Jasanoff's research is only a first step toward that goal. So far, he has tested the sensor in test-tube solutions with and without calcium, scanning the interactions with MRI. The initial results, published in a recent issue of the Proceedings of the National Academies of Sciences, are promising: scans were able to pick up high-contrast images of the Velcro-like balls clustering in the presence of calcium. Although the images were only visible after many seconds, or even minutes, Jasanoff says the sensor is highly tweakable, and he plans to improve its time response in future trials. For now, he plans to inject calcium sensors into single cells of flies and eventually rats.

Outsider observers like Greg Sorensen of Harvard Medical School are cautiously optimistic about this new generation of brain imaging, particularly for human applications. Sorensen, an associate professor of radiology, is focused on applying novel imaging techniques to the treatment of neurological diseases.

"Intracellular iron oxide particles have in some studies had an unfavorable safety profile in humans," Sorensen says. "If we learned that this method had some risks but in exchange could identify the best treatment for, say, schizophrenia, then the risk may well be worth the benefit."