The Method in a Nutshell
The Julich-Brain is based on 23 post mortem brains from the body donor programme at the University of Düsseldorf. Brains were subjected to MRI and cut into 20 μm thick sections which were stained for cell bodies before digital imaging. Images of sections were 3D reconstructed, and aligned to a standard reference brain.
Borders between cytoarchitectonic areas were identified in brain sections using image analysis and statistical tools. Ten brains, five male and five female were studied to map each area. The areas were then 3D reconstructed, and superimposed in the reference brain. This allowed us to compute probability maps which provide measures of variability in areal size and localisation. Within the probability maps, colours code for the probability that an area can be found at a particular position. For these maps, regions which are not yet mapped are represented by so-called gap maps.
Probability maps can be simplified to show all areas at a glance: for this purpose, maximum probability maps were generated. Each position in the reference brain was assigned to the area with highest probability.