Facilitating Myoelectric-Control with Transcranial Direct Current Stimulation

Neuromuscular Electrical Stimulation (NMES) can electrically activate paretic muscles of the lower extremities to assist walking following stroke. Here the electrical stimulation can be modulated, and controlled by residual muscle activity of the patients recorded by electromyogram (EMG) from the paretic muscles. However such direct EMG control of stimulation envelope assumes normative EMG patterns during walking. Unfortunately the muscle activity in the hemiparetic lower limb often suffers from delays in initiation and termination during walking. Thus patients have to learn movement-related muscle contraction for fine-tuning of NMES. The objective of this study in 10 healthy volunteers was to investigate the effect of an intervention at the central nervous system level - anodal transcranial direct current stimulation (tDCS) of primary motor cortex (M1) and cerebellar cortex - on delays in initiation and termination of isometric tibialis anterior (TA) contraction following audible prompt. The results suggested that, 1. Cerebellar anodal tDCS increased the delay in initiation of TA contraction while M1 anodal tDCS decreased the same when compared to sham tDCS, 2. Cerebellar anodal tDCS decreased the delay in termination of TA contraction while M1 anodal tDCS increased the same when compared to Sham. These preliminary results from healthy subjects may have significant clinical implications on EMG-controlled NMES-assisted gait therapy, however controlled interventional trials are needed to elucidate the optimal therapy protocol in stroke survivors