Modularity, flexibility, speed and stability: compromises in spinal reflex behaviours

The motor primitive concept has proven a useful one. It may be most effective to describe reflexes. The success of a force-field description for capturing multi-joint dynamic feedback effects in reflex behaviors in a simple way supports the force-field primitive framework. In the work summarized here reflexes can be expressed as a superposition of fields. It is possible that the primitives found at the spinal level in frogs and rats in reflex behaviors could also be directly incorporated in higher motor learning. Alternatively the primitives could form a way station that has been used in evolution and/or transiently during ontogeny to bootstrap stable learning systems which ultimately produce the collection of adult motor processes we think of as human motor learning, while primitives remain as the basis of the reflex repertoire of the unperturbed spinal cord