efference

Efference is a term used in neurophysiology to refer to motor commands that originate in the central nervous system and travel to effectors, such as muscles or glands. It contrasts with afferent signals, which carry sensory information from the body back to the CNS. The word efference derives from Latin efferre, meaning to carry away; its adjective is efferent, and the noun efference denotes the act or state of sending out signals.

In many theories of motor control, the CNS generates an efference copy, an internal duplicate of the motor command, which is used by forward models to predict the expected sensory consequences of an action. This prediction helps distinguish self-generated sensations from those produced by external events and supports rapid, accurate motor adjustments. The brain may use corollary discharge to modulate sensory processing, such as dampening tactile or visual responses during self-initiated movement.

Historically, the concept was developed in the mid-20th century by von Holst and Mittelstaedt as part of the corollary discharge/forward model framework. In contemporary neuroscience, efference copy and related terms are used across studies of perception, action, and sensorimotor disorders, and the concept has been extended to artificial systems and robotics for stable interaction with dynamic environments.

Key distinctions: efference refers to outgoing motor signals; efference copy (or corollary discharge) refers to the internal signal used for prediction; reafference is the resulting sensory input produced by one's own actions, which the brain predicts and often attenuates.