Dynamic task-specific brain network connectivity in children with severe reading difficulties

We investigated patterns of sensor-level functional connectivity derived from single-trial whole-head magnetoencephalography data during a pseudoword reading and a letter-sound naming task in children with reading difficulties (RD) and children with no reading impairments (NI). The Phase Lag Index (PLI), a linear and nonlinear estimator, computed for each pair of sensors, was used to construct graphs and obtain estimates of local and global network efficiency according to graph theory. In the 8-13 Hz (alpha band) and 20-30 Hz (gamma band) range, RD students showed significantly lower global efficiency than NI children, for the entire MEG recording epoch. RD students also displayed reduced local network efficiency in the alpha band. Correlations between phonological decoding ability and graph metrics were particularly evident during the task that posed significant demands for phonological decoding, and followed distinct time courses depending on signal frequency. Results are consistent with the notion of task-dependent, aberrant long- and short-range functional connectivity in RD children.

Research highlights▶ Instantaneous phase of MEG signals is extracted using continuous Morlet wavelet. ▶ Binary undirected Graphs are formed by the significant Phase Lag Index. ▶ Graphs are explored using the mean degree, the global-, and local- efficiency. ▶ Small world network was preserved in reading disabled and normal readers. ▶ Reading disabled and normal readers were distinguished by the graph parameters.