Elsevier

Brain Stimulation

Volume 12, Issue 6, November–December 2019, Pages 1464-1474
Brain Stimulation

After-effects of 10 Hz tACS over the prefrontal cortex on phonological word decisions

https://doi.org/10.1016/j.brs.2019.06.021Get rights and content
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Highlights

  • 10 Hz tACS significantly facilitates phonological word decisions.

  • 10 Hz tACS significantly increases task-related theta power.

  • Increased theta power is positively correlated with the behavioral facilitation.

  • The inclusion of a control frequency is important to test for frequency specificity.

Abstract

Introduction

Previous work in the language domain has shown that 10 Hz rTMS of the left or right posterior inferior frontal gyrus (pIFG) in the prefrontal cortex impaired phonological decision-making, arguing for a causal contribution of the bilateral pIFG to phonological processing. However, the neurophysiological correlates of these effects are unclear. The present study addressed the question whether neural activity in the prefrontal cortex could be modulated by 10 Hz tACS and how this would affect phonological decisions.

Methods

In three sessions, 24 healthy participants received tACS at 10 Hz or 16.18 Hz (control frequency) or sham stimulation over the bilateral prefrontal cortex before task processing. Resting state EEG was recorded before and after tACS. We also recorded EEG during task processing.

Results

Relative to sham stimulation, 10 Hz tACS significantly facilitated phonological response speed. This effect was task-specific as tACS did not affect a simple control task. Moreover, 10 Hz tACS significantly increased theta power during phonological decisions. The individual increase in theta power was positively correlated with the behavioral facilitation after 10 Hz tACS.

Conclusion

Our results show a facilitation of phonological decisions after 10 Hz tACS over the bilateral prefrontal cortex. This might indicate that 10 Hz tACS increased task-related activity in the stimulated area to a level that was optimal for phonological performance. The significant correlation with the individual increase in theta power suggests that the behavioral facilitation might be related to increased theta power during language processing.

Keywords

Alpha
Prefrontal cortex
Plasticity
Language
Non-invasive brain stimulation

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