Focal and bidirectional modulation of lower limb motor cortex using anodal transcranial direct current stimulation

Abstract

Background-Because we are interested in non-invasive transcranial brain stimulation as an adjuvant to post-stroke walking therapy, we applied direct current stimulation (tDCS) preferentially to either the left or right lower limb motor cortex (M1) in two separate sessions and assessed the resulting modulation in both cortices.

Transcranial direct-current stimulation reduced the excitability of diaphragmatic corticospinal pathways whatever the polarity used

“…The after-effects of c/tDCS were comparable to those reported for limb muscles. However, a/tDCS had an inhibiting effect on the diaphragm that contrasted with the activating effect described for the limb muscles (Hummel et al, 2005;Lang et al, 2004;Madhavan and Stinear, 2010;Paulus, 2000, 2001;Nitsche et al, 2005). We used 35 cm 2 size electrodes and 2 mA current intensity and found that both a/tDCS and c/tDCS had inhibitory effects on the diaphragm when Batsikadze and colleagues (in the same conditions) had rather found excitatory effects of both a/tDSC and c/tDCS on the first dorsal interosseous muscle (Batsikadze et al, 2013).…”

Effects of anodal tDCS of the lower limb M1 on ankle reaction time in young adults

“…All participants performed a visuomotor task using ankle dorsiflexion and plantarflexion during anodal/sham tDCS. This motor task has been explained previously (Madhavan and Stinear 2010; Shah et al 2013; Sriraman et al 2014). In brief, participants were seated comfortably with their non-dominant foot attached to a custom made ankle tracker device.…”

Transcranial Direct Current Stimulation of the Leg Motor Cortex Enhances Coordinated Motor Output During Walking With a Large Inter-Individual Variability

“…First, tDCS could have caused facilitation of ipsilateral pathways that travel to the non-targeted leg. That is, Madhavan and colleagues [29] showed that an increase in excitability of the contralateral pathways to the leg muscles after tDCS was accompanied by an increase in excitability of the ipsilateral pathway. Second, DUAL tDCS could have caused facilitation of the indirect pathways via subcortical structures to the lower leg muscles.…”

“…They showed that approximately 50% responded as expected and showed a facilitatory effect of the stimulation. A previous study of Madhavan and colleagues [29] showed that, in response to anodal stimulation over the leg cortex, 60 % of the subjects showed an increase of corticomotor excitability in leg muscle. These "response rates" are in accordance with the findings of our study.…”