Characteristics of Early Expressive Vocabulary in Mandarin-Speaking Children With Cochlear Implants.

PURPOSE: The aim of this study is to evaluate whether Mandarin-speaking children with cochlear implants (CIs) demonstrated early lexical composition similar to their hearing peers who were at the same vocabulary level and the extent to which children with CIs were sensitive to linguistic and conceptual properties when developing early lexicon. METHOD: Participants were 77 Mandarin-speaking children with CIs who received CIs before 30 months of age. Their expressive vocabulary was documented using the Infant Checklist of the Early Vocabulary Inventory for Mandarin Chinese 9 or 12 months after CI activation. Percent social words, common nouns, predicates (verbs, adjectives), and closed-class words in total vocabulary were computed for children at different vocabulary levels. Common nouns and verbs were further coded for their word class (noun, verb), word frequency, word length, and imageability to predict how likely a given noun or verb would be produced by children with CIs. RESULTS: Like children with typical hearing, social words were the most dominant category when vocabulary size in children with CIs was smaller than 20 words; common nouns became the most dominant category when the vocabulary size reached 21 words. The difference in percent common nouns and percent predicates (i.e., noun bias) was similar in children with CIs and their hearing peers. In addition, verbs, common words, monosyllabic words, and more imageable words were more likely to be produced by children with CIs than their counterparts. CONCLUSIONS: Mandarin children with CIs showed language-specific patterns in early lexical composition like their hearing peers. They were able to use multiple linguistic and conceptual cues when approaching early expressive vocabulary despite perceptual and processing constraints. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21357723.

Relationship Between the Ability to Detect Frequency Changes or Temporal Gaps and Speech Perception Performance in Post-lingual Cochlear Implant Users.

Previous studies, using modulation stimuli, on the relative effects of frequency resolution and time resolution on CI users' speech perception failed to reach a consistent conclusion. In this study, frequency change detection and temporal gap detection were used to investigate the frequency resolution and time resolution of CI users, respectively. Psychophysical and neurophysiological methods were used to simultaneously investigate the effects of frequency and time resolution on speech perception in post-lingual cochlear implant (CI) users. We investigated the effects of psychophysical results [frequency change detection threshold (FCDT), gap detection threshold (GDT)], and acoustic change complex (ACC) responses (evoked threshold, latency, or amplitude of ACC induced by frequency change or temporal gap) on speech perception [recognition rate of monosyllabic words, disyllabic words, sentences in quiet, and sentence recognition threshold (SRT) in noise]. Thirty-one adult post-lingual CI users of Mandarin Chinese were enrolled in the study. The stimuli used to induce ACCs to frequency changes were 800-ms pure tones (fundamental frequency was 1,000 Hz); the frequency change occurred at the midpoint of the tones, with six percentages of frequency changes (0, 2, 5, 10, 20, and 50%). Temporal silences with different durations (0, 5, 10, 20, 50, and 100 ms) were inserted in the middle of the 800-ms white noise to induce ACCs evoked by temporal gaps. The FCDT and GDT were obtained by two 2-alternative forced-choice procedures. The results showed no significant correlation between the CI hearing threshold and speech perception in the study participants. In the multiple regression analysis of the influence of simultaneous psychophysical measures and ACC responses on speech perception, GDT significantly predicted every speech perception index, and the ACC amplitude evoked by the temporal gap significantly predicted the recognition of disyllabic words in quiet and SRT in noise. We conclude that when the ability to detect frequency changes and the temporal gap is considered simultaneously, the ability to detect frequency changes may have no significant effect on speech perception, but the ability to detect temporal gaps could significantly predict speech perception.

Vocabulary Growth in Mandarin-Speaking Children With Bilateral Cochlear Implants, Bimodal Stimulation, or Unilateral Cochlear Implants During the First Year After Activation.

PURPOSE: The purpose of this study was to evaluate vocabulary development in Mandarin-speaking children with bilateral cochlear implants (CIs), bimodal stimulation (CI plus hearing aids [HAs]), or unilateral CIs during the first year after CI activation. METHOD: Participants included 23 children with simultaneous bilateral CIs, 23 children with bimodal stimulation, and 15 children with unilateral CIs. They all received CIs before 30 months of age. Parents were asked to endorse words that their child could understand only or understand and say using the Early Vocabulary Inventory for Mandarin Chinese at the day of CI activation and 1, 3, 6, 9, and 12 months after CI activation. Receptive and expressive vocabulary sizes were computed. RESULTS: Growth curve analysis revealed that children with simultaneous bilateral CIs demonstrated faster growth of receptive vocabulary than those with bimodal stimulation, followed by those with unilateral CIs. Moreover, children with simultaneous bilateral CIs reached the 100-word mark for receptive vocabulary earlier than children with bimodal stimulation, followed by those with unilateral CIs. There were no significant differences among the three groups in expressive vocabulary. CONCLUSIONS: Bilateral CIs have an advantage over bimodal stimulation in early receptive vocabulary development in Mandarin, a tone language. HA usage is still recommended for those who receive one CI.

Reverberation Degrades Pitch Perception but Not Mandarin Tone and Vowel Recognition of Cochlear Implant Users.

OBJECTIVES: The primary goal of this study was to investigate the effects of reverberation on Mandarin tone and vowel recognition of cochlear implant (CI) users and normal-hearing (NH) listeners. To understand the performance of Mandarin tone recognition, this study also measured participants' pitch perception and the availability of temporal envelope cues in reverberation. DESIGN: Fifteen CI users and nine NH listeners, all Mandarin speakers, were asked to recognize Mandarin single-vowels produced in four lexical tones and rank harmonic complex tones in pitch with different reverberation times (RTs) from 0 to 1 second. Virtual acoustic techniques were used to simulate rooms with different degrees of reverberation. Vowel duration and correlation between amplitude envelope and fundamental frequency (F0) contour were analyzed for different tones as a function of the RT. RESULTS: Vowel durations of different tones significantly increased with longer RTs. Amplitude-F0 correlation remained similar for the falling Tone 4 but greatly decreased for the other tones in reverberation. NH listeners had robust pitch-ranking, tone recognition, and vowel recognition performance as the RT increased. Reverberation significantly degraded CI users' pitch-ranking thresholds but did not significantly affect the overall scores of tone and vowel recognition with CIs. Detailed analyses of tone confusion matrices showed that CI users reduced the flat Tone-1 responses but increased the falling Tone-4 responses in reverberation, possibly due to the falling amplitude envelope of late reflections after the original vowel segment. CI users' tone recognition scores were not correlated with their pitch-ranking thresholds. CONCLUSIONS: NH listeners can reliably recognize Mandarin tones in reverberation using salient pitch cues from spectral and temporal fine structures. However, CI users have poorer pitch perception using F0-related amplitude modulations that are reduced in reverberation. Reverberation distorts speech amplitude envelopes, which affect the distribution of tone responses but not the accuracy of tone recognition with CIs. Recognition of vowels with stationary formant trajectories is not affected by reverberation for both NH listeners and CI users, regardless of the available spectral resolution. Future studies should test how the relatively stable vowel and tone recognition may contribute to sentence recognition in reverberation of Mandarin-speaking CI users.