fMRI Scanning Shows Transcranial Direct Current Stimulation Enhances Motor Learning Ability After Stroke

Neuro-rehabilitation techniques such as physical therapy and occupational therapy help hemaparetic stroke patients dealing with loss of motor skills on one side of their body, to regain some of their motor functions after a cerebrovascular accident. One of the most promising possibilities in neuro-rehabilitation consists of amplifying the motor learning ability after a stroke, having patients learning how (again) to make movements with the parts of the human body impacted after a stroke.

Pilot studies have shown that transcranial direct current stimulation (tDCS)—a noninvasive and painless cerebral stimulation technology—modulated the cerebral activity and increased the motor performance of patients who have had a stroke. This technique consists of applying low voltage electric currents to the patient’s head by means of electrodes during short periods of time. In 2012, a first study conducted by the teams of Profs. Yves Vandermeeren and Patrice Laloux, from Université Catholique de Louvain (UCL; Louvain-la-Neuve, Belgium) demonstrated that tDCS intensified the motor learning and the long-term motor memory of the patient after a stroke. The study’s findings were published online December 9, 2014, in the journal Brain.

This study was awarded the Fernand Depelchin Prize of the Université Catholique de Louvain and allowed the CHU neurology team to continue its research, specifically, with the use of functional magnetic resonance imaging (fMRI) of the brain. Nineteen hemiparetic stroke patients (with a motor deficit in the upper limb) participated in this new clinical trial. In order to avoid study bias, the stimulations were performed in a double-blind, randomized fashion. Each patient received a real stimulation as well as a placebo-stimulation during two separate sessions. It was impossible for patients to determine whether they received a true or a placebo-stimulation.

During the first stimulation session (real or placebo), the patients learned how to perform a task with a paralyzed hand, combining speed and accuracy. One week later, they performed the learned task while the functional MRI scanner recorded their cerebral activity. After one week, this experience was repeated with the other stimulation (placebo or real).

As in the previous study, the noninvasive cerebral stimulation amplified the motor learning capacity with the paralyzed hand and the long-term memory retention in a spectacular way for patients following chronic stroke.

Due to the use of functional MRI, this second study demonstrated that the combination of motor learning and noninvasive cerebral stimulation improves the efficiency of the cerebral activity. Indeed, one week after the placebo stimulation, the cerebral activations measured via the functional MRI scanning was very diffuse. Large cerebral zones were somehow “recruited” although motor performance was low (poor retention).

Contrarily, one week after real stimulation, the cerebral activation was focused on the basic motor zones, almost identical to an individual without stroke-impact, although the motor performance was substantially better (enhanced task retention). In other words, the combination of motor learning and tDCS reinforced the essential motor zones and this specific network was reactivated one week after the real intervention.

For thousands of stroke victims, this study opens considerable perspectives in the domain of neuro-rehabilitation. According to the scientists, a better determination of the brain’s functions after a stroke and how noninvasive cerebral stimulation works will help researchers to develop the neuro-rehabilitation of the future. The study’s findings will be implemented within the consortium Louvain Bionics, inaugurated recently at UCL.

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