The Developing European Computerized Human Brain Database for All Imaging Modalities

Figure 1 shows Brodmann’s map of cytoarchitectural areas (Brodmann, 1909). This map is in essence a concept of the structural–functional relations in the human brain. It postulates that the functional elements of the brain are the cytoarchitectural subdivisions. But is it really true that the areas delimited by Brodmann are functionally homogenous? Second, does this parcellation of the cerebral cortex of man really reveal the functional units of the cerebral cortex? To examine this hypothesis and find out which are the functional units of the cerebral cortex and which are the structural units, Karl Zilles and I started, in 1990, a project to more systematically examine the hypothesis of the structural–functional heterogeneity of the human cerebral cortex.Although Brodmann’s map (Fig. 1) is known to every neurobiologist and has survived for almost 90 years, it reflects the parcellation of the cerebral cortex based on subjective criteria of where borders of cortical areas should be. This map and others (Economo and Koskinas, 1925; Campbell, 1905; Smith, 1907; Brodmann, 1912; Bailey and von Bonin, 1951) are usually based on a single or very few brains. These representations of cytoarchitectonic subdivisions do not take into consideration the large variations in extent and topography from brain to brain (Filimonoff, 1932; Stensaas et al., 1974; Roland and Zilles, 1994). Moreover, the presented maps are useless for metaanalyses since they cannot be translatedwith any faithfulness into the true 3D format of the brain nor into a flat-mounted 2D format. Consequently new mapping approaches must: (i) be based on quantitative cytoand myeloarchitectonic studies, which require the analysis of histological sections (postmortem studies); (ii) take intersubject variability into account; (iii) be transferable onto MR images and 3D reconstructions of these images; and (iv) be based on additional and independent techniques showing the regional inhomogeneities of neurochemical markers (e.g., transmitter binding sites). Clearly other criteria such as quantitative receptor architectonics should also be included in an anatomical parcellation of the cerebral cortex. Because brains differ macroscopically as well as microscopically from individual to individual, it is not possible from observations of single individuals to make general observations about the parcellation based on structural information and parcellation based on functional information [for example, from PET and functional magnetic resonance tomography (fMRI)]. For this reason, we developed the computerized Human Brain Atlas (HBA) (Roland et al., 1994). This is a software which is not landmark based, and which can be used to fuse images from different modalities. It is a system open to any future additions of spatially definable data. Thus, data from histological sections, positron emission tomography images, magnetic resonance images, etc., can be put into a standard brain format. Data in the standard brain format are displayed on the basis of a single male brain, which was chosen in such a way that the brain differed the least from other male brains. Having a standard brain format to present data implies that one automatically ends up by having a database consisting of structural and functional information. Thus the database is not made for the sake of collecting data and putting them into a database, but it is made for the sake of examining a scientific hypothesis. The available or planned contents of the database at present are: