title: A Systematic Review and Meta-Analysis of the Effects of Transcranial Direct Current Stimulation (tDCS) Over the Dorsolateral Prefrontal Cortex in Healthy and Neuropsychiatric Samples: Influence of Stimulation Parameters.
abstract: Research into the effects of transcranial direct current stimulation of the dorsolateral prefrontal cortex on cognitive functioning is increasing rapidly. However, methodological heterogeneity in prefrontal tDCS research is also increasing, particularly in technical stimulation parameters that might influence tDCS effects.
  
  
  
  To systematically examine the influence of technical stimulation parameters on DLPFC-tDCS effects.
  
  
  
  We performed a systematic review and meta-analysis of tDCS studies targeting the DLPFC published from the first data available to February 2016. Only single-session, sham-controlled, within-subject studies reporting the effects of tDCS on cognition in healthy controls and neuropsychiatric patients were included.
  
  
  
  Evaluation of 61 studies showed that after single-session a-tDCS, but not c-tDCS, participants responded faster and more accurately on cognitive tasks. Sub-analyses specified that following a-tDCS, healthy subjects responded faster, while neuropsychiatric patients responded more accurately. Importantly, different stimulation parameters affected a-tDCS effects, but not c-tDCS effects, on accuracy in healthy samples vs.
  
  
  
  increased current density and density charge resulted in improved accuracy in healthy samples, most prominently in females; for neuropsychiatric patients, task performance during a-tDCS resulted in stronger increases in accuracy rates compared to task performance following a-tDCS.
  
  
  
  Healthy participants respond faster, but not more accurate on cognitive tasks after a-tDCS. However, increasing the current density and/or charge might be able to enhance response accuracy, particularly in females. In contrast, online task performance leads to greater increases in response accuracy than offline task performance in neuropsychiatric patients. Possible implications and practical recommendations are discussed.
authors.affiliation: Department of Psychiatry and Medical Psychology, Ghent University, University Hospital Ghent (UZ Ghent), Ghent, Belgium; Ghent University, Ghent Experimental Psychiatry (GHEP) lab, Ghent, Belgium. Electronic address: josefien.dedoncker@gmail.com.
authors.forename: Josefien
authors.initials: J
authors.lastname: Dedoncker
authors.affiliation: Department and Institute of Psychiatry, Service of Interdisciplinary Neuromodulation, Laboratory of Neurosciences (LIM-27), University of São Paulo, São Paulo, Brazil. Electronic address: brunoni@usp.br.
authors.forename: Andre R
authors.initials: AR
authors.lastname: Brunoni
authors.affiliation: Department of Psychiatry and Medical Psychology, Ghent University, University Hospital Ghent (UZ Ghent), Ghent, Belgium; Ghent University, Ghent Experimental Psychiatry (GHEP) lab, Ghent, Belgium; Department of Psychiatry, Vrije Universiteit Brussel (VUB), Faculty of Medicine and Pharmacy, University Hospital Brussel (UZ Brussel), Brussels, Belgium.
authors.forename: Chris
authors.initials: C
authors.lastname: Baeken
authors.affiliation: Department of Psychiatry and Medical Psychology, Ghent University, University Hospital Ghent (UZ Ghent), Ghent, Belgium; Ghent University, Ghent Experimental Psychiatry (GHEP) lab, Ghent, Belgium; Department of Psychiatry, Vrije Universiteit Brussel (VUB), Faculty of Medicine and Pharmacy, University Hospital Brussel (UZ Brussel), Brussels, Belgium; Department of Experimental Clinical and Health Psychology, Ghent University, Ghent, Belgium.
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Vanderhasselt
mesh_terms: D003071:Cognition / Q000502:physiology*; D006801:Humans; D017397:Prefrontal Cortex / Q000502:physiology* / Q000503:physiopathology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods / Q000706:statistics & numerical data*
keywords: Cognition; Dorsolateral prefrontal cortex; Meta-analysis; Noninvasive brain stimulation; Stimulation parameters; Transcranial direct current stimulation