and training of hearing-impaired children.

Prespeech vocalizations of a deaf infant: a comparison with normal metaphonological development.

A comparative study of the speech-like vocalizations of a deaf infant and a group of 11 hearing infants was conducted in order to examine the role of auditory experience in the development of the phonological and metaphonological capacity. Results indicated that from 8 to 13 months of age, the deaf subject differed strikingly from hearing infants of comparable age. She produced no repetitive canonical babbling, whereas all the hearing infants produced many canonical syllables. The topography of the deaf infant's vocalizations resembled that of 4-6-month-old (i.e., Expansion stage) hearing infants. Detailed comparisons of the proportion of production of various metaphonologically defined categories by the deaf infant and Expansion stage hearing infants demonstrated many similarities in vocalization, although possible differences were noted. It is concluded that hearing impairment notably affects vocalization development by the end of the first year of life, if not earlier. Spectrographic displays illustrate the categories of infant sounds produced by the deaf and hearing infants.

An analysis of psychophysical tuning curves in normal and pathological ears.

Simultaneous psychophysical tuning curves were obtained from normal-hearing and hearing-impaired listeners, using probe tones that were either at similar sound pressure levels or at similar sensation levels for the two types of listeners. Tuning curves from the hearing-impaired listeners were flat, erratic, broad, and/or inverted, depending upon the frequency region of the probe tone and the frequency characteristics of the hearing loss. Tuning curves from the normal-hearing listeners at low-SPL's were sharp as expected; tuning curves at high-SPL's were discontinuous. An analysis of high-SPL tuning curves suggests that tuning curves from normal-hearing listeners reflect low-pass filter characteristics instead of the sharp bandpass filter characteristics seen with low-SPL probe tones. Tuning curves from hearing-impaired listeners at high-SPL probe levels appear to reflect similar low-pass filter characteristics, but with much more gradual high-frequency slopes than in the normal ear. This appeared as abnormal downward spread of masking. Relatively good temporal resolution and broader tuning mechanisms were proposed to explain inverted tuning curves in the hearing-impaired listeners.

Sympsium on hearing loss--the otolaryngologist's responsibility. Habilitation and rehabilitation of patients with sensorineural hearing losses.

A philosophy of the (re)habilitation of patients with sensorineural hearing losses from a communication point of view is presented. Pediatric and adult populations are discussed separately. Topics of consideration for pediatric patients include the appropriate use of amplification, team management of the hearing handicap, educational placement and the importance of parent counseling. The discussion of the management of adult patients reviews some problems in hearing aid fitting, patient counseling and appropriate case follow-up. The guiding principle behind these (re)habilitation processes is the integration of the hearing-impaired patient into a hearing world.