Cerebellar functions in motor control.

How does the cerebellum help to harness the machinery of movement to the intent of the individual, or how is motor "set" implemented? Cerebellar guidance is essential for this purpose, and there is growing agreement that this guidance is based on comparisons of intended and ongoing motor activity. Surprisingly little information exists however, on how guidance is translated into muscle action. Three cerebellar contributions to motor control are considered: Conveyance of set (implemention of motor programs), adaptibility of implementing set under changed conditions (plasticity), and incidental adjustment to circumstances of the moment (ongoing control). Current evidence is examined and found largely negative as to whether these cerebellar functions are carried out through modulation of alpha-gamma coactivation, with the possible exception of the fine control of learned movements.