Altered effective connectivity on rapid automatized naming deficits in Chinese children with developmental dyslexia: An rs-fMRI study with Ganger causality analysis.

Rapid Automatized Naming (RAN) is the core defect of developmental dyslexia (DD), requiring collaboration among brain areas to complete. However, it's still unclear which effective connectivity (EC) among brain areas are crucial for RAN deficits in Chinses children with DD. The current study aims to explore the EC among brain areas related to RAN deficits in Chinese children with DD. We recruited 36 Chinese children with DD and 64 typically developing (TD) children aged 8-12 to complete resting-state functional magnetic resonance imaging (rs-fMRI) scan. Granger causality analysis (GCA) was employed to analysis the EC among brain areas related to RAN, and to calculate the relationship between EC and RAN scores. Compared to TD group, the DD group exhibited significantly decreased EC from left precentral gyrus (PG) to right precuneus, left anterior cingulate and paracingulate gyrus (ACG), left calcarine and right angular, from left middle frontal gyrus (MFG) to left calcarine. Additionally, the DD group showed increased EC from right cuneus to left inferior frontal gyrus triangular part (IFGtri). The EC from left PG to left ACG was positively correlated with letters-RAN score. The results showed Chinese children with DD had both defect and compensatory mechanisms for their RAN deficits. The decreased EC output from left PG may be the core problem of the RAN deficits, which may influence the integration of visual-spatial information, attention, memory retrieval, and speech motor in speech production. The current study has important clinic implications for establishing intervention measures targeted brain.

White matter substrates underlying morphological awareness deficit in Chinese children with developmental dyslexia.

BACKGROUND: Morphological awareness (MA) deficit is strongly associated with Chinese developmental dyslexia (DD). However, little is known about the white matter substrates underlying the MA deficit in Chinese children with DD. METHODS: In the current study, 34 Chinese children with DD and 42 typical developmental (TD) children were recruited to complete a diffusion magnetic resonance imaging scan and cognitive tests for MA. We conducted linear regression to test the correlation between MA and DTI metrics, the structural abnormalities of the tracts related to MA, and the interaction effect of DTI metrics by group on MA. RESULTS: First, MA was significant related to the right inferior occipito-frontal fascicle (IFO) and inferior longitudinal fsciculus (ILF), the bilateral thalamo-occipital (T_OCC) and the left arcuate fasciculus (AF); second, compared to TD children, Chinese children with DD had lower axial diffusivity (AD) in the right IFO and T_OCC; third, there were significant interactions between metrics (fractional anisotropy (FA) and radial diffusivity (RD)) of the right IFO and MA in groups. The FA and RD of the right IFO were significantly associated with MA in children with DD but not in TD children. CONCLUSION: In conclusion, compared to TD children, Chinese children with DD had axonal degeneration not only in the ventral tract (the right IFO) but also the visuospatial tract (the right T_OCC) which were associated with their MA deficit. And Chinese MA involved not only the ventral tracts, but also the visuospatial pathway and dorsal tracts.