Decoded: How the brain, spinal cord make us walk

Chuck Bednar for – Your Universe Online
Researchers from the Medical University of Vienna have identified the mechanisms used by the spinal cord to trigger activity in leg muscles, marking the first time that the spinal cord activation patterns responsible for walking have been successfully decoded.
Previous research has demonstrated that this activity can be triggered in the leg muscles, even in patients suffering complete spinal paralysis, through the use of an implanted stimulator. Now, the new study identifies the mechanisms used by the spinal cord to control this activity, which still work even if the neural pathways from the brain are damaged due to an injury to the spinal cord.
Simon Danner of the Center for Medical Physics and Biomedical Engineering at the Medical University of Vienna (MedUni Vienna) and an international team of colleagues explain in the journal Brain that paraplegics still have neural connections (also known as locomotion centers) below the site of the injury and these can trigger rhythmic movements in the legs.
“Using statistical methods, we were able to identify a small number of basic patterns that underlie muscle activities in the legs and control periodic activation or deactivation of muscles to produce cyclical movements, such as those associated with walking,” Danner said in a statement. “Just like a set of building blocks, the neural network in the spinal cord is able to combine these basic patterns flexibly to suit the motor requirement.”
While the brain or brain stem serves at the command center of the body, complex motor patterns are actually generated by those neural networks in the spine in most vertebrates. One example of this phenomenon can be found in chickens that continue to running around, even after their heads have been cut off, the study authors explained. While the brain’s control has been lost, the spinal cord keeps sending out motor signals which are translated into movements of its wings and legs.
“These new findings relating to the basic patterns for triggering and coordinating muscle movements in the legs should also help in developing new approaches to rehabilitation aimed at utilizing those neural networks that are still functional following an accident and the resulting paralysis by stimulating them electrically,” the university said. “This opens the way to new therapeutic options for helping paraplegics to at least partially regain lost rhythmic movements.”
The specific method through which the neural networks need to be stimulated varies by patient and is based upon both his or her injury profile. This will be the topic of future research, Danner and his colleagues said. To assist with this they have developed a new, non-invasive method of stimulating the spinal cord that involves attaching electrodes to the surface of the skin.
“This method allows easy access to the neural connections in the spinal cord below a spinal injury and can therefore be offered to those suffering from paraplegia without exposing them to any particular medical risks or stresses,” said senior author Karen Minassian.
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