| dc.description.abstracteng | The purpose of this work was to investigate the impact of tDCS applied over the lower limb motor network on cortical excitability, motor learning, and corporal balance control in healthy humans. According to the literature, tDCS effects are stimulation parameter-dependent. In our first study, we investigated the effect of electrode size, and placement on lower limb motor cortex excitability in healthy subjects, for optimization of tDCS effects over the lower limb motor cortex representation by systematically exploring the impact of electrode size, and current flow direction based on computational modeling.
It was shown that administration of tDCS over M1 enhances motor performance, associated with respective physiological alterations, via its impact on cortical excitability, and plasticity. Most of these studies were however conducted for tDCS applied over the upper limb motor cortex area. Taking into account the importance of lower limb motor functions for daily life, for the second study, we explored the impact of tDCS on performance of a visuo-motor lower limb motor learning task in healthy humans. Based on the relevance of stimulation focality, which is particularly challenging for cortical areas remote from the brain surface as the leg motor cortex representation, we investigated the specificity of tDCS by finite element modeling regarding two different sizes of electrodes (8 cm 2 vs. 35 cm 2 ). As tDCS had interindividual heterogeneous effects on motor performance, and sensitivity to transcranial magnetic stimulation (TMS) has been revealed as a potential marker of responsivity to tDCS for the upper limb motor cortex (156), we furthermore aimed to explore the relevance of this parameter for the stimulation effects.
Beyond its impact on motor cortex plasticity, recent studies have shown that tDCS applied over the cerebellum (ctDCS) impacts also on motor functions in humans, thus for the third study, we explored the effects of cerebellar tDCS on corporal balance in healthy humans. The impact of tDCS on performance was explored via tests of static (right and left Athlete Single Leg tests) and dynamic balance (Limits of Stability test) performed using the Biodex Balance System before and immediately after cerebellar tDCS. The knowledge we aimed to gain via these studies might perspectively help to optimize the effects of tDCS on cortical plasticity and motor (re-) learning for clinical therapeutic interventions. | de |