In Madeline L’Engle’s fictional work The Arm of the Starfish, Calvin O’Keefe discovered a way to help mammals regenerate tissue the way starfish do. Nonfictional research has not gotten quite that far, but it might not have to. A new paper has found that rhesus macaques can spontaneously reform connections among their spinal neurons following injury.
It has been known for some time that the mammalian spinal cord can extensively recover from partial, but not complete, injury. Although the general consensus has been that the axonal projections, which connect the neurons of the spinal cord, did not have the plasticity required to recover after injury, our heroes (the authors) thought otherwise and set out to test it.
To do so, they gave what’s called C7 lateral hemisection lesions to 5-8 year old rhesus monkeys (Macaca mulatta), which involves severing one side of the spinal cord. They then examined structural, elecrophysiological, and functional responses to the lesion at either two weeks or 4-8 months later. They focused on the corticospinal projections, which primates use for many features of fine voluntary movement.
This is a very specific type of injury, where the nerves in the spine controlling one side are cut.
After a few weeks, some function returns. This is because the nerves in primates do not just travel down one side of the spine. Some cross over. The increase in function comes from the uncut nerves that cross over to the damaged side.
This does not happen much in rodents so cutting one side results in lose of function pretty much forever.
I wonder what other differences in the nervous system we will find.