Spinal plasticity refers to short-or long-term alterations of the excitability of the spine's neural pathways. Although the mammalian spinal cord is a unique part of the central nervous system, it is most commonly identified as a transmitter of information to and from the brain and as a repository of various reflex functions that allow an automatic response to external stimuli. But spinal cord pathways are dynamic and continuously changing systems, not static, hard-wired entities simply transmitting information from the body to the brain and back.

Spinal reflexes appear to be hard-wired functional circuits whose excitability temporarily varies with descending activity from the brain or with repeated sensory input. In the 1930s, however, work began to show that the spinal reflex pathways might be altered in ways that have many characteristics of learning and memory in the intact mammal.

Nonassociative Excitability Changes

Researchers have long been aware...