Map of brain-to-spinal cord nerve connections offers new hope for repairs

May 2 (UPI) — A system that maps critical brain-to-spinal cord nerve connections offers hope for paralyzed people to regain movement in forelimbs, according to a study.

Researchers at Cincinnati Children’s Hospital Medical Center are working on a process for specific repair strategies for patients that became paralyzed after an injury or disease caused damage to the central nervous system. The research was published this week in the journal Cell Reports.

“The map described in this study should allow us to explore which corticospinal-spinal interneuron connections are good targets for repair and restoration of voluntary movement,” Dr. Yutaka Yoshida, lead investigator in the Division of Developmental Biology at the hospital, said in a press release.

He said it will be several years before their findings can be put to use by humans.

“More research is necessary before human therapies are possible, but this information is very helpful for future repair strategies,” Yoshida said.

They are now studying a way to build on the basic neuronal architecture where these circuits can be reconstructed to stimulate the recovery of motor function.

How the corticospinal network of nerve connections between the brain and spinal cord are organized and function together hasn’t been determined in past research. Simple tasks such as reaching for something require precise coordination.

The Cincinnati scientists have studied these circuits in laboratory mice.

In past research, they tracked corticospinal connections from the brain’s cerebral cortex near the top of the head to the spinal cord. The organization and function of corticospinal circuits were also tracked using mouse genetics and a viral tracer — a de-armed rabies virus.

The researchers were able to map corticospinal neurons that control forelimb and sensory nerve impulses. In addition, they found specific neurons that control different skilled movements.

They found nerve fibers express a transcription factor called Chx10, which is a gene that instructs other genes to turn on or off. Chx10 also is part of nervous system function in other parts of the body, including the eyes.

When Chx10 was silenced only in the cervical spinal cord, it prevented the animals’ ability to grab for food.

The researchers also found the connections that control the animals’ ability to sense and convert external stimuli into electrical impulses. Unlike the neurons in the motor cortex that directly trigger movement, the neurons in the sensory cortex don’t connect directly to premotor neurons. In this case, they connect to other spinal interneurons in a gene called Vglut3.

And when these neurons expressing Vglut3 were blocked, it also prevented animals from handling tasks that included grabbing and releasing food pellets.

The researchers say findings in the study will be important for future studies as they devise strategies to treat people with stroke or spinal cord injuries.

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