A mouse brain imaged using the CLARITY technique.
Brain research has been getting lots of press since President Barack Obama announced his BRAIN initiative to map the human brain. Earlier this week, Nature published a paper by a group of Stanford researchers or a new technique called CLARITY. This technique allows the researchers to make whole organs transparent. They can then use different chemical compounds to label and highlight specific cells or features of the organ. They were able to demonstrate on brain tissue. From Popular Science:
Making these images is an eight-day process. The Stanford researchers started by infusing a mouse brain with a hydrogel solution. They then put the gel and brain into an incubator to set. (Like making Jell-O! Except that the setting, in this case, required a higher temperature rather than a lower one.)
The set gel bound to and physically supported most of the things in the brain. The gel didn’t bind to lipids, or fats, in the brain, however. Such fat is opaque and surrounds each cell. When researchers extracted this unbound fat, they were left with a clear view of everything else, frozen in place. For example, proteins that were originally embedded in cell membranes and the little spines that come off of neurons both remained.
At this point, the researchers could add different molecules to color the parts of the brain they want to study and look at the whole thing under a light microscope.