Changes in neuronal properties and spinal reflexes during development of spasticity following spinal cord lesions and stroke: studies in animal models and patients

It is a well-known fact that spinal reflexes may gradually change and often become enhanced following spinal cord lesions. Although these phenomena are known, the underlying mechanisms are still unknown and under investigation, mainly in animal models. Over the last twenty years, new methods have been developed that can reliably estimate the activity of specific spinal pathways in humans at rest and during voluntary movement. These methods now make it possible to describe components of the spinal pathophysiology in spasticity in humans following spinal lesions or stroke. We now know that spinal networks are capable of generating the basic pattern of locomotion in a large number of vertebrates, including the monkey--and in all likelihood, humans. Although spinal networks are capable of generating locomotor-like activity in the absence of afferent signals, functional gait is not possible without sensory feedback. The results of animal studies on the sensory control of and the transmitter systems involved in the spinal locomotor centers are now being used to improve rehabilitation of walking in persons with spinal cord injury and hemiplegia.