Efference copy
[4] 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.
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.
[5] 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.
In his book "Beytrag zur Physiologie der Sinne”, Steinbuch presented a very careful analysis of the tactile recognition of objects by the grasping hand.
[6] The first person to propose the existence of efferent copies was the German physician and physicist Hermann von Helmholtz in the middle of the 19th century.
"The view [of von Helmholtz and his followers] which dispenses with peripheral organs and afferent nerves for the muscular sense has had powerful adherents .
[3][10] The Nobel Prize winner, Roger Wolcott Sperry argued for the basis of corollary discharges following his research upon the optokinetic reflex.
During trunk rotational movements there is a learned CNS anticipation of Coriolis effects, mediated by generation of an appropriate efference copy that can be compared to re-afferent information.
[12][13] It has been proposed that efference copy has an important role in maintaining gaze stability with active head movement by augmenting the vestibulo-ocular reflex (aVOR) during dynamic visual acuity testing.
[16] With the use of the efference copy the internal model can predict a future hand trajectory, thus allowing for the parallel grip to the particular load of the known object.
They have postulated that this is because when a person sends a motor command to produce the tickling motion, the efference copy anticipates and cancels out the sensory outcome.
This idea is further supported by evidence that a delay between the self-produced tickling motor command and the actual execution of this movement (mediated by a robotic arm) causes an increase in the perceived tickliness of the sensation.
[23] In the case of auditory verbal hallucinations, it is thought that a breakdown along the efference copy and forward model route creates a mismatch between what is expected and what is observed, leading to the experience that speech is not produced by oneself.
[24] The differences in the ERP signal of the efference copy are so severe that machine learning algorithms can distinguish between schizophrenia patients and healthy control subjects, for example.
