corollary discharge
a neuronal signal that encodes a copy of an intended motor command, which is sent to a structure in the brain (a brain comparator) that can compare the intended movement with the sensory feedback (reafference) that results from the actual movement. For example, when the eyes move, the world does not appear to move, even though the image of the world moves across the retina. The corollary discharge of the intended movement in effect cancels out the movement of the world over the retina. When the eye is moved passively by gently pushing on the eyelid, there is no corollary discharge, and the world appears to jump. Also called efference copy.