Bimodal Benefits for Lexical Tone Recognition: An Investigation on Mandarin-speaking Preschoolers with a Cochlear Implant and a Contralateral Hearing Aid

Abstract

Pitch perception is known to be difficult for individuals with cochlear implant (CI), and adding a hearing aid (HA) in the non-implanted ear is potentially beneficial. The current study aimed to investigate the bimodal benefit for lexical tone recognition in Mandarin-speaking preschoolers using a CI and an HA in opposite ears. The child participants were required to complete tone identification in quiet and in noise with CI + HA in comparison with CI alone. While the bimodal listeners showed confusion between Tone 2 and Tone 3 in recognition, the additional acoustic information from the contralateral HA alleviated confusion between these two tones in quiet. Moreover, significant improvement was demonstrated in the CI + HA condition over the CI alone condition in noise. The bimodal benefit for individual subjects could be predicted by the low-frequency hearing threshold of the non-implanted ear and the duration of bimodal use. The findings support the clinical practice to fit a contralateral HA in the non-implanted ear for the potential benefit in Mandarin tone recognition in CI children. The limitations call for further studies on auditory plasticity on an individual basis to gain insights on the contributing factors to the bimodal benefit or its absence.

A Review of Speech Perception of Mandarin-Speaking Children With Cochlear Implantation

“…Although significant improvement in the recognition of Tone 2 in quiet with bimodal stimulation was noted in Cheng et al (2018) , a ceiling effect was evident where listeners performed nearly perfectly regardless of conditions (CI + HA or CI-only). Zhang et al (2020a) showed bimodal benefits in lexical tone recognition in speech spectrum-shaped noise at +5 dB but not in quiet, whereas Yuen et al (2009a) also found significant bimodal benefits in lexical tone recognition when speech was presented from the front and noise from the CI side. Zhang et al (2020b) investigated categorial perception using synthetic tone-pair continuums, showing enhanced categorical perception in Tone 1–2 continuums with bimodal stimulation compared to CI-only condition.…”

“…Four out of seven studies evaluated lexical tone perception in quiet and/or in noise. Three of these studies focused on bimodal benefits on lexical tone identification ( Yuen et al, 2009a ; Cheng et al, 2018 ; Zhang et al, 2020a ), specified as the performance differences of bimodal stimulation (i.e., CI + HA) condition over CI-only condition. All studies found significant bimodal benefits in lexical tone recognition in quiet and/or in noise.…”

“…Four out of six studies examined the correlation between demographic factors and speech perception ( Yuen et al, 2009a ; Cheng et al, 2018 ; Liu Y. W. et al, 2019 ; Zhang et al, 2020a ). A summary of these studies can be found in Table 6 .…”

“…Effects of hearing thresholds in the non-implanted ear were examined in all four studies. Significant correlations were found between low-frequency hearing thresholds in the non-implanted ear and disyllables recognition in noise ( Yuen et al, 2009a ), lexical tone recognition in noise ( Zhang et al, 2020a ); and sentence recognition in quiet ( Cheng et al, 2018 ) and in noise ( Liu Y. W. et al, 2019 ) (please see Table 6 ). Similar to studies in unilateral CI use, age at testing, AAI and DCI were examined.…”

Central Auditory Plasticity from Molecules to Behavior

“…Individuals with unilateral cochlear implant have difficulty with pitch perception, and adding a hearing aid in the non-implanted ear is potentially beneficial. In Zhang et al [ 7 ], authors provide evidence for the practice of fitting a hearing aid in the non-implanted ear to take advantage of the potential bimodal benefit, to facilitate speech learning in kindergarten-aged children with a unilateral cochlear implant.…”