Figure 5. Transformation of a sensory error into a subsequent change in behavior in the oculomotor vermis.

Experience of a visual error in the post-saccadic period increases the probability of generating a CS in a population of P-cells that prefer that error direction. If a CS is generated, it causes plasticity in the P-cells, modifying the simple spikes that are produced collectively by the population, altering their prediction of state x̂. At the deep cerebellar nucleus cell, the predicted state is an inhibitory signal that is compared with an excitatory signal from the mossy fibers, which possibly carry information about the desired state x_d. The output of the nucleus neuron is the difference between these two variables, reflecting a state correction xtilde; associated with the ongoing motor command u. This correction affects motor behavior in a specific direction: the direction of force specified by vector Δu. The preferred direction of visual error that produced a CS in the P-cells (i.e., CS-on) is parallel to the direction of force Δu in the effectors that the P-cells project to. Black filled circles are inhibitory neurons, and white filled circles are excitatory neurons.