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The association of mCIMT with brain stimulation improves clinical gains in rehabilitation after stroke. The improvement in motor recovery (assessed by Fugl-Meyer scale) was only observed after anodal tDCS. The modulation of damaged hemisphere demonstrated greater improvements than the modulation of unaffected hemispheres.

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Mental practice can induce significant neural plasticity and result in motor performance improvement if associated with motor imagery tasks. Given the effects of transcranial direct current stimulation (tDCS) on neuroplasticity, the current study tested whether tDCS, using different electrode montages, can increase the neuroplastic effects of mental imagery on motor learning. Eighteen healthy right-handed adults underwent a randomised sham-controlled crossover experiment to receive mental training combined with either sham or active anodal tDCS of the right primary motor cortex (M1), right supplementary motor area, right premotor area, right cerebellum or left dorsolateral prefrontal cortex (DLPFC). Motor performance was assessed by a blinded rater using: non-dominant handwriting time and legibility, and mentally trained task at baseline (pre) and immediately after (post) mental practice combined with tDCS. Active tDCS significantly enhances the motor-imagery-induced improvement in motor function as compared with sham tDCS. There was a specific effect for the site of stimulation such that effects were only observed after M1 and DLPFC stimulation during mental practice. These findings provide new insights into motor imagery training and point out that two cortical targets (M1 and DLPFC) are significantly associated with the neuroplastic effects of mental imagery on motor learning. Further studies should explore a similar paradigm in patients with brain lesions.

Objective: Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) involves passing low currents through the brain and is a promising tool for the modulation of cortical excitability. In this study, we investigated the effects of cathode location and the size of anode for anodal tDCS of the right-leg area of the motor cortex, which is challenging due to its depth and orientation in the inter-hemispheric fissure.Methods: We first computationally investigated the effects of cathode location and the size of the anode to find the best montage for specificity of stimulation effects for the targeted leg motor area using finite element analysis (FEA). We then compared the best electrode montage found from FEA with the conventional montage (contralateral supraorbital cathode) via neurophysiological testing of both, the targeted as well as the contralateral leg motor area.Results: The conventional anodal tDCS electrode montage for leg motor cortex stimulation using a large-anode (5 cm × 7 cm, current strength 2 mA) affected the contralateral side more strongly in both the FEA and the neurophysiological testing when compared to other electrode montages. A small-anode (3.5 cm × 1 cm at 0.2 mA) with the same current density at the electrode surface and identical contralateral supraorbital cathode placement improved specificity. The best cathode location for the small-anode in terms of specificity for anodal tDCS of the right-leg motor area was T7 (10–10 EEG system).Conclusion: A small-anode (3.5 cm × 1 cm) with the same current density at the electrode surface as a large-anode (5 cm × 7 cm) resulted in similar cortical excitability alterations of the targeted leg motor cortex respresentation. In relation to the other stimulation conditions, the small-anode montage with the cathode positioned at T7 resulted in the best specificity.