Central nervous system lesions leading to disability

The introductory tutorial to this special issue was written for readers with engineering background with the aim to provide the basis for comprehending better the natural motor control and the terminology used in description of impairments and disability caused by to CNS injuries and diseases. The tutorial aims to emphasize the differences between natural and artificial control, complexity of sensory-motor systems in humans, the high level of articulation redundancy, and the fact that all of the said systems are modified after the central nervous system lesion. We hope that the tutorial will simplify the following of the subsequent papers in this special issue dedicated to the use of electrical stimulation with surface electrodes for assisting motor functions.