Spinal cord is 'smarter' than previously thought

Credit: CC0 Public Domain

We often think of our brains as being at the centre of complex motor function and control, but how 'smart' is your spinal cord?

Turns out it is smarter than we think.

It is well known that the circuits in this part of our nervous system, which travel down the length of 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 is also able to process and control more complex functions, like the positioning of your hand in external space.

"This research has shown that a least one important function is being done at the level of the spinal cord and it opens up a whole new area of investigation to say, 'what else is done at the spinal level and what else have we potentially missed in this domain?'" said the study's senior and supervising researcher Andrew Pruszynski, Ph.D., assistant professor at Western's Schulich School of Medicine & Dentistry and Canada Research Chair in Sensorimotor Neuroscience.

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

This kind of hand control requires from multiple joints—mainly the elbow and the wrist—and these inputs was previously thought to be processed and converted into motor commands by the brain's cerebral cortex.

Using specialized robotic technology, a three degree of freedom exoskeleton at Western's Brain and Mind Institute, subjects were asked to maintain their hand in a target position and then the robot bumped it away from the target by simultaneously flexing or extending the wrist and elbow. The researchers measured the time that it took for the muscles in the elbow and wrist to respond to the bump from the robot and whether these responses helped bring the hand back to the initial target.

By measuring the latency, or 'lag', in the response, they were able to determine whether the processing was happening in the brain or the spinal cord.

"We found that these responses happen so quickly that the only place that they could be generated from is the spinal circuits themselves," said the study's lead researcher Jeff Weiler, Ph.D., a post-doctoral fellow at Schulich Medicine & Dentistry. "What we see is that these spinal circuits don't really care about what's happening at the individual joints, they care about where the hand is in the external world and generate a response that tries to put the hand back to where it came from."

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

This finding adds immensely to our understanding of neuroscience and neurocircuitry, and provides new information and targets for rehabilitation science.

"A fundamental understanding of the neurocircuits is critical for making any kind of progress on 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 kinds of training regimens that focus on the spinal circuitry."

Explore further

Microglia transmit pain to the brain during stress

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

Citation: Spinal cord is 'smarter' than previously thought (2019, February 11) retrieved 18 October 2019 from https://medicalxpress.com/news/2019-02-spinal-cord-smarter-previously-thought.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Feb 11, 2019
How much of our 'Pain' circuitry in in the spinal column? Since we pull our hands away from pain inducing events and the quickest path would be to use those same spinal neurons, so is there a possible target for pain control at the nerve level directly?

Feb 11, 2019
When musicians play together do individual players move and position hands and wrists, elbows so the next note in the performance will be played on beat?

Or, are even fast songs no match for the speed of messages to/from the spinal column?

Feb 11, 2019
I've done spinal exercises extensively (pilates and yoga) and my hand control is superfine (fine artist).

Note this research only scratches the surface of what the spine is capable of doing. Further research will prove its versatility and importance.

Feb 11, 2019
If we are only now just learning that essentially some processing happens at levels outside the brain. And we have also recently found brain cells around the heart, liver and gut from what I remember.
Why are we playing with genetics when we don't fully understand how the body works?
Consistently, it seems, the only thing we learn is how much we do not know.
I would think that genetics manipulation should not be allowed outside the experimental lab at this stage of development. Who knows what damage that could be being done to generations of people. Science belongs to everyone. But in the wrong hands its dangerous. And how its used on populations should be strictly controlled by governments not business.
Just a humble opinion.
That said. This new information is truly amazing.

Feb 13, 2019
"how its used on populations should be strictly controlled by governments not business." Governments murdered over 100 million people in the 20th century alone.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more