@article{BiehlMerzDresleretal.2016,
  author    = {Biehl, Stefanie C. and Merz, Christian J. and Dresler, Thomas and Heupel, Julia and Reichert, Susanne and Jacob, Christian P. and Deckert, J{\"u}rgen and Herrmann, Martin J.},
  title     = {Increase or Decrease of fMRI Activity in Adult Attention Deficit/ Hyperactivity Disorder: Does It Depend on Task Difficulty?},
  series = {International Journal of Neuropsychopharmacology},
  volume    = {19},
  journal   = {International Journal of Neuropsychopharmacology},
  number    = {10},
  doi       = {10.1093/ijnp/pyw049},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-147551},
  pages     = {pyw049},
  year      = {2016},
  abstract  = {Background: Attention deficit/hyperactivity disorder has been shown to affect working memory, and fMRI studies in children and adolescents with attention deficit/hyperactivity disorder report hypoactivation in task-related attentional networks. However, studies with adult attention deficit/hyperactivity disorder patients addressing this issue as well as the effects of clinically valid methylphenidate treatment are scarce. This study contributes to closing this gap. Methods: Thirty-five adult patients were randomized to 6 weeks of double-blind placebo or methylphenidate treatment. Patients completed an fMRI n-back working memory task both before and after the assigned treatment, and matched healthy controls were tested and compared to the untreated patients. Results: There were no whole-brain differences between any of the groups. However, when specified regions of interest were investigated, the patient group showed enhanced BOLD responses in dorsal and ventral areas before treatment. This increase was correlated with performance across all participants and with attention deficit/hyperactivity disorder symptoms in the patient group. Furthermore, we found an effect of treatment in the right superior frontal gyrus, with methylphenidate-treated patients exhibiting increased activation, which was absent in the placebo-treated patients. Conclusions: Our results indicate distinct activation differences between untreated adult attention deficit/hyperactivity disorder patients and matched healthy controls during a working memory task. These differences might reflect compensatory efforts by the patients, who are performing at the same level as the healthy controls. We furthermore found a positive effect of methylphenidate on the activation of a frontal region of interest. These observations contribute to a more thorough understanding of adult attention deficit/hyperactivity disorder and provide impulses for the evaluation of therapy-related changes.},
  language  = {en}
}
@article{BiehlDreslerReifetal.2011,
  author    = {Biehl, Stefanie C. and Dresler, Thomas and Reif, Andreas and Scheuerpflug, Peter and Deckert, J{\"u}rgen and Herrmann, Martin J.},
  title     = {Dopamine Transporter (DAT1) and Dopamine Receptor D4 (DRD4) Genotypes Differentially Impact on Electrophysiological Correlates of Error Processing},
  series = {PLoS One},
  volume    = {6},
  journal   = {PLoS One},
  number    = {12},
  doi       = {10.1371/journal.pone.0028396},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137930},
  pages     = {e28396},
  year      = {2011},
  abstract  = {Recent studies as well as theoretical models of error processing assign fundamental importance to the brain's dopaminergic system. Research about how the electrophysiological correlates of error processing—the error-related negativity (ERN) and the error positivity (Pe)—are influenced by variations of common dopaminergic genes, however, is still relatively scarce. In the present study, we therefore investigated whether polymorphisms in the DAT1 gene and in the DRD4 gene, respectively, lead to interindividual differences in these error processing correlates. One hundred sixty participants completed a version of the Eriksen Flanker Task while a 26-channel EEG was recorded. The task was slightly modified in order to increase error rates. During data analysis, participants were split into two groups depending on their DAT1 and their DRD4 genotypes, respectively. ERN and Pe amplitudes after correct responses and after errors as well as difference amplitudes between errors and correct responses were analyzed. We found a differential effect of DAT1 genotype on the Pe difference amplitude but not on the ERN difference amplitude, while the reverse was true for DRD4 genotype. These findings are in line with predictions from theoretical models of dopaminergic transmission in the brain. They furthermore tie results from clinical investigations of disorders impacting on the dopamine system to genetic variations known to be at-risk genotypes.},
  language  = {en}
}