title: Recovery of neuronal and network excitability after spinal cord injury and implications for spasticity.
abstract: The state of areflexia and muscle weakness that immediately follows a spinal cord injury (SCI) is gradually replaced by the recovery of neuronal and network excitability, leading to both improvements in residual motor function and the development of spasticity. In this review we summarize recent animal and human studies that describe how motoneurons and their activation by sensory pathways become hyperexcitable to compensate for the reduction of functional activation of the spinal cord and the eventual impact on the muscle. Specifically, decreases in the inhibitory control of sensory transmission and increases in intrinsic motoneuron excitability are described. We present the idea that replacing lost patterned activation of the spinal cord by activating synaptic inputs via assisted movements, pharmacology or electrical stimulation may help to recover lost spinal inhibition. This may lead to a reduction of uncontrolled activation of the spinal cord and thus, improve its controlled activation by synaptic inputs to ultimately normalize circuit function. Increasing the excitation of the spinal cord with spared descending and/or peripheral inputs by facilitating movement, instead of suppressing it pharmacologically, may provide the best avenue to improve residual motor function and manage spasticity after SCI.
authors.affiliation: Centre for Neuroscience, University of Alberta Edmonton, AB, Canada ; Faculty of Medicine and Dentistry, University of Alberta Edmonton, AB, Canada.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: D'Amico
authors.affiliation: Centre for Neuroscience, University of Alberta Edmonton, AB, Canada ; Faculty of Medicine and Dentistry, University of Alberta Edmonton, AB, Canada ; Department of Biomedical Engineering, University of Alberta Edmonton, AB, Canada ; Division of Physical Medicine and Rehabilitation, University of Alberta Edmonton, AB, Canada.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Condliffe
authors.affiliation: Centre for Neuroscience, University of Alberta Edmonton, AB, Canada ; Faculty of Physical Education and Recreation, University of Alberta Edmonton, AB, Canada.
authors.forename: Karen J B
authors.initials: KJ
authors.lastname: Martins
authors.affiliation: Centre for Neuroscience, University of Alberta Edmonton, AB, Canada ; Faculty of Rehabilitation Medicine, University of Alberta Edmonton, AB, Canada.
authors.forename: David J
authors.initials: DJ
authors.lastname: Bennett
authors.affiliation: Centre for Neuroscience, University of Alberta Edmonton, AB, Canada ; Faculty of Medicine and Dentistry, University of Alberta Edmonton, AB, Canada ; Department of Biomedical Engineering, University of Alberta Edmonton, AB, Canada.
authors.forename: Monica A
authors.initials: MA
authors.lastname: Gorassini
keywords: motoneuron; noradrenaline; persistent inward currents; reflexes; serotonin; spinal cord injuries