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Raz J.1,2, Soroker N.3,4, Liebermann D.G.5, Friedman J.5
1Loewenstein Rehabilitation Hospital, Physical Therapy, Ra'anana, Israel, 2Tel Aviv University, Physical-Therapy, Tel Aviv, Israel, 3Loewenstein Rehabilitation Hospital, Neurological Rehabilitation, Ra'anana, Israel, 4Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel, 5Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel Aviv University, Physical Therapy Dept., Tel Aviv, Israel
Background: Recovery of upper limb (UL) motor function after stroke is incomplete. Commonly used neuro-rehabilitative treatments induce partial recovery of motor function. Recent research in stroke patients shows that transcranial direct current stimulation (tDCS) can modulate intra-hemispheric excitability and inter-hemispheric dynamics, promoting plasticity and facilitating functional recovery. However, important theoretical questions have to be answered before tDCS can become part of the standard clinical practice in stroke rehabilitation.
Purpose: To study the effects of different stimulation modes: anodal (excitatory, a-tDCS), cathodal (inhibitory, c-tDCS) and sham tDCS (s-tDCS) on motor learning of upper limb reaching movements in healthy and in sub- acute stroke patients.
Methods: 14 healthy adults (mean age 50±5.2years) and 12 stroke subjects (mean age 61±3.1) participated
(up till now) in a mixed experimental design, whereas individuals completed a series of planar reaching movements (on a graphic tablet controlled by custom-designed software) before and after a-tDCS, c-tDCS and s-tDCS conditions in a counterbalanced order. The stimulation was administered via external electrodes placed on the motor cortex (M1) of both sides, once with the anode on the contralateral side of the training arm and once with the cathode on the contralateral side of the training arm. Spatio-temporal kinematic variables derived from the minimum-jerk model (i.e., a maximal smoothness assumption) were compared before and after training with different tDCS modalities.
Results: Preliminary kinematic analyses of point-to-point hand movements showed that under real stimulation conditions (a-tDCS and c-tDCS) arm flexion and extension resulted in significantly straighter paths with reduced movement time and fewer number of peaks (p 0.05), and in general closer to the minimum-jerk description, meaning smoother and more coordinated movements. These findings were greater in a-tDCS (p 0.05).
Conclusion(s): Our results suggest that stimulation applied on the contralateral hemisphere combined with motor training shows immediate positive effects on spatiotemporal features of upper-limb motor execution in terms of path smoothness and straightness. Further research in progress will confirm these preliminary observations. However, we may cautiously conclude that, in line with existing literature, non-invasive anodal brain stimulation to the contralateral hemisphere might enhance functional arm movement recovery in stroke patients.
Implications: tDCS documented effect on cortex excitability makes it a potential strong adjuvant in stroke rehabilitation. This research aims to answer fundamental concerns about tDCS clinical implementation, specifically whether the current experimental practice of exciting the motor cortex of the lesioned hemisphere (and/or inhibiting the contralateral hemisphere) has a similar or distinct effect on motor learning in the case of minor versus severe motor impairment. By shedding light on these questions this research project is likely to facilitate the use of tDCS in neuro-rehabilitation clinical practice.
Funding acknowledgements: This project is funded by Loewenstein Rehabilitation Hospital Research Foundation and Elsa and Leo Abramson Foundation, Tel Aviv University.
Topic: Neurology: stroke
Ethics approval: This project has been approved by the Loewenstein Helsinki committee and by Tel- Aviv University ethics committee.
All authors, affiliations and abstracts have been published as submitted.
