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The Role of Sleep in Language Acquisition in Children with Autism Spectrum Disorder
Sleep plays a crucial role in the consolidation of newly learnt language, strengthening memory traces and integrating them into existing semantic and lexical networks. Numerous studies have examined the immediate consequences of new word learning in ASD, but the nature and time course of vocabulary consolidation is currently unclear. This is particularly salient given that sleep problems are highly prevalent in children with ASD, present in up to 80% of children. These sleep problems are largely characterised by difficulties in the initiation and maintenance of sleep but emerging evidence suggests differences may also exist in the microstructure of sleep, including the extent of slow wave activity. However, the extent to which the sleep profiles of children with ASD contribute to the complex and heterogeneous language development in this population of children remains untested.
Objectives:
To characterise the time course of the consolidation of new lexical and semantic information in children with and without ASD. Additionally, to explore the role that sleep plays in the heterogeneity of these processes across children ASD.
Methods:
In an initial study 19 boys with ASD aged 7-13 years and 19 typically developing (TD) boys matched on age and receptive vocabulary were exposed to the phonological forms of 16 novel words (e.g., dolpheg). Children were tested immediately after training and 24 hours later. Explicit recall was measured via cued recall and 2AFC old-new recognition. Lexical integration was measured via a pause detection task, in which children made speeded responses about the presence/absence of a 200ms pause in the basewords (e.g., dolphin) and a set of control words for which no new competitors had been taught. Our more recent studies have addressed how children with ASD and typical peers learn and integrate new semantic information. In these latter studies children learned rare animals and then completed a size congruency task in which they made speeded judgements about the size of existing and new animal pairs. Children also underwent overnight polysomnography to capture the relationship between sleep architecture and overnight changes in memory for the new language.
Results:
Explicit word knowledge improved significantly from day 1 to day 2. There was no interaction between group and day, whereby the increase in explicit word knowledge was comparable between children with ASD and TD children. Whilst typical children showed evidence of integration after sleep (with larger increases in lexical integration correlating with greater slow oscillation activity), children with ASD did not show evidence of integration after sleep.
Conclusions:
The consolidation of explicit word knowledge appears in tact in ASD. However, there may be an aberrant time course for the integration of new vocabulary knowledge in children with ASD, which may be attributed to differences in sleep-associated memory consolidation. These results suggest that sleep difficulties may contribute to the language learning difficulties which often characterise ASD, and emphasise the importance of identifying and treating sleep difficulties in this disorder.
*This research was funded by an ESRC grant awarded to L.M Henderson and G. Gaskell