Children with reading disorder show modality independent brain abnormalities during semantic tasks

Abstract

Neuroimaging studies have suggested that left inferior frontal gyrus, left inferior parietal lobule and left middle temporal gyrus are critical for semantic processing in normal children. The goal of the present functional magnetic resonance imaging (fMRI) study was to determine whether these regions are systematically related to semantic processing in children (9- to 15-year-old) diagnosed with reading disorders (RD). Semantic judgments required participants to indicate whether two words were related in meaning. The strength of semantic association varied continuously from higher association pairs (e.g., king-queen) to lower association pairs (e.g. net-ship). We found that the correlation between association strength and activation was significantly weaker for RD children compared to controls in left middle temporal gyrus and left inferior parietal lobule for both the auditory and the visual modalities and in left inferior frontal gyrus for the visual modality. These results suggest that the RD children have abnormalities in semantic search/retrieval in the inferior frontal gyrus, integration of semantic information in the inferior parietal lobule and semantic lexical representations in the middle temporal gyrus. These deficits appear to be general to the semantic system and independent of modality.

Fig. 1

Greater neural activation for the related word pairs compared to the null condition for the auditory modality (top row) and for the visual modality (bottom row). Control group is represented in green, RD group is represented in red, and the overlap between the control and RD group is represented in blue. For the auditory modality, both groups showed activation in left inferior frontal gyrus (a) and left middle temporal gyrus (b). For the visual modality, both groups showed activation in left inferior frontal gyrus (c), left middle temporal gyrus (d), and left fusiform gyrus. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)

Fig. 2

Greater neural activation correlated with lower association in left inferior frontal gyrus for the auditory modality (a) and in left middle temporal gyrus for the visual modality (b). Control group is represented in green, and the overlap between the control and RD group is represented in blue. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)

Fig. 3

Controls show a stronger correlation between association strength and neural activation than RD children. Green represents correlation for the control group and red represents that this correlation is stronger for the control compared to the RD group. For the auditory modality, greater activation correlated with lower association in left middle temporal gyrus (a) and left inferior frontal gyrus (b), and with higher association in left inferior parietal lobule (c). For the visual modality, greater activation correlated with lower association in left middle temporal gyrus (d) and with higher association in left inferior parietal lobule (e). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)