Speech-specific categorical perception deficit in autism: An Event-Related Potential study of lexical tone processing in Mandarin-speaking children

Xiaoyue Wang,Yang Zhang,Suiping Wang,Yuebo Fan,Dan Huang

doi:10.1038/srep43254

Abstract

Recent studies reveal that tonal language speakers with autism have enhanced neural sensitivity to pitch changes in nonspeech stimuli but not to lexical tone contrasts in their native language. The present ERP study investigated whether the distinct pitch processing pattern for speech and nonspeech stimuli in autism was due to a speech-specific deficit in categorical perception of lexical tones. A passive oddball paradigm was adopted to examine two groups (16 in the autism group and 15 in the control group) of Chinese children’s Mismatch Responses (MMRs) to equivalent pitch deviations representing within-category and between-category differences in speech and nonspeech contexts. To further examine group-level differences in the MMRs to categorical perception of speech/nonspeech stimuli or lack thereof, neural oscillatory activities at the single trial level were further calculated with the inter-trial phase coherence (ITPC) measure for the theta and beta frequency bands. The MMR and ITPC data from the children with autism showed evidence for lack of categorical perception in the lexical tone condition. In view of the important role of lexical tones in acquiring a tonal language, the results point to the necessity of early intervention for the individuals with autism who show such a speech-specific categorical perception deficit.

Highlights

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects communication and social interaction[1]
For the Mismatch Response (MMR) amplitudes in the speech condition (Table 1 and Figs 1 and 2), there was a significant interaction between deviant type and subject group (F(1, 29) = 4.244, p = 0.048, partial η2 = 0.128), suggesting that neural discriminatory sensitivity to the within- and between- category lexical tone differences depended on the subject group factor
The MMR patterns for the lexical tone in the TD control group were consistent with previous reports on categorical perception of lexical tones in normal adults and children[27,28], indicating that phonological representations of lexical tones in 10-year-old typically developing Chinese children are similar to those in healthy adults[28]

Summary

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects communication and social interaction[1]. A similar pattern was found in an ERP study including both ASD and age-matched TD control groups[25] In this ERP study, Mandarin-speaking children with autism showed enhanced MMN response for detecting a pitch change in pure tones and nonspeech complex stimuli but reduced MMN to lexical tone contrasts in both spoken words and nonwords. Chinese children with autism would not demonstrate enhanced lexical tone discrimination for between-category stimulus pairs relative to within-category stimulus pairs when pitch differences are physically equated This hypothesis is in line with previous autism studies showing that individuals with autism show impairment in discriminating higher-level categorical information such as ellipses and faces[30,31,32], but intact discrimination of pure tones and colors[8,33]. Our previous report stopped short of providing direct empirical evidence to support this theory[25]

Methods

Results

Conclusion