Compensatory Mechanisms in Visual Sequence Learning: An fMRI Study of Children with Developmental Language Disorder
Symptoms of developmental language disorder (DLD) may in part result from an underlying deficit in statistical learning (SL). This learning deficit may be related to the ability to extract probabilistic properties of events in the environment, which is based on the functions of cortical and subcortical brain regions underlying SL. Using a behavioral SL task and functional magnetic resonance imaging (fMRI), we tested SL ability in the visual domain and its neural correlates in children with DLD and their typically developing (TD) peers. During fMRI, children performed SL tasks involving sequences of two types of stimuli: easy-to-name (EN) objects and difficult-to-name (DN) objects. The children underwent a pre-training fMRI, one week of behavioural training and a post-training fMRI. Similar task performance was observed in both groups during the experimental sessions, with an improvement in performance following training in the SL tasks involving both EN and DN objects. FMRI results revealed that, after training, the DLD group presented greater involvement of the frontal cortex and temporal pole for EN objects. Furthermore, in the TD group, the left putamen, globus pallidus (GP) and thalamus were involved in the early stages of SL, whereas in the DLD group, these areas were involved in SL after training. For DN objects, after training, the DLD group presented greater involvement of the parietal and precuneus regions in the SL task performance. Our results suggest that children with DLD may employ different cognitive processes in SL than TD children, possibly as a compensatory mechanism.