We know a lot about the cerebellum, but do we know what motor learning is?

In the behavioral literature on human movement, a distinction is made between the learning of parameters and the learning of new movement forms or topologies. Whereas the target articles by Thach, Smith, and Houk et al. provide evidence for cerebellar involvement in parametrization learning and adaptation, the evidence in favor of its involvement in the generation of new movement patterns is less straightforward. A case is made for focusing more attention on the latter issue in the future. This would directly help to bridge the gap between current neurophysiological approaches to the role of the cerebellum and the behavioral expressions of human motor learning.