Miranda Cleary

Measures of working memory span and verbal rehearsal speed in deaf children after cochlear implantation

Large individual differences in spoken word recognition performance have been found in deaf children after cochlear implantation. Recently, Pisoni and Geers (2000) reported that simple forward digit span measures of verbal working memory were significantly correlated with spoken word recognition scores even after potentially confounding variables were statistically controlled for. The present study replicates and extends these initial findings to the full set of 176 participants in the CID cochlear implant study. The pooled data indicate that despite statistical “partialling-out” of differences in chronological age, communication mode, duration of deafness, duration of device use, age at onset of deafness, number of active electrodes, and speech feature discrimination, significant correlations still remain between digit span and several measures of spoken word recognition. Strong correlations were also observed between speaking rate and both forward and backward digit span, a result that is similar to previously reported findings in normal-hearing adults and children. The results suggest that perhaps as much as 20% of the currently unexplained variance in spoken word recognition scores may be independently accounted for by individual differences in cognitive factors related to the speed and efficiency with which phonological and lexical representations of spoken words are maintained in and retrieved from working memory. A smaller percentage, perhaps about 7% of the currently unexplained variance in spoken word recognition scores, may be accounted for in terms of working memory capacity. We discuss how these relationships may arise and their contribution to subsequent speech and language development in prelingually deaf children who use cochlear implants.

Some Measures of Verbal and Spatial Working Memory in Eight- and Nine-Year-Old Hearing-Impaired Children with Cochlear Implants

Objective The purpose of this study was to examine working memory for sequences of auditory and visual stimuli in prelingually deafened pediatric cochlear implant users with at least 4 yr of device experience. Design Two groups of 8- and 9-yr-old children, 45 normal-hearing and 45 hearing-impaired users of cochlear implants, completed a novel working memory task requiring memory for sequences of either visual-spatial cues or visual-spatial cues paired with auditory signals. In each sequence, colored response buttons were illuminated either with or without simultaneous auditory presentation of verbal labels (color-names or digit-names). The child was required to reproduce each sequence by pressing the appropriate buttons on the response box. Sequence length was varied and a measure of memory span corresponding to the longest list length correctly reproduced under each set of presentation conditions was recorded. Additional children completed a modified task that eliminated the visual-spatial light cues but that still required reproduction of auditory color-name sequences using the same response box. Data from 37 pediatric cochlear implant users were collected using this modified task. Results The cochlear implant group obtained shorter span scores on average than the normal-hearing group, regardless of presentation format. The normal-hearing children also demonstrated a larger “redundancy gain” than children in the cochlear implant group—that is, the normal-hearing group displayed better memory for auditory-plus-lights sequences than for the lights-only sequences. Although the children with cochlear implants did not use the auditory signals as effectively as normal-hearing children when visual-spatial cues were also available, their performance on the modified memory task using only auditory cues showed that some of the children were capable of encoding auditory-only sequences at a level comparable with normal-hearing children. Conclusions The finding of smaller redundancy gains from the addition of auditory cues to visual-spatial sequences in the cochlear implant group as compared with the normal-hearing group demonstrates differences in encoding or rehearsal strategies between these two groups of children. Differences in memory span between the two groups even on a visual-spatial memory task suggests that atypical working memory development irrespective of input modality may be present in this clinical population.

Imitation of Nonwords by Hearing-Impaired Children with Cochlear Implants: Segmental Analyses

In this study, we examined two prosodic characteristics of speech production in 8-10-year-old experienced cochlear implant (CI) users who completed a nonword repetition task. We looked at how often they correctly reproduced syllable number and primary stress location in their responses. Although only 5% of all nonword imitations were produced correctly without errors, 64% of the imitations contained the correct syllable number and 61% had the correct placement of primary stress. Moreover, these target prosodic properties were correctly preserved significantly more often for targets with fewer syllables and targets with primary stress on the initial syllable. Syllable and stress scores were significantly correlated with measures of speech perception, intelligibility, perceived accuracy, and working memory. These findings suggest that paediatric CI users encode the overall prosodic envelope of nonword patterns, despite the loss of more detailed segmental properties. This phonological knowledge is also reflected in other language and memory skills.

Learning, Memory, and Cognitive Processes in Deaf Children Following Cochlear Implantation

A cochlear implant is a sensory aid that uses a surgically implanted electrode array threaded within the scala tympani of the cochlea to present an electrical representation of sound directly to the auditory nerve of individuals who have a severe to profound bilateral sensorineural hearing loss. Cochlear implants work and they work reasonably well in many profoundly deaf adults and children. For these patients, a cochlear implant (CI) is a form of intervention, an alternative way of providing access to sound using electrical stimulation of the auditory system (see Niparko, Chapter 3). For postlingually deafened adults, a cochlear implant serves primarily as a sensory aid to restore lost hearing and regain contact with the world of sound as they knew it before the onset of their deafness. For the prelingually deaf child, in contrast, the electrical stimulation provided by a cochlear implant represents the introduction of a new sensory modality and an additional way to acquire knowledge about sound, sound sources, and the correlations between objects and events in their environment. Perhaps the most important benefit of a cochlear implant, however, is that it provides the prelingually deaf child with access to information about speech and spoken language.

TALKER DISCRIMINATION BY PRELINGUALLY DEAF CHILDREN WITH COCHLEAR IMPLANTS: PRELIMINARY RESULTS

Forty-four school-age children who had used a multichannel cochlear implant (CI) for at least 4 years were tested to assess their ability to discriminate differences between recorded pairs of female voices uttering sentences. Children were asked to respond “same voice” or “different voice” on each trial. Two conditions were examined. In one condition, the linguistic content of the sentence was always held constant and only the talkers voice varied from trial to trial. In another condition, the linguistic content of the utterance also varied so that to correctly respond “same voice,” the child needed to recognize that Two different sentences were spoken by the same talker. Data from normal-hearing children were used to establish that these tasks were well within the capabilities of children without hearing impairment. For the children with CIs, in the “fixed sentence condition” the mean proportion correct was 68%, which, although significantly different from the 50% score expected by chance, suggests that the children with CIs found this discrimination task rather difficult. In the “varied sentence condition,” however, the mean proportion correct was only 57%, indicating that the children were essentially unable to recognize an unfamiliar talkers voice when the linguistic content of the paired sentences differed. Correlations with other speech and language outcome measures are also reported.

Imitation of nonwords by deaf children after cochlear implantation: Preliminary findings

Fourteen prelingually deafened pediatric users of the Nucleus-22 cochlear implant were asked to imitate auditorily presented nonwords. The childrens utterances were recorded, digitized, and broadly transcribed. The target patterns and the childrens imitations were then played back to normal-hearing adult listeners in order to obtain perceptual judgments of repetition accuracy. The results revealed wide variability in the childrens ability to repeat the novel sound sequences. Individual differences in the component processes of encoding, memory, and speech production were strongly reflected in the nonword repetition scores. Duration of deafness before implantation also appeared to be a factor associated with imitation performance. Linguistic analyses of the initial consonants in the nonwords revealed that coronal stops were imitated best, followed by the coronal fricative /s/, and then the labial and velar stops. Labial fricatives were poorly imitated. The theoretical significance of the nonword repetition task as it has been used in past studies of working memory and vocabulary development in normal-hearing children is discussed.

Picture Naming and Verbal Fluency in Children With Cochlear Implants

PURPOSE In the present study, the authors examined lexical naming in children with cochlear implants (CIs). The goal was to determine whether children with CIs have deficits in lexical access and organization as revealed through reaction time in picture-naming and verbal fluency (VF) experiments. METHOD Children with CIs (n = 20, ages 7-10) were compared with 20 children with normal hearing (NH) matched for age and nonverbal IQ. Lexical abilities were examined using two naming tasks: a timed picture-naming task and a phonological and semantic VF naming task. Picture naming taps into lexical access capabilities and the VF task elucidates lexical organization. RESULTS No group differences were found between children with CIs and children with NH on the timed picture-naming task. Children with CIs generated significantly fewer words than the children with NH on the VF tasks. Larger group differences were found for the phonological VF task compared with the semantic VF task. CONCLUSIONS Limited early linguistic and auditory experiences may affect lexical representations and organization (lexical-semantic connections) in school-age children with hearing loss who use CIs. Further analyses and studies should continue to examine these underlying linguistic deficits. The present results suggest a need to emphasize not only increasing the size of childrens vocabularies during therapy, but also expanding and increasing the semantic and phonological richness of their lexical representations.

Auditory phonological priming in children and adults during word repetition

Short‐term auditory phonological priming effects involve changes in the speed with which words are processed by a listener as a function of recent exposure to other similar‐sounding words. Activation of phonological/lexical representations appears to persist beyond the immediate offset of a word, influencing subsequent processing. Priming effects are commonly cited as demonstrating concurrent activation of word/phonological candidates during word identification. Phonological priming is controversial, the direction of effects (facilitating versus slowing) varying with the prime‐target relationship. In adults, it has repeatedly been demonstrated, however, that hearing a prime word that rhymes with the following target word (ISI=50 ms) decreases the time necessary to initiate repetition of the target, relative to when the prime and target have no phonemic overlap. Activation of phonological representations in children has not typically been studied using this paradigm, auditory‐word + picture‐naming tasks be...