Scientists can also study brain tissue dissected from animals or cadavers, allowing them to run much longer MRI scans--up to 24 hours--than a living person could tolerate. The longer the scan, the better the resolution of the resulting map.
This image shows half the cerebral hemisphere of a macaque monkey. The blue bundle of fibers running horizontally across the middle of the image is called the cingulum bundle, described by Wedeen as “a multilane highway” that runs from the prefrontal cortex, which is involved in planning and higher cognitive function, to the parietal cortex, which is mainly involved in synthesizing sensory information.
While this image looks quite complicated, it represents only a fraction--about 10 to 20 percent--of the wiring in that part of the brain. “The images are so informationally rich that it’s a challenging engineering problem to show them in a useful way,” says Wedeen. “We want to show a large image to give context but a small enough fraction to give detail.”