発達言語障害児における文法様シーケンスの学習：電気生理学的検討

Developmental language disorder (DLD) is a prevalent neurodevelopmental condition that affects approximately 7% of children in the United States. One notable characteristic of DLD is difficulty in mastering nonadjacent dependencies, such as the third-person singular -s or passive construction be -ed. This study examines behavioral and electrophysiological measures of nonadjacent dependencies learning in children with DLD in the context of a visual grammar-like learning paradigm.

Fifty-one children (22 DLD, 29 typical language development [TD]) aged 8;0-12;4 (years;months) completed an aXb/cXd grammar learning task, followed by an immediate and 1-week follow-up test. Neurophysiological responses to grammatical and nongrammatical stimuli were measured by recording electroencephalography during the immediate test.

Children with and without DLD performed similarly and above chance level during the immediate test. Performance on the follow-up test indicated improved accuracy in children with TD. The DLD group, on the other hand, no longer exhibited above chance-level performance, pointing to limited consolidation. Event-related potentials extracted in relation to the grammaticality of the test items highlighted processing differences in responses to grammatical violations between the two groups (TD and DLD). While a P600 was found sensitive to grammatical violations in the TD group, a frontal N400-like activation was found sensitive to violations in the DLD group. These findings are interpreted to suggest familiarity-based associative learning rather than rule-based processing in children with DLD.

Children with DLD achieved comparable scores on the immediate behavioral test as their TD peers but did not show evidence of rule abstraction and long-term retention.