The map of sensory information coming from different body parts is redrawn in the rat's brain after spinal cord injury. This study published online this week in Nature Neuroscience, resolves the previous discrepancies in the rodent models of spinal cord injury.
When the neural connections between the brain and limbs are severed during spinal cord injury, the surviving neurons can form new connections. Arko Ghosh and colleagues map out the rat's corticospinal neurons ― which are neurons that connect the spinal cord to the brain ― and monitored the cortical areas where these neurons originated from. They found that following a spinal cord injury that affects the rat's hindlimb functions, the surviving hindlimb's corticospinal neurons can become opportunistically incorporated into brain areas that are related to forelimb circuitry. This is accompanied by an expansion of the sensory representation from the forelimb areas in the brain. These results functionally link the anatomical rearrangements seen in the spinal cord with the changes that occur in the cortex.
Although the reason for this anatomical rearrangement is unclear, these findings suggest that the brain areas that no longer receive inputs are not put to waste, and are rewired to handle the compensatory increase in information from the injury-spared limbs.