@article{GramAlbertovaSchirmeretal.2022,
  author    = {Gram, Maximilian and Albertova, P. and Schirmer, V. and Blaimer, M. and Gamer, M. and Herrmann, M. J. and Nordbeck, P. and Jakob, P. M.},
  title     = {Towards robust in vivo quantification of oscillating biomagnetic fields using Rotary Excitation based MRI},
  series = {Scientific Reports},
  volume    = {12},
  journal   = {Scientific Reports},
  number    = {1},
  doi       = {10.1038/s41598-022-19275-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300862},
  year      = {2022},
  abstract  = {Spin-lock based functional magnetic resonance imaging (fMRI) has the potential for direct spatially-resolved detection of neuronal activity and thus may represent an important step for basic research in neuroscience. In this work, the corresponding fundamental effect of Rotary EXcitation (REX) is investigated both in simulations as well as in phantom and in vivo experiments. An empirical law for predicting optimal spin-lock pulse durations for maximum magnetic field sensitivity was found. Experimental conditions were established that allow robust detection of ultra-weak magnetic field oscillations with simultaneous compensation of static field inhomogeneities. Furthermore, this work presents a novel concept for the emulation of brain activity utilizing the built-in MRI gradient system, which allows REX sequences to be validated in vivo under controlled and reproducible conditions. Via transmission of Rotary EXcitation (tREX), we successfully detected magnetic field oscillations in the lower nano-Tesla range in brain tissue. Moreover, tREX paves the way for the quantification of biomagnetic fields.},
  language  = {en}
}
@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}
}