Objective-To use Cambridge Neuropsychological Test Automated Battery (CANTAB) test battery to assess the effects of discontinuation of treatment with methylphenidate on the neuropsychological performance of children with attention deficit hyperactivity disorder (ADHD) and to compare this performance with normative data. Methods-Fifteen boys meeting criteria for Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV ADHD aged between 4.5-14.6 yrs were selected. The CANTAB test battery was conducted after discontinuation of methylphenidate for a minimum of 24 hours and was repeated one week after the recommencement of treatment. Results-Performance differences between the unmedicated/medicated groups were found on the pattern recognition memory task (F=0.37, p=0.041) and intra/extra-dimensional (IED) Set-Shifting task [number of stages completed (z=-4.572, p=0.001) and total errors (F= 1.36, p=0.046)]. In the unmedicated group, total errors made on IED Set-Shifting correlated with a lower strategy score on the Spatial Working Memory (SWM) task (r=0.518, p=0.048). In the medicated group, greater Spatial Span Length correlated with fewer “between search” errors made on the SWM test (r=0.657, p=0.008). Conclusion-Discontinuation of methylphenidate impairs performance on the CANTAB test battery in children with ADHD. These impairments, primarily in executive function, could be indicative of dysfunction in fronto-striatal networks, that methylphenidate can improve through manipulation of catecholaminergic pathways in the brain.
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