A tiny wearable positron emission tomography (PET) scanner has been used to track chemical activity in the brains of unrestrained animals while an animal behaves naturally; it could be modified for people.

By revealing neurological circuitry as the subjects perform normal tasks, researchers say, the technology could greatly broaden the understanding of learning, addiction, depression, and other conditions.

A conventional PET scanner is so large that these studies have to be performed with the subject lying inside a large tube.