Figure 1.

Perturbation task. Rhesus monkeys used a robotic manipulandum to control a “+” style cursor and make four types of very fast reaching movements between a yellow start and red end cue target displayed on a computer monitor. A, PD REACH epoch: Movements made across eight directions with no robot forces identified the PD of a Purkinje cell. All subsequent reaching movements during a recording session were along this direction. B, BASELINE EC epoch: Error clamp (EC) trials used robot-generated virtual walls (blue arrows) to restrict perpendicular movement to an hourglass-shaped area (blue). C, ADAPT epoch: The equation below describes a predictable, bell-shaped perturbation force [P(t), orange] that either assisted or resisted movements inside the EC. Colored arrows illustrate perturbation components that were randomized between recording sessions: black, magnitude (M); red, duration (D); blue, start position (P). D, CATCH epoch: The same adapt parameters were repeated (D2) with the addition of randomly occurring catch trials (D1). Catch trial parameters matched baseline EC. In all panels, black dashed lines illustrate actual channel width and black arrows movement direction. E, Locations of microelectrode entry into the cerebellar cortex based on modeling using MRI and CT imaging. Shown are locations at which Purkinje cells with significant learning-related modulation were recorded. Dashed line is the location of the primary fissure (Pf).