Can electric fields explain inter-individual variability in transcranial direct current stimulation of the motor cortex?

Ilkka Laakso, Marko Mikkonen, Soichiro Koyama, Akimasa Hirata, Satoshi Tanaka

Research output: Contribution to journalArticle

Abstract

The effects of transcranial direct current stimulation (tDCS) on motor cortical excitability are highly variable between individuals. Inter-individual differences in the electric fields generated in the brain by tDCS might play a role in the variability. Here, we explored whether these fields are related to excitability changes following anodal tDCS of the primary motor cortex (M1). Motor evoked potentials (MEPs) were measured in 28 healthy subjects before and after 20 min sham or 1 mA anodal tDCS of right M1 in a double-blind crossover design. The electric fields were individually modelled based on magnetic resonance images. Statistical analysis indicated that the variability in the MEPs could be partly explained by the electric fields, subjects with the weakest and strongest fields tending to produce opposite changes in excitability. To explain the findings, we hypothesized that the likely locus of action was in the hand area of M1, and the effective electric field component was that in the direction normal to the cortical surface. Our results demonstrate that a large part of inter-individual variability in tDCS may be due to differences in the electric fields. If this is the case, electric field dosimetry could be useful for controlling the neuroplastic effects of tDCS.

Original languageEnglish
Article number626
JournalScientific Reports
Volume9
Issue number1
DOIs
Publication statusPublished - 01-12-2019

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Motor Cortex
Motor Evoked Potentials
Individuality
Cross-Over Studies
Transcranial Direct Current Stimulation
Healthy Volunteers
Magnetic Resonance Spectroscopy
Hand
Brain

All Science Journal Classification (ASJC) codes

  • General

Cite this

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Can electric fields explain inter-individual variability in transcranial direct current stimulation of the motor cortex? / Laakso, Ilkka; Mikkonen, Marko; Koyama, Soichiro; Hirata, Akimasa; Tanaka, Satoshi.

In: Scientific Reports, Vol. 9, No. 1, 626, 01.12.2019.

Research output: Contribution to journalArticle

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