Altered muscular activation patterns and force feedback after spinal cord injury

Abstract

One of the major clinical problems associated with spinal cord injury (SCI) is the lack of animal's ability to maintain weight support during standing or walking. We hypothesize that following SCI there is reorganization of the postural limb reflexes driven by stretch and load receptors in addition to loss of excitatory inputs from supraspinal structures to spinal interneurons that could result in altered intermuscular interactions. In control decerebrate animals there is a proximal to distal gradient in the strength of inhibitory force feedback among the limb muscles. We propose that pathways mediating this inhibition may remain inhibitory after spinal hemisection but their strengths may change to a distal to proximal gradient in the animal resulting in a loss of weight support. We also propose that ventral horn pathways are important for regulating the distribution of intermuscular force feedback. To test our hypothesis we are studying two types of SCI, namely dorsal and lateral hemisections, at both acute and chronic time points post‐injury. We measured intermuscular force feedback using combinations of stretches applied to pairs of muscles. Our most recent evidence supports our hypothesis and shows that the intermuscular force feedback is reversed after lateral but not dorsal hemisections.This work is supported by NIH grant HD32571, 1 I01 RX000243‐01A1, State of Florida BSCIRTF