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. Author manuscript; available in PMC: 2015 Nov 1.
Published in final edited form as: Exp Brain Res. 2014 Sep 9;232(11):3379–3395. doi: 10.1007/s00221-014-4087-6

Figure 1.

Figure 1

Illustration of the three main principles of the action of tDCS on neural activity and motor behavior. In all panels, light and dark gray neurons are associated with slightly active and very active neurons. Sun and music notes are associated with visual and auditory stimulus, respectively. In panels A and C, vertical black traces represent action potentials over time. In panel B, black traces on the far right schematically illustrate the degree of muscle activity. In panel A, dark-gray neurons representing polarized neurons exhibit higher spontaneous (top) or evoked (bottom) discharge rate. In panel B, before polarization, neither a flash of light nor a tone elicited a movement when presented (top). After a period of polarization during which a flash of light was repeatedly presented, the light now elicited a motor response while the tone did not. In panel C, a flash of light did not elicit a response in a neuron of the visual cortex. After polarization of the visual cortex and 3Hz visual stimulation, a single flash of light elicited a 3Hz response in the neurons.