Sneha V. Bharadwaj

Developmental Patterns in Children’s Speech: Patterns of Spectral Change in Vowels

The aim of this chapter is to compare the patterns of spectral change in American English vowels spoken by children and adults from the North Texas region. Children’s speech differs from adult speech in several important ways. First, children have smaller larynges and supra-laryngeal vocal tracts than adults, with the result that their formants and fundamental frequencies are higher. Second, the temporal and spectral properties of children’s speech are inherently more variable, a consequence of developmental changes in motor control. Both of these sources of variability raise interesting questions for the representation of vowel inherent spectral change (VISC) and theories of vowel specification. Acoustic analyses of children’s vowels indicate reliable VISC properties as early as age five, the youngest group studied here. Consistent with developmental changes in vocal tract anatomy, the frequencies of vowel formants show an overall systematic decrease with age, and these changes are larger in males than females. The effects of age on formant frequencies vary somewhat from vowel to vowel, but these discrepancies do not appear to interact systematically with VISC. Pattern classification tests indicate that (1) vowels are more accurately recognized when two analysis frames, sampled around 20 and 70 % of the vowel duration, are presented to the classifier, compared to any single frame; (2) adding a third analysis frame does not yield substantially higher recognition scores; and (3) the optimum locations for sampling the formant trajectory are consistent across different age groups of children.

Effects of auditory feedback on fricatives produced by cochlear-implanted adults and children: Acoustic and perceptual evidence

Acoustic analyses and perception experiments were conducted to determine the effects of brief deprivation of auditory feedback on fricatives produced by cochlear implant users. The words /si/ and /Si/ were recorded by four children and four adults with their cochlear implant speech processor turned on or off. In the processor-off condition, word durations increased significantly for a majority of talkers. These increases were greater for children compared to adults, suggesting that children may rely on auditory feedback to a greater extent than adults. Significant differences in spectral measures of /S/ were found between processor-on and processor-off conditions for two of the four children and for one of the four adults. These talkers also demonstrated a larger /s/-/S/ contrast in centroid values compared to the other talkers within their respective groups. This finding may indicate that talkers who produce fine spectral distinctions are able to perceive these distinctions through their implants and to use this feedback to fine tune their speech. Two listening experiments provided evidence that some of the acoustic changes were perceptible to normal-hearing listeners. Taken together, these experiments indicate that for certain cochlear-implant users the brief absence of auditory feedback may lead to perceptible modifications in fricative consonants.

Multisensory processing in children with cochlear implants

OBJECTIVE The objective of the study was to investigate the functions of the vestibular, tactile, visual, and proprioceptive modalities in children with prelinguistic hearing loss. Specifically, the study sought to examine evidence for the compensation hypothesis (auditory deprivation leads to enhancements in functions of other sensory systems) versus the deficiency hypothesis (functions of the spared senses are compromised as a result of auditory deprivation). METHODS Twelve children between the ages of 5 years, 1 month and 8 years, 11 months with bilateral severe-profound hearing loss participated in the study. All children used bilateral cochlear implants. Subtests of two norm-referenced instruments, the Sensory Integration and Praxis Test and the Beery-Buktenica Developmental Test of Visual-Motor Integration, were administered to all of the children. Mean subtest scores for children with hearing loss were compared with the mean scores for the normative group. RESULTS As expected, a majority of children demonstrated vestibular dysfunction. Assessment of other modalities revealed significantly below average performance on two tasks by children with hearing loss when compared to the normative group. Both tasks involved temporal processing of tactile or proprioceptive signals. Conversely, children with hearing loss showed significantly better performance compared to the normative group for a spatial task that involved localization of a tactile stimulus. No group differences were found for any of the visual tasks. CONCLUSIONS Results supported both the compensation and the deficiency hypotheses. The findings have implications for both assessment and intervention of young children with hearing loss. Further investigations are necessary to replicate these findings with a more comprehensive set of measures on a larger cohort of children with prelinguistic, severe-profound hearing loss.

An exploratory study of visual sequential processing in children with cochlear implants

OBJECTIVE The objective of the study was to compare visual sequential processing in school-age children with cochlear implants (CIs) and their normal-hearing (NH) peers. Visual sequential processing was examined using both behavioral and an event-related potential (ERP) measures. METHODS Eighteen children with CIs and nineteen children who had hearing within normal limits (NH) participated in the behavioral study. Subtests from the Test of Visual Perceptual Skills and the Sensory Integration and Praxis Test were administered to all children. ERP measures were collected from five children with CI and five age-matched peers. Peak latencies (N200 and P300) and reaction times for visual sequential processing were compared in these two groups. RESULTS The findings of the study revealed significant group differences in visual sequential memory and visuo-motor sequencing tasks suggesting that children with severe-profound hearing loss may have difficulties in visual sequential tasks. The study also revealed longer P300 latencies and longer reaction times for a visual sequential matching task in children with CI when compared to their NH peers suggesting slower or delayed processing of visual sequential stimuli. CONCLUSIONS This exploratory study involving behavioral and ERP measures showed that as a group, children with prelingual, severe-profound hearing loss who use CIs have difficulties with visual sequential processing. These findings may have implications for rehabilitation for children with hearing loss in the light of recent evidence that accurate and efficient processing of sequentially presented visual stimuli is important for language and reading outcomes.

Working memory, short-term memory and reading proficiency in school-age children with cochlear implants

OBJECTIVE The objective of the study was to examine short-term memory and working memory through both visual and auditory tasks in school-age children with cochlear implants. The relationship between the performance on these cognitive skills and reading as well as language outcomes were examined in these children. METHODS Ten children between the ages of 7 and 11 years with early-onset bilateral severe-profound hearing loss participated in the study. Auditory and visual short-term memory, auditory and visual working memory subtests and verbal knowledge measures were assessed using the Woodcock Johnson III Tests of Cognitive Abilities, the Wechsler Intelligence Scale for Children-IV Integrated and the Kaufman Assessment Battery for Children II. Reading outcomes were assessed using the Woodcock Reading Mastery Test III. RESULTS Performance on visual short-term memory and visual working memory measures in children with cochlear implants was within the average range when compared to the normative mean. However, auditory short-term memory and auditory working memory measures were below average when compared to the normative mean. Performance was also below average on all verbal knowledge measures. Regarding reading outcomes, children with cochlear implants scored below average for listening and passage comprehension tasks and these measures were positively correlated to visual short-term memory, visual working memory and auditory short-term memory. Performance on auditory working memory subtests was not related to reading or language outcomes. CONCLUSIONS The children with cochlear implants in this study demonstrated better performance in visual (spatial) working memory and short-term memory skills than in auditory working memory and auditory short-term memory skills. Significant positive relationships were found between visual working memory and reading outcomes. The results of the study provide support for the idea that WM capacity is modality specific in children with hearing loss. Based on these findings, reading instruction that capitalizes on the strengths in visual short-term memory and working memory is suggested for young children with early-onset hearing loss.

Developmental study of vowel‐inherent spectral change.

Children’s speech differs from adult speech in several important ways. First, children have smaller larynges and supra‐laryngeal vocal tracts than adults, with the result that their formants and fundamental frequencies are higher. Second, the temporal and spectral properties of children’s speech are inherently more variable, a consequence of developmental changes in motor control. Both of these sources of variability raise interesting questions for theories of talker normalization and vowel specification. In the present study we compare the pattern of time‐varying spectral change in vowels from a database of vowel recordings from adults and children ranging in age from 5 through 18 years from the Dallas, Texas region. Preliminary findings indicate systematic age‐related differences in the average frequencies of the formants, but the pattern of vowel‐inherent spectral change is well preserved across the age span investigated.

Effects of auditory feedback deprivation length on the vowel ∕ε∕ produced by pediatric cochlear-implant users

Effects of auditory deprivation on speech production by ten cochlear-implanted children were investigated by turning off the implant for durations ranging from 0.3 to 5.0s and measuring the formant frequencies (F1 and F2) of the vowel ∕e∕. In five of the ten talkers, F1 and/or F2 shifted when auditory feedback was eliminated. Without feedback, F2 frequency lowered consistently, suggesting vowel centralization. Phonetic transcription indicated that some of these acoustic changes led to perceptible shifts in phonetic quality. The results provide evidence that brief periods of auditory deprivation can produce perceptible changes in vowels produced by some cochlear-implanted children.

Effects of auditory feedback deprivation on non-native French vowels produced by children with cochlear implants

The objective of the present study was to examine alternative explanations for changes in speech demonstrated by individuals with a cochlear implant, in response to auditory feedback deprivation. By employing French vowels, for which monolingual English speakers do not have internal representations, this study compared formant frequencies of vowels produced in the presence and absence of auditory feedback. It was hypothesized that the lack of auditory feedback should not lead to vowel formant frequency shifts for these novel sounds. However, if, in addition to formants frequency shifts, increases in speaking rate and fundamental frequencies are observed in the absence of auditory feedback, the data would support the idea that talkers attempt to speak more clearly to maximize information from other sensory channels. Four children with cochlear implants (7–11 years of age) and four children with normal hearing (mean age 8.6 years) repeated English (familiar) and French (unfamiliar) vowels presented through a loudspeaker. In addition, the CI children repeated the syllables with the processor turned off for approximately 0.95–1.5 s before repeating each syllable. Formant frequencies, fundamental frequency and vowel durations were estimated from the vowels. Results showed that while there were some differences between children with CI and NH with respect to English vowels, there were no outstanding differences with respect to French vowels. Further, the results of the study showed formant frequency shifts in addition to increases in vowel durations and fundamental frequency in the absence of auditory feedback. While preliminary, the findings support the notion that talkers may attempt to speak clearly in the absence of auditory feedback, to attain information about their speech through other sensory channels. Future studies are necessary to confirm and extend these findings with a larger group of talkers.

Role of auditory feedback in speech produced by cochlear implanted adults and children

A prominent theory of speech production proposes that speech segments are largely controlled by reference to an internal model, with minimal reliance on auditory feedback. This theory also maintains that suprasegmental aspects of speech are directly regulated by auditory feedback. Accordingly, if a talker is briefly deprived of auditory feedback speech segments should not be affected, but suprasegmental properties should show significant change. To test this prediction, comparisons were made between speech samples obtained from cochlear implant users who repeated words under two conditions (1) implant device turned ON, and (2) implant switched OFF immediately before the repetition of each word. To determine whether producing unfamiliar speech requires greater reliance on auditory feedback than producing familiar speech, English and French words were elicited from English‐speaking subjects. Subjects were congenitally deaf children (n=4) and adventitiously deafened adults (n=4). Vowel fundamental frequency ...

Comprehension monitoring strategy intervention in children with hearing loss: a single case design study

ABSTRACT The objective of this single case design study was to examine the effectiveness of teaching comprehension monitoring strategy on strategy use as well as on reading comprehension performance. Four children with bilateral severe-profound hearing loss between the ages of 10–11 years and enrolled in the 3rd–5th grade classroom in a regional day school for the deaf participated in the study. Two comprehension monitoring strategies, namely retell and questioning, were taught to all four children. A third strategy, namely prediction, was used as a control strategy. Children received intervention for 20 min, twice a week for 13 weeks across a total of 26 sessions. During the first three sessions, children participated in probe sessions only. Following this baseline period, children participated in one intervention session and one probe session each week. Sessions were videotaped to monitor for treatment fidelity and to code for strategy use. Results showed a moderate evidence for a functional relation between comprehension strategy instruction and strategy use. Similarly, across participants, data also revealed moderate evidence for a functional relation between strategy implementation and reading comprehension performance. Future studies should investigate the effects of teaching a combination of reading comprehension monitoring strategies by increasing the duration and number of intervention sessions on reading comprehension performance by a larger group of children with hearing loss.