Semantic overreliance as a suboptimal compensation for syntactic impairments in children with Developmental Language Disorder

The neurocognitive dynamics of semantic-syntactic interplay are not well understood in children with and without Developmental Language Disorder (DLD). This study examined the N400, P600 and their interplay in Cantonese-speaking children with DLD and age-matched typically developing (TD) children, by manipulating semantic and syntactic violations in Chinese classifier-noun agreement. Behaviorally, children with DLD demonstrated overall lower accuracy in grammaticality judgment. The N400 and P600 analyses respectively confirmed robust semantic processing but attenuated syntactic processing in the DLD group. Crucially, the N400-P600 interplay analyses revealed that TD children prioritized syntactic processing over semantic processing for outright syntactic violations, as indicated by less N400-P600 dependence and robust P600 dominance, whereas children with DLD relied on semantic processing and showed reduced P600 dominance. These results underscore a challenge to prioritize syntactic processing and (suboptimal) compensatory reliance on semantic processing in children with DLD, compatible with the predictions of the Procedural circuit Deficit Hypothesis.