What’s the News: A new thumbnail-sized microscope will give researchers a way to see what’s happening in the brain of a mouse as it moves around and goes about its business. The microscope, described earlier this week in Nature Methods, weighs less than 2 grams—little enough that it can be fitted atop a rodent’s head—and tracks the activity of up to 200 brain cells.
What’s the Context:
- To watch a living brain in action, researchers usually have to make sure the animal that brain belongs to is keeping very still, be it a human in an MRI machine or a mouse under a benchtop microscope. That’s not such a problem for researchers studying, say, vision or memory—but it’s difficult to investigate the neuroscience of movement or behavior when your subjects can’t move around and behave.
How the Heck:
- The new device is a fluorescence microscope, meaning it shines light on a sample, then captures the glow that bounces back. Despite the scope’s tiny size, the researchers fit all the necessary optical components—lenses, sensors, a mirror, an LED light, and more—inside it.
- In addition to being mobile, the microscope captures the activity of more cells than a traditional benchtop microscope does, letting researchers see what’s happening in a larger area of the brain.
- To test out this new tool, the researchers cut small holes in the skulls of lab mice, then mounted the microscope, top hat-like, on the mice’s heads. For this study, they placed the scope over the cerebellum, the brain area involved in motor coordination.
- The team injected the mice with a fluorescent dye that stuck to particular molecules in the brain and glowed under the LED light, providing a real-time feed of what the cells were doing. They then set the mice free to walk around a small enclosure or run on a wheel, recording their brain activity all the while. The video below shows the mice moving around on the left, and their concurrent brain activity—captured by the microscope—on the right.
The Future Holds:
- “For the animal to be able to carry the whole microscope along with it opens a lot more possibilities in studying behavior,” bioengineer Daniel Fletcher, who wasn’t involved with the study, told Technology Review.
- While the prototype of the microscope cost $50,000 to make, all of the optical components either are or easily could be mass produced, which could vastly decrease the price.
- The researchers see possibilities for this portable, soon-to-be-affordable microscope beyond neuroscience research, such as using it for diagnostic tests in areas without advanced medical facilities.
Reference: Kunal K. Ghosh et al. “Miniaturized integration of a fluorescence microscope.” Nature Methods, published online September 11, 2011. DOI: 10.1038/nmeth.1694
Image courtesy of Dan Stober, Stanford News Service / Video courtesy of Ghosh et al, Nature Methods