Repaving Old Roads After Spinal Cord Injury

The World Health Organization estimates that as many as 500,000 people will experience spinal cord injuries (SCI) every year.  Researchers at the Center for Neuroprosthetics and Brain Mind Institute in Switzerland reported that approximately half of human spinal cord injuries lead to paralysis severe enough to keep the person in a wheelchair for the rest of his or her life.  An incomplete spinal cord injury is sufficient to cause severe motor impairments.  However, in most of these patients, a few nerve fiber bridges remain at the site of injury.  Can researchers figure out a way to repair these paths and help the patient regain functional movement after spinal cord injury?

Researchers at the University of Zurich are putting these spared fibers center stage as a means of restoring locomotor ability by increasing the movement control commands that are carried by these remaining intact highways.  The lumbar spinal cord has a locomotor central pattern generator (CPG) that produces rhythmic output without sensory or motor feedback from muscle targets.  Spinal cords that have been isolated from the body can still produce activity patterns associated with locomotion.  However, to initiate movement the organism needs input from the brain command center.

Previous research in spinal cord injury has focused on promoting the growth of interrupted fibers to reconnect the supraspinal (above the spinal cord) motor cortex to neurons below the site of injury.  This type of recovery relies on inducing new circuit formation in individuals who have been newly injured and have retained plasticity.  It is more challenging to restore locomotion in individuals, who have been living with their injury for years.

In a new study published in Science Translational Medicine, researchers set out to reactivate the inactive networks below a spinal cord injury in rats with chronic, severe, and incomplete SCI.  Despite the requirement of the brain for modulating movement in response to the environment, basic locomotion can be initiated by the midbrain, the brainstemThe part of the brain found just above the spinal cord (in r... More, and the spinal cord.  These results suggest that activity in the regions comprising “evolutionarily ancient” areas can give rise to movement independent of the frontal cortex!  Deep brain stimulation in the mesencephalic locomotor region (MLR) of rats with severe spinal cord injury immediately improved locomotor performance in the previously paralytic hindlimbs.

MLR Neuroanatomy Nature Reviews 500

This research may have broader implications for other degenerative disorders.  Individuals with midbrain ataxiaA disorder of movement that involves loss of muscle coordin... More show a deficit in the initiation of walking and have damage in their MLR regions.  Parkinson’s patients have severe gait disturbances and reduced activity in the supraspinal motor circuits; they also demonstrate severe neuronThe functional unit of the nervous system, a nerve cell that... More loss in the MLR motor region.  What do these disorders have in common with spinal cord injury?  All three scenarios describe conditions where there is a reduction in the brain-controlled motor command signals that reach the spinal cord.  The results of this study suggest that excitatory stimulation in the MLR by deep brain stimulation could be key to improving gait disturbances in Parkinson’s patients!  Unraveling the overlap between motor impairments in neurodegeneration and spinal cord injury may lead to a new therapeutic approach for restoring function in both conditions.

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To explore further advances in spinal cord injury recovery, we recommend you watch this TED talk, originally recorded in June 2013 at TedGlobal2013, entitled “The Paralyzed Rat That Walked” with Gregoire Courtine.

Repaving Old Roads After Spinal Cord Injury by Knowing Neurons

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References:

Bachmann L.C., Matis A., Lindau N.T., Felder P., Gullo M. & Schwab M.E. (2013). Deep Brain Stimulation of the Midbrain Locomotor Region Improves Paretic Hindlimb Function After Spinal Cord Injury in Rats, Science Translational Medicine, 5 (208) 208ra146-208ra146. DOI:

Courtine, C. (2013, June). The Paralyzed Rat That Walked [Video file]. Retrieved from  http://www.ted.com/talks/gregoire_courtine_the_paralyzed_rat_that_walked.html

van den Brand R., Heutschi J., Barraud Q., DiGiovanna J., Bartholdi K., Huerlimann M., Friedli L., Vollenweider I., Moraud E.M., Duis S. & Dominici N. (2012). Restoring Voluntary Control of Locomotion after Paralyzing Spinal Cord Injury, Science, 336 (6085) 1182-1185. DOI: 

Images adapted from SEBASTIAN KAULITZKI/Science Photo Library/Corbis and from

Goulding M. (2009). Circuits controlling vertebrate locomotion: moving in a new direction, Nature Reviews Neuroscience, 10 (7) 507-518. DOI: 

Jillian L. Shaw

Jillian decided to dedicate herself to a life of exploring the mysteries of the brain after reading neurological case studies by Oliver Sachs and Ramachandran as a student at Vassar College.After completing a B.A. in Neuroscience with honors in 2009, Jillian headed to USC to pursue a Ph.D. in Neuroscience where she is now in her 5th year.A research stint in Belgium exposed Jillian to the complexities of cell signaling pathways, and her interests shifted from cognitive neuroscience to cellular and molecular neuroscience.Her current research focuses on the link between Down syndrome and Alzheimer’s disease using Drosophila as a genetic model to explore axonal transport, mitochondria dysfunction, synaptic defects, and neurodegeneration.When she is not in the lab, Jillian is forming new synapses by rock climbing throughout Southern California.

Jillian L. Shaw

Jillian decided to dedicate herself to a life of exploring the mysteries of the brain after reading neurological case studies by Oliver Sachs and Ramachandran as a student at Vassar College. After completing a B.A. in Neuroscience with honors in 2009, Jillian headed to USC to pursue a Ph.D. in Neuroscience where she is now in her 5th year. A research stint in Belgium exposed Jillian to the complexities of cell signaling pathways, and her interests shifted from cognitive neuroscience to cellular and molecular neuroscience. Her current research focuses on the link between Down syndrome and Alzheimer’s disease using Drosophila as a genetic model to explore axonal transport, mitochondria dysfunction, synaptic defects, and neurodegeneration. When she is not in the lab, Jillian is forming new synapses by rock climbing throughout Southern California.

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