Atypical processing of changes in words and pseudowords in children with autism spectrum disorder

Objective: The present study explored the neural basis of speech perception in school-aged children with ASD but without language impairments and typically developing control children. Methods: Event related potentials reflecting stimulus encoding, discrimination, and orientation were recorded to five different speech sound changes (consonant or vowel identity, vowel duration, fundamental frequency, intensity) in carefully matched words and pseudowords. Perceptual discrimination of prosodic changes was assessed with a behavioral test. Results: Impaired speech sound encoding was found for both word and pseudoword stimuli in children with ASD. Reduced neural discrimination of vowel identity changes, consonant changes in pseudowords and vowel duration changes in both words and pseudowords were found in children with ASD. Also, reduced involuntary attention shifting to changes in vowel duration was found in children with ASD. Conclusions: Results indicate altered speech-sound encoding and reduced cortical discrimination of and orienting to speech-sound changes in complex word-level speech stimuli in school-aged children with ASD but without language impairments. Significance: The results support the theories suggesting weaknesses in phonemic processing in ASD.