Interaction Between Simultaneously Applied Neuromodulatory Interventions in Humans

Schabrun, Siobhan M., Chipchase, Lucinda S., Zipf, Natasha, Thickbroom, Gary W. and Hodges, Paul W. (2013) Interaction Between Simultaneously Applied Neuromodulatory Interventions in Humans. Brain Stimulation, 6 4: 624-630. doi:10.1016/j.brs.2012.09.009


Author Schabrun, Siobhan M.
Chipchase, Lucinda S.
Zipf, Natasha
Thickbroom, Gary W.
Hodges, Paul W.
Title Interaction Between Simultaneously Applied Neuromodulatory Interventions in Humans
Journal name Brain Stimulation   Check publisher's open access policy
ISSN 1935-861X
1876-4754
Publication date 2013-07
Year available 2012
Sub-type Article (original research)
DOI 10.1016/j.brs.2012.09.009
Volume 6
Issue 4
Start page 624
End page 630
Total pages 7
Place of publication Philadelphia, United States
Publisher Elsevier
Collection year 2014
Language eng
Formatted abstract
Background
Transcranial direct current stimulation (tDCS) is a neuromodulatory technique with the potential to enhance the efficacy of traditional therapies such as neuromuscular electrical stimulation (NMES). Yet, concurrent application of tDCS/NMES may also activate homeostatic mechanisms that block or reverse effects on corticomotor excitability. It is unknown how tDCS and NMES interact in the human primary motor cortex (M1) and whether effects are summative (increase corticomotor excitability beyond that of tDCS or NMES applied alone) or competitive (block or reduce corticomotor excitability effects of tDCS or NMES applied alone).
Objective
To investigate corticomotor excitability in response to NMES after concurrent application of tDCS protocols that enhance (anodal tDCS) or suppress (cathodal tDCS) excitability of M1.
Methods
We used transcranial magnetic stimulation (TMS) to examine corticomotor excitability before and after the concurrent application of: i) NMES with anodal tDCS; and ii) NMES with cathodal tDCS. Effects were contrasted to four control conditions: i) NMES alone, ii) anodal tDCS alone, iii) cathodal tDCS alone, and iv) sham stimulation.
Results
Concurrent application of two protocols that enhance excitability when applied alone (NMES and anodal tDCS) failed to induce summative effects on corticomotor excitability, as predicted by homeostatic plasticity mechanisms. Combined cathodal tDCS and NMES suppressed the enhanced excitation induced by NMES, an effect that might be explained by calcium dependent anti-gating models.
Conclusions
These novel findings highlight the complex mechanisms involved when two neuromodulatory techniques are combined and suggest that careful testing of combined interventions is necessary before application in clinical contexts.
Keyword Homeostatic metaplasticity
Neuromuscular electrical stimulation
Primary motor cortex
Transcranial direct current stimulation
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: UQ Centre for Clinical Research Publications
Official 2014 Collection
School of Health and Rehabilitation Sciences Publications
 
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