What does the cerebellum really do?

Abstract

Summary The cerebellum is a large part of the brain in all vertebrates. In humans it constitutes about ten percent of the total brain weight, but the small granule cells of the cerebellar cortex are densely packed so that the cerebellum contains more neurons than all of the rest of the brain. Although it has a uniform cellular structure in mammals and birds, there is great variability in the relative size of its parts. In mammals the cerebellum can be roughly divided into three parasagittal divisions; a midline vermis (Latin: a worm) and two lateral hemispheres. The hemispheres are large in the higher primates and they are very large in the human brain. Because the cerebellar hemispheres are particularly large in humans and the higher primates, from time to time claims have been made that in addition to its role in motor control, the cerebellum is important for cognitive functions, such as learning, attention, and language. Here I review some of the evidence for and against that claim.