Feed-forward mode

For the execution of well-practiced, very fast (i.e., ballistic) movements (example, playing fast passages on a musical instrument or a tennis serve), there is inadequate time for feed-back alteration of errors. For such movements the cerebellum activates in a feed-forward mode in which it runs a program which predicts the motor consequences of its own action. Unpredicted perturbations which take place whenever the cerebellum is in this mode cannot be corrected for in time and therefore performance will be degraded.