Functional magnetic resonance imaging (fMRI) was employed to determine area
s of activation in the cerebellar cortex in 46 human subjects during a seri
es of motor tasks. To reduce the variance due to differences in individual
anatomy, a specific transformational procedure for the cerebellum was intro
duced. The activation areas for movements of lips, tongue, hands, and feet
were determined and found to be sharply confined to lobules and sublobules
and their sagittal zones in the rostral and caudal spine-cerebellar cortex.
There was a clear symmetry mirroring at the midline. The activation mapped
as two distinct homunculoid representations. One, a more extended represen
tation, was located upside down in the superior cerebellum, and a second on
e, doubled and smaller, in the inferior cerebellum. The two representations
were remarkably similar to those proposed by Snider and Eldred [1951] five
decades ago. In the upper representation, an intralimb somatotopy for the
right elbow, wrist, and fingers was revealed. The maps seem to confirm earl
ier electrophysiological findings of sagittal zones in animals. They differ
, however, from micromapping reports on fractured somatotopic maps in the c
erebellar cortex of mammals. We assume that the representations that we obs
erved are not solely the result of spatial integration of hemodynamic event
s underlying the fMRI method and may reflect integration of afferent periph
eral and central information in the cerebellar cortex. (C) 2001 Wiley-Liss,
Inc.