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The Journal of Neuroscience, August 8, 2007, 27(32):8558-8562; doi:10.1523/JNEUROSCI.1635-07.2007

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Brief Communications
The Rodent Lumbar Spinal Cord Learns to Correct Errors in Hindlimb Coordination Caused by Viscous Force Perturbations during Stepping

Chad Heng¹ and Ray D. de Leon²

¹Department of Biological Science and ²School of Kinesiology and Nutritional Science, California State University, Los Angeles, California 90032

Correspondence should be addressed to Dr. Ray D. de Leon, Associate Professor, Department of Kinesiology and Nutritional Science, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA 90032-8162. Email: rdeleon{at}calstatela.edu

The nervous system can adapt to external forces that perturb locomotion by correcting errors in limb movements. It is believed that supraspinal structures mediate these adaptations, whereas the spinal cord contributes only reflexive responses to perturbations. We examined whether the lumbar spinal cord in postnatal day 5 neonatal spinally transected (ST) rats corrected errors in hindlimb coordination through repetitive exposure to an external perturbation. A robotic device was used to deliver a viscous (velocity-dependent) force that opposed only the forward movement of the ankle in one hindlimb while the ST rats performed hindlimb stepping on a treadmill. We measured the interval between paw contact in the perturbed hindlimb and toe off in the unperturbed hindlimb. Before the force was activated, a normal pattern of coordination occurred: paw contact in the perturbed hindlimb occurred before toe off in the unperturbed hindlimb. This sequence was initially disrupted when the force was activated and the unperturbed hindlimb initiated swing during the swing phase of the perturbed hindlimb. Within five step cycles of exposure to the unilateral viscous force, however, the ST rats regained the preforce pattern of hindlimb coordination. These findings suggest that in the absence of supraspinal input, the lumbar spinal circuitry is capable of processing a complex ensemble of sensory information to maintain locomotor stability. Thus, the lumbar spinal circuitry may play a greater role in generating locomotor adaptations than previously thought.

Key words: rat; adaptation; transection; treadmill; stepping; robot

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Received April 11, 2007; revised June 26, 2007; accepted June 28, 2007.

Correspondence should be addressed to Dr. Ray D. de Leon, Associate Professor, Department of Kinesiology and Nutritional Science, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA 90032-8162. Email: rdeleon{at}calstatela.edu

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