Examining Cognitive Processing in Children with an Arithmetic Disability

Currently there is no consensus as to the specific cognitive impairments that characterize mathematical disabilities (MD) or specific subtypes such as an arithmetic disability (AD). The present study sought to address this concern by examining cognitive processes that might undergird AD in children. The present study utilized archival data to conduct two investigations. The first investigation examined the executive functioning and working memory of children with AD. An age-matched achievement-matched design was employed to explore whether children with AD exhibit developmental lags or deficits in these cognitive domains. While children with AD did not exhibit impairments in verbal working memory or colour word inhibition, they did demonstrate impairments in shifting attention, visual-spatial working memory, and quantity inhibition. As children with AD did not perform more poorly than their younger achievement-matched peers on any of these tasks, impairments in specific areas of executive functioning and working memory appeared to reflect a developmental lag rather than a cognitive deficit. The second study examined the phonological processing performance of children with AD compared to children with comorbid disabilities in arithmetic and word recognition (AD/WRD) and to typically achieving (TA) children. Results indicated that, while children with AD did demonstrate impairments on all isolated naming speed tasks, trail making digits, and memory for digits, they did not demonstrate impairments on measures of phonological awareness, nonword repetition, serial processing speed, or serial naming speed. In contrast, children with AD/WRD demonstrated impairments on measures of phonological awareness, phonological short-term memory, isolated naming speed, serial processing speed, and the alphabet a-z task. Overall, results suggested that phonological processing impairments are more prominent in children with a WRD than children with an AD. Together, these studies further our understanding of the nature of the cognitive processes that underlie AD by focusing upon rarely used methods (i.e., age-matched achievement-matched design) and under-examined cognitive domains (i.e., phonological processing).

ENVIRONMENTAL INFLUENCES AND EPIGENETIC MECHANISMS IN RISK FOR DEPRESSION

Genetic and environmental factors interact to influence vulnerability for internalizing psychopathology, including Major Depressive Disorder (MDD). The mechanisms that account for how environmental stress can alter biological systems are not yet well understood yet are critical to develop more accurate models of vulnerability and targeted interventions. Epigenetic influences, and more specifically, DNA methylation, may provide a mechanism by which stress could program gene expression, thereby altering key systems implicated in depression, such as frontal-limbic circuitry and its critical role in emotion regulation. This thesis investigated the role of environmental factors from infancy and throughout the lifespan affecting the serotonergic (5-HT) system in the vulnerability to and treatment of depression and anxiety and potential underlying DNA methylation processes. First, we investigated the contributions of additive genetic vs. environmental factors on an early trait phenotype for depression (negative emotionality) in infants and their stability over time in the first 2 years of life. We provided evidence of the substantial contributions of both genetic and shared environmental factors to this trait, as well as genetically- and environmentally- mediated stability and innovation. Second, we studied how childhood environmental stress is associated with peripheral DNA methylation of the serotonin transporter gene, SLC6A4, as well as long-term trajectories of internalizing behaviours. There was a relationship between childhood psychosocial adversity and SLC6A4 methylation in males, as well as between SLC6A4 methylation and internalizing trajectory in both sexes. Third, we investigated changes in emotion processing and epigenetic modification of the SLC6A4 gene in depressed adolescents before and after Mindfulness-Based Cognitive Therapy (MBCT). The alterations from pre- to post-treatment in connectivity between the ACC and other network regions and SLC6A4 methylation suggested that MBCT may work to optimize the connectivity of brain networks involved in cognitive control of emotion as well as also normalize the relationship between SLC6A4 methylation and activation patterns in frontal-limbic circuitry. Our results from these three studies strengthen the theory that environmental influences are critical in establishing early vulnerability factors for MDD, driving epigenetic processes, and altering brain processes as an individual undergoes treatment, or experiences relapse.

The Efficacy of a Novel Video Game Intervention (MindLight) in Reducing Children's Anxiety

Anxiety disorders are the most prevalent form of psychopathology among children and adolescents. Because demand for treatment far exceeds availability, there is a need for alternative approaches that are engaging, accessible, cost-effective, and incorporate practice to reach as many youth as possible. One novel approach is a video game intervention called MindLight that uses two evidence-based strategies to target childhood anxiety problems. Using neurofeedback mechanics to train players to: (1) attend to positive rather than threatening stimuli and (2) down-regulate arousal during stressful situations, MindLight teaches children how to practice overcoming anxious thoughts and arousal in a fun and engaging context. The present study examined the effectiveness of MindLight versus online cognitive-behavioural therapy (CBT) based psychoeducation sessions as a comparison in reducing anxiety in a sample of 144 anxious children, which was measured in three ways: (1) anxiety symptoms, (2) state anxiety in response to stress, and (3) psychophysiological arousal in response to stress. Children between the ages of 8.05–17.78 years (M=13.61, SD=1.79) were randomly assigned to play MindLight or complete psychoeducation for five hours over three weeks. State anxiety and psychophysiological arousal were assessed in response to two stress tasks before and after exposure to MindLight or psychoeducation. Anxiety symptoms were also measured via a questionnaire. Overall, participants showed significant reductions in anxiety symptoms and state anxiety in response to stress, but not psychophysiological arousal in response to stress. Moreover, the magnitude of reductions in anxiety did not differ between interventions but by age and sex. Specifically, older participants showed a greater decrease in severity of state anxiety in response to a social stressor than younger participants and girls showed a greater decrease in severity of state anxiety in response to a cognitive stressor than boys. The present study suggests that playing MindLight results in similar reductions in anxiety as one of the more common means of delivering CBT principles to youth.