10 Minutes Frontal 40 Hz tACS—Effects on Working Memory Tested by Luck-Vogel Task

Abstract

Working memory is a cognitive process that involves short-term active maintenance, flexible updating, and processing of goal- or task-relevant information. All frequency bands are involved in working memory. The activities of the theta and gamma frequency bands in the frontoparietal network are highly involved in working memory processes; theta oscillations play a role in the temporal organization of working memory items, and gamma oscillations influence the maintenance of information in working memory. Transcranial alternating current stimulation (tACS) results in frequency-specific modulation of endogenous oscillations and has shown promising results in cognitive neuroscience. The electrophysiological and behavioral changes induced by the modulation of endogenous gamma frequency in the prefrontal cortex using tACS have not been extensively studied in the context of working memory. Therefore, we aimed to investigate the effects of frontal gamma-tACS on working memory outcomes. We hypothesized that a 10-min gamma tACS administered over the frontal cortex would significantly improve working memory outcomes. Young healthy participants performed Luck–Vogel cognitive behavioral tasks with simultaneous pre- and post-intervention EEG recording (Sham versus 40 Hz tACS). Data from forty-one participants: sham (15 participants) and tACS (26 participants), were used for the statistical and behavioral analysis. The relative changes in behavioral outcomes and EEG due to the intervention were analyzed. The results show that tACS caused an increase in the power spectral density in the high beta and low gamma EEG bands and a decrease in left-right coherence. On the other hand, tACS had no significant effect on success rates and response times. CONCLUSION: 10 min of frontal 40 Hz tACS was not sufficient to produce detectable behavioral effects on working memory, whereas electrophysiological changes were evident. The limitations of the current stimulation protocol and future directions are discussed in detail in the following sections.

No effects of the theta-frequency transcranial electrical stimulation for recall, attention control, and relation integration in working memory

“…As WM mechanisms are frequently associated with patterns of neural oscillations (Axmacher et al, 2010 ; Palva et al, 2010 ; Lisman and Jensen, 2013 ; Roux and Uhlhaas, 2014 ; Sauseng et al, 2019 ), the tACS technique has been especially popular in the ongoing attempts to enhance WM. A number of tACS studies (e.g., Hoy et al, 2015 ; Alekseichuk et al, 2016 ; Feurra et al, 2016 ; Santarnecchi et al, 2016 ; Tseng et al, 2016 ; Möller et al, 2017 ; Borghini et al, 2018 ; Pahor and Jaušovec, 2018 ; Misselhorn et al, 2020 ; Thompson et al, 2021 ; Kim et al, 2022 ; Palm et al, 2022 ; Park et al, 2022 ; Zeng et al, 2022 ; Grover et al, 2023 ; Kvašnák et al, 2023 ) targeted the fast rhythms, such as the gamma (>30 Hz) and, more rarely, the beta band (14 Hz−30 Hz), following the fact that coordinated fast oscillations were linked with active maintenance of particular objects in WM (e.g., Lisman and Jensen, 2013 ; Leszczyński et al, 2015 ). Several such studies reported positive effects of stimulation on WM (e.g., Hoy et al, 2015 ; Alekseichuk et al, 2016 ).…”

Effects of θ High Definition-Transcranial Alternating Current Stimulation in the Anterior Cingulate Cortex on the Dominance of Attention Focus in Standing Postural Control

“…Researchers also found tACS in the theta frequency band to the midfrontal area increased immersion in virtual reality [ 14 ] and improved post-error behavioral coordination [ 15 , 16 ]. It has also been shown to improve working memory [ 17 , 18 ], memory capacity [ 19 ], and fluid intelligence [ 20 ]. More recently, high-definition tACS (HD-tACS) has been used to improve the effect of tACS.…”