BackgroundTranscranial direct current stimulation (tDCS) is a technique for brain modulation that has potential to be used in motor neurorehabilitation. Considering that the cerebellum and motor cortex exert influence on the motor network, their stimulation could enhance motor functions, such as motor imagery, and be utilized for brain-computer interfaces (BCIs) during motor neurorehabilitation.MethodsA new tDCS montage that influences cerebellum and either right-hand or feet motor area is proposed and validated with a simulation of electric field. The effect of current density (0, 0.02, 0.04 or 0.06 mA/cm2) on electroencephalographic (EEG) classification into rest or right-hand/feet motor imagery was evaluated on 5 healthy volunteers for different stimulation modalities: 1) 10-minutes anodal tDCS before EEG acquisition over right-hand or 2) feet motor cortical area, and 3) 4-seconds anodal tDCS during EEG acquisition either on right-hand or feet cortical areas before each time right-hand or feet motor imagery is performed. For each subject and tDCS modality, analysis of variance and Tukey-Kramer multiple comparisons tests (p <0.001) are used to detect significant differences between classification accuracies that are obtained with different current densities. For tDCS modalities that improved accuracy, t-tests (p <0.05) are used to compare μ and β band power when a specific current density is provided against the case of supplying no stimulation.ResultsThe proposed montage improved the classification of right-hand motor imagery for 4 out of 5 subjects when the highest current was applied for 10 minutes over the right-hand motor area. Although EEG band power changes could not be related directly to classification improvement, tDCS appears to affect variably different motor areas on μ and/or β band.ConclusionsThe proposed montage seems capable of enhancing right-hand motor imagery detection when the right-hand motor area is stimulated. Future research should be focused on applying higher currents over the feet motor cortex, which is deeper in the brain compared to the hand motor cortex, since it may allow observation of effects due to tDCS. Also, strategies for improving analysis of EEG respect to accuracy changes should be implemented.

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Today, technology provides many ways for humans to exchange their points of view about pretty much everything. Visual, audio and tactile media are most commonly used by humans, and they support communication in such a natural way that we don't even actively think about using them. But what about people who have lost motor or sensory capabilities for whom it is difficult or impossible to control or perceive the output of such technologies? In this case, perhaps the only way to communicate might be to use brain signals directly. The goal of this study is therefore towards providing people with tetraplegia, who may be confined to their room or bed, with a telepresence tool that facilitates the daily interactions so many of us take for granted. In our case, the telepresence tool is a robot that is remotely controlled. It can act as a medium for the user in their everyday life with the design of a virtual link with friends and relatives located in remote rooms or places or with different environments to explore. Therefore, the objective is to design a Human-Machine System that enables the control of a robot using thoughts alone. The technological part is composed of a brain-computer interface and a visual interface to implement an "emulated haptic shared control" of the robot. Shared motion control is implemented between the user and the robot as well as an adaptive function allocation to manage the difficulty of the situation. The control schema that exploits this "emulated haptic feedback" has been designed and evaluated using a Human-Machine Cooperation framework and the benefit of this type of interaction has been evaluated with five participants. Initial results indicate better control and cooperation with the "emulated haptic feedback" than without.

This literature review is aimed to explore the main technical characteristics of both transcranial direct current stimulation (tDCS) and transcranial alternate current stimulation (tACS) using the latest research on both healthy and impaired subjects. These techniques have no official standards developed yet. Our intent is to underline the main properties and problems linked with the application of those techniques which show diverse, and sometimes even opposite, results depending mainly on electrode positioning and underlying brain activity.