Monday, May 6, 2024
5/6/2024
Project Summary Understanding individual differences in language understanding and use in autism is a top priority of research, as the acquisition of language early in life has been consistently linked with long-term outcomes in individuals with autism. Typically developing children look to visual cues of speech (i.e., mouth movements), early in life during language acquisition, and visual cues facilitate speech processing across the lifespan. Looking to visual speech cues has been associated with language ability, but the neural mechanism underlying this link is not well understood. Multisensory speech processing may explain individual differences in language understanding and use. Electroencephalography (EEG) research has illustrated a boost in speech processing efficiency in response to audiovisual speech via a decrease, or suppression, in the amplitude of the event- related potential (ERP) signal in response to audiovisual speech versus auditory-only speech. Children with autism show highly variable amplitude suppression, and the degree of amplitude suppression is associated with language ability. However, it is unclear at present how early in development this phenomenon emerges and whether it explains observed links between looking to audiovisual speech and language understanding and use. This dissertation project seeks to evaluate the emergence of amplitude suppression and to statistically test whether speech processing efficiency mediates the association between early looking to audiovisual speech and language understanding and use in infants at increased likelihood for autism. A low demand measure of speech processing with the temporal precision necessary to evaluate immediate responses to speech (EEG) and a state-of-the-art measure of eye gaze with high precision to attentional focus (eye-tracking) will be used. We hypothesize that relatively low, general population level likelihood infants will display amplitude suppression at 12-18 months of age. Additionally, we hypothesize that infants at increased familial likelihood for autism on average will display less amplitude suppression compared to their lower likelihood peers. However, based on previous observations of variable audiovisual speech processing in autism, we expect to see a wide range of individual differences in the amount of amplitude suppression experienced in response to audiovisual speech. We anticipate that the degree of amplitude suppression will explain the relation between looking to audiovisual speech and language understanding and use. IMPACT: If our hypotheses are born out, the proposed work will yield empirical support for a novel framework of language learning in early development and improve our understanding of the neural mechanisms underlying differential language development in infants at elevated likelihood for autism and communication disorders. This improved understanding of early language development has the potential to facilitate early identification of children who may struggle with language acquisition and guide our development of preventative interventions that may mitigate the long-term consequences of language impairments.
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