I n August, three graduate students at Carnegie Mellon University were crammed together in a small, windowless basement lab, using a jury-rigged 3D printer frame to zap a slice of mouse brain with electricity.

The brain fragment, cut from the hippocampus, looked like a piece of thinly sliced garlic. It rested on a platform near the center of the contraption. A narrow tube bathed the slice in a solution of salt, glucose, and amino acids. This kept it alive, after a fashion: neurons in the slice continued to fire, allowing the experimenters to gather data. An array of electrodes beneath the slice delivered the electric zaps, while a syringe-like metal probe measured how the neurons reacted. Bright LED lamps illuminated the dish. The setup, to use the lab members’ lingo, was kind of hacky.