Browsing by Author "Harik, Lindsey M."
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Item The impact of pediatric traumatic brain injury on written expression: a diffusion tensor imaging study utilizing tract-based spatial statistics(2015-08) Harik, Lindsey M.; Hannay, H. Julia; Ewing-Cobbs, Linda; Juranek, Jenifer; Massman, Paul J.; Taylor, PatriciaThe aim of this study was to determine if cerebral white matter integrity is predictive of Written Expression (WE) performance in children, and if the relation between white matter integrity and WE performance differs between children with traumatic brain injury (TBI) and children with orthopedic injury (OI). White matter integrity was approximated via diffusion tensor imaging (DTI) using tract-based spatial statistics. The current study utilized two DTI metrics, fractional anisotropy (FA) and mean diffusivity (MD), to assess integrity of white matter tracts. White matter tract integrity values were used to predict WE performance in the TBI group and the OI comparison group. General linear modeling (GLM) and multiple mediation analyses were used to predict performance on measures of WE at twelve months post-injury from white matter integrity at three months post-injury. Measures of WE included Thematic Maturity, Writing Fluency, and Spelling. Children with OI demonstrated significantly stronger performance on Writing Fluency and Spelling than children with TBI but there was no significant difference between groups on TMI performance. Children with TBI showed significantly decreased white matter integrity three months post-injury as compared to children with OI. Writing Fluency and TMI performance were fully mediated by FA values of the anterior thalamic radiation and corticospinal tract and Writing Fluency performance was also predicted by group differences in cingulum bundle microstructure. Taken together, these findings suggest that TBI negatively impacts the microstructural integrity of specific pathways that support WE performance and that these microstructural alterations account for post-traumatic changes in the content and fluency of production of written narratives. These findings are relevant for further understanding the role of white matter in academic performance and the impact of TBI on the developing brain.Item WRITTEN EXPRESSION FOLLOWING PEDIATRIC TRAUMATIC BRAIN INJURY IN SCHOOL-AGED CHILDREN(2012-05) Harik, Lindsey M.; Ewing-Cobbs, Linda; Hannay, H. Julia; Swank, Paul R.; Fletcher, Jack M.; Tian, T. SivaThe purpose of this thesis was to investigate the effect of traumatic brain injury on written expression in school-aged children. In particular, the mediating effect of core and supporting processes of written expression on the effect of traumatic brain injury on written expression was explored. Core skills are those that are thought to be specific to written expression, and in particular, the mechanical execution of written language. The core skills assessed in this study were graphomotor speed, fine motor speed and coordination, spelling and writing fluency. Supporting skills are those processes that are not unique to writing but are necessary for completing most cognitive tasks, and are frequently affected by traumatic brain injury. The supporting skills assessed in this study were processing speed, working memory, and sustained and focused attention. The performance of children with traumatic brain injury was compared to a group of children with orthopedic injuries. Principal components analysis was used to elucidate the primary core and supporting components of written expression. Four components were retained: orthographic output, fine motor skills, working memory and vigilance. Consistent with previous literature, children in the head-injured group performed more poorly on the primary outcome measure of written expression, both core components and working memory. There was no difference between groups, however, on vigilance performance. Bootstrap regression analyses revealed that the effect of traumatic brain injury on written expression was significantly mediated by orthographic output. This finding is relevant for intervening on written expression difficulties in children with traumatic brain injury. Emphasizing orthographic output as a part of already well-established written expression interventions may provide added benefit in this population.