Figure 2 .

(A) Twenty raw responses showing light-reflecting deoxyhemoglobin (HbR) intensity in the lumbar spinal cord on the ipsilateral side of the stimulated muscle. (B) Average response on the ipsilateral side. (C) Twenty raw responses representing light-reflecting HbR intensity in the lumbar spinal cord on the contralateral side of the stimulated muscle. (D) Average responses on the contralateral side. Note: The first large deflection between 0 and 2 seconds in each graph is a movement artifact caused by hind limb muscle contraction and is not considered a physiological signal. Thus, physiological optical responses were recorded between 2 and 16 seconds.