Preserved force control by the digits via minimal sparing of cortico-spinal connectivity after stroke.

The ability to regulate finger forces is critical for manipulating objects during everyday tasks but is impaired after damage to white matter tracts that transmit motor commands into the spinal cord. This study examines cortico-spinal connectivity required for force control by the digits after neurological injury. We report on a unique case of a stroke survivor who retained the ability to control finger forces at a level comparable to neurologically intact adults despite extensive loss of white matter volume and severely compromised transmission from cortical motor areas onto the final common pathway. Using a combination of imaging methods and noninvasive stimulation techniques, we illustrate the structure and function of a slow-conducting, cortico-spinal pathway minimally spared by stroke that underlies this stroke survivor's ability to transition and stabilize finger forces of the paretic hand during precision grip. We interpret findings in the context of physiological mechanisms underlying distal limb control and current thinking on neural adaptation after brain injury due to stroke.