Kim, T.H. et al. Cell Rep. 17, 3385–3394 (2016).
Thinned-skull or glass windows provide optical access to the mouse brain and can be used to obtain a glimpse of the activity of neurons in a small area of the brain. Kim et al. have now developed a window preparation that allows imaging neurons across a much larger area, spanning the dorsal surface of the brain. Their Crystal Skull approach involves implanting a curved coverglass after removal of the skullcap. The coverglass is shaped by heating and simply pressing it onto a curved mold. In contrast to the use of flat windows, this approach avoids applying pressure to the brain, thereby minimizing aberrant effects and allowing long-term optical access to up to 1 million neurons. The researchers used this preparation to image the morphology and activity of fluorescently labeled neurons with two-photon microscopy.