A new brain map

Cognitive and other simpler sensory and motor tasks activate different brain regions, as demonstrated by functional imagingstudies, such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET). The cerebral cortex plays an important role here. It has long been known that the cerebralcortex is not homogeneous, but is organised in the form of specialised cortical areas. These cortical areas are characterised by a distinct cellular and molecular architecture as well as connectivity. However, so far no one has succeeded in shedding light on the relationship between brain structure and function on the complex systems level, because data from microstructural examinations could not be directly compared with the findings of functional imaging studies in the same spatial coordinate system. Moreover, the extent, localisation and microstructure of cortical areas vary from brain to brain. Such variability was not accounted for in previous brain atlases, and the sources and relevance of structural intersubject variability for brain function and human behaviour are not well understood. Intersubject variability is influenced by genes and other factors such as environment, education and training, as shown by violinists’ and pianists’ enlarged motor and sensory areas.

A unique electronic atlas system for the brain is currently being created encompassing the cell architecture, the regional organisation of the cortex and the distribution of signal-carrying receptor molecules, and allocates functions to individual cortical areas with levels of defined probability. Professor Katrin Amunts and Professor Karl Zilles from Forschungszentrum Jülich are working on this international research project with colleagues from three big American and Canadian research institutions. The neuroscientists combine information from living test subjects, obtained by imaging procedures such as MRT and PET, with information from tissue sections to make “probability maps”. Amunts explains that they give the probability of locating a particular function and structure in an element with a volume of one cubic millimetre. And Zilles adds that this data will create a virtual human brain, a tool for the interpretation of functional imaging data and also a significant contribution to basic research. Parts of the new atlas are already available to the scientific community on the internet and new findings are being added on an ongoing basis.