Effects of transcranial Direct Current Stimulation (tDCS) on cortical activity: A computational modeling study

• Published in: Brain stimulation 2013, Vol.6 (1), p.25-39
• Main Authors: Molaee-Ardekani, Behnam, Márquez-Ruiz, Javier, Merlet, Isabelle, Leal-Campanario, Rocio, Gruart, Agnès, Sánchez-Campusano, Raudel, Birot, Gwenael, Ruffini, Giulio, Delgado-García, José-Maria, Wendling, Fabrice
• Format: Article
• Language: English
• Subjects: Animals; Bioengineering; Computational model; Computer Science; Computer Simulation; Engineering Sciences; Evoked potentials; Evoked Potentials - physiology; Interneurons; Life Sciences; Male; Modeling and Simulation; Neurology; Neurons - physiology; Neurons and Cognition; Pyramidal cells; Rabbit; Rabbits; Signal and Image processing; Somatosensory cortex; Somatosensory Cortex - physiology; tDCS; Transcranial Magnetic Stimulation
• ISSN: 1935-861X; 1876-4754
• DOI: 10.1016/j.brs.2011.12.006

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.