P207 Affecting declarative long-term memory with transcranial alternating current stimulation (tACS)

• Published in: Clinical neurophysiology Vol. 128; no. 3; p. e114
• Main Authors: de Lara, G, Alekseichuk, I, Turi, Z, Antal, A, Paulus, W
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2017
• Subjects: Neurology
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2016.10.324

Introduction and objective Previous studies imply that tACS can entrain the ongoing physiological neuronal oscillations depending on the targeted function and the parameters (frequency, intensity and phase) of the stimulation. The aim of the present study was to clarify if tACScould influence the performance of healthy subjects on a verbal paired-associate learning paradigm. Methods For that, we conducted three different crossover, randomized, single-blind, placebo-controlled studies, using a battery-driven Starstim stimulator system (Neuroelectrics, Barcelona, Spain). In the first study ( n = 6), we applied 100 Hz tACS with 1.5 mA (active electrode T7, return Fpz and T8); in the second one ( n = 6), 1.0 mA, 6 Hz (3 s) followed by 80 Hz (5 s) tACS during ISI and Stimulus presentation using the same electrodes configuration; in the third one ( n = 15), we combined a temporal- and pre-frontal stimulation using 7 electrodes. Here the stimulation intensity was 1 mA at 6 Hz (temporal) and 80 Hz (pre-frontal) combined stimulation. For all the studies, we used 8 cm 2 round rubber electrodes inside a saline-soaked sponge pocket, applying 10 min stimulation during the word-pairs learning phase. After the learning phase, the subjects had a 10 min pause, followed by a test phase with a cued recall. The subjects returned after 24 h for a second cued-recall test. All subjects receivedactive and sham tACS in a counterbalanced, randomized-manner. Results In the first two studies, no significant difference were found in the accuracy performance between days across conditions, as well as between days within conditions; in the third study, we found no significant difference between days across conditions, but significant difference between days in the active ( t = 2.98, p = 0.010) and sham ( t = 2.52, p = 0.024) stimulation. Conclusion The stimulation parameters tested could not influence the memory performance assessed by this memory task with the present number of subjects in the first two studies. Further variations of waveforms, intensity and stimulation parameters should be tested with the same task in order to probe the possible influence of tACS on episodic long-term memory. The final results will be presented in the conference.