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Efference copy
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Efference copy
In physiology, an efference copy or efferent copy is an internal copy of an outflowing (efferent), movement-producing signal generated by an organism's motor system. It can be collated with the (reafferent) sensory input that results from the agent's movement, enabling a comparison of actual movement with desired movement, and a shielding of perception from particular self-induced effects on the sensory input to achieve perceptual stability. Together with internal models, efference copies can serve to enable the brain to predict the effects of an action.
An equivalent term with a different history is corollary discharge.
Efference copies are important in enabling motor adaptation such as to enhance gaze stability. They have a role in the perception of self and nonself electric fields in electric fish. They also underlie the phenomenon of tickling.
A motor signal from the central nervous system (CNS) to the periphery is called an efference, and a copy of this signal is called an efference copy. Sensory information coming from sensory receptors in the peripheral nervous system to the central nervous system is called afference. On a similar basis, nerves into the nervous system are afferent nerves and ones out are termed efferent nerves.
When an efferent signal is produced and sent to the motor system, it has been suggested that a copy of the signal, known as an efference copy, is created so that exafference (sensory signals generated from external stimuli in the environment) can be distinguished from reafference (sensory signals resulting from an animal's own actions).
This efference copy, by providing the input to a forward internal model, is then used to generate the predicted sensory feedback that estimates the sensory consequences of a motor command. The actual sensory consequences of the motor command are then deployed to compare with the corollary discharge to inform the CNS about how well the expected action matched its actual external action.
Corollary discharge is characterized as an efference copy of an action command used to inhibit any response to the self generated sensory signal which would interfere with the execution of the motor task. The inhibitory commands originate at the same time as the motor command and target the sensory pathway that would report any reafference to higher levels of the CNS. This is unique from the efference copy, since the corollary discharge is actually fed into the sensory pathway to cancel out the reafferent signals generated by the movement. Alternatively, corollary discharges briefly alters self-generated sensory responses to reduce self-induced desensitization or help distinguish between self-generated and externally generated sensory information.
In 1811 Johann Georg Steinbuch (1770–1818) referred repeatedly to the problem of efference copy and reafference in his book "Beytrag zur Physiologie der Sinne" ("Contribution to the Physiology of Senses"). After studying medicine, Steinbuch worked for a number of years as lecturer at the University of Erlangen and thereafter as physician in Heidenheim, Ulm, and Herrenberg (Württemberg, South Germany). As a young university teacher, he was particularly interested in the brain mechanisms which enable the perception of space and objects, but in later years his attention shifted to the more practical problems of clinical medicine. Together with Justinus Kerner he gave a very precise description in 1817 of the clinical symptoms of botulism. In his book "Beytrag zur Physiologie der Sinne”, Steinbuch presented a very careful analysis of the tactile recognition of objects by the grasping hand. Hereby, he developed the hypothesis that the cerebral mechanisms controlling the movement of the hands interact within the brain with the afferent signal flow evoked in the mechanoreceptors while the grasping hand is moving across the surface of the object. The cerebral signals controlling the movement were called "Bewegidee" (motion idea). According to Steinbuch’s model, only by the interaction of the "Bewegidee" with the afferent signal flow did object recognition become possible. He illustrated his statements by a simple experiment: if an object passively activates the mechanoreceptors of the palm and fingers of a resting hand for sufficient sequences and time, object recognition is not achieved. When the hand, however, grasps actively, object recognition occurs within a few seconds.
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Efference copy
In physiology, an efference copy or efferent copy is an internal copy of an outflowing (efferent), movement-producing signal generated by an organism's motor system. It can be collated with the (reafferent) sensory input that results from the agent's movement, enabling a comparison of actual movement with desired movement, and a shielding of perception from particular self-induced effects on the sensory input to achieve perceptual stability. Together with internal models, efference copies can serve to enable the brain to predict the effects of an action.
An equivalent term with a different history is corollary discharge.
Efference copies are important in enabling motor adaptation such as to enhance gaze stability. They have a role in the perception of self and nonself electric fields in electric fish. They also underlie the phenomenon of tickling.
A motor signal from the central nervous system (CNS) to the periphery is called an efference, and a copy of this signal is called an efference copy. Sensory information coming from sensory receptors in the peripheral nervous system to the central nervous system is called afference. On a similar basis, nerves into the nervous system are afferent nerves and ones out are termed efferent nerves.
When an efferent signal is produced and sent to the motor system, it has been suggested that a copy of the signal, known as an efference copy, is created so that exafference (sensory signals generated from external stimuli in the environment) can be distinguished from reafference (sensory signals resulting from an animal's own actions).
This efference copy, by providing the input to a forward internal model, is then used to generate the predicted sensory feedback that estimates the sensory consequences of a motor command. The actual sensory consequences of the motor command are then deployed to compare with the corollary discharge to inform the CNS about how well the expected action matched its actual external action.
Corollary discharge is characterized as an efference copy of an action command used to inhibit any response to the self generated sensory signal which would interfere with the execution of the motor task. The inhibitory commands originate at the same time as the motor command and target the sensory pathway that would report any reafference to higher levels of the CNS. This is unique from the efference copy, since the corollary discharge is actually fed into the sensory pathway to cancel out the reafferent signals generated by the movement. Alternatively, corollary discharges briefly alters self-generated sensory responses to reduce self-induced desensitization or help distinguish between self-generated and externally generated sensory information.
In 1811 Johann Georg Steinbuch (1770–1818) referred repeatedly to the problem of efference copy and reafference in his book "Beytrag zur Physiologie der Sinne" ("Contribution to the Physiology of Senses"). After studying medicine, Steinbuch worked for a number of years as lecturer at the University of Erlangen and thereafter as physician in Heidenheim, Ulm, and Herrenberg (Württemberg, South Germany). As a young university teacher, he was particularly interested in the brain mechanisms which enable the perception of space and objects, but in later years his attention shifted to the more practical problems of clinical medicine. Together with Justinus Kerner he gave a very precise description in 1817 of the clinical symptoms of botulism. In his book "Beytrag zur Physiologie der Sinne”, Steinbuch presented a very careful analysis of the tactile recognition of objects by the grasping hand. Hereby, he developed the hypothesis that the cerebral mechanisms controlling the movement of the hands interact within the brain with the afferent signal flow evoked in the mechanoreceptors while the grasping hand is moving across the surface of the object. The cerebral signals controlling the movement were called "Bewegidee" (motion idea). According to Steinbuch’s model, only by the interaction of the "Bewegidee" with the afferent signal flow did object recognition become possible. He illustrated his statements by a simple experiment: if an object passively activates the mechanoreceptors of the palm and fingers of a resting hand for sufficient sequences and time, object recognition is not achieved. When the hand, however, grasps actively, object recognition occurs within a few seconds.