White matter connectome associations with reading functions in children
Abstract
This thesis investigated associations between the white matter connectome and reading in children with a wide range of reading abilities. It is well established that the connectome supports the interplay among brain regions and connections within an integrated system. In this dissertation, I examine the hypothesis that it could therefore represent multiple mapping processes among reading components and further explain variations in reading performance. Such associations between the organization of the connectome and reading skills have not been well explored. This thesis aimed to address this issue by considering both the relationship between connectome measures and standardized reading performance out of scanner, and neural activations during in-scanner reading tasks. Chapter 2 examined the rich-club organization of the white matter connectome and its association with sight word reading, phonemic decoding, reading comprehension, and rapid automatized naming in children. I found that feeder connections that link hub and reading network regions were associated with word-level reading skills. Chapter 3 further examined how the left thalamus influences reading skills by coordinating information flow between the reading network and hub regions. Results showed that the efficiency metrics and routing cost of the left thalamus within a subnetwork, which contains the reading network and hub regions, were associated with rapid automatized naming and phonemic decoding scores, respectively. Chapter 4 applied network control theory to investigate if the white matter connectome could explain the dynamics of functional activation. Specifically, I examined if control energy, which reflects the level of cognitive demands from a task, showed differences across different conditions of an in-scanner rhyming task. I found that conditions requiring more effort were associated with higher control energy within reading network areas. In addition, the control energy of the superior temporal gyrus and fusiform gyrus showed dissociations regarding different modalities of stimulus presentation. Moreover, children with better word-level reading scores required lower control energy. Chapter 5 summarizes the findings and discusses their implications to the connectome-reading relationship.