Neuron d

uhave been used extensively to study motor learning in the context of reaching movements (Debicki and Gribble, 2004; Flanagan et al., 2003; Held and Rekosh, 1963; Imamizu et al., ered by updating an appropriate internal model, which is then used to guide movement. An alternative view is that a new control policy might be learned directly through trial and error1995; Krakauer et al., 1999; Lackner and Dizio, 1994; Malfait et al., 2005; Miall et al., 2004; Pine et al., 1996; Scheidt et al., until successful motor commands are found. No explicit model of the perturbation is necessary in this approach and thus itbasedmotor task. (1) Adaptation of an internal model channels movements toward successful error reduc-tion in visual space. (2) Repetition of the newly adap-ted movement induces directional biases toward the repeated movement. (3) Operant reinforcement through association of the adapted movement with successful error reduction is responsible for savings