Elucidating the neurophysiological underpinnings of Dyslexia: Relationships with resting and task-based EEG markers, behavioural measures and response to neurofeedback intervention

Abstract

Dyslexia is a cross-cultural, neurodevelopmental disorder of unknown aetiology that encircles behavioural, neurophysiological, neurobiological and genetic deficits. The experiments that make up this thesis systematically explored the neurophysiological underpinnings of dyslexia in a hierarchical fashion and tested whether aberrations in EEG/ERPs were amenable to treatment, through the use of neurofeedback training, in a pre to post fashion. In Study 1, resting state behavioural and EEG investigations examined the differences in the behavioural output and fundamental neurophysiological changes between dyslexia and neurotypical control children. Building from the first study, Study 2, employed an auditory oddball paradigm to explore the nature and timing of downstream cognitive processing, as reflected by the P300 ERP, in dyslexia along with its topographical distribution. Study 3, sought to explore whether a relationship exists between baseline pre-stimulus EEG states and post-stimulus cognitive processing, as reflected by the P300 component, in dyslexia. Collectively, the findings from the 3 aforementioned studies place the origin of the neurophysiologic abnormalities reported in children with dyslexia at a time window prior to post-stimulus cognitive processing, which may be reflective of compromised preparatory networks. Study 4 sought to examine whether the reported abnormalities in dyslexia, were amenable to a physical intervention such as neurofeedback. Findings indicate a modest but significant normalisation effect in the resting state EEG, P300 amplitude and latency measures and were accompanied by behavioural improvements. The findings generated by this body of work have provided new insights into our understanding of the mechanisms involved in dyslexia and have identified a potential efficacious treatment option for the early intervention of this clinical group.