The Behavioral Catastrophe Is Rooted in Injury to White Matter

Abstract

The biological basis for the functional loss accompanying spinal cord injury is mostly rooted in the loss of nerve impulse conduction (electrical traffic) through the lesion in injured white matter (Blight 1991; Folis et al. 1993). White matter owes its name to its staining characteristics as studied by the nineteenth century anatomist. This light staining was due to high concentrations of myelin, a fatty substance insulating most spinal cord nerve fibers or axons. White matter is comprised of myelinated and unmyelinated axons, many organized into numerous tracts, collective bundles of nerve processes coursing in the same direction to common target regions of the nervous system. This region is comprised solely of the processes of nerve cells (and not their cell bodies) surrounding the centrally located gray matter (darker in staining due to the presence of the nerve cell bodies). The connection between brain and body is made possible by the direction of nerve impulse traffic in the so-called long-tract pathways of white matter. Sensory information projects into the spinal cord via sensory nerve fibers that ascend the spinal cord to the base of the brain, while motor nerve impulse traffic (for example, initiating volitional movement) leaves the brain by descending the spinal cord in organized tracts of nerve fibers in the white matter.