Fundamental frequency processing in Mandarin-speaking children with cochlear implants as revealed by the peak latency of positive mismatch response (p-MMR).

Abstract

Purpose: Fundamental frequency (F0) serves as the primary acoustic cue for Mandarin tone perception. Recent studies on the use of F0 contours for Mandarin tone perception suggest that F0 contours may be differently processed between Mandarin-speaking normal-hearing (NH) children and children with cochlear implants. The aim of the current study was to explore this issue from the perspective of electrophysiology. Method: Positive mismatch responses (p-MMR) to the change of two acoustic dimensions of F0, i.e., F0 contour and F0 level change, were respectively recorded in Mandarin-speaking kindergarten-aged children with CIs and their age-matched NH peers. Mean amplitude and peak latency of p-MMRs to F0 contour/F0 level change were compared between these two groups of children. Results: The mean amplitude of p-MMR to either F0 contour or F0 level change did not show any significant differences between children with CIs and NH children. While the peak latency of p-MMR to F0 contour change was significantly longer than that to F0 level change in NH children, opposite pattern was seen in children with CIs. Moreover, p-MMR to F0 contour change in children with CIs exhibited the shortest peak latency, which was significantly shorter than those to F0 contour and F0 level change in NH children. No significant correlation was found between CI-related demographic factors (e.g., age at implantation, duration of CI use) and amplitude/peak latency of p-MMRs to F0 contour/F0 level change. Conclusions: Consistent with the previously reported behavioral findings, the discrepant neural responses to F0 change between children with CIs and NH children in this study suggest different F0 processing in these two groups, which may partially explain the unsatisfactory speech perception outcomes with new speech processing strategies among CI users speaking tonal languages.