title: On the possible role of stimulation duration for after-effects of transcranial alternating current stimulation.
abstract: Transcranial alternating current stimulation is a novel method that allows application of sinusoidal currents to modulate brain oscillations and cognitive processes. Studies in humans have demonstrated transcranial alternating current stimulation (tACS) after-effects following stimulation durations in the range of minutes. However, such after-effects are absent in animal studies using much shorter stimulation protocols in the range of seconds. Thus, stimulation duration might be a critical parameter for after-effects to occur. To test this hypothesis, we repeated a recent human tACS experiment with a short duration. We applied alpha tACS intermittently for 1 s duration while keeping other parameters identical. The results demonstrate that this very short intermittent protocol did not produce after-effects on amplitude or phase of the electroencephalogram. Since synaptic plasticity has been suggested as a possible mechanism for after-effects, our results indicate that a stimulation duration of 1 s is too short to induce synaptic plasticity. Future studies in animals are required that use extended stimulation durations to reveal the neuronal underpinnings. A better understanding of the mechanisms of tACS after-effects is crucial for potential clinical applications.
authors: Experimental Psychology Laboratory, Department of Psychology, Center for Excellence 'Hearing4all', European Medical School, Carl von Ossietzky University Oldenburg, Germany ; Research Center Neurosensory Science, University of Oldenburg Oldenburg, Germany.
authors: Daniel
authors: D
authors: Strüber
authors: Department of Epidemiological Methods and Etiologic Research, Leibniz Institute for Prevention Research and Epidemiology - BIPS Bremen, Germany.
authors: Stefan
authors: S
authors: Rach
authors: Center for Mind/Brain Sciences (CIMeC), University of Trento Rovereto, Italy.
authors: Toralf
authors: T
authors: Neuling
authors: Experimental Psychology Laboratory, Department of Psychology, Center for Excellence 'Hearing4all', European Medical School, Carl von Ossietzky University Oldenburg, Germany ; Research Center Neurosensory Science, University of Oldenburg Oldenburg, Germany.
authors: Christoph S
authors: CS
authors: Herrmann
keywords: EEG; NIBS; electroencephalography; entrainment; non-invasive brain stimulation; synaptic plasticity; tACS