UBC Theses and Dissertations
Connectivity in cortical networks during word reading Bedo, Nicolas
The neural processes underlying word reading remain much of a mystery. In particular, the flow of information within and between language networks during word reading has not been adequately explored. The present study investigated local spectral power changes and functional and effective (causal) connectivity at each stage of word reading. EEG was used to record brain activity from healthy volunteers (n = 15), during a reading task. Independent component analysis yielded multiple sources of activation previously identified with fMRI and PET as being crucial to word reading. A combination of event-related spectral perturbation and phase synchrony analyses was performed on these independent components. Additionally, analyses of transfer entropy were conducted to investigate the possible causal information flow between sites of interest. Results confirm the VWFA as a central hub for word reading, showing a progression of theta band phase synchrony with early visual areas and then later with high-level language processing areas. Transfer entropy analyses largely converged with the theta synchrony results, again emphasizing the VWFA as a crucial node in the reading network, initially receiving information from early visual cortex, and then sending information to high-level areas. These results highlight the interplay between local and long-distance neural dynamics involved at each stage of processing during reading. Additionally, these measures of functional and causal connectivity may be used as a benchmark for comparison with clinical populations (e.g. individuals with certain kinds of dyslexia), such that disturbances in connectivity may provide insight as to underlying neurological problems.
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