Activity in the human primary motor cortex related to arm and finger movements.

With the purpose of mapping representations of the finger and proximal arm in the human primary motor cortex (MI), we measured regional cerebral blood flow (rCBF) in eight right-handed normal volunteers during self-paced finger and proximal arm movements. Each movement activated two different fields in MI, one located deep in the anterior lip of the central sulcus and the other relatively close to the surface of the precentral gyrus. Arm fields were located higher than finger fields. A superficial arm field and a deep finger field partially, overlapped. The results indicate that there are two spatially separate motor representations of the finger and proximal arm in the human MI.