Spinal responses. A: six superimposed spinal responses after homonymous gastrocnemius muscle stimulation. The line marks the spinal responses. B: six superimposed spinal responses after dipolar cortico-muscular stimulation (dCMS). C: six superimposed spinal responses after motor cortex (M1) stimulation. The first and second arrows and the line mark the first, second, and third motoneuronal responses to dCMS, respectively, recorded from the contralateral spinal cord to stimulated M1. D: the average latency of spinal responses after muscle stimulation, dCMS (second and third responses), and after M1 stimulation. Ipsilateral spinal response to M1 stimulation (Ip) was significantly faster than the contralateral response (Co) (p < 0.05). Muscle stimulation generated significantly shorter response at ipsilateral motoneuron than the ones at the contralateral side (p < 0.05).