A remarkable progress in recent years toward understanding the brain architecture is made by few Neuroscientists around the world. At the start of the 20th century, a German neuroanatomist named Korbinian Brodmann parceled the human cortex into nearly 50 different areas by looking at the structure and organization of sections of brain under a microscope. In coming years, Europe’s Human Brain Project will attempt to create a computational simulation of the human brain, while the U.S. BRAIN Initiative will try to create a wide-ranging picture of brain activity.
Now he and his coworkers are redoing Brodmann’s work as they map the borders between brain regions. The result may show something more like 100 to 200 distinct areas, providing scientists with a far more accurate road map for studying the brain’s different functions.
As part of the Human Brain Project, an international team of researchers led by German and Canadian scientists has produced a three-dimensional atlas of the brain that has 50 times the resolution of previous such maps. The atlas, which took a decade to complete, required slicing a brain into thousands of thin sections and digitally stitching them back together with the help of supercomputers. Able to show details as small as 20 micrometers, roughly the size of many human cells, it is a major step forward in understanding the brain’s three-dimensional anatomy.
To guide the brain’s digital reconstruction, researchers led by Katrin Amunts at the Jülich Research Centre in Germany initially used an MRI machine to image the post mortem brain of a 65-year-old woman. The brain was then cut into ultrathin slices. The scientists stained the sections and then imaged them one by one on a flatbed scanner.
Alan Evans and his coworkers at the Montreal Neurological Institute organized the 7,404 resulting images into a data set about a terabyte in size. Slicing had bent, ripped, and torn the tissue, so Evans had to correct these defects in the images. He also aligned each one to its original position in the brain. The result is mesmerizing: a brain model that you can swim through, zooming in or out to see the arrangement of cells and tissues.
An more innovative technique called Clarity, developed in the lab of Karl Deisseroth, a neuroscientist and bioengineer at Stanford University that allows scientists to directly see the structures of neurons and circuitry in an intact brain. The brain, like any other tissue, is usually opaque because the fats in its cells block light. Clarity melts the lipids away, replacing them with a gel-like substance that leaves other structures intact and visible.
Such a map of the brain might contain several petabytes of data, which computers today can’t easily navigate in real time, though it is optimistic that they will be able to in the future. Advances could come from new techniques that allow scientists to see the arrangement of cells and nerve fibers inside intact brain tissue at very high resolution.
Though Clarity can be used on a whole mouse brain, the human brain is too big to be studied fully intact with the existing version of the technology. The technique is already be used on blocks of human brain tissue thousands of times larger than a thin brain section, making 3-D reconstruction easier and less error prone. Clarity and polarized-light imaging currently give fantastic resolution to pieces of brain, in the future it is hoped that this technology can be expanded to include a whole human brain.
( Sources and Citation : Katrin Amunts, Jülich Research Centre Alan Evans, Montreal Neurological Institute Karl Deisseroth, Stanford University )
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