Why build something so seemingly ridiculous? Well here’s the deal. Currently, researchers can observe the brain activity of a laboratory mouse using a technique known as two-photon imaging, but the imaging technology has a major limitation — it only works when a mouse is stationary. This hindrance means researchers can only study mice as they stand still and cannot explore the much more interesting interactions that occur when mice are moving and responding to their environment. So, to overcome this stumbling block, scientists at Howard Hughes Medical Institute’s Janelia Research lab are developing a novel, whisker-based virtual reality system that allows them to study mice as they experience movement and respond to external stimuli.
For several years, scientists have been using ocular virtual reality systems to trick mice into thinking they were running on top of a large ball. This system was cumbersome, requiring weeks of training before the mice could run as part of an experiment. Working at the Janelia Research Campus, scientists Nicholas Sofroniew and Jeremy Freeman have developed a virtual reality system that uses whiskers, the mice’s natural navigation system. In the system, the walls around the mouse move as it walks on a treadmill, giving it the rodent the sensation that it is walking and running forward even though its head remains in a fixed position. Even though it is not moving forward, the mouse is still engaged in active sensation says senior researcher Karel Svoboda.
The researchers are able to track the neuron activity in a mouse’s brain using fluorescent proteins from jellyfish. When neurons fire, they release calcium which causes these fluorescent protein tags to light up. This lighting can be traced using a literal window into the rat’s brain that is formed when researchers remove a portion of the animal’s skull and replace it with a clear window. Unlike earlier studies that focus on one neuron at a time, this technique allows researchers to study multiple neurons at once.
The team hopes to use this research to gain a better understanding of how our brains “do everything involved in sensing, learning, and decision-making.” Not only can they learn normal brain activity, this type of research may also provide insight into what happens with the brain when disorders such as autism are present.
