A computer-interfaced rotarod accelerating from 4–40 rotations per min over 300 s was used (ENV-575M, Med Associates). Animals were trained with ten trials per day for either 1 d or 8 d (trained every other day). This training protocol was chosen on the basis of studies determining the time course of sensitivity of this task to interference, protein synthesis blockers (data not shown) and dopamine receptor antagonists (Fig. 5d). Each trial ended when the mouse fell off the rotarod or after 300 s had elapsed and there was a resting period of approximately 300 s between trials. Yoked animals were handled and placed in the rotarod in the same manner as the trained animals, but without the rotation of the rod. During the in vivo recordings, the beginning and end of the running period were signaled to the MAP recording system (Plexon) as events. The D1 receptor antagonist SCH-23390 (0.4 mg per kg of body weight, Sigma-Aldrich) and D2 receptor antagonist raclopride (2.0 mg per kg, Sigma-Aldrich) were dissolved in phosphate-buffered saline with 1% DMSO by volume (control injection) and injected intra-peritoneally at 10 ml kg–1 (these doses completely block the effects of 3,4-dihydroxy-l-phenylalanine after dopamine depletion49 (link), indicating complete block of D1 and D2 receptors in vivo).