EJN Best Publication Award lecture

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

When

Thursday, 19 June

14:15-15:00

Where

University of Oslo,
campus Blindern

Room TBA

Speaker: Anna Lena Biel, University of Münster, Germany

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), where anti-phase tACS led to slower and in-phase tACS to faster response times in a verbal WM task compared to placebo stimulation. This ‘synchronization-desynchronization’ effect has only been partly replicated, and electrophysiological modelling suggests that in-phase tACS with a shared return electrode might not primarily stimulate the fronto-parietal network. This provides one possible reason for inconsistency in the literature. In this study, we aimed to reproduce the findings by Polanía et al. (2012) and to investigate whether in-phase theta tACS with multiple close-by return electrodes for focal stimulation of frontal and parietal cortices has at least as much of an effect. 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 letter discrimination task and stimulation parameters in two experiments, 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. This study also highlights the importance of reproduction attempts incorporating new methodological developments and that studies where initial results cannot be directly replicated might nevertheless describe effects that can be reproduced with optimized experimental approaches.