A new technique that takes time-lapse snapshots of individual cells in deep brain regions could help researchers better understand how neurons change over time in response to drug dependence.

Current techniques allow researchers working with open skulls in animals to photograph cells in shallow areas of the brain such as the neocortex, but there’s not enough light at deeper levels of the brain, such as the hippocampus and striatum, for these techniques to be effective. In a study published in January in Nature Medicine (Vol. 17, No. 2), Stanford University biophysicist Mark Schnitzer, PhD, led a research team that developed a technique called time-lapse fluorescence microendoscopy, in which they surgically implant tiny tubes into the brains of mice. They then inserted microscopic camera lenses with lamps through the tubes to take better photos than have ever been possible before.

To test the technique, researchers injected cancerous glial cells into the mice’s brains and used the microscopic cameras to take a photo every day over the course of two weeks. The resulting time-lapse sequence showed the cancerous cells extending new blood vessels outward toward neighboring glial cells.

The new technique could prove to be a boon to psychologists looking to better understand how brain cells and neuronal connections adapt to changes in their chemical environment. For example, researchers could watch as neurons in the dorsal striatum exposed to addictive substances become gradually less responsive to the increased dopamine levels caused by cocaine or amphetamine, a process that ups the amount of drugs needed to reach a high.

“This should permit researchers interested in the reward system to address a range of issues that were previously out of reach,” Schnitzer says.

—M. Price