EEG Interchannel Causality to Identify Source/Sink Phase Connectivity Patterns in Developmental Dyslexia

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[Formula: see text]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 assumption of the temporal sampling framework 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.

Causal Mechanisms of Dyslexia via Connectogram Modeling of Phase Synchrony

“…The direct preliminary representation of the Granger matrices in the control and dyslexia groups offers, at first glance, greater causal connectivity in the dyslexia group, as noted in [17]. Figure 3 (Connectogram of causality in dyslexic group) indicates this greater connection exemplified for the theta band than the control group (Figure 2).…”