To explore the most intricate structures of the brain in order to decipher how it functions – Stefan Hell's team of researchers at the Max Planck Institute for Biophysical Chemistry in Göttingen has made a significant step closer to this goal. Using the STED microscopy developed by Hell, the scientists have, for the first time, managed to record detailed live images inside the brain of a living mouse. Captured in the previously impossible resolution of less than 70 nanometers, these images have made the minute structures visible which allow nerve cells to communicate with each other. This application of STED microscopy opens up numerous new possibilities for neuroscientists to decode fundamental processes in the brain.
Every day a huge quantity of information travels not only over our information superhighways; our brain must process an enormous amount of data as well. In order to do this, each of the approximately hundred billion nerve cells establishes contact with thousands of neighboring nerve cells. The entire data exchange takes place via contact sites – the synapses. Only if the nerve cells communicate via such contact sites at the right time and at the right place can the brain master its complex tasks: We play a difficult piece of piano, learn to juggle, or remember the names of people we have not seen for years.
We can learn most about these important contact sites in the brain by observing them at work. When and where do new synapses form and why do they disappear elsewhere? This is not easy to determine, since details in living nerve cells can only be observed with optical microscopes. Due to the diffraction of light, however, structures located closer together than 200 nanometers (200 millionths of a millimeter) appear as a single blurred spot. The STED microscopy developed by Stefan Hell and his team at the Max Planck Institute for Biophysical Chemistry is a groundbreaking method devised to surpass this resolution limit. They use a simple trick: Closely-positioned elements are kept dark under a special laser beam so that they emit fluorescence sequentially one after the other, rather than simultaneously, and can therefore be distinguished. Using this technique, Hell's team has been able to increase the resolution by approximately tenfold compared to conventional optical microscopes.
STED microscopy has already found wide application in fields ranging from materials research to cell biology. Under this microscope, cell cultures and histological preparations have offered unique insights into the cellular nanocosmos. The first real-time video clips from the interior of a nerve cell have demonstrated how tiny transmitter vesicles migrate within the long nerve cell endings.
