Project

Investigating neural mechanisms for speech and voice processing deficits and plasticity in children with autism

Goal: Very few autism research studies have investigated the neural basis of domain-general auditory processing atypicalities in relation to language-specific perceptual difficulties. This NSFC-funded (Natural Science Foundation of China) overseas collaborative project aims to 1) refine neurobehavioral measurements of atypical speech and voice processing at cortical and subcortical levels in school-aged Chinese children with autism; 2) examine whether and how acoustic, affective, and linguistic levels of pitch perception are associated with each other, and 3) how perceptual training of lexical tone recognition may impact children's speech perception as well as higher-level receptive and productive verbal skills.

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Yang Zhang
added a research item
Lay abstract: Differences in understanding others' emotions and attitudes through features in speech (e.g. intonation) have been observed in individuals with autism spectrum conditions, which contribute greatly to their social communication challenges. However, some studies reported that individuals with autism spectrum condition performed comparably to typically developing individuals on affective prosody recognition. Here, we provide a comprehensive review with statistical analysis of 23 existing studies on this topic to examine potential factors that could explain the discrepancies. Compared with typically developing individuals, autism spectrum condition participants generally appeared to encounter more difficulties in affective prosody recognition. But this finding was likely due to the tendency of the existing research to overly focus on deficits in autism. The affective prosody recognition performance in individuals with autism spectrum condition was closely related to the number of answer options offered to them. Moreover, the degree of difficulty in affective prosody recognition encountered by individuals with autism spectrum condition varied across emotions. The findings of this systematic review highlighted the need for further research on affective prosody recognition in autism (e.g. studies that include tonal language speakers and autism spectrum condition individuals with lower cognitive or verbal abilities).
Yang Zhang
added a research item
The presence of vowel exaggeration in infant‐directed speech (IDS) may adapt to the age‐appropriate demands in speech and language acquisition. Previous studies have provided behavioral evidence of atypical auditory processing towards IDS in children with autism spectrum disorders (ASD), while the underlying neurophysiological mechanisms remain unknown. This event‐related potential (ERP) study investigated the neural coding of formant‐exaggerated speech and nonspeech in 24 4‐ to 11‐year‐old children with ASD and 24 typically‐developing (TD) peers. The EEG data were recorded using an alternating block design, in which each stimulus type (exaggerated/non‐exaggerated sound) was presented with equal probability. ERP waveform analysis revealed an enhanced P1 for vowel formant exaggeration in the TD group but not in the ASD group. This speech‐specific atypical processing in ASD was not found for the nonspeech stimuli which showed similar P1 enhancement in both ASD and TD groups. Moreover, the time‐frequency analysis indicated that children with ASD showed differences in neural synchronization in the delta‐theta bands for processing acoustic formant changes embedded in nonspeech. Collectively, the results add substantiating neurophysiological evidence (i.e., a lack of neural enhancement effect of vowel exaggeration) for atypical auditory processing of IDS in children with ASD, which may exert a negative effect on phonetic encoding and language learning. Lay summary Atypical responses to motherese might act as a potential early marker of risk for children with ASD. This study investigated the neural responses to such socially relevant stimuli in the ASD brain, and the results suggested a lack of neural enhancement responding to the motherese even in individuals without intellectual disability.
Yang Zhang
added a research item
Objective: This autism study investigated how inter-trial phase coherence (ITPC) drives abnormalities in auditory evoked potential (AEP) responses for speech and nonspeech stimuli. Methods: Auditory P1-N2 responses and ITPCs in the theta band (4~7 Hz) for pure tones and words were assessed with EEG data from 15 school-age children with autism and 16 age-matched typically developing (TD) controls. Results: The autism group showed enhanced P1 and reduced N2 for both speech and nonspeech stimuli in comparison with the TD group. Group differences were also found with enhanced theta ITPC for P1 followed by ITPC reduction for N2 in the autism group. The ITPC values were significant predictors of P1 and N2 amplitudes in both groups. Conclusions: Abnormal trial-to-trial phase synchrony plays an important role in AEP atypicalities in children with autism. ITPC-driven enhancement as well as attenuation in different AEP components may coexist, depending on the stage of information processing. Significance: It is necessary to examine the time course of auditory evoked potentials and the corresponding inter-trial coherence of neural oscillatory activities to better understand hyper- and hypo- sensitive responses in autism, which has important implications for sensory-based treatment. Web link: https://www.sciencedirect.com/science/article/pii/S1388245718309003
Yang Zhang
added 3 research items
Although many studies have reported domain-general impaired duration perception for speech and nonspeech sounds in children with autism, it remained unclear whether this phenomenon is universally applicable regardless of language background. In some languages such as Finnish and Japanese, vowel duration serves a phonemic role that can signify semantic distinction, and in others (e.g., Mandarin Chinese), vowel duration does not carry this phonemic function. The present event-related potential study investigated neural sensitivity to duration contrasts in speech and nonspeech contexts in Mandarin-speaking children with autism and a control group of age-matched typically developing (TD) children. A passive oddball paradigm was adopted to elicit the mismatch negativity (MMN) and involuntary orienting response (P3a) for change detection. A pure tone condition and a vowel condition were used. The MMN results showed that the autism group had diminished response amplitudes and delayed latency in the pure tone condition compared to the TD group, whereas no group difference was found in the vowel condition. The P3a results showed no significant between-group MMN difference in the pure tone condition. In the vowel condition, the autism group had smaller P3a than the TD group. Together, the distinct patterns of discrimination and orienting responses for duration contrasts in pure tones and vowels are consistent with the “allophonic perception” theory for autism, which may reflect a compromised perceptual weighting system for speech learning.This article is protected by copyright. All rights reserved.
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.
Yang Zhang
added a project goal
Very few autism research studies have investigated the neural basis of domain-general auditory processing atypicalities in relation to language-specific perceptual difficulties. This NSFC-funded (Natural Science Foundation of China) overseas collaborative project aims to 1) refine neurobehavioral measurements of atypical speech and voice processing at cortical and subcortical levels in school-aged Chinese children with autism; 2) examine whether and how acoustic, affective, and linguistic levels of pitch perception are associated with each other, and 3) how perceptual training of lexical tone recognition may impact children's speech perception as well as higher-level receptive and productive verbal skills.