The human cerebellum contains half of all neurons in the brain but only one tenth of its volume. Some diagrams from Gray's Anatomy, 1918:
In the summer of 2006 I interned with IBM Research at the TJ Watson Research Center in Yorktown Heights, NY. I worked with the Biometaphorical Computing Research group. My project was to take an idea for a novel cerebellum model (designed by Charles Peck, my mentor and group leader), implement it in software, and test its capabilities on various motor learning and conditioning tasks. See Peck et al 2007 and these posters for more details:
The following plots show the change in activity of various model components during learning:
The video below is a visual demonstration of the model learning to control an articulated arm with 6 distinct muscles. Note how, at the beginning, the basal ganglia provide most of the control signal, but over time the cerebellum learns the reaching task, offloading most of the work from the basal ganglia.