A quick note about the third talk in the “Frontiers of Physics” session, this one delivered by Karl Deisseroth, an assistant professor of bioengineering and psychiatry at Stanford University. Deisseroth and his team have been experimenting with implanting halo rhodopsin pumps into mammalian brains. These pumps occur naturally in alae, which have no brains and so rely on external light cues to tell them when to move and react. In mammals, an optic fiber running into the skull causes ion-channel excitation in cells, which induces some sort of change in the body. The light stimuli can cause the mouse to do different things, like run in a circle or wake from a deep sleep, and the team believes they will be able to use different colors to stimulate different behavior. (Image credit: Raag Airan et al., Stanford University)