Mice that have been bred or genetically engineered to have diseases similar to human afflictions are usually used to study diseases of the deep brain.
"Researchers will now be able to study mouse models in these deep areas in a way that wasn't available before," said senior author Mark Schnitzer, associate professor of biology and of applied physics.
Because light microscopy can only penetrate the outermost layer of tissues, any region of the brain deeper than 700 microns or so (about 1/32 of an inch) cannot be reached by traditional microscopy techniques. Recent advances in micro-optics had allowed scientists to briefly peer deeper into living tissues, but it was nearly impossible to return to the same location of the brain and it was very likely that the tissue of interest would become damaged or infected.
With the new method, "Imaging is possible over a very long time without damaging the region of interest," said Juergen Jung, operations manager of the Schnitzer lab. Tiny glass tubes, about half the width of a grain of rice, are carefully placed in the deep brain of an anaesthetized mouse. Once the tubes are in place, the brain is not exposed to the outside environment, thus preventing infection. When researchers want to examine the cells and their interactions at this site, they insert a tiny optical instrument called a microendoscope inside the glass guide tube. The guide tubes have glass windows at the ends through which scientists can examine the interior of the brain.