title: Investigation of tDCS volume conduction effects in a highly realistic head model.
abstract: OBJECTIVE
  We investigate volume conduction effects in transcranial direct current stimulation (tDCS) and present a guideline for efficient and yet accurate volume conductor modeling in tDCS using our newly-developed finite element (FE) approach.
  
  
  METHODS
  We developed a new, accurate and fast isoparametric FE approach for high-resolution geometry-adapted hexahedral meshes and tissue anisotropy. To attain a deeper insight into tDCS, we performed computer simulations, starting with a homogenized three-compartment head model and extending this step by step to a six-compartment anisotropic model.
  
  
  RESULTS
  We are able to demonstrate important tDCS effects. First, we find channeling effects of the skin, the skull spongiosa and the cerebrospinal fluid compartments. Second, current vectors tend to be oriented towards the closest higher conducting region. Third, anisotropic WM conductivity causes current flow in directions more parallel to the WM fiber tracts. Fourth, the highest cortical current magnitudes are not only found close to the stimulation sites. Fifth, the median brain current density decreases with increasing distance from the electrodes.
  
  
  CONCLUSIONS
  Our results allow us to formulate a guideline for volume conductor modeling in tDCS. We recommend to accurately model the major tissues between the stimulating electrodes and the target areas, while for efficient yet accurate modeling, an exact representation of other tissues is less important. Because for the low-frequency regime in electrophysiology the quasi-static approach is justified, our results should also be valid for at least low-frequency (e.g., below 100 Hz) transcranial alternating current stimulation.
authors: Institute for Biomagnetism and Biosignal Analysis, University of Münster, Münster, Germany.
authors: S
authors: S
authors: Wagner
authors: S M
authors: SM
authors: Rampersad
authors: Ü
authors: Ü
authors: Aydin
authors: J
authors: J
authors: Vorwerk
authors: T F
authors: TF
authors: Oostendorp
authors: T
authors: T
authors: Neuling
authors: C S
authors: CS
authors: Herrmann
authors: D F
authors: DF
authors: Stegeman
authors: C H
authors: CH
authors: Wolters
mesh_terms: D016880:Anisotropy; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D020342:Finite Element Analysis; D006257:Head; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008953:Models, Anatomic; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology; D012886:Skull / Q000033:anatomy & histology