A landmark three-dimensional (3-D) digital reconstruction of a complete human brain, called the BigBrain, now for the first time shows the brain anatomy（解剖学） in microscopic detail -- at a spatial resolution of 20 microns, smaller than the size of one fine strand of hair -- exceeding that of existing reference brains presently in the public domain. The new tool is made freely available to the broader scientific community to advance the field of neuroscience. Researchers from Germany and Canada, who collaborated on the ultra-high resolution brain model, present their work in the 21 June issue of the journal Science.

"The authors pushed the limits of current technology," said Science's senior editor Peter Stern about the international scientific effort. "Such spatial resolution exceeds that of presently available reference brains by a factor of 50 in each of the three spatial dimensions."

The sophisticated modern image processing methods reveal an unprecedented look at the very fine details of the human brain's microstructure, or cellular level. The anatomical tool will allow for three-dimensional cytoarchitectonic mapping of the human brain and serve as an atlas（地图集） for small cellular circuit data, or single layers or sublayers of the cerebral cortex, explained the researchers.

Until recently, reference brains did not probe further than the macroscopic, or visible, components of the brain. Now, the BigBrain provides a resolution much finer than the typical 1 mm resolution from MRI studies.

The project "has been a tour-de-force to assemble images of over 7,400 individual histological sections, each with its own distortions, rips and tears, into a coherent 3-D volume," said senior author Dr. Alan Evans, a professor at the Montreal Neurological Institute at McGill University in Montreal, Canada. "This dataset allows for the first time a 3-D exploration of human cytoarchitectural anatomy."

Thin sections of a 65-year-old human female brain, which was embedded in paraffin wax, were cut with a special large-scale tool called a microtome. Then, the 20-micrometer thick histological sections were mounted on slides, stained to detect cell structures and finally digitized with a high-resolution flatbed scanner so researchers could reconstruct the high-resolution 3-D brain model. It took approximately 1,000 hours to collect the data. The resulting images reveal differences in the laminar pattern between brain areas.

The new reference brain, which is part of the European Human Brain Project, serves as a powerful tool to facilitate neuroscience research and "redefines traditional maps from the beginning of the 20th century," explained lead author Dr. Katrin Amunts from the Research Centre Jülich and director of the Cecile and Oskar Vogt Institute for Brain Research at the Heinrich Heine University Düsseldorf in Germany. "The famous cytoarchitectural atlases of the early 1900's were simplified drawings of a brain and were based on pure visual analysis of cellular organization patterns," added Dr. Amunts.