Student Competition (Knowledge Generation) ID 1985185

Transcutaneous spinal cord stimulation (tSCS) facilitates spinal networks involving motor function. The purpose of this study is to compare the effect of stimulators used and amplitude of tSCS, applied at the cervical region of the spinal cord, on propriospinal modulation of lower limbs. Corticospinal and spinal reflex excitability were assessed with lower limb motor evoked potentials (MEPs), and Hoffman (H-) reflexes, respectively. Neurologically intact participants (n=6) were recruited. Two stimulators (NeoStim-5 and DS8R) were used, and different tSCS amplitudes at threshold (thresh) and maximum tolerance (max) were applied. The effect of tSCS on the amplitude of the H-reflex evoked in the soleus muscle was assessed, as well as the effect of cervical tSCS on MEPs evoked in the tibialis anterior muscle. Participants completed five conditions including: 1) Control (no stimulation) 2) DS8R Thresh 3) DS8R Max 4) NeoStim-5 Thresh 5) NeoStim-5 Max. At the same tSCS amplitude, the participants subjectively tolerated the NeoStim-5 better than the DS8R. The maximum tolerated amplitude for NeoStim-5 was higher than that of the DS8R, for all participants. Preliminary analysis suggests changes in tSCS amplitude delivered, do not appear to have an effect on the H-reflex and MEP in this small sample of participants. Preliminary findings indicate that different stimulators produce different sensations at the same tSCS amplitudes. Changes in stimulator amplitudes do not appear to have an effect on the electrophysiological outcome on propriospinal modulation. This study sets the basis for understanding mechanisms of tSCS, including cutaneous activation.