Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: crossing internal and external tools

Journal of NeuroEngineering and Rehabilitation, Jun 2016

Background Transcranial direct current stimulation is a safe technique which is now part of the therapeutic armamentarium for the neuromodulation of motor functions and cognitive operations. It is currently considered that tDCS is an intervention that might promote functional recovery after a lesion in the central nervous system, thus reducing long-term disability and associated socio-economic burden. Discussion A recent study shows that kinesthetic illusion and motor imagery prolong the effects of tDCS on corticospinal excitability, overcoming one of the limitations of this intervention. Conclusion Because changes in excitability anticipate changes in structural plasticity in the CNS, this interesting multi-modal approach might very soon find applications in neurorehabilitation.

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Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: crossing internal and external tools

Bodranghien et al. Journal of NeuroEngineering and Rehabilitation Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: crossing internal and external tools Florian Bodranghien 2 Mario Manto 1 2 3 Florent Lebon 0 4 0 Laboratoire INSERM U1093 Cognition, Action et Plasticité Sensorimotrice, Université de Bourgogne Franche-Comté , Dijon , France 1 Service des Neurosciences, Université de Mons , Mons , Belgium 2 Unité d'Etude du Mouvement, Laboratoire de Neurologie Expérimentale, ULB , Brussels , Belgium 3 UEM, FNRS-ULB , 808 Route de Lennik, 1070 Bruxelles , Belgium 4 UFR STAPS, Université de Bourgogne Franche-Comté , Dijon , France Background: Transcranial direct current stimulation is a safe technique which is now part of the therapeutic armamentarium for the neuromodulation of motor functions and cognitive operations. It is currently considered that tDCS is an intervention that might promote functional recovery after a lesion in the central nervous system, thus reducing long-term disability and associated socio-economic burden. Discussion: A recent study shows that kinesthetic illusion and motor imagery prolong the effects of tDCS on corticospinal excitability, overcoming one of the limitations of this intervention. Conclusion: Because changes in excitability anticipate changes in structural plasticity in the CNS, this interesting multi-modal approach might very soon find applications in neurorehabilitation. Direct current stimulation; Motor imagery; Kinesthetic illusion; Excitability; Rehabilitation - Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique, which consists of delivering a low (usually between 1 and 2.5 mA) constant current between two electrodes positioned on the skull. Depending on the polarity chosen, tDCS is either cathodal or anodal. In the first set up, the cathodal electrode is positioned over the target brain area and lowers the underlying neurons’ action potential firing rate, therefore decreasing neural excitability. In the second set up, the anodal electrode is positioned over the target area and increases the action potential firing rate, therefore inducing a hyperexcitability [ 3 ]. The socalled after-effects depend on the set up, the duration and the intensity of the stimulation [ 11 ]. For anodal DCS, the intra-DCS effects are much less prominent when compared to the after-effects. However, for cathodal DCS, the intra-DCS effects and the after-effects are nearly similar [ 16 ]. One of the limitations of DCS is related to the fact that the after-effects will disappear after a few hours, hence the importance of repeating the application in the following days or weeks. Despite this limitation, due to its ease of use, its safety and its low cost, tDCS is growingly applied to modulate central nervous system (CNS) excitability in fundamental research [ 19 ] as well as in trials involving human healthy volunteers or patients [ 2 ]. In particular, there is a great hope that tDCS will be helpful not only for the acute management or rehabilitation of motor neurological disorders, but even beyond, for instance in cognitive or psychiatric disorders, although optimizations of the stimulation parameters are still clearly required [ 7, 13 ]. While tDCS artificially modulates neural excitability, other methods use afferent inputs or even internal representations of movement to induce cortical plasticity. Kinesthetic illusion (KI) is based on various sources of sensory stimuli to activate cerebral networks. For example, a hand motion video, if positioned appropriately, induces the subjective feeling of movement in one’s hand [ 9 ]. It is usually assumed that the right cerebral hemisphere plays a critical role in the conscious experience of the body. This is confirmed by recent fMRI studies demonstrating that kinesthetic illusory movement activates the right frontoparietal regions [ 1 ]. Considered globally, investigations of proprioceptive bodily illusions show a hierarchy of three brain systems: the motor network processing afferent inputs from skeletal muscles in order to build kinematic/dynamic postural models of limbs, parietal regions integrating the information across different coordinate systems in order to maintain the adaptability of the body representation, and the right inferior fronto-parietal network recruited when bodily illusions are concerned [ 14 ]. One of the potential clinical applications of KIs in the coming years is the management of painful states [ 4 ]. Interestingly, motor imagery (MI), the internal representation of movement without concomitant contraction, induces similar brain activation as the actual motor performance [ 17 ]. These neuroanatomical correlates legitimate the benefits of MI-based mental practice on motor learning [ 8 ]. MI-based motor learning impacts on brain networks, especially the functional connectivity of the default mode network [ (...truncated)


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Florian Bodranghien, Mario Manto, Florent Lebon. Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: crossing internal and external tools, Journal of NeuroEngineering and Rehabilitation, 2016, pp. 50, 13, DOI: 10.1186/s12984-016-0156-3