Multiple somatotopic representations in the human cerebellum

THE classic view of representation in the cerebellum assumes two homunculi, one in the anterior lobe and one in the posterior lobe. Functional imaging has confirmed this somatotopy in the human anterior lobe but not, so far, in the posterior lobe. Using fMRI, we found separate peaks of activation fo r finger and toe in three ipsilateral cerebellar regions. In both the anter ior and posterior lobe, the toe representation was semicircular around the finger area, with peaks of activation aligned in accord with the classic ho munculi. Also, segregated peaks of activation were found in the pyramis ver mis. These results confirm the existence of a second homunculus in the post erior lobe of the human cerebellum and suggest a third one. (C) 1999 Lippin cott Williams & Wilkins.