Today, researchers have unveiled the most detailed 3-D image of the human brain ever taken. The image reveals structures as tiny as 20 microns, 50 times smaller than those created using the best MRI technology.
The image, made as part of a project called the BigBrain, is part of a larger effort to create a high-resolution computer model of the human brain that can serve as a reference point for future studies. Data from other studies can be combined with this model to allow scientists to link brain function to specific groups of nerve cells.
That information can be used to test theories about brain activity as well as lead to treatments for disease and disorders.
"When you are interested a disorder like Alzheimer's disease, you have the first ever brain model where you can look into details of the hippocampus, which is the brain region that is extremely important for memory," said Karl Zilles, one of the co-authors of the paper and senior professor of the Jülich Aachen Research Alliance in Germany.
Until now, brain scans have been made using MRI and PET technology. But these imagers can only capture structures as small as a millimeter. To understand what happens when a person gets Alzheimer's disease or epilepsy, it's necessary to study individual groups of cells. A millimeter just isn't fine enough to see them.
To create the ultra-detailed images, the scientists used a brain from a deceased 65-year-old woman. Dr. Katrin Amunts, director of the Cecile and Oskar Vogt Institute for Brain Research at the Heinrich Heine University Düsseldorf in Germany, and lead author, said the woman who donated the brain didn't have any diagnosed psychiatric problems or diseases that would have affected the brain's anatomy.
Scientists then used a tool called a microtome to cut the brain into 7,400 slices, each 20 microns thick. That alone was a difficult thing to do. While pathologists often section brains, they are usually much thicker.
The sections were then stained to bring out the details and then a standard laboratory camera was used to create a high-resolution digital image of every slice. Each image was 13,000 by 11,000 pixels and by the time the researchers were done creating the images, the amount of data they compiled totaled about a terabyte. Next, they used a computer to combine the images into one large, three-dimensional computer model.
The idea is to perform computer simulations using the three-dimensional model, also called an atlas, in ways that weren't possible before, said a professor of neurology at the Montréal Neurological Institute at McGill University, and another co-author. Functional MRI scans are relatively crude.
Other scientists in the field say BigBrain could be a helpful tool. "For instance, you can perform MRIs in patients with severe traumatic injury, both with favorable and unfavorable outcome, apply the atlas and determine by which regions they differ," said Damien Galanaud, at the department of neuroradiology at Pitié-Salpêtrière Hospital in Paris, who studies traumatic brain injuries, and was not involved in the study.
The only down side, Galanaud added, such a study wouldn't necessarily offer a complete picture, because sometimes brain anatomy is changed when there's a severe injury. So it would require additional "smoothing" of the differences between the inured brain and the model.
Warren Selman, chairman of the department of neurological surgery at University Hospitals Case Medical Center in Cleveland, said one issue is connectivity: the model brain, being from a dead person, won't show the communications signals between neurons that makes a brain work. "You've got to find out what kind of talk [between cells] is going on at this level," he said. "Then it starts to get exciting."
He added the work is still tremendously useful, as it will help scientists pinpoint what functions are localized where in the brain.