Interactions between descending and spinal circuits on motor output.

Area of Science:

• Neuroscience
• Motor Control
• Spinal Cord Injury Research

Background:

• Supraspinal control of spinal networks is vital for motor function recovery after neurological damage.
• Neuromodulation offers potential for aiding recovery and studying supraspinal-spinal interactions.

Purpose of the Study:

• To investigate how motor cortex stimulation interacts with spinal stimulation to modulate sensorimotor networks.
• To explore the effects of varying spinal stimulation intensity and timing on cortically evoked responses.

Main Methods:

• Elicited hindlimb muscle responses via paired motor cortex and spinal stimulation (epidural or transcutaneous) in rats and pigs.
• Varied spinal stimulation intensity and timing relative to cortical stimulation.

Main Results:

• Spinal stimulation modulated descending volleys, increasing motor evoked potentials by 400-500% at near-motor-threshold levels.
• Response modulation shifted from cortical to spinal dominance with increasing spinal stimulation intensity.
• Responses were abolished when spinal stimulation exceeded supra-motor-threshold.
• Peak modulation occurred when spinal stimulation latency matched cortical central conduction time.

Conclusions:

• Cortical stimulation can modulate spinal modulation, indicating supraspinal-spinal network convergence on motor pathways.
• Results suggest strategies for leveraging supraspinal-spinal interactions for motor recovery without focal targeting.