Resting-state functional connectivity in reading-related brain regions : a meg study in monozygotic twins

Abstract

Reading requires functional interaction between distinct reading-related regions located in the frontal and posterior parts of the left hemisphere. Abnormalities in the functional connectivity among these regions have been previously associated with dyslexia. In this study, we investigated resting-state functional connectivity (RSFC) in the reading-related regions, including inferior frontal gyrus, temporoparietal junction, and the visual word form area (VWFA) in fusiform gyrus. RSFC is a suitable method to investigate intrinsic brain networks without the influence of specific task demands or cognitive processes. Our aim was to identify significant RSFC in the reading-related regions and explore its association to reading fluency using magnetoencephalography (MEG). Additionally, we examined the familial heritability of the reading-related RSFC. The study included 90 adult monozygotic (MZ) twins with heterogenous reading competence. The RSFC analysis between reading-related regions was conducted using imaginary part of coherency (IPC), in the alpha and theta frequency bands. In order to study the association between the RSFC and reading fluency, a new variable was constructed of three reading speed tasks to measure reading fluency among Finnish participants. The heritability examination was carried out by comparing the MZ twin pairs’ obtained correlation to the permutated sample distributions of r. The main finding of our study was a significant RSFC in both the left hemisphere (between the inferior frontal gyrus and temporoparietal junction) and in their right hemisphere homologues, in the theta frequency band. The RSFC displayed no association with reading fluency but demonstrated a significant similarity between MZ twin pairs compared to non-related pairs, thus indicating a moderate heritability of the RSFC in the reading-related regions. The results suggest that RSFC can be detected utilising MEG and the RSFC in the reading-related regions may have a heritable component.