[PS-1.2] Effects of task complexity on neural activity in children with dyslexia

Morken, F. , Specht, K. & Helland, T.

University of Bergen

This study aimed to investigate brain activity in children with and without dyslexia while reading words and sentences with increasing linguistic and orthographic complexity. In earlier studies the caudate nucleus has been implicated in language comprehension and silent articulatory processes, whereas the anterior cingulate has been tied to reading comprehension and attention. Examining how reading complexity impacts brain activity in children has, however, to our knowledge, not been done previously. Twenty-nine 11-year-old children were recruited through ?The Bergen Longitudinal Dyslexia Study?. After literacy assessment, a dyslexia group (DYS: N=11, 5 male, 6 female) and a typical group (TYP: N=18, 10 male, 8 female) were identified. The children were assessed using block design fMRI. Stimuli were presented visually in three runs with three conditions representing different levels of complexity (C1: alphabetical, C2: orthographic, C3: sentences). Data were first subjected to factorial analysis. Second, regions showing an interaction effect of group by task were selected for regions of interest (ROI) analysis. Tukey HSD for unequal N was used as follow-up. Finally, t-tests were performed to further investigate group differences. The factorial analysis returned three main areas with a significant interaction effect of group by task; left anterior cingulate (LACC), left caudate nucleus (LCN) and the right anterior cingulate towards the medial frontal gyrus (RACC). The ROI showed that all three areas responded to increased complexity with up-regulation of neuronal activity in the DYS group, and down-regulation in the TYP group. Post-hoc testing indicated that the interaction was mainly driven by the sentence condition. T-tests showed significant group differences on C1 (LACC and LNC, DYS<TYP, p<.04) and C3 (all three regions, DYS>TYP, p<.04). These findings suggest that areas associated with substrates of language processing may show opposite patterns of neuronal activity in children with and without dyslexia when reading increasingly complex stimuli.