Rats whose spinal cords have been severed can regain movement by reorganizing brain circuits associated with muscle control.
A team led by Karen Moxon at the University of California, Davis, treated rats with completely severed spinal cords using a combination of drugs and physical exercise. The rats partially recovered the ability to move their hind limbs unassisted, and brain circuits associated with activation of the rats’ trunk muscles were found to be reorganized. These muscles span the location at which the spinal cord was cut, and the researchers suggest they could be responsible for the regained movement.
The reorganized brain circuit seemed to use the trunk muscles to bypass the break in the animals’ spinal cords, enabling them to walk and support their own weight without transmitting information through the severed region. When the reorganized circuit was later damaged, the rats lost the movement they had regained.