The researchers built a map of brain activity and discovered that neurons in the lateral part of the hypothalamus were highly involved in recovery of walking function. focusing on the hypothalamus they found a new “command center' that can help restore movement when the usual direct routes are disrupted.

It's wild.

First they let animals with spinal cord injuries attempt to walk on a treadmill. At different stages of recovery they checked which neurons were active

Then they injected viruses into the spinal cord that move backward along nerve pathways up into the brain. By seeing exactly which brain cells the virus ended up in they could figure out which neurons in the brain directly connect to the spinal cord segments controlling the legs.

To analyze the entire brain at once they used tissue “clearing” techniques that make the brain transparent. They then used specialized microscopes to scan and reconstruct the brain in 3D.

They wrote algorithms to align these images to a brain map so they could count active, spinal cord connected neurons in precise brain regions.

Combining these markers connectivity tracers and 3D imaging they created a complete atlas of which brain cells became engaged during walking recovery. This approach highlighted the lateral hypothalamus as a site that sends signals down to the spinal cord to help restore walking function even when the usual direct routes are damaged.