Transcranial Direct Current Stimulation over Bi-Lateral motor Cortices shows No Effect on Simple Visual Motor Reaction Time
-
1
University of Melbourne, Melbourne School of Psychological Sciences, Australia
Background
During the past fifteen years, several lines of evidence have emerged that suggest transcranial direct current stimulation (tDCS) of the motor cortex can modulate corticospinal excitability as measured using varied evoked muscular potential paradigms. Unfortunately, evidence as to whether or not these physiological changes lead to commensurate behavioral effects is heavily conflicted. To address this, we systematically examined the effects of tDCS over bi-lateral motor cortices on a well-elucidate neurobehavioral system: short duration simple visual motor reaction time (RT).
Methods
Fifty healthy participants were randomly divided into five groups: 2 mA anodal, 2 mA cathodal, 1 mA anodal, 1 mA cathodal, and sham tDCS (20 minutes stimulation time) Starting ~5 minutes prior to stimulation and running continuously for ~30 minutes, participants were presented with an easily perceivable gabor patch centered on a computer monitor and asked to press a response button as quickly as possible at onset of stimuli (stimuli number: 100 pre-, 400 during-, and 100-post stimulation - interstimulus interval: 1-3 seconds). Data was collected continuously, however, for the purpose of analysis the RTs were binned into 6 groups of 100 to assess any effects of repeated testing over time. Medians were then determined for each bin of 100 RTs, normalized to pre-stimulation levels, and compared using a two-way ANOVA (group x time).
Results
Although each group displayed significantly slower RTs with repeated testing (F(5, 270)=6.193, p=0.001: suggesting general fatigue over time), there were no significant effects of stimulation type on RT times (F(4, 270)=0.239, p=0.916) nor significant interaction effects (F(20, 270)=0.187, p=0.999).
Discussion
Our results suggest that that bi-lateral motor tDCS, regardless of stimulation strength, does not modulate short duration simple visual motor reaction time. This finding raises interesting questions with regards to the utility and behavioral translatability of the often reported physiological modulations generated by tDCS. In addition, our finding calls into question the simplistic mechanisms by which several researchers have argued motor behavioral modulation by tDCS may be generated. However, our findings do not rule out the possibility that other tDCS parameters (such as varied electrode montages or stimulation durations) may have an effect on simple visual motor reaction time.
Keywords:
transcranial direct current stimulation (tDCS),
Reaction Time,
Motor Cortex,
noninvasive brain stimulation,
cortical excitability
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Poster
Topic:
Other
Citation:
Horvath
JC,
Carter
O and
Forte
JD
(2013). Transcranial Direct Current Stimulation over Bi-Lateral motor Cortices shows No Effect on Simple Visual Motor Reaction Time.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00055
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Mr. Jared C Horvath, University of Melbourne, Melbourne School of Psychological Sciences, Melbourne, VIC, 3010, Australia, jch155@mail.harvard.edu