title: On the Use of the Terms Anodal and Cathodal in High-Definition Transcranial Direct Current Stimulation: A Technical Note.
abstract: BACKGROUND
  The terms "anodal" and "cathodal" are widely used to describe transcranial direct current stimulation (tDCS) of opposing polarities, often interpreted as excitatory and inhibitory, respectively. However, high-definition tDCS allows for complex electrode configurations that may not be characterized accurately as "anodal" and "cathodal."
  
  
  METHODS
  To illustrate challenges to data interpretation that may result from unclarity about the neuromodulatory effects of different field orientations, we present two high-definition tDCS experiments in the language domain, with different electrode configurations. We also present the modeled electric fields for a traditional tDCS setup, showing how brain stimulation may far exceed target regions.
  
  
  CONCLUSIONS
  More research is warranted on the hypothesized inhibitory or excitatory effects of different electrode configurations. Moreover, conventional bicephalic 1 × 1 configurations using sponges or HD electrodes may not be accurately described by the terms "anodal" and "cathodal" either, as these terms only pertain to the desired effects over an area of interest, but not any other areas affected. Therefore, design and interpretation of (HD-)tDCS and conventional tDCS research studies should not be constrained by the anodal/cathodal dichotomy.
authors.affiliation: Department of Communication Sciences and Disorders, University of South Carolina, Columbia, SC, USA.
authors.forename: Emily O
authors.identifier: http://orcid.org/0000-0003-1490-9541
authors.initials: EO
authors.lastname: Garnett
authors.affiliation: Department of Communication Sciences and Disorders, University of South Carolina, Columbia, SC, USA.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Malyutina
authors.affiliation: Soterix Medical, Inc., New York, NY, USA.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Datta
authors.affiliation: Department of Communication Sciences and Disorders, University of South Carolina, Columbia, SC, USA.
authors.forename: Dirk-Bart
authors.initials: DB
authors.lastname: den Ouden
mesh_terms: D001931:Brain Mapping; D065711:Broca Area / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D004566:Electrodes; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D007839:Functional Laterality; D006801:Humans; D008959:Models, Neurological; D065908:Transcranial Direct Current Stimulation / Q000145:classification / Q000379:methods*
keywords: Anodal; brain stimulation; cathodal; polarity; tDCS