Lab animals can be genetically modified so their cells express fluorescent proteins. By engineering them to express a particular protein that only fluoresces in the presence of calcium, we can have the fluorescence of neurons turn on as they fire, and then turn off afterward. We can even select specific neurons by type and location to have this property. Thus, calcium imaging is the technique of observing the firing of neurons in a living animal’s brain with fluorescent microscopy. In many cases though, researchers go a step further: they use really small, lightweight microscopes that can be mounted on an animal’s skull in a way that allows the animal to run around through a maze or otherwise freely behave. Then, they can look at which circuits of neurons light up immediately when the animal makes a certain decision or when something happens to it. This kind of research may have far-reaching applications from the purely academic to potentially medical or pharmaceutical, which is why it is done by researchers at different organizations around the world.
Written by: Daniel Shteinbok