Transformation of descending commands into muscle activity by spinal interneurons in behaving primates

Ever since Sherrington’s pioneering experiments led him to conclude that reflexes were “the unit reaction in nervous integration,” physiologists have conceived of descending systems recruiting spinal circuitry to produce voluntary movements. This insight has evolved to the present view that transmission through spinal pathways, which execute the stereotyped, stimulus-driven motor behaviors referred to as reflexes, is mutable, dynamically modulated, and under differential control by supraspinal structures.