Neural encoding of limb movement

We published an “Innovative Methodology” paper (Hayes et al 2009; attached) on a newly-developed isolated in vitro rat spinal cord with intact hindlimbs freely stepping on a custom-built treadmill. It combines the neural accessibility of in vitro preparations with modulatory influence of sensory feedback from physiological hindlimb movement. A currently submitted manuscript provides the first-ever intracellular neuronal recordings during mechanically-unrestrained locomotion. Using additional pioneering techniques in another submitted manuscript, we investigated how hindlimb mechanics influence sensory input during locomotion. We found that stance-phase force on the opposite limb strongly and linearly encoded the magnitude and timing of afferent presynaptic inhibition in the swinging limb, thus binding interlimb sensorimotor states by adjusting sensory inflow to the swing limb based on forces generated by the stance limb. These studies suggest that stroke or spinal cord injury rehabilitative approaches that involve loading the unaffected limb may provide a novel means of reducing spasticity and hyperreflexia in the affected limb.

Hayes, H.B., Y.-H. Chang, and S. Hochman. An in vitro spinal cord-hindlimb preparation for studying behaviorally relevant rat locomotor function. J Neurophysiol, 101:1114-22 (2009).

HOCHMAN, S.,  HAYES, H.B., SPIEGEL, I. AND CHANG, Y.-H.Force-sensitive afferents recruited during stance encode sensory depression in the contralateral swinging limb during locomotion.  Ann N Y Acad Sci 1279:103-13. doi: 10.1111/nyas.12055. (2013).

Hayes, H.B., Chang, Y-H, and HOchman, S. Stance-phase force on the opposite limb dictates swing-phase afferent presynaptic inhibition during locomotion. J. Neurophysiol. (2012). PMID: 22442562

Hochman, S., Gozal, E.A., Hayes, H.B., Anderson, j., deweerth, s.d., and Chang, Y.-H. Enabling techniques for in vitro studies on mammalian spinal locomotor mechanisms: integrating afferent feedback and attached hindlimbs.  Frontiers in Bioscience Jun 1;17:2158-80 (2012). PMID: 22652770