FIG. 5.

Two windows with relative time-intervals between the S1 and L2 stimulation pulses result in the best bipedal stepping. (A) Four windows with inter-stimulation time-intervals were defined with reference to the S1 pulse at “0” and a subsequent L2 pulse (blue dots) that was 1) 0–2.9 msec (window 1 [W1]), 2) 3–10 msec (window 2 [W2]), 3) 10.1–18 msec (window 3 [W3]), and 4) 18.1–25 msec (window 4 [W4]) after the S1 stimulation pulse. (B) The stepping ability (rank) of a rat in each spatiotemporally-independent monopolar stimulation to electrically-enabled motor control (SIM-eEmc) trial is represented relative to the time delay between stimulation pulses (four time windows W1, W2, W3 or W4) and S1 stimulation frequency (5, 10, 20, or 40 Hz). Each shaded circle therefore represents the stepping ability at a given frequency in a specific time window. The majority of the good steppers (rank 1-3), irrespective of stimulation frequency, fell in the time windows when L2 was at 3-10 (W2) or 18–25 msec (W4) after the onset of the S1 pulse. Rank 1 corresponds to the best stepping. (C) Progression of a SIM-eEmc sequence that consisted of multiple SIM-eEmc trials, each having the same frequency (L2 40 Hz; S1 40 Hz) but different pulse intervals (onset of L2 stimulation pulse at 13ms, 5ms, and 23 msec after the S1 pulse) in the same animal. (D) Limb kinematics and (E) corresponding electromyographic (EMG) signals indicate more a robust stepping pattern (bilateral coordinated steps and trajectory pattern) for the SIM-eEmc segments in W4 and W2 than W3. Color image is available online at www.liebertpub.com/neu