A model after spinal cord injury suggests that kinesthesia aids in the recovery of movement

Nearly 50 years ago, a jawless fish called a lamprey intrigued scientists because of its remarkable ability to recover from spinal cord injuries. a New study It reveals a potential technique lampreys might use to swim again, despite sparse neural regeneration.

Christina Hamlet of Bucknell University and collaborators, including Jennifer R. Morgan of the Marine Biological Laboratory (MBL), used a mathematical model to show how lampreys might use body-sensing feedback to restore swimming abilities after a spinal injury. The study could inspire new treatment approaches in humans or algorithms for navigation in soft robots. The paper was published in Proceedings of the National Academy of Sciences.

said Morgan, MBL’s chief scientist and director of MBL’s Eugene Bell Center for Regenerative Biology and Tissue Engineering.

Unlike humans and other mammals, lampreys recover quickly and almost completely even after severe spinal cord injuries. Morgan previously discovered that although neural regeneration aids recovery in lampreys, it doesn’t tell the whole story. Only a small percentage of neurons and synapses are restored via spinal injury, so another mechanism must be used.

“I had all these questions about how that might work. How do you get a nervous system to work with just a few scattered little connections?” Morgan asked.

Scientists hypothesized that lampreys might use body-sensing feedback (called proprioception or kinesthesia) to direct their movements in addition to the descending nerve connections in the spinal cord. Morgan reached out to discuss this with an old friend of hers from MBL, Eric Teitel, an associate professor of biology at Tufts University and a former investigator at the MBL Whitman Center. Eric was already collaborating with Lisa Fossey, a professor of mathematics at Tulane University, and Christina Hamlet, who was a postdoctoral professor at Tulane.

Tytell, Fauci, and Hamlet were using mathematical models to mimic locomotion in lampreys. They teamed up “to see if we can model some of the effects of sensory feedback on lamprey swimming behavior,” said Hamlet, who is now an assistant professor of mathematics at Bucknell University.

The team began by playing with different scenarios for spinal lampreys—including both biologically plausible and unreasonable species—all of which assumed no neural regeneration via a spinal cord lesion. That’s the benefit of modeling, Hamlet said, “We can break things that you can’t break in biology.” The model took into account the bending and stretching that occurred in the body over the lesion and sent this information to the rest of the body through the muscles, not the spinal cord.

Even with a moderate amount of sensory feedback, the models showed a surprising rebound in the biologically plausible models’ swimming patterns. Stronger sensory feedback led to greater improvement.

Since lampreys regrow some of their neurons after injury and therefore have a descending command from the brain to drive movement, they may need even fewer sensory feedback than a model. The team hopes to add neuron regeneration to the model and test how this affects movement and interaction with sensory feedback.

“If you have a good computational model, you can run through many more manipulation scenarios than is practical with experimentation,” Morgan said.

The team hopes that this study and future research will contribute to treatments for people with spinal injuries and diseases that affect movement. Brain and stimulator interfaces are starting to integrate body sensor feedback to create smoother movements after injury, and this research could show how much and what type of feedback humans need.

“Whether you’re an animal like an eel (recovers) spontaneously or a human who needs medication or an electrical stimulation device, you’ve gotten to the point where you have a few things in the right place and then you reuse what is already there should be something more achievable than Trying to recapitulate the original, identical pattern of connections and synaptic growth,” Morgan said.