The term area 4p of Geyer refers to the more posterior of two parts of primary motor cortex defined on the basis of cytoarchitecture and neurotransmitter binding in the human ( Matelli-2004 ). The more anterior part is area 4a of Geyer. The relation of area 4p to the caudal sector of primary motor cortex, which is defined in the macaque on the basis of function and connectivity, is undetermined.