title: Online Effects of Transcranial Direct Current Stimulation in Real Time on Human Prefrontal and Striatal Metabolites.
abstract: Studies have reported that transcranial direct current stimulation (tDCS) can modulate human behaviors, symptoms, and neural activity; however, the neural effects during stimulation are unknown. Most studies compared the effects of tDCS before and after stimulation. The objective of our study was to measure the neurobiological effect of a single tDCS dose during stimulation.
  
  
  
  We conducted an online and offline protocol combining tDCS and magnetic resonance spectroscopy (MRS) in 17 healthy participants. We applied anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC) and cathodal tDCS over the right DLPFC for 30 minutes, one of the most common montages used with tDCS. We collected MRS measurements in the left DLPFC and left striatum during tDCS and an additional MRS measurement in the left DLPFC immediately after the end of stimulation.
  
  
  
  During stimulation, active tDCS, as compared with sham tDCS, elevated prefrontal N-acetylaspartate and striatal glutamate + glutamine but did not induce significant differences in prefrontal or striatal gamma-aminobutyric acid level. Immediately after stimulation, active tDCS, as compared with sham tDCS, did not significantly induce differences in glutamate + glutamine, N-acetylaspartate, or gamma-aminobutyric acid levels in the left DLPFC.
  
  
  
  These observations indicate that tDCS over the DLPFC has fast excitatory effects, acting on prefrontal and striatal transmissions, and these effects are short lived. One may postulate that repeated sessions of tDCS might induce similar longer lasting effects of elevated prefrontal N-acetylaspartate and striatal glutamate + glutamine levels, which may contribute to its behavioral and clinical effects.
authors.affiliation: Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, Faculté de médecine, Université Laval, Quebec City, Quebec, Canada.
authors.forename: Antoine
authors.initials: A
authors.lastname: Hone-Blanchet
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland; F.M. Kirby Center for Functional Brain Imaging, Baltimore, Maryland.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Edden
authors.affiliation: Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, Faculté de médecine, Université Laval, Quebec City, Quebec, Canada; Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.. Electronic address: shirley.fecteau@fmed.ulaval.ca.
authors.forename: Shirley
authors.initials: S
authors.lastname: Fecteau
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives; D003342:Corpus Striatum / Q000378:metabolism*; D004311:Double-Blind Method; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D064368:Healthy Volunteers; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D017397:Prefrontal Cortex / Q000378:metabolism* / Q000502:physiology; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C000179:N-acetylaspartate
keywords: Dorsolateral prefrontal cortex; Glx; Magnetic resonance spectroscopy; N-acetylaspartate; Striatum; Transcranial direct current stimulation