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.
To perceive object motion, two sources of information are required in order to distinguish it from an eye movement: 1. image of movement of object (X) across the retina (image-retina system), 2. signal to the extra ocular muscles (eye-head system). The latter (the efferent copy) is subtracted from the output of the image-retina system, the most likely locus for this comparator (see figure below) being the parietal cortex.
Modeling the previous figure to include a comparator that takes account of signals from the image-retina system and the eye-head system (motor area).
See Cerebellum (functions), Feedforward, Motor control, Parietal cortex, Prospective control (neurophysiology), Retina