We tested the hypothesis that combining treadmill walking with transcranial direct current stimulation (tDCS) enhances the gait improvements associated with treadmill walking in Parkinson disease. We explored the effects of these combined methodologies on corticospinal parameters.
Eighteen participants with Parkinson disease were evaluated under the following three conditions: treadmill walking alone (treadmill), treadmill walking combined with anodal tDCS (AtDCS+treadmill) delivered over the motor cortex, and treadmill walking combined with sham stimulation (StDCS+treadmill). Overground walking performance, soleus H-reflex, reciprocal Ia inhibition from the tibialis anterior to the soleus muscle, intracortical facilitation, and short intracortical inhibition of the tibialis anterior muscle, were measured before and after each treadmill condition. The soleus H-reflex and walking performance on the treadmill were also evaluated.
All treadmill conditions improved walking performance and modulated spinal and corticospinal parameters in a similar way. However, AtDCS+treadmill lead to a different modulation of reciprocal Ia inhibition in comparison with the other treadmill conditions.
A single session combining treadmill walking and anodal tDCS delivered over the motor cortex resulted in a specific modulation of the reciprocal Ia inhibition from the tibialis anterior to the soleus muscle. However, this acute effect did not result in improvements of gait parameters associated with treadmill walking in Parkinson disease.