Neural source/sink phase connectivity in developmental dyslexia by means of interchannel causality

TL;DR

This study uses EEG and phase Granger causality to analyze directional brain connectivity differences in developmental dyslexia, confirming right-lateralized Theta anomalies and achieving high classification accuracy.

Contribution

It introduces a novel method for assessing causal brain connectivity in dyslexia, considering source and sink roles of channels, and demonstrates its effectiveness for classification.

Findings

Confirmed right-lateralized Theta sampling network anomaly in dyslexia.

Sink-related causal relationships show more pronounced anomalies.

Achieved classification accuracies of 84-88% with high AUC in Theta and Gamma bands.

Abstract

While the brain connectivity network can inform the understanding and diagnosis of developmental dyslexia, its cause-effect relationships have not yet enough been examined. Employing electroencephalography signals and band-limited white noise stimulus at 4.8 Hz (prosodic-syllabic frequency), we measure the phase Granger causalities among channels to identify differences between dyslexic learners and controls, thereby proposing a method to calculate directional connectivity. As causal relationships run in both directions, we explore three scenarios, namely channels' activity as sources, as sinks, and in total. Our proposed method can be used for both classification and exploratory analysis. In all scenarios, we find confirmation of the established right-lateralized Theta sampling network anomaly, in line with the temporal sampling framework's assumption of oscillatory differences in the Theta and Gamma bands. Further, we show that this anomaly primarily occurs in the causal relationships of channels acting as sinks, where it is significantly more pronounced than when only total activity is observed. In the sink scenario, our classifier obtains 0.84 and 0.88 accuracy and 0.87 and 0.93 AUC for the Theta and Gamma bands, respectively.