New concepts in cerebellar function.

In the past 3 decades our knowledge of the cerebellum has increased enormously and yielded important new concepts which include the parasagittal band organization of the cerebellum, synaptic plasticity, motor learning, etc. Very recently, knowledge of the cerebellum at the levels of ion channels, receptors and messengers has advanced greatly and is expanding at the level of gene regulation. Our knowledge about the cerebellum at systems level has also advanced and facilitated theoretical modelling of the cerebellum as a complex learning machine. The cerebellum acquires and retains the dynamics, or inverse dynamics, of a control object by learning. By using this "dynamics memory" it permits automatic, precise and smooth execution of learned movements. It is postulated that this control principle may also apply to the brain mechanisms underlying human thought, in which ideas and concepts are "manipulated", as opposed to limbs as in movement. Finally, the control system scheme of the cerebellum will be generalized to encompass the whole learned behavior including movements and thoughts.