Transcranial Alternating Current Stimulation (tACS) Enhances Mental Rotation Performance during and after Stimulation

Abstract

Transcranial alternating current stimulation (tACS) has been repeatedly demonstrated to modulate endogenous brain oscillations in a frequency specific manner. Thus, it is a promising tool to uncover causal relationships between brain oscillations and behavior or perception. While tACS has been shown to elicit a physiological aftereffect for up to 70 min, it remains unclear whether the effect can still be elicited if subjects perform a complex task interacting with the stimulated frequency band. In addition, it has not yet been investigated whether the aftereffect is behaviorally relevant. In the current experiment, participants performed a Shepard-like mental rotation task for 80 min. After 10 min of baseline measurement, participants received either 20 min of tACS at their individual alpha frequency (IAF) or sham stimulation (30 s tACS in the beginning of the stimulation period). Afterwards another 50 min of post-stimulation EEG were recorded. Task performance and EEG were acquired during the whole experiment. While there were no effects of tACS on reaction times or event-related-potentials (ERPs), results revealed an increase in mental rotation performance in the stimulation group as compared to sham both during and after stimulation. This was accompanied by increased ongoing alpha power and coherence as well as event-related-desynchronization (ERD) in the alpha band in the stimulation group. The current study demonstrates a behavioral and physiological aftereffect of tACS in parallel. This indicates that it is possible to elicit aftereffects of tACS during tasks interacting with the alpha band. Therefore, the tACS aftereffect is suitable to achieve an experimental manipulation.

Occipital tACS bursts during a visual task impact ongoing neural oscillation power, coherence and LZW complexity

“…While concurrent tACS 10 enhanced α-oscillations (8-13Hz), as previously reported in literature [26,27], in our study, tACS 10 also enhanced and entrained γ-oscillations. In addition, the concurrent α-power increase due to tACS 10 in occipital electrodes was also observed in post and postII-EEEG intervals (as compared to control and tACS 70 , p<0.001), replicating previous results reported in both bursting [2,46] and continuous α-tACS protocols [27,33,49].…”

Transcranial Alternating Current Stimulation (tACS) Entrains Alpha Oscillations by Preferential Phase Synchronization of Fast-Spiking Cortical Neurons to Stimulation Waveform

“…Targeted modulation of cortical oscillations and associated long-lasting cognitive and behavioral functions by tACS have been demonstrated in a number of human studies (Antal et al, 2008;Boyle and Frohlich, 2013;Helfrich et al, 2014;Herrmann et al, 2016a;Kasten and Herrmann, 2017;Neuling et al, 2013;Polanía et al, 2012;Vossen et al, 2015;Zaehle et al, 2010). In addition we have recently reported several clinical trials of tACS for the treatment of schizophrenia (Ahn et al, 2019), chronic pain (Ahn et al, 2018) and major depressive disorder .…”

Signal-space projection suppresses the tACS artifact in EEG recordings

“…The mental rotation task (Shepard and Metzler 1971) is known to modulate ongoing alpha activity; while the stimuli are presented, occipital alpha oscillations desynchronize (Michel et al 1994; Klimesch 1999). This event-related desynchronization (ERD; Pfurtscheller and Lopes da Silva 1999) has been used in studies to estimate the performance of methods for tACS artifact correction in MEG (Kasten and Herrmann 2017). We thus employed a mental rotation task highly similar to Kasten and Herrmann (2017) to test the performance of the SSP-correction.…”

“…This event-related desynchronization (ERD; Pfurtscheller and Lopes da Silva 1999) has been used in studies to estimate the performance of methods for tACS artifact correction in MEG (Kasten and Herrmann 2017). We thus employed a mental rotation task highly similar to Kasten and Herrmann (2017) to test the performance of the SSP-correction.…”

“…The goal of transcranial alternating current stimulation (tACS) is often the modulation of oscillatory brain activity and the concurrent demonstration of behavioral consequences of the intervention (Herrmann et al, 2013). Thus far, most studies combining tACS with electroencephalography (EEG) have demonstrated effects on oscillatory brain activity only by comparing the EEG before and after tACS (Zaehle et al 2010; Vossen et al 2015; Kasten and Herrmann 2017), because EEG data recorded during stimulation is contaminated by the huge tACS-generated artifact. As a workaround, behavioral effects found during application of tACS have been interpreted as a proxy of changes of brain oscillations (Polanía et al 2012; Neuling et al 2012; Cecere et al 2015).…”