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Attention-deficit/hyperactivity disorder (ADHD) with its core symptoms inattention, impulsivity and hyperactivity is one of the most common mental disorders in childhood and adolescence. ADHD research focused predominantly on neuropsychological models of etiopathogenesis of ADHD in the last couple of years. Executive dysfunction, especially concerning attention and working memory, is common in patients with ADHD. With this in mind, the development of diagnostic instruments that assess neuropsychological deficits and result in specific treatment options is of extraordinary importance.
In this cumulus three studies will be presented dealing with neuropsychological assessment of ADHD on the one hand, and, on the other hand, with one new treatment option for neuropsychological deficits in adolescents suffering from ADHD.
So far there are only few studies addressing the psychometric properties of neuropsychological assessment and their benefits. The first study investigated the psychometric properties of the Quantified behavior Test (QbTest 6-12). Until now, the QbTest is the only neuropsychological test to objectively assess the three core symptoms inattention, hyperactivity and impulsivity of ADHD. Furthermore, it was tested whether the QbTest was able to discriminate better between children with and without ADHD than another computer based neuropsychological test called the KiTAP (Kinderversion der Testbatterie zur Aufmerksamkeitsprüfung). In a multitrait-multimethod analysis the criteria for convergent and discriminant validity of the QbTest were only partially supported. However, with an overall correct classification rate of 73.8 % the QbTest achieved a superior discrimination rate compared to the KiTAP.
Children and adolescents with ADHD show lower working memory performance compared to healthy subjects. This has been attributed to diminished activation of the dorsolateral prefrontal cortex (DLPFC). A normalization of the activity in this brain area could possibly reduce this deficit. By means of transcranial direct current stimulation (tDCS), it is possible to change the excitability of different cortical areas. The second study therefore dealt with the question whether anodal tDCS over the DLPC in adolescents with ADHD may lead to a reduction of neuropsychological deficits (assessed by the QbTest) and clinical symptoms. Finally, the third study investigated the effect of anodal tDCS over the DLPC on achievements in a working memory test and the activation of relevant neuronal networks compared to a sham stimulation. Therefore functional magnetic resonance imaging (fMRI) was used. Explorative analysis based on clinical assessments by the parents showed an improvement of attention and impulsivity. The QbTest revealed a significant reduction of hyperactivity and an improvement of the attention performance. FMRI analysis showed a significantly higher activation of the areas of the left DLPC, the left premotor cortex (PMC), the left supplementary motor area (SMA) and the posterior parietal cortex (PPC) in the tDCS condition compared to the sham condition.
In summary, the present study results suggest that the QbTest, especially because of its objective measurement of hyperactivity, provides an additional diagnostic value. Furthermore the studies point the potential of anodal tDCS as an alternative treatment option for ADHD.