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Restor Neurol Neurosci. 2015;33(5):663-9. doi: 10.3233/RNN-140469.

Recurrence quantification analysis of surface electromyogram supports alterations in motor unit recruitment strategies by anodal transcranial direct current stimulation.

Author information

1
DEMAR team of INRIA, Université de Montpellier, CNRS, Montpellier Cedex 5, France.
2
Neuromuscular and Rehabilitation Robotics Laboratory (NeuRRO Lab), Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI, USA.
3
Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
4
Moss Rehabilitation Research Institute, Elkins Park, PA, USA.
5
Department of Kinesiology, Michigan State University, East Lansing, MI, USA.
6
Department of Clinical Neurophysiology, University Medical Center, Göttingen, Germany.

Abstract

PURPOSE:

Recent evidence indicates that anodal transcranial direct current stimulation (tDCS) can selectively alter the EMG/force relationship of agonist arm muscles; however, the mechanisms mediating those changes are less clear. The purpose of this study was to evaluate the effect of anodal tDCS on motor unit synchronization by using a sophisticated non-linear EMG analysis called recurrence quantification analysis (RQA).

METHODS:

Surface EMG signals were collected from the biceps brachii muscle of eighteen healthy young adults (9 tDCS and 9 control) at various force levels (12.5%, 25%, 37.5%, and 50% maximum) before and after the application of anodal tDCS over the primary motor cortex. RQA was employed to quantify the changes in percentage of determinism (% DET) and laminarity (% LAM) of the surface EMG signals, which are surrogate measures of motor unit synchronization.

RESULTS:

RQA analyses indicated that the changes in % DET and % LAM scores were significantly higher in the tDCS group than in the control group (p < 0.05) and this effect was particularly pronounced at higher force levels.

CONCLUSION:

The results of this study provide novel evidence supporting that anodal tDCS significantly alters motor unit firing strategies (i.e., the degree of synchronization) of the biceps brachii muscle.

KEYWORDS:

Recurrence analysis; brain stimulation; electromyography; motor unit; nonlinear analysis; synchronization

PMID:
25791041
DOI:
10.3233/RNN-140469
[Indexed for MEDLINE]

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