Transcranial Direct Current Stimulation Enhances Motor Skill Learning but Not Generalization in Chronic Stroke

I'm not sure what the weasel words used in this mean, so ask your doctor for clarification.
http://journals.sagepub.com/doi/abs/10.1177/1545968318769164

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Manuela Hamoudi¹

Manuela Hamoudi

1University Hospital Freiburg, Freiburg, Germany
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, Heidi M. Schambra, MD²³

Heidi M. Schambra

2New York University, NY, USA3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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, Brita Fritsch, MD¹

Brita Fritsch

1University Hospital Freiburg, Freiburg, Germany
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Annika Schoechlin-Marx, MD¹

Annika Schoechlin-Marx

1University Hospital Freiburg, Freiburg, Germany
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, Cornelius Weiller, MD¹

Cornelius Weiller

1University Hospital Freiburg, Freiburg, Germany
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, Leonardo G. Cohen, MD³

Leonardo G. Cohen

3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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, Janine Reis, MD¹³

Janine Reis

1University Hospital Freiburg, Freiburg, Germany3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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, Manuela Hamoudi¹

Manuela Hamoudi

1University Hospital Freiburg, Freiburg, Germany
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, Heidi M. Schambra, MD²³

Heidi M. Schambra

2New York University, NY, USA3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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, Brita Fritsch, MD¹

Brita Fritsch

1University Hospital Freiburg, Freiburg, Germany
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, Annika Schoechlin-Marx, MD¹

Annika Schoechlin-Marx

1University Hospital Freiburg, Freiburg, Germany
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, Cornelius Weiller, MD¹

Cornelius Weiller

1University Hospital Freiburg, Freiburg, Germany
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, Leonardo G. Cohen, MD³

Leonardo G. Cohen

3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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, Janine Reis, MD¹³

Janine Reis

1University Hospital Freiburg, Freiburg, Germany3National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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First Published April 22, 2018 Research Article

https://doi.org/10.1177/1545968318769164

Article information

Article Information

Volume: 32 issue: 4-5, page(s): 295-308

Article first published online: April 22, 2018; Issue published: April 1, 2018

https://doi.org/10.1177/1545968318769164

Manuela Hamoudi¹, Heidi M. Schambra, MD^{2, 3}, Brita Fritsch, MD¹, Annika Schoechlin-Marx, MD¹, Cornelius Weiller, MD¹, Leonardo G. Cohen, MD³, Janine Reis, MD^{1, 3}

¹University Hospital Freiburg, Freiburg, Germany

²New York University, NY, USA

³National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA

Corresponding Author: Janine Reis, MD, Department of Neurology, Albert-Ludwigs-University Freiburg, Breisacher Str 64, 79106 Freiburg, Germany. Email: janine.reis@uniklinik-freiburg.de

• Abstract

Abstract

Background. Motor training alone or combined with transcranial direct current stimulation (tDCS) positioned over the motor cortex (M1) improves motor function in chronic stroke. Currently, understanding of how tDCS influences the process of motor skill learning after stroke is lacking. Objective. To assess the effects of tDCS on the stages of motor skill learning and on generalization to untrained motor function.  
Methods. In this randomized, sham-controlled, blinded study of 56 mildly impaired chronic stroke patients, tDCS (anode over the ipsilesional M1 and cathode on the contralesional forehead) was applied during 5 days of training on an unfamiliar, challenging fine motor skill task (sequential visual isometric pinch force task). We assessed online and offline learning during the training period and retention over the following 4 months. We additionally assessed the generalization to untrained tasks. Results. With training alone (sham tDCS group), patients acquired a novel motor skill. This skill improved online, remained stable during the offline periods and was largely retained at follow-up. When tDCS was added to training (real tDCS group), motor skill significantly increased relative to sham, mostly in the online stage. Long-term retention was not affected by tDCS. Training effects generalized to untrained tasks, but those performance gains were not enhanced further by tDCS. Conclusions. Training of an unfamiliar skill task represents a strategy to improve fine motor function in chronic stroke. tDCS augments motor skill learning, but its additive effect is restricted to the trained skill.