Continuous theta burst stimulation over the left dorsolateral prefrontal cortex decreases medium load working memory performance in healthy humans.

Nathalie Schicktanz,Dominique J.-F De Quervain,Thomas Nyffeler,Klara Spalek,Bianca Auschra,Kyrill Schwegler,Matthias Fastenrath,Andreas Papassotiropoulos,Annette Milnik,Ramesh Balasubramaniam

doi:10.1371/journal.pone.0120640

Nathalie Schicktanz, Dominique J.-F De Quervain + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0120640

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Abstract

The dorsolateral prefrontal cortex (DLPFC) plays a key role in working memory. Evidence indicates that transcranial magnetic stimulation (TMS) over the DLPFC can interfere with working memory performance. Here we investigated for how long continuous theta-burst stimulation (cTBS) over the DLPFC decreases working memory performance and whether the effect of cTBS on performance depends on working memory load. Forty healthy young subjects received either cTBS over the left DLPFC or sham stimulation before performing a 2-, and 3-back working memory letter task. An additional 0-back condition served as a non-memory-related control, measuring general attention. cTBS over the left DLPFC significantly impaired 2-back working memory performance for about 15 min, whereas 3-back and 0-back performances were not significantly affected. Our results indicate that the effect of left DLPFC cTBS on working memory performance lasts for roughly 15 min and depends on working memory load.

Highlights

Working memory (WM) is a process allowing temporary storage and manipulation of information [1]
The dorsolateral prefrontal cortex (DLPFC) target region for transcranial magnetic stimulation (TMS) was identified based on the results of a 0- and 2-back functional magnetic resonance imaging (fMRI) study [18]: We identified the peaks of a large activation cluster in the DLPFC: Montreal Neurological Institute space (MNI) [-44, 25, 28], T = 50.13, family-wise error corrected for the whole brain p < 0.05
No significant differences in ACC before TMS were found between stimulation groups when each load was analyzed separately, and no significant differences in the last n-back block before TMS

Summary

Introduction

Working memory (WM) is a process allowing temporary storage and manipulation of information [1]. While online studies can provide information regarding to when a brain region is active within a process, the advantage of an offline approach is that nonspecific disruption of performance due to concurrent discomfort, stimulation noise and muscle twitches is avoided [5]. It is crucial for offline TMS studies or combined offline TMS-fMRI studies to have an estimation of the duration of the aftereffect for a specific phenotype, as this period should ideally last throughout the subsequent task [5]

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