Brains as Clear as Jell-O for Scientists to Explore

http://www.nytimes.com/2013/04/11/science/brains-as-clear-as-jell-o-for-scientists-to-explore.html?_r=0

Scientists at Stanford University reported on Wednesday that they have made a whole mouse brain, and part of a human brain, transparent, so that networks of neurons that receive and send information can be highlighted in stunning color and viewed in all their three-dimensional complexity without slicing up the organ.

Two views of the same intact adult mouse brain, before, at left, and after a new technique developed by researchers at Stanford University was applied to it to make its tissue transparent. 

Even more important, experts say, is that unlike earlier methods for making the tissue of brains and other organs transparent, the new process, called Clarity by its inventors, preserves the biochemistry of the brain so well that researchers can test it over and over again with chemicals that highlight specific structures within a brain and provide clues to its past activity. The researchers say this process may help uncover the physical underpinnings of devastating mental disorders like schizophrenia, autism, post-traumatic stress disorder and others. 

There are several ways to make tissue transparent. The key to the new technique is a substance called a hydrogel, a material that is mostly water held together by larger molecules to give it some solidity. 

Dr. Chung said the hydrogel forms a kind of mesh that permeates the brain and connects to most of the molecules, but not to the lipids, which include fats and some other substances. The brain is then put in a soapy solution and an electric current is applied, which drives the solution through the brain, washing out the lipids. Once they are out, the brain is transparent, and its biochemistry is intact, so it may be infused with chemicals, like antibody molecules that also have a dye attached, that show fine details of its structure and previous activity.