Individual differences in TMS sensitivity influence the efficacy of tDCS in facilitating sensorimotor adaptation

L Labruna; A Stark-Inbar; A Breska; M Dabit; B Vanderschelden; M A Nitsche; R B Ivry

doi:10.1016/j.brs.2019.03.008

Individual differences in TMS sensitivity influence the efficacy of tDCS in facilitating sensorimotor adaptation

Brain Stimul. 2019 Jul-Aug;12(4):992-1000. doi: 10.1016/j.brs.2019.03.008. Epub 2019 Mar 13.

Authors

L Labruna¹, A Stark-Inbar², A Breska², M Dabit³, B Vanderschelden³, M A Nitsche⁴, R B Ivry²

Affiliations

¹ Department of Psychology, University of California, 94704, Berkeley, CA, USA; Helen Wills Neuroscience Institute, University of California, 94704, Berkeley, CA, USA. Electronic address: lulabrun@gmail.com.
² Department of Psychology, University of California, 94704, Berkeley, CA, USA; Helen Wills Neuroscience Institute, University of California, 94704, Berkeley, CA, USA.
³ Department of Psychology, University of California, 94704, Berkeley, CA, USA.
⁴ Leibniz Research Center for Working Environment and Human Factors, 44139, Dortmund, Germany.

Abstract

Background: Transcranial direct current stimulation (tDCS) can enhance cognitive function in healthy individuals, with promising applications as a therapeutic intervention. Despite this potential, variability in the efficacy of tDCS has been a considerable concern.

Objective: /Hypothesis: Given that tDCS is always applied at a set intensity, we examined whether individual differences in sensitivity to brain stimulation might be one variable that modulates the efficacy of tDCS in a motor learning task.

Methods: In the first part of the experiment, single-pulse transcranial magnetic stimulation (TMS) over primary motor cortex (M1) was used to determine each participant's resting motor threshold (rMT). This measure was used as a proxy of individual sensitivity to brain stimulation. In an experimental group of 28 participants, 2 mA tDCS was then applied during a motor learning task with the anodal electrode positioned over left M1. Another 14 participants received sham stimulation.

Results: M1-Anodal tDCS facilitated learning relative to participants who received sham stimulation. Of primary interest was a within-group analysis of the experimental group, showing that the rate of learning was positively correlated with rMT: Participants who were more sensitive to brain stimulation as operationalized by our TMS proxy (low rMT), showed faster adaptation.

Conclusions: Methodologically, the results indicate that TMS sensitivity can predict tDCS efficacy in a behavioral task, providing insight into one source of variability that may contribute to replication problems with tDCS. Theoretically, the results provide further evidence of a role of sensorimotor cortex in adaptation, with the boost from tDCS observed during acquisition.

Keywords: Individual differences; Sensorimotor learning; TMS; rMT; tDCS.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Adaptation, Physiological / physiology*
Adult
Cognition / physiology
Female
Humans
Individuality*
Learning / physiology
Male
Motor Cortex / physiology
Psychomotor Performance / physiology
Rest / physiology
Sensorimotor Cortex / physiology*
Transcranial Direct Current Stimulation / methods*
Transcranial Magnetic Stimulation / methods*

Abstract

Publication types

MeSH terms

Grants and funding