Neural coding of formant‐exaggerated speech and nonspeech in children with and without autism spectrum disorders

Abstract

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.

Autism Spectrum Disorder and auditory sensory alterations: a systematic review on the integrity of cognitive and neuronal functions related to auditory processing

“…When vowel and pure tone are compared within tone languages (smaller physical difference between standard and deviants compared to non-tone languages), ASD children still presented diminished response amplitudes and delayed latency of MMN for pure tones, and smaller P3a for vowel (Huang et al 2018 ). At a pre-attentive perceptual processing level, low-functional ASD children present increased response onset latencies during sustained vowel production, with reduced P1 ERP amplitudes (Patel et al 2019 ; Bidet-caulet et al 2017 ; Charpentier et al 2018 ), lacking neural enhancement in formant-exaggerated speech tasks (Chen et al 2021 ). When a non-speech sound is followed by a speech sound, TD children present match/mismatch effects at approximately 600 ms, as opposite to ASD (Galilee et al 2017 ).…”

“…When a non-speech sound is followed by a speech sound, TD children present match/mismatch effects at approximately 600 ms, as opposite to ASD (Galilee et al 2017 ). Interestingly, when speech and non-speech sounds are compared between high-functioning ASD children matched on age, gender, and non-verbal IQ with TD group, ASD children show impaired processing ability regarding speech pitch information, but no differences are observed for non-speech sounds (Zhang et al 2019 ; Chen et al 2021 ). Regarding speech differentiation, there seems to be no differences in voice perception.…”

Neurocognitive Dynamics of Prosodic Salience over Semantics during Explicit and Implicit Processing of Basic Emotions in Spoken Words

“…Though conventional ERP waveform analysis can shed light on the event-locked regularities of brain dynamics based on time-domain information averaged across trials, it may underestimate trial-by-trial response variability in the time-frequency domain [22][23][24]. A line of studies have applied time-frequency analyses to explore the time-locked neural substrates of auditory processing [23,[25][26][27][28], though these investigations were often conducted with non-emotional stimuli. In these studies, evoked neural synchrony can be evaluated through inter-trial phase coherence (ITPC) in five frequency bands, including delta (1-4 Hz), theta (4-8 Hz), alpha (8)(9)(10)(11)(12), beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma (over 30 Hz).…”

“…A line of studies have applied time-frequency analyses to explore the time-locked neural substrates of auditory processing [23,[25][26][27][28], though these investigations were often conducted with non-emotional stimuli. In these studies, evoked neural synchrony can be evaluated through inter-trial phase coherence (ITPC) in five frequency bands, including delta (1-4 Hz), theta (4-8 Hz), alpha (8)(9)(10)(11)(12), beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma (over 30 Hz). Higher ITPC values suggest better phase alignment of cortical oscillations, while smaller values indicate poorer consistency or larger neural "jittering" across trials [29].…”

Neurocognitive Dynamics of Prosodic Salience over Semantics during Explicit and Implicit Processing of Basic Emotions in Spoken Words

“…Though conventional ERP waveform analysis can shed light on the event-locked regularities of brain dynamics based on time-domain information averaged across trials, it may underestimate trial-by-trial response variability in the time-frequency domain [ 22 , 23 , 24 ]. A line of studies have applied time-frequency analyses to explore the time-locked and phase-locked neural substrates of auditory processing [ 23 , 25 , 26 , 27 , 28 , 29 ], though these investigations were often conducted with non-emotional stimuli. In these studies, event-related cortical oscillations can be evaluated through inter-trial phase coherence (ITPC) and event-related spectral perturbation (ERSP) in five frequency bands, including delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz) and gamma (over 30 Hz).…”