tDCS possibly stimulates glial cells

Objective: Explore the possibility that transcranial direct current stimulation (tDCS) of the brain affects glial cells. Methods: Cable theory is used to estimate roughly transmembrane potential in neurons and glial cells. tDCS is additionally compared to neuronal stimulation techniques for which the mechanisms are well known. Results: Theoretical calculations indicated that tDCS can affect the glial transmembrane potential. The change is similar to what is physiologically observed in astrocytes during neuronal activation. In neurons, transmembrane potential changes are much weaker than the threshold for eliciting action potentials. Conclusions: Based on simplified cable theory, tDCS may affect glial cells' transmembrane potential and thereby the balance of neurotransmitters. No physiological evidence or proof is available, however. Significance: It is an exciting possibility that tDCS could manipulate glial cells because they are active participants in brain function, and have multiple essential roles in the human brain. This approach may change greatly the therapeutic potential of tDCS, and also affects the safety considerations. (C) 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.