It’s the time of year when things ice up and it can be a struggle to get down a sidewalk without breaking a hip. But most of us manage to do it. Scientists have recently discovered that this minor miracle is the result of a cluster of nerves in our spinal cord that serve as a “mini brain,” aiding in balance.
Salk Institute for Biological Studies scientists have identified an “spinal circuit” that serves as control center to integrate commands from the brains with sensory information from the limbs. It helps you to automatically process what your limbs are telling you and react quickly without wasting time on conscious effort, useful for not falling on your butt when attempting a difficult feat of balance.
“When we stand and walk, touch sensors on the soles of our feet detect subtle changes in pressure and movement. These sensors send signals to our spinal cord and then to the brain,” says Martyn Goulding, a Salk professor and senior author on the paper. “Our study opens what was essentially a black box, as up until now we didn’t know how these signals are encoded or processed in the spinal cord. Moreover, it was unclear how this touch information was merged with other sensory information to control movement and posture.”
The Salk scientists identified the spinal structures by studying mice. The traced the nerves in the their mousey feet back to a group of neurons known as RORα Neurons, which also connect to the motor region in the brain.
Unfortunate genetically modified mice had these neurons disabled. These mice were less sensitive to touch in their feet, but had no problem with standard walking around stuff any slobby mouse could do.
When tasked with walking over a balance beam, however, things went poorly for the modified mice and they were significantly more clumsy. The scientists found they were a lot less able to tell when their feet were slipping and quickly react.
The findings supported the theory that this “mini-brain” keeps us upright.
“We think these neurons are responsible for combining all of this information to tell the feet how to move,” says Steeve Bourane, a postdoctoral researcher in Goulding’s lab and first author on the paper. “If you stand on a slippery surface for a long time, you’ll notice your calf muscles get stiff, but you may not have noticed you were using them. Your body is on autopilot, constantly making subtle corrections while freeing you to attend to other higher-level tasks.”
Scientists say understanding how this works may one day lead to better treatments for spinal cord injuries and diseases that affect motor skills and balance and to methods that may help prevent falls for the elderly.
[Source: Salk Institute]