ABSTRACT
The gyrencephalic human cerebral cortex is distributed over a folded cerebral surface, thereby allowing for a larger area of cortical surface in the same volume than in case of a lissencephalic brain with a smooth cerebral surface (Zilles, 1990). Early neuroanatomical and electrophysiological studies supported the hypothesis that cytoarchitectonically-defined cortical areas may represent distinct functional units, and that the cerebral sulci may coincide with the areal borders (Brodmann, 1909; Vogt and Vogt, 1919). Consequently, the Brodmann map has become the most influential anatomical reference system for the analysis of structure-function correlations in the human brain. It is used as a twodimensional template for a cytoarchitectonically-based parcellation of the cerebral cortex,
tional magnetic resonance imaging, subdivide the human cerebral cortex with increasing spatial resolution. For analysis, the resulting foci of activation are related to visible macroanatomic landmarks, because even the most advanced imaging protocols do not permit direct visualization of the laminar heterogeneities which define the cytoarchitectonic pattern. It is the general assumption of many brain mapping studies that these gyral and sulcal landmarks coincide with the borders of cytoarchitectonic areas, as shown in the Brodmann map. It has also been hypothesized that the intrasulcal cortices may play a distinctive role in higher cognitive processing, because the most rapid changes in neuronal activity are frequently observed in the sulcal fundi (Markowitsch and Tulving, 1995). However, the available knowledge about the precise relationship between the topography of specific cytoarchitectonic fields and the sulcal and gyral patterns in the general population is not adequate compared to the demands of structural and functional brain mapping techniques (Rademacher et al., 1992; Zilles et al., 1995; Geyer, 1996; van Essen et al., 1998; Roland and Zilles, 1998; Schormann and Zilles, 1998; Amunts et al., 1999).
