Abstract
PurposeTo investigate how auditory working memory relates to speech perception performance by Mandarin-speaking cochlear implant (CI) users.MethodAuditory working memory and speech perception was measured in Mandarin-speaking CI and normal-hearing (NH) participants. Working memory capacity was measured using forward digit span and backward digit span; working memory efficiency was measured using articulation rate. Speech perception was assessed with: (a) word-in-sentence recognition in quiet, (b) word-in-sentence recognition in speech-shaped steady noise at +5 dB signal-to-noise ratio, (c) Chinese disyllable recognition in quiet, (d) Chinese lexical tone recognition in quiet. Self-reported school rank was also collected regarding performance in schoolwork.ResultsThere was large inter-subject variability in auditory working memory and speech performance for CI participants. Working memory and speech performance were significantly poorer for CI than for NH participants. All three working memory measures were strongly correlated with each other for both CI and NH participants. Partial correlation analyses were performed on the CI data while controlling for demographic variables. Working memory efficiency was significantly correlated only with sentence recognition in quiet when working memory capacity was partialled out. Working memory capacity was correlated with disyllable recognition and school rank when efficiency was partialled out. There was no correlation between working memory and lexical tone recognition in the present CI participants.ConclusionsMandarin-speaking CI users experience significant deficits in auditory working memory and speech performance compared with NH listeners. The present data suggest that auditory working memory may contribute to CI users' difficulties in speech understanding. The present pattern of results with Mandarin-speaking CI users is consistent with previous auditory working memory studies with English-speaking CI users, suggesting that the lexical importance of voice pitch cues (albeit poorly coded by the CI) did not influence the relationship between working memory and speech perception.
Highlights
The cochlear implant (CI) has been very successful in restoring hearing and communication to many adult and pediatric patients with severe hearing loss
Results showed that forward digit span scores were significantly better than backward digit span scores [F(1,51) = 72.81, p,0.001] and that normal hearing (NH) performance was significantly better than CI performance [F(1,51) = 8.14, p = 0.006]; there were no significant interactions [F(1,51) = 0.027, p = 0.871]
Major findings include: 1. Working memory performance was significantly poorer for CI than for NH participants, suggesting that Mandarin-speaking CI users experience limited working memory capacity and efficiency
Summary
The cochlear implant (CI) has been very successful in restoring hearing and communication to many adult and pediatric patients with severe hearing loss. Pisoni and colleagues [9,10,11] have investigated some of these ‘‘higher-level’’ measures to explain individual differences in information processing that may underlie speech performance and language development. One such higher-level process is working memory, which can be defined as a temporary storage mechanism for awareness, sensory perception or information retrieved from long-term memory [12]. Forward and backward digit span can be used to estimate the capacity of short-term working memory [10]
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