Affiliations: Burke Institute of Medical Research, White Plains, NY,
USA | Department of Neurology and Neuroscience, Weill
Medical College, Cornell University, New York, NY, USA | Berenson-Allen Center for Non-Invasive Brain
Stimulation, Harvard Medical School, Boston, MA, USA | Centre for Neuromuscular and Neurological Disorders,
University of Western Australia, WA, Australia | Mechanical Engineering Department, Massachusetts
Institute of Technology, Cambridge, MA, USA | Department of Neurology, University of Maryland,
School of Medicine, Baltimore, MD, USA
Note: [] Corresponding author: Dylan J. Edwards PhD, The Burke Medical
Research Institute, 785 Mamaroneck Av, White Plains New York, 10605, USA. Tel.:
+1 617 8203765; Fax: +1 914 597 2796; E-mail: dje2002@med.cornell.edu
Abstract: Anodal transcranial direct current stimulation (tDCS) can
transiently increase corticomotor excitability of intrinsic hand muscles and
improve upper limb function in patients with chronic stroke. As a preliminary
study, we tested whether increased corticomotor excitability would be similarly
observed in muscles acting about the wrist, and remain present during robotic
training involving active wrist movements, in six chronic stroke patients with
residual motor deficit. Methods: Transcranial magnetic stimulation (TMS) generated
motor evoked potentials (MEP) in the flexor carpi radialis (FCR) and provided a
measure of corticomotor excitability and short-interval cortical inhibition
(SICI) before and immediately after a period of tDCS (1 mA, 20 min, anode and
TMS applied to the lesioned hemisphere), and robotic wrist training (1hr). Results: Following tDCS, the same TMS current strength evoked
an increased MEP amplitude (mean 168 ± 22%SEM; p < 0.05), that
remained increased after robot training (166 ± 23%; p < 0.05).
Conditioned MEPs were of significantly lower amplitude relative to
unconditioned MEPs prior to tDCS (62 ± 6%, p < 0.05), but not after
tDCS (89 ± 14%, p = 0.40), or robot training (91 ± 8%, p =
0.28), suggesting that the increased corticomotor excitability is associated
with reduced intracortical inhibition. Conclusion: The persistence of these effects after robotic
motor training, indicates that a motor learning and retraining program can
co-exist with tDCS-induced changes in cortical motor excitability, and supports
the concept of combining brain stimulation with physical therapy to promote
recovery after brain injury.
