Word Processing of Child-Directed Speech in Young Preverbal Children with ASD

Background: Previous investigations have shown that word processing, the cognitive retrieval of previously acquired words from mental storage, can be measured using event-related potentials (ERPs) and could be a useful predictor of language outcomes in young children with autism spectrum disorders (ASD). Other investigations have suggested that, in children with ASD, neural processing of linguistic stimuli may be aided by their tendency to attend to social stimuli, such as child-directed speech (CDS; also known as motherese).

Objectives: The current project examined processing of CDS word stimuli in young children with ASD in order to determine (a) whether they exhibited a typical neural response (at the location and time window documented in previous investigations of typically developing children), (b) the extent to which a brain measure of word processing derived from the response to CDS word stimuli was associated with a concurrent measure of receptive language, and (c) whether this association was conditional on the child’s tendency to attend to CDS.

Methods: This study was a secondary analysis of data collected from a longitudinal study of preverbal children with ASD. Thirty-four children with ASD aged 2-5 in preverbal or early verbal stages listened to a set of 10 words typically understood by infants aged 8-12 mo, and 10 nonsense words (Mills et al., 2004), while ERPs were collected using dense-array EEG technology. All stimuli were recorded by a young, female, native speaker, using speech features characteristic of CDS, and presented 3 times each in random order. Receptive language was evaluated using MacArthur-Bates Communicative Development Inventories (MCDI; Fenson et al., 2007). Participants’ level of attention to CDS was measured twice across the course of the longitudinal study using a structured procedure in which child-friendly stimuli that featured CDS were presented from a puppet theater (Watson et al., 2010). Scores from each administration were aggregated to create a single score representing the child’s generalized tendency to attend to CDS.

Results: ERP amplitudes at the left temporal electrode cluster (~T3) between 200-500 ms were more negative for CDS words vs. nonword stimuli, indicating a typical neural response associated with word processing. The word-nonword amplitude difference was not significantly correlated with receptive language (r =-.17), though the association was in the expected direction. However, further analyses indicated that this measure statistically interacted with attention to CDS (β = -0.47, p = 0.04): the association between word processing and receptive language was stronger for children who displayed moderate or high levels of attention to CDS compared to those who did not.

Conclusions: Children with ASD as a group do exhibit the typical neural response to word stimuli delivered in CDS. However, the utility of this measure as a correlate of language outcomes is conditional upon the child’s tendency to attend to CDS. Further work is needed to understand whether subgroups of children with ASD may benefit from language interventions that use other types of speech.