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The spinal cord is "smarter" than previously thought


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We often think that our brain is at the center of complex motor function and control, but how intelligent is your spinal cord?

It turns out he's smarter than we think.

It is well known that the circuits in this part of our nervous system, which travel along our spine, control seemingly simple things like the pain reflex in humans and some motor control functions in animals.

Now, new research from Western University has shown that the spinal cord can also process and control more complex functions, such as the position of your hand in outer space.

"This research has shown that at least one important function is being performed at the level of the spinal cord and opens a new area of ​​research to say," What else is done at the spinal level and what else have we missed? " In this domain? "Said lead researcher and study supervisor, Andrew Pruszynski, Ph.D., assistant professor at Western Schulich School of Medicine and Dentistry and Canadian Research Chair at Sensorimotor Neuroscience.

The study, "Spinal stretch reflexes support efficient manual control," will be published online in the high-impact journal. Nature neuroscience.

This type of manual control requires sensory input from multiple joints, mainly the elbow and wrist, and previously it was thought that these inputs were processed and converted into motor commands by the cerebral cortex of the brain.

Using specialized robotic technology, an exoskeleton with three degrees of freedom at the Western Brain and Mind Institute, subjects were asked to keep their hand in the target position and then the robot pushed it away from the target by flexing or extending simultaneously the wrist and the elbow. The researchers measured the time it took for the muscles in the elbow and wrist to respond to the robot's blow and whether these responses helped the hand return to the initial target.

By measuring the latency, or "delay," in the response, they were able to determine if the processing was taking place in the brain or spinal cord.

"We found that these responses happen so quickly that the only place from which they can be generated is in the vertebral circuits themselves," said the study's principal investigator, Jeff Weiler, Ph.D., a postdoctoral fellow at Schulich Medicine & Dentistry. "What we see is that these vertebral circuits do not really care about what is happening in the individual joints, they care where the hand is in the external world and they generate a response that tries to put the hand back in its place."

This response generated by the spinal cord is called "stretch reflex" and was previously thought to be very limited in terms of how the movement helps. "Historically, it was believed that these spinal reflexes only act to restore muscle length to what happened before the stretch occurred," said Pruszynski. "We are showing that they can really do something much more complicated: control the hand in space."

This finding adds tremendously to our understanding of neuroscience and neurosurgery and provides new information and goals for the science of rehabilitation.

"A fundamental understanding of neurocircuits is fundamental to making any kind of progress on the rehabilitation front," said Pruszynski, who is also a scientist at Western's Robarts Research Institute and the Brain and Mind Institute. "Here we can see how this knowledge could lead to different types of training regimens that focus on the circuits of the spine."

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More information:
Spinal stretch reflexes support efficient manual control, Nature neuroscience (2019). DOI: 10.1038 / s41593-019-0336-0, https://www.nature.com/articles/s41593-019-0336-0

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University of Western Ontario

The spinal cord is & # 39; more intelligent & # 39; of what was previously thought (2019, February 11)
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