Doctor of Philosophy
Health and Rehabilitation Sciences
Archibald, Lisa M. D.
Joanisse, Marc F.
In this thesis, I investigated the relationship between functional and structural connectivity and reading ability in children. Prior research has tended to use single word reading measures or composite measures, however this is problematic as reading is a complex skill relying on multiple subskills, such as decoding efficiency, sight word reading efficiency, reading comprehension, and rapid automatized naming. As a result, the multi-faceted relationship between brain connectivity and reading ability is not well understood. I aimed to address this issue by considering multiple reading subskills while examining the neural substrates of reading. In Chapter 2, I examined how individual differences in decoding efficiency, sight word reading efficiency, reading comprehension, and rapid automatized naming relate to resting-state functional connectivity from regions of the brain’s reading network. I found that distinct functional networks in both hemispheres of the brain support different components of reading in children. In Chapter 3, I built on these findings to examine how individual differences in the same reading subskills are associated with structural connectivity in reading-related white matter tracts, as measured by diffusion tensor imaging. Similar to Chapter 2, the results of Chapter 3 suggested that different components of reading ability are supported by structural characteristics in distinct bilateral tracts of the brain. Importantly, many of the effects observed in Chapters 2 and 3 were found to be specific to reading subskills and were not associated with more general cognitive abilities. In Chapter 4, I examined how improvements in reading ability are related to changes in structural and functional connectivity, by measuring brain connectivity pre- and post-intervention in a group of children with reading disability. I also investigated whether individual differences in the amount of improvement in reading ability post-intervention was predicted by pre-intervention brain connectivity. I found that gains in reading ability were associated with changes in resting-state functional connectivity, particularly between reading-related regions and frontal regions as well as regions of the default mode network. Changes in white matter microstructure of the right arcuate fasciculus were strongly associated with gains in single word reading abilities. Additionally, results showed that distinct pre-intervention characteristics of resting-state functional connectivity and white matter integrity predicted the magnitude of subsequent gains in reading ability following the reading intervention. Chapter 5 summarizes the findings of this thesis in relation to the current literature and presents recommendations for future research on reading ability and brain connectivity.
Summary for Lay Audience
Reading is an extraordinarily complex skill. Readers must fluently integrate visual information about letters and words with their knowledge of the sounds of their language, and map this onto their existing conceptual knowledge in order to successfully understand what they are reading. Many previous neuroimaging studies have shown that the brain regions supporting reading are widely distributed across the brain, and that connections between these brain regions are important for supporting coordinated processing across this complex, widespread network. However, as previous studies have tended to use composite measures of reading ability, the distinct roles of these connections in supporting different types of skills involved in reading are not well understood. For example, reading relies on one’s ability to rapidly recognize letters and familiar words, decode unfamiliar words, and understand sentences. The goal of this thesis was to explore the role of connectivity between these brain areas in supporting different aspects of reading in school-aged children.
In the first two studies described in this thesis, I investigated how coordinated activity among different brain regions and anatomical connections between these regions were associated with different subskills of reading in children. The results of these studies showed that distinct networks of coordinated activity and distinct anatomical connections in both hemispheres of the brain were important for supporting different components of reading ability. In my third study, I was interested in extending these findings to examine how improvements in reading ability are related to changes in brain connectivity. Children in this final study were struggling readers who were participating in an intensive reading intervention program at their school. Results showed that improvements in reading ability were associated with measurable changes in anatomical connections and coordination of activity in the brain. Overall, the findings of the present thesis further our understanding of the role of brain connectivity in supporting distinct aspects of reading ability. Additionally, they shed new light on the changes in the brain that underlie improvements in reading ability in struggling readers who receive reading intervention.
Cross, Alexandra M., "Examining Brain Connectivity and Reading Ability in Children" (2020). Electronic Thesis and Dissertation Repository. 7356.