RT Journal Article
SR Electronic
T1 Epidural Stimulation Induced Modulation of Spinal Locomotor Networks in Adult Spinal Rats
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 6022
OP 6029
DO 10.1523/JNEUROSCI.0080-08.2008
VO 28
IS 23
A1 Igor Lavrov
A1 Christine J. Dy
A1 Andy J. Fong
A1 Yury Gerasimenko
A1 Grégoire Courtine
A1 Hui Zhong
A1 Roland R. Roy
A1 V. Reggie Edgerton
YR 2008
UL http://www.jneurosci.org/content/28/23/6022.abstract
AB The importance of the in vivo dynamic nature of the circuitries within the spinal cord that generate locomotion is becoming increasingly evident. We examined the characteristics of hindlimb EMG activity evoked in response to epidural stimulation at the S1 spinal cord segment in complete midthoracic spinal cord-transected rats at different stages of postlesion recovery. A progressive and phase-dependent modulation of monosynaptic (middle) and long-latency (late) stimulation-evoked EMG responses was observed throughout the step cycle. During the first 3 weeks after injury, the amplitude of the middle response was potentiated during the EMG bursts, whereas after 4 weeks, both the middle and late responses were phase-dependently modulated. The middle- and late-response magnitudes were closely linked to the amplitude and duration of the EMG bursts during locomotion facilitated by epidural stimulation. The optimum stimulation frequency that maintained consistent activity of the long-latency responses ranged from 40 to 60 Hz, whereas the short-latency responses were consistent from 5 to 130 Hz. These data demonstrate that both middle and late evoked potentials within a motor pool are strictly gated during in vivo bipedal stepping as a function of the general excitability of the motor pool and, thus, as a function of the phase of the step cycle. These data demonstrate that spinal cord epidural stimulation can facilitate locomotion in a time-dependent manner after lesion. The long-latency responses to epidural stimulation are correlated with the recovery of weight-bearing bipedal locomotion and may reflect activation of interneuronal central pattern-generating circuits.