A concept introduced into the study of motor control by Erich von Holst (1908-1962) to indicate the sending of a copy of the efferent signal ahead of a movement so that it prepares the system for incoming sensory feedback or for a future motor command. ‘Efferent’ means the conduction of nerve impulses ‘away from the central nervous system’ to muscles and glands. Further details about this concept are depicted in the two figures below.