Author:

Abstract:

Acute and long-term impairments in cognitive functioning and academic skills have been reported following pediatric traumatic brain injury (TBI), even after mild TBI (mTBI). Understanding these cognitive and academic sequelae is particularly relevant because doing well with schoolwork is one of the major concerns of children and their parents after an injury. It turns out that mathematics rather than reading or spelling is the most compromised after pediatric (m)TBI. However, a precise characterization of the mathematical impairments in children with mTBI as well as their neural correlates is currently unavailable. Although the exact origin of the mTBI-related deficits in cognitive and behavioral functioning is not known, they may be the consequence of diffuse axonal injury (DAI). Conventional neuroimaging fails to adequately visualize DAI, yet diffusion tensor imaging (DTI) has demonstrated to be sensitive to detect DAI. Furthermore, electrophysiological techniques such as event-related potentials (ERPs) have started to unravel the underlying neurophysiological bases of cognitive dysfunctions associated with mTBI. Against this background the current dissertation aimed to further improve the understanding of mathematical difficulties in children with mTBI as well as the neural substrates underlying these deficits. In order to achieve this objective, specific mathematical skills were evaluated in children with mTBI during the subacute stage of injury (i.e. within 4 weeks post-injury) and re-evaluated at a more chronic stage of recovery (i.e. 6-8 months post-injury). In addition, differences in brain structure and function between children with mTBI and their typically developing peers were examined with DTI and ERP. Because knowledge about the underlying neural substrates of mathematical skills in typically developing children is limited, but needed to draw conclusions from findings in children with mTBI, the first two studies of this dissertation were devoted to the investigation of the neural correlates of mathematics in typically developing children. The DTI study described in chapter 2, showed that left fronto-parietal white matter plays a role in arithmetic processing in typically developing children, particularly in multiplications and additions. Findings from chapter 3 indicated that the ‘ERP arithmetic problem size paradigm’ might be an excellent paradigm to investigate arithmetic impairments in children with mathematical difficulties, such as children with mTBI. Chapters 4-6 report studies in children with mTBI. Data from chapter 4 showed that immediately after the injury pediatric mTBI patients have difficulties in rapid apprehension of small numbers of objects (or ‘subitizing’), non-symbolic magnitude processing and procedural problem solving and that these mathematical difficulties may be related to impairments in visuospatial working memory. These behavioral impairments were accompanied by subtle white matter abnormalities in the corpus callosum (in both the genu and splenium), but these abnormalities were not significantly related to the observed mathematical difficulties in the pediatric mTBI patients. In chapter 5 we studied the electrophysiological correlates of arithmetical difficulties in children with mTBI immediately after their injury by using the ‘ERP arithmetic problem size paradigm’. The results of this chapter showed that arithmetical difficulties in pediatric mTBI were particularly prominent in more complex arithmetic processes that are known to be less automated. In chapter 6 we investigated how the aforementioned subtle mathematical impairments and white matter abnormalities in children with mTBI evolve over time. Findings from this study indicate that both the mathematical difficulties and the white matter abnormalities in the corpus callosum were resolved after 6-8 months of recovery. However, subtle working memory deficits were reported in the pediatric mTBI patients at both the subacute and chronic stage of recovery. These problems may interfere with patients’ learning at school. Finally, in chapter 7 the clinical implications of our results and avenues for future research in pediatric mTBI are discussed.