The prefrontal cortex: comparative architectonic organization in the human and the macaque monkey brains

Detailed cytoarchitectonic studies of the human cerebral cortex appeared during the first quarter of the 20th century. The incorporation of the cytoarchitectonic map by Brodmann (1909) in the Talairach proportional stereotaxic space (Talairach and Tournoux, 1988) has established the Brodmann numerical nomenclature as the basis for describing the cortical location of structural and functional findings obtained with modern neuroimaging. In experimental anatomical and physiological investigations of the macaque monkey performed during the last 50 years, the numerical architectonic nomenclature used to describe findings in the prefrontal cortex has been largely based on the map by Walker (1940). Unfortunately, the map by Walker was not based on a comparative investigation of the cytoarchitecture of the human and macaque monkey prefrontal cortex and, as a result, the nomenclature and the criteria for demarcating areas in the two primate species are not always consistent. These discrepancies are a major obstacle in the ability to compare experimental findings from nonhuman primates with results obtained in functional and structural neuroimaging of the human brain. The present article outlines these discrepancies in the classical maps and describes comparative investigations of the cytoarchitecture of the prefrontal cortex of the macaque monkey and human (Petrides and Pandya, 1994, 1999, 2002a) in order to resolve these discrepancies and enable easy translation of experimental research in the monkey to findings in the human brain obtained with modern neuroimaging.