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Abstract

Developmental dyslexia is a neurodevelopmental disorder characterized by difficulties in acquiring accurate and fluent reading. In addition to its associations with cognitive and language impairments, dyslexia is linked to disruptions in the brain’s functional and structural organization. Dyslexia is identified by verbal processing deficits but may also involve visuospatial impairments. Examining these cognitive domains can help clarify cognitive profiles and inform targeted interventions. Additionally, few studies have examined whole-brain resting-state functional connectivity before and after reading interventions in reading difficulties. This dissertation aimed to investigate disrupted cognitive and neural mechanisms in children with poor and typical reading abilities and evaluate the impact of a reading intervention. Chapter 2 examined cognitive performance in poor and typical readers across verbal and visuospatial tasks, with poor readers showing significantly lower performance on all tasks, suggesting broader cognitive impairments beyond reading disorders in dyslexia. Chapter 3 extends the investigation from Chapter 2 by examining the neurological basis of these cognitive difficulties, focusing on connectivity between reading-related brain regions and the dorsal, ventral, and lateral visual processing pathways in poor readers, as well as the effects of a reading intervention on these connections. While no group differences were observed initially, post-intervention results showed reduced connectivity between these visual and reading regions in poor readers. This reduction may be linked to altered brain organization associated with atypical underlying structural connectivity patterns in dyslexia. Moreover, post-intervention functional connectivity was positively associated with word recognition fluency in the full group of participants. In Chapter 4, the resting-state fMRI data were re-examined with a broader perspective to study both whole-brain and reading-related connectivity before and after the reading intervention. Before the intervention, poor readers exhibited reduced connectivity across attention, visual, and sensorimotor networks compared to typical readers. The intervention enhanced connectivity across some of these networks and revealed compensatory neural connections in poor readers. These findings, particularly from Chapter 2’s study of visuospatial functions, Chapter 3’s evidence of non-reading-specific neural involvement, and Chapter 4’s results on domain-general functional connectivity, highlight the importance of addressing domain-general functions in addition to reading-specific difficulties and support the multiple deficit theory of dyslexia.