title: Effects of transcranial Direct Current Stimulation (tDCS) on cortical activity: a computational modeling study.
abstract: Although it is well-admitted that transcranial Direct Current Stimulation (tDCS) allows for interacting with brain endogenous rhythms, the exact mechanisms by which externally-applied fields modulate the activity of neurons remain elusive. In this study a novel computational model (a neural mass model including subpopulations of pyramidal cells and inhibitory interneurons mediating synaptic currents with either slow or fast kinetics) of the cerebral cortex was elaborated to investigate the local effects of tDCS on neuronal populations based on an in-vivo experimental study. Model parameters were adjusted to reproduce evoked potentials (EPs) recorded from the somatosensory cortex of the rabbit in response to air-puffs applied on the whiskers. EPs were simulated under control condition (no tDCS) as well as under anodal and cathodal tDCS fields. Results first revealed that a feed-forward inhibition mechanism must be included in the model for accurate simulation of actual EPs (peaks and latencies). Interestingly, results revealed that externally-applied fields are also likely to affect interneurons. Indeed, when interneurons get polarized then the characteristics of simulated EPs become closer to those of real EPs. In particular, under anodal tDCS condition, more realistic EPs could be obtained when pyramidal cells were depolarized and, simultaneously, slow (resp. fast) interneurons became de- (resp. hyper-) polarized. Geometrical characteristics of interneurons might provide some explanations for this effect.
authors.affiliation: INSERM, U642, Rennes, F-35000, France.
authors.forename: Behnam
authors.initials: B
authors.lastname: Molaee-Ardekani
authors.forename: Javier
authors.initials: J
authors.lastname: Márquez-Ruiz
authors.forename: Isabelle
authors.initials: I
authors.lastname: Merlet
authors.forename: Rocio
authors.initials: R
authors.lastname: Leal-Campanario
authors.forename: Agnès
authors.initials: A
authors.lastname: Gruart
authors.forename: Raudel
authors.initials: R
authors.lastname: Sánchez-Campusano
authors.forename: Gwenael
authors.initials: G
authors.lastname: Birot
authors.forename: Giulio
authors.initials: G
authors.lastname: Ruffini
authors.forename: José-Maria
authors.initials: JM
authors.lastname: Delgado-García
authors.forename: Fabrice
authors.initials: F
authors.lastname: Wendling
mesh_terms: D000818:Animals; D003198:Computer Simulation; D005071:Evoked Potentials / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D011817:Rabbits; D013003:Somatosensory Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation