Efference copy

Efference copy is a concept in neuroscience and psychology referring to an internal copy of an outgoing motor command generated by the brain that is used to predict the expected effects of that command. This mechanism allows the brain to anticipate and plan for the outcomes of its own actions, facilitating smooth and coordinated motor control. The concept plays a crucial role in understanding how the brain distinguishes between self-generated and external sensory events.

The term "efference" refers to signals sent from the central nervous system (CNS) to peripheral effectors, such as muscles and glands, commanding them to perform an action. An efference copy is essentially a duplicate of these commands, retained within the CNS to inform the brain about actions it has initiated. This internal feedback system is critical for the sensory processing of self-generated movements, helping to maintain a stable perception of the world despite the constant changes caused by our own actions.

For example, when an individual decides to move their arm, the motor cortex sends an efferent signal to the muscles to initiate the movement. Simultaneously, an efference copy of this signal is sent to sensory areas of the brain. This copy is used to predict the sensory consequences of the movement, such as the expected position of the arm and the feeling of the movement through proprioception. By comparing the predicted sensory feedback with the actual sensory feedback, the brain can adjust motor commands in real-time, improving the accuracy and efficiency of movements.

The concept of efference copy is also fundamental in explaining the phenomenon of sensory attenuation, where sensory signals generated by self-initiated actions are perceived as less intense than identical, externally generated sensory events. This is thought to be due to the brain's ability to predict the sensory consequences of its own actions and thus dampen the response to self-generated sensory input.

Efference copies are involved in various aspects of cognitive functions, including the perception of visual stability during eye movements. As the eyes move, the brain sends an efference copy of the eye movement command to the visual system, which uses this information to maintain a stable perception of the environment despite the rapid changes in visual input.