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. History Steinbuch "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." von Helmholtz 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. He argued that the brain needed to create an efference copy for the motor commands that controlled eye muscles so as to aid the brain's determining the location of an object relative to the head. His argument used the experiment in which one gently presses on one's own eye. If this is done, one notices that the visual world seems to have "moved" as a result of this passive movement of the eyeball. In contrast, if the eyeball is actively moved by the eye muscles