Anne Fleur Kortekaas-Rijlaarsdam

81 MPH EFFECTS ON MATH PERFORMANCE: INFLUENCE OF COGNITION, MOTIVATION AND PERCEIVED COMPETENCE 4 and inconsistent. One study showed no improvement in self-rated perceived academic competence with MPH compared to placebo (Ialongo, Lopez, Horn, 1994), whereas another study showed that MPH improved reward sensitivity for delayed rewards in children with ADHD, suggesting enhanced extrinsic motivation (Shiels et al., 2009). The lack of studies on the effect of stimulant medication on motivational deficits in ADHD, despite the abundant use of this type of medication to treat ADHD and the evidence that such pharmacological agents have substantial effects on the motivational attitude of healthy subjects (Nora D. Volkow et al., 2004), is striking. Stimulant medication is thought to impact on the dopamine-based brain networks, which include structures such as the ventral striatum, which are active during reward processing (Volkow et al., 2004) and activity in these networks is found to increase the salience of outcomes and improve the motivation to perform (Shiels et al., 2009; Swanson et al., 2004). Thus, it is likely that stimulant medication improves aspects of academic motivation in children with ADHD. The current study aimed to gain more insight into the effects of MPH on a number of specific cognitive processes known to be associated with ADHD, and deficits in both motivation and competence; factors that are important for academic performance. The acute effects of MPH on cognition (working memory, lapses of attention and interference control), academic motivation (intrinsic and extrinsic) and perceived academic competence were investigated using a double blinded, placebo-controlled cross-over design. Previously, we demonstrated that MPH improved mathematical productivity and accuracy, and that improvements in mathematical productivity were mediated by symptom improvements (Kortekaas-Rijlaarsdam et al., 2017b). Here, we extended these findings to unravel the mechanism behind medication-related improvements in math performance. We therefore investigated the mediating role of these cognitive functions, motivation and competence in MPH-related improvements in math. Performance of children with ADHD on placebo was compared to performance of TD children. We expected children with ADHD on placebo to show deficits in cognition, motivation and perceived competence (Carlson et al., 2002; Luman et al., 2005; Mullane et al., 2009b; Scholtens et al., 2013; Willcutt et al., 2005). Further, we hypothesized MPH to improve math performance through (1) improvements in working memory, lapses of attention and interference control (Coghill et al., 2013; Mayes & Calhoun, 2007; Pietrzak et al., 2006; Preston et al., 2009; Thorell, 2007) and (2) increases in intrinsic academic motivation, extrinsic motivation and perceived academic competence (DuPaul et al., 2004; Gut et al., 2012; Langberg et al., 2012; Volkow et al., 2004).