title: Neurocognitive Effects of Transcranial Direct Current Stimulation in Arithmetic Learning and Performance: A Simultaneous tDCS-fMRI Study.
abstract: A small but increasing number of studies suggest that non-invasive brain stimulation by means of transcranial direct current stimulation (tDCS) can modulate arithmetic processes that are essential for higher-order mathematical skills and that are impaired in dyscalculic individuals. However, little is known about the neural mechanisms underlying such stimulation effects, and whether they are specific to cognitive processes involved in different arithmetic tasks.
  
  
  
  We addressed these questions by applying tDCS during simultaneous functional magnetic resonance imaging (fMRI) while participants were solving two types of complex subtraction problems: repeated problems, relying on arithmetic fact learning and problem-solving by fact retrieval, and novel problems, requiring calculation procedures. Twenty participants receiving left parietal anodal plus right frontal cathodal stimulation were compared with 20 participants in a sham condition.
  
  
  
  We found a strong cognitive and neural dissociation between repeated and novel problems. Repeated problems were solved more accurately and elicited increased activity in the bilateral angular gyri and medial plus lateral prefrontal cortices. Solving novel problems, in contrast, was accompanied by stronger activation in the bilateral intraparietal sulci and the dorsomedial prefrontal cortex. Most importantly, tDCS decreased the activation of the right inferior frontal cortex while solving novel (compared to repeated) problems, suggesting that the cathodal stimulation rendered this region unable to respond to the task-specific cognitive demand.
  
  
  
  The present study revealed that tDCS during arithmetic problem-solving can modulate the neural activity in proximity to the electrodes specifically when the current demands lead to an engagement of this area.
authors: Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London WC1N 3BG, UK; Max Planck UCL Centre for Computational Psychiatry and Ageing Research, 10-12 Russel Square, London WC1B 5EH, UK. Electronic address: t.hauser@ucl.ac.uk.
authors: Tobias U
authors: TU
authors: Hauser
authors: Institute for Behavioral Sciences, ETH Zurich, Clausiusstrasse 59, 8092 Zürich, Switzerland.
authors: Bruno
authors: B
authors: Rütsche
authors: Institute for Behavioral Sciences, ETH Zurich, Clausiusstrasse 59, 8092 Zürich, Switzerland.
authors: Karoline
authors: K
authors: Wurmitzer
authors: Department of Child and Adolescent Psychiatry and Psychotherapy, Psychiatric Hospital, University of Zurich, 8032 Zürich, Switzerland; Neuroscience Center Zurich, University of Zurich and ETH Zurich, Switzerland.
authors: Silvia
authors: S
authors: Brem
authors: Neuroscience Center Zurich, University of Zurich and ETH Zurich, Switzerland; Laboratory for Social and Neural Systems Research (SNS-Lab), Department of Economics, University of Zurich, Bluemlisalpstrasse 10, 8006 Zürich, Switzerland.
authors: Christian C
authors: CC
authors: Ruff
authors: Institute of Psychology, University of Graz, Universitaetsplatz 2, 8010 Graz, Austria.
authors: Roland H
authors: RH
authors: Grabner
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Arithmetic; Functional magnetic resonance imaging (fMRI); Mathematics; Simultaneous tDCS-fMRI; Transcranial direct current stimulation (tDCS)