Cytoarchitectural maps of the human brain in standard anatomical space.

The remarkable intersubject variability of the human cerebral cortex poses major problems for the systematic study of functional-structural relationships. Lack of homology and macroscopical landmarks between brains implies that one cannot in three or two dimensions find which part of one gyrus or sulcus matches which part of another subject's cerebral cortex. Furthermore, the frequent lack of correspondence between cytoarchitectural borders and the bottom of sulci invalidates correlations between gross morphology and microstructure. Therefore, we proposed that microstructural criteria should be used to define an anatomical space for comparison of individual brains and for establishing a probability map for each cytoarchitecturally defined area by quantitative means [Roland and Zilles, 1994; Trends Neurosci 17:458-467]. Here we examined the mapping of cytoarchitectural areas 4a, 4p, 3a, 3b, V1, and V2 into two commonly used anatomical standard reference spaces. Linear global transformations into Talairach space produced minimal overlap of corresponding cytoarchitectural areas. Global affine and nonaffine transformations into the anatomical space of the Human Brain Atlas (HBA) gave significantly larger volumes of overlap of corresponding cytoarchitectural areas. It is expected that local transformations can further improve the registration of corresponding cytoarchitectural areas and thereby define a common standard anatomical space in which to study variations in gross anatomical structure and function.