The researchers used imaging equipment to analyze genetically modified mice. The imaging equipment tracked the movement of a reengineered rabies virus. This allowed the researchers to follow the transmission of nerve signals from the feet’s light touch sensors to their connections in the spinal cord.
Based on the imaging data, the researchers discovered that sensory fibers connect to a group of neurons in the spinal cord called RORα. The RORα neurons, in turn, connect to the brain’s motor region. This suggests that this cluster of neurons is key in linking the feet and the brain.
Next, the researchers observed a group of mice whose RORα neurons had been disabled. The mice without the RORα neurons were substantially less sensitive to light sensations on their skin and feet. These mice were able to walk and stand normally on flat ground, but when they walked across a narrow, elevated beam, the mice were much clumsier than mice with active RORα neurons. This suggests that the RORα neurons form a “mini-brain” in the spinal cord. This mini-brain serves to integrate information from the body and the brain. It also helps coordinate limbs without conscious effort.
Martyn Goulding, senior study author and a Salk professor, says that the study is opening up new avenues of research into motion and perception. “How the brain creates a sensory percept and turns it into an action is one of the central questions in neuroscience. Our work is offering a really robust view of neural pathways and processes that underlie the control of movement and how the body senses its environment. We’re at the beginning of a real sea change in the field.”
This research is published in the journal Cell.
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