Modulating verbal working memory with fronto‐parietal transcranial electric stimulation at theta frequency: Does it work?

Abstract

Oscillatory theta activity in a fronto‐parietal network has been associated with working memory (WM) processes and may be directly related to WM performance. In their seminal study, Polanía et al. (2012) (de‐)coupled a fronto‐parietal theta‐network by applying transcranial alternating current stimulation (tACS), and showed that anti‐phase tACS led to slower and in‐phase tACS to faster response times in a verbal WM task compared to placebo stimulation. In the literature, this ‘synchronization‐desynchronization’ effect has only been partly replicated, and electric field modelling suggests that it might not be the fronto‐parietal network that is primarily stimulated during in‐phase tACS with a shared return electrode. This provides one possible reason for inconsistency in the literature. In this study, we aimed to reproduce the findings reported by Polanía et al. (2012). We also aimed to investigate whether in‐phase theta tACS with multiple close‐by return electrodes for focal stimulation of the frontal and the parietal cortex will have at least as much of a facilitatory effect as the in‐phase stimulation as indicated by Polania et al. (2012). In a single‐trial distributional analysis, we explored whether mean, variation and right‐skewness of the response time distribution are affected. Against our hypothesis, we found no ‘synchronization‐desynchronization’ effect by fronto‐parietal theta tACS on response times using the same delayed letter discrimination task and stimulation parameters in two experiments, both between‐subjects and within‐subjects. However, we could show that in a more demanding 3‐back task, fronto‐parietal in‐phase and in‐phase focal theta tACS substantially improved task performance compared to placebo stimulation.

The Effects of Electroencephalogram Feature-Based Transcranial Alternating Current Stimulation on Working Memory and Electrophysiology

“…Overall, accordance to with several previous studies ( Vosskuhl et al, 2015 ; Pahor and Jaušovec, 2018 ; Abellaneda-Pérez et al, 2020 ; Biel et al, 2021 ), our findings indicated that theta band activity was strongly associated with verbal working memory, and that theta tACS improved verbal working memory performance. Moreover, our study extends these findings, as we investigating the EEG characteristics correspond to the improvements in working memory performance in both HP and LP groups.…”

“…Compared with sham-tACS and transcranial direct current stimulation (tDCS), 40 Hz tACS resulted in increased performance in terms of d prime (an accuracy discriminability index). Biel et al (2021) also recently reported that frontoparietal in-phase and in-phase focal theta tACS substantially improved verbal three-back task performance when compared with placebo stimulation.…”

The effects of electroencephalogram feature-based transcranial alternating current stimulation on working memory and electrophysiology

“…Overall, accordance to with several previous studies (Biel et al, 2021;Kilian et al, 2020;Pahor & Jaušovec, 2018;Vosskuhl et al, 2015), our findings indicated that theta band activity was strongly associated with verbal working memory, and that theta tACS improved verbal working memory performance. Moreover, our study extends these findings, as we investigating the EEG characteristics correspond to the improvements in working memory performance in both HP and LP groups.…”

Is frontoparietal electroencephalogram activity related to the level of functional disability in patients emerging from a minimally conscious state? A preliminary study

“… Cavaliere et al (2018) also observed that patients have predominant posterior theta activity. Theta activity is generally considered to reflect fundamental cognitive functions ( Biel et al, 2022 ; Cowley et al, 2022 ). An association between increased theta connectivity and cognitive dysfunction has been reported in some diseases such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia ( Andreou et al, 2015 ; Iyer et al, 2020 ; Yan et al, 2021 ).…”