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Front. Neurosci. | doi: 10.3389/fnins.2019.00161

Motor task-dependent dissociated effects of transcranial random noise stimulation in a finger-tapping task versus a go/no-go task on corticospinal excitability and task performance

 Andreas Jooss1*,  Linus Haberbosch1,  Arvid Köhn1, Maria Rönnefarth1,  Rouven Bathe-Peters1,  Leonard Kozarzewski1, Robert Fleischmann1, 2, Michael Scholz3,  Sein Schmidt1 and  Stephan A. Brandt1
  • 1Department of Neurology, Charité Medical University of Berlin, Germany
  • 2Department of Neurology, Universitätsmedizin Greifswald, Germany
  • 3Neural Information Processing Group, Technische Universität Berlin, Germany

Background and Objective:
Transcranial random noise stimulation (tRNS) is an emerging non-invasive brain stimulation technique to modulate brain function, with previous studies highlighting its considerable benefits in therapeutic stimulation of the motor system. However, high variability of results and bidirectional task-dependent effects limit more widespread clinical application. Task dependency largely results from a lack of understanding of the interaction between externally applied tRNS and the endogenous state of neural activity during stimulation. Hence, the aim of this study was to investigate the task dependency of tRNS-induced neuromodulation in the motor system using a finger-tapping task (FT) versus a go/no-go task (GNG). We hypothesized that the tasks would modulate tRNS’ effects on corticospinal excitability (CSE) and task performance in opposite directions.

Methods:
30 healthy subjects received 10 minutes of tRNS of the dominant primary motor cortex in a double-blind, sham-controlled study design. tRNS was applied during two well-established tasks tied to diverging brain states. Accordingly, participants were randomly assigned to two equally-sized groups: The first group performed a simple motor training task (finger-tapping task), known primarily to increase CSE, while the second group performed an inhibitory control task (go/no-go task) associated with inhibition of CSE. To establish task-dependent effects of tRNS, CSE was evaluated prior to- and after stimulation with navigated transcranial magnetic stimulation.

Results:
In an ‘activating’ motor task, tRNS during FT significantly facilitated CSE. FT task performance improvements, shown by training-related reductions in intertap intervals (ITIs) and increased number of finger taps, were similar for both tRNS and sham stimulation. In an ‘inhibitory’ motor task, tRNS during GNG left CSE unchanged while inhibitory control was enhanced as shown by slowed reaction times (RTs) and enhanced task accuracy during and after stimulation.

Conclusion:
We provide evidence that tRNS-induced neuromodulatory effects are task-dependent and that resulting enhancements are specific to the underlying task-dependent brain state. While mechanisms underlying this effect require further investigation, these findings highlight the potential of tRNS in enhancing task-dependent brain states to modulate human behavior.

Keywords: random noise stimulation, transcranial electrical stimulation (TES), task dependency, Finger-tapping task, go/no-go task, corticospinal excitability, neuroplasticity

Received: 30 Oct 2018; Accepted: 12 Feb 2019.

Edited by:

Mikhail Lebedev, Duke University, United States

Reviewed by:

Raffaella Ricci, University of Turin, Italy
Makii Muthalib, Université de Montpellier, France
Takashi Hanakawa, National Center of Neurology and Psychiatry (Japan), Japan  

Copyright: © 2019 Jooss, Haberbosch, Köhn, Rönnefarth, Bathe-Peters, Kozarzewski, Fleischmann, Scholz, Schmidt and Brandt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Andreas Jooss, Charité Medical University of Berlin, Department of Neurology, Berlin, Germany, andreas.jooss@charite.de