Researchers have a hard time understanding how tiny changes to networks of neurons in an animal's brain can affect its behavior. Now a team of researchers has figured out a way to tinker with the neural networks of mice in real time, using a wireless controller that can both shine light on the brain and deliver drugs to it. The device even lets scientists control the movements of their test mice from afar.

 Neural circuits are thought to be key for various neurological disorders having to do with stress, depression, addiction, and pain—researchers can study them by adding various chemicals or light to neurons to mimic the disease. But observing or manipulating neural circuits to figure out how they work has been notoriously difficult. When researchers do tests on mice, the animals have to be awake and moving around, but the devices to monitor their brain activity are usually hooked up to wires, so they can't move freely.