Complex spikes perturb movements, revealing the sensorimotor map of Purkinje cells.

We lack general principles that can describe how changes in a P-cell's simple spikes might alter behavior. Here, we show that a brief suppression of a P-cell's simple spikes in the oculomotor vermis consistently pulls the eyes in a direction that corresponds to the preferred location of the sensory space as conveyed probabilistically to that P-cell from the inferior olive. Thus, the inferior olive defines the coordinate system regarding the information that a P-cell is providing to the rest of the brain.