A multiarchitectonic approach for the definition of functionally distinct areas and domains in the monkey frontal lobe

Over the last century, anatomical studies have shown that the cerebral cortex can be subdivided into structurally distinct regions, giving rise to a new branch of neuroanatomy: 'architectonics'. Since then, architectonics has been often accused of being overly subjective, and its validity for the definition of functionally different cortical fields has been seriously questioned. Since the late 1980s, however, the problem of localization has become particularly important in functional studies of the primate motor cortex, because of evidence that (1) the primate motor cortex is made up of a mosaic of functionally specialized areas and (2) the human motor cortex shares several general organizational principles with the monkey motor cortex. Studies of the macaque agranular frontal cortex that used a multimodal cyto-, myelo- and immuno-architectonic approach have shown that architectonic borders can be reliably and consistently defined across different individuals, even at a qualitative level of analysis. The validity of this approach has been confirmed by its ability to localize functionally distinct areas precisely and to predict the existence of new functional areas. After more than a century, architectonics as a discipline goes far beyond its original aim of generating cortical maps.