Lexical tone and word recognition in noise of Mandarin-speaking children who use cochlear implants and hearing aids in opposite ears

Abstract

The benefits of bimodal hearing (cochlear implant and hearing aid in opposite ears) in children are well documented in English-speaking populations (Ching et al., 2000; Holt et al., 2005) but not much evidence has been reported from populations using tonal languages. The lexical tones in tonal languages are heavily loaded with semantic and grammatical information, which are essentially represented by the fundamental frequency (F0) and low-order harmonics of the speech signal. This unique linguistic feature means that tonal language-speaking CI recipients may achieve more bimodal benefits than their non-tonal language peers may. Twenty Mandarin-speaking children using the Nucleus 24 cochlear implant system and a hearing aid on the non-implant ear were assigned to either one of the two groups to investigate the head-shadow and binaural redundancy effects. A computerized speech test - MAPPID-N (Yuen et al., 2007) was used to present Mandarin lexical tones in monosyllabic words, and disyllabic words with a four- and eight-alternative forced choice picture-identification task, respectively. Individualized signal-to-noise ratio was used to capture the speech scores in the 30%-70% range and was fixed throughout the CI alone and bimodal experimental conditions. Hearing aid fitting was optimized before the first test phase, which was followed by the second test phase after three months. Significant head shadow but not binaural redundancy benefits were observed, suggesting that subjects have not yet developed central binaural processing abilities to improve speech recognition when speech and noise are mixed, in the bimodal condition, in this group of Mandarin-speaking paediatric CI recipients. No subject experienced any degradation of performance in the bimodal versus the CI-only test condition. This may be the first study that demonstrated the bimodal benefits in CI paediatric recipients speaking tonal language, particularly in lexical tone perception. Hearing aid amplification for the non-implant ear should be a standard for the paediatric tonal-language CI population.

Mandarin Tone and Vowel Recognition in Cochlear Implant Users: Effects of Talker Variability and Bimodal Hearing

“…The mean Mandarin tone recognition score increased by 8% with CI+HA than with CI alone, similar to the results in Yuen et al (2009). Improved Mandarin tone recognition directly led to improved Mandarin syllable recognition in the CI+HA condition.…”

“…Speech recognition scores in the CI alone and CI+HA conditions and the performance difference between them (i.e., bimodal benefits) were characterized by great inter-subject variability (e.g., Ching et al, 2004; Gifford et al, 2007; Yuen et al, 2009). The age at implantation and duration of CI use have been identified as two major demographic factors that may predict performance in pediatric CI users (e.g., Kirk et al, 2002; Zwolan et al, 2004; Han et al, 2009).…”

“…The age at implantation and duration of CI use have been identified as two major demographic factors that may predict performance in pediatric CI users (e.g., Kirk et al, 2002; Zwolan et al, 2004; Han et al, 2009). Studies have also tested pure-tone thresholds among other psychophysical measures in the non-implanted ear as potential factors underlying individual differences in bimodal performance/benefits (e.g., Ching et al, 2004; Gifford et al, 2007; Yuen et al, 2009). Following these studies, we computed a series of Pearson correlations between the aided hearing thresholds in the non-implanted ear (at 250, 500, 1000 Hz, or averaged across these frequencies) and the bimodal performance/benefits in each listening task (i.e., Mandarin tone, vowel, and syllable recognition).…”

“…Compared to CI alone, CI+HA has been shown effective in improving word and sentence recognition, although evidence of bimodal benefits to phoneme and lexical tone recognition has been mixed (Dorman et al, 2008; Luo and Fu, 2006; Yuen et al, 2009). More talker voice information may be contained in aided residual acoustic hearing than in electric hearing, as indicated by better talker (especially gender) identification with CI+HA than with CI alone (Krull et al, 2010).…”

Contrasting benefits from contralateral implants and hearing aids in cochlear implant users

“…Numerous studies show speech intelligibility benefits when adding a contralateral hearing aid to a CI in children, both in quiet and in noise (Chmiel et al, 1995;Ching et al, 2001;Dettman et al, 2004;Holt et al, 2005;Beijen et al, 2008;Lee et al, 2008;Keilmann et al, 2009;Yuen et al, 2009;Mok et al, 2010). Percentage-point improvements in quiet show benefits ranging from about 5 to 20 pp, and around 10 pp on average.…”