Controlling the central pattern generator locomotion after spinal cord injury: Problems and solutions

Many years ago, my colleagues and I presented evidence that a larval lamprey with a spinal transection can recover full and normal function. (The larval lamprey is a stable life phase of 3-5 years) We now can show that the functional status of the animal depends on the temperature at which the animal recovers from its injury. At room temperature, it is more likely than not to recover full function. However, at its normal coldroom temperature, it is more likely to develop dysfunctional behavior patterns. It appears that one problem is that serotonin does not regenerate properly in any of the injured animals. I will present the data from these studies and an hypothesis regarding why this might be involved in the dysfunctional behavior. Thus, regeneration even in this primitive vertebrate can be problematic, despite the fact that it regenerates spontaneously. Indeed, its best recovery is not under its normal conditions. These results suggest that regeneration in humans is, therefore, likely to require considerably more work in order to obtain full functional recovery. Consequently, we have begun to consider the use of neuroprosthetic devices based on neuromorphic engineering principles to aid spinal cord injury patients. As a first step, I will present data from work done in collaboration with Ralph Etienne-Cummings, Anthony Lewis and Mitra Hartmann demonstrating that an analog VLSI chip can control a pair of legs in a way similar to that offered by the spinal pattern generator for locomotion including responses to sensors to adaptively control the step cycle.