How much about the human brain do we really know? Not enough, says bioengineer Karl Deisseroth. A milky, opaque tissue coats much of the organ, preventing researchers from seeing the all-important connections between neurons. So Deisseroth’s team developed a way to remove this cloud by chemically dissolving the opaque fatty tissue in a dead brain and replacing it with a transparent hydrogel.
This technique, called CLARITY gives researchers an unprecedented ability to study the neurostructure and circuitry of the brain. “Our goal is to understand the system in its entirety but also at high resolution,” says Deisseroth, the D.H. Chen Professor in Stanford School of Medicine and a professor of bioengineering and of psychiatry and behavioral sciences.
The accompanying video, produced by Miles O’Brien and Ann Kellan of Science Nation, and published here with permission by Stanford Engineering, shows how CLARITY could lead to new treatments for conditions like depression, and pave the way for medical advances outside the brain such as offering researchers new ways to understand electrical pathways in the heart or learn why damaged fibers in the spinal cord cause pain.
Deisseroth recently combined CLARITY with another technique he pioneered called optogenetics. It involves the use of light to control the behavior of cells. Using CLARITY and optogenetics together for the first time, Deisseroth’s team showed how certain neurons in the prefrontal cortex are built to respond to reward or aversion, a finding with implications for treating mental illness and addictions.