A 20 micron resolution 3D map of a human brain
Resolution is now often measured in pixels, but the more familiar method is to use measures of distance. Resolution is not the same as size, although the two terms are sometimes conflated. As the world’s notebook tells us, Basically, resolution quantifies how close lines can be to each other and still be visibly resolved.[i]
The chart below depicts various material and biological things in the size range from 1 millimeter to 1 Ångstrom.
After looking at the chart, you might wonder if a 20 micron resolution includes individual neurons. The human neuronal trunk or axon is 1/1,000,000 meter (10 ^ -6 or one micron) in diameter. If you took a human hair and cut it the long-way into 100 equal fibers, each would be the diameter of a neuron. The gold leaf that jewelers use – which cannot be held up in a room apparently breathlessly still without being whipped about and torn as if there were a hurricane blowing through the room – is 1/10 this thickness. A brain-size can would hold 9.62 1010 or about 100,000,000,000 (one hundred billion) neurons packed like sardines. It is cell-body staining which allows for visualization of neurons in this preparation.
Kurzweil News (http://www.kurzweilai.net/bigbrain-an-ultra-high-resolution-3d-roadmap-of-the-human-brain) lets us in on more of the fun.
A landmark three-dimensional (3-D) digital reconstruction of a complete human brain, called the BigBrain, shows for the first time the brain anatomy 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 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 for small cellular circuit data, or single layers or sublayers of the cerebral cortex, explained the researchers.
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.
Teams from the Research Centre Jülich of the Cecile and Oskar Vogt Institute for Brain Research at the Heinrich Heine University Düsseldorf, Germany and from Montreal Neurological Institute at McGill University in Montreal, Canada accomplished this work over many years.
By integrating the BigBrain with other maps, researchers expect to achieve a
1 micron resolution, allowing for study of cellular morphology. But even before this happens, you can now make hypotheses about neuronal anatomy and then test them by looking them up on BigBrain!
Free access to the data set is available after registering at https://bigbrain.cbrain.mcgill.ca/.
[i] Wikipedia contributors, “Image resolution,” Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Image_resolution&oldid=559919181 (accessed June 29, 2013).