Modulation of Training by Single-Session Transcranial Direct Current Stimulation to the Intact Motor Cortex Enhances Motor Skill Acquisition of the Paretic Hand

Abstract

Background and Purpose Mechanisms of skill learning are paramount components for stroke recovery. Recent noninvasive brain stimulation studies demonstrated that decreasing activity in the contralesional motor cortex might be beneficial, providing transient functional improvements after stroke. The more crucial question, however, is whether this intervention can also enhance the acquisition of complex motor tasks, yielding longer-lasting functional improvements. In the present study, we tested the capacity of cathodal transcranial direct current stimulation (tDCS) applied over the contralesional motor cortex during training to enhance the acquisition and retention of complex sequential finger movements of the paretic hand. Method Twelve well-recovered chronic patients with subcortical stroke attended 2 training sessions during which either cathodal tDCS or a sham intervention were applied to the contralesional motor cortex in a double-blind, crossover design. Two different motor sequences, matched for their degree of complexity, were tested in a counterbalanced order during as well as 90 minutes and 24 hours after the intervention. Potential underlying mechanisms were evaluated with transcranial magnetic stimulation. Results tDCS facilitated the acquisition of a new motor skill compared with sham stimulation (P=0.04) yielding better task retention results. A significant correlation was observed between the tDCS-induced improvement during training and the tDCS-induced changes of intracortical inhibition (R2=0.63). Conclusions These results indicate that tDCS is a promising tool to improve not only motor behavior, but also procedural learning. They further underline the potential of noninvasive brain stimulation as an adjuvant treatment for long-term recovery, at least in patients with mild functional impairment after stroke.

Functional near-infrared spectroscopy maps cortical plasticity underlying altered motor performance induced by transcranial direct current stimulation

“…1 Stimulation of the cortex with transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and epidural cortical stimulation, results in beneficial neuroplasticity by modulating the excitability of the underlying neural circuitry. Contingent on the cortical location, stimulation can lead to improvements in speech, 2 motor control, [3][4][5][6][7][8][9] pain, 10 depression, 11 neglect, 12 and the reduction of sensory deficit 13,14 in patients with various brain disorders.…”

“…3,7,[9][10][11][12] TDCS is a noninvasive cortical stimulation technique which modulates the cortical activity with intensities below the motor threshold. 16 Depending on the current polarity, tDCS can either excite or suppress the underlying cortical regions 17,18 similar to TMS, though with less topographical specificity than TMS.…”

Optogenetic Approaches to Target Specific Neural Circuits in Post-stroke Recovery

“…However, the role of contralesional cortex activation is still unclear. Activation in the contralesional cortex at the early post-stroke phase (i.e., 10 days) has been associated with improved recovery [25,141]. Furthermore, disrupting the contralesional cortex activity using TMS also resulted in motor impairment [45].…”

Measuring motor-training induced neuroplasticity using diffusion and functional MRI: a sensitive, pathology-robust approach

“…For example, the use of TMS has revealed that maladaptive neuroplasticity, seen as increased contralesional sensorimotor activity, can undermine recovery from stroke in adults. 41 Trials in which transcranial direct current stimulation (tDCS) has been used to restore the interhemispheric balance of activation in the sensorimotor system and thereby improve clinical upper-limb motor scores [42][43][44][45] and acquisition of motor skills 46 have had some success. These findings have led to an investigation in which children with spastic diplegia underwent treadmill training and concurrent anodal tDCS over the primary motor cortex contralateral to the dominant side of the body.…”

“…TMS and fMRI + TMS studies have provided direct evidence for this hypothesis in subjects with CP, 147 TBI, 148 and stroke. 41,110 Contralesional activity may even have a net-negative influence: direct inhibition of such activity with transcranial direct current stimulation can improve motor scores 42 and motor-skill acquisition 46 in adults with chronic stroke.…”