FIG. 3.

Spatiotemporally-independent monopolar stimulation to electrically-enabled motor control (SIM-eEmc) at higher frequencies results in electromyographic (EMG) temporal patterns similar to pre–spinal cord injury (SCI). (A) Peak tibialis anterior (TA) and medial gastrocnemius (MG) amplitudes of the rectified EMG linear envelopes before (pre-SCI) and post–spinal cord transection (ST) for all rats during 8-12 steps. Superimposed averaged (+SEM) integrated EMG linear envelopes normalized to the step cycle for the TA and MG pre-SCI (B) and post-ST (C, 1-9) for each combination of stimulation (n = 10 rats, 8-12 steps). The purple arrow connects the time of onset with the time to reach peak amplitude for the MG burst, while the numbers indicate the slope at which the MG burst reaches peak amplitude. Most SIM-eEmc configurations and SI-L2 bipolar stimulation showed similar slopes to pre-SCI, whereas trials 1, 3, and 4 showed a slower rate to reach peak amplitude. The red arrows indicate an irregular pattern in the MG burst during the stance phase (note the sharp increases and decreases in the EMG amplitudes for trials 1-7). Despite well-coordinated kinematics of movement, inadequate plantar placements during monopolar S1 stimulation can be attributed to an altered time-to-peak MG EMG (∼80% into the step cycle) and the rate at which this peak was reached (trial 4). (D) Timing of peak TA (light gray circles) and MG (dark gray circles) EMG normalized to the step cycle for all animals. The distance between the light and dark gray circles reflects the amount of co-contraction (i.e., the smaller the distance, the greater the amount of co-contraction). *, †: Significantly different from trial 1 and trial 3, respectively. Color image is available online at www.liebertpub.com/neu