brain scan: A technique to view structures inside the brain, typically with X-rays or a magnetic resonance imaging (or MRI) machine. With MRI technology — especially the type known as functional MRI (or fMRI) — the activity of different brain regions can be viewed during an event, such as viewing pictures, computing sums or listening to music.

canine: Members of the biological family of canids. These are carnivores and omnivores. The family includes dogs, wolves, foxes, jackals and coyotes. (in anatomy) The pointed tooth in a mammal that separates its incisors from its premolars. These canine teeth tend to be especially long in carnivores.

feline: Adjective for something having to do with cats (wild or domestic) or their behaviors.

MRI: Short for magnetic resonance imaging. It’s an imaging technique to visualize soft, internal organs, like the brain, muscles, heart and cancerous tumors. MRI uses strong magnetic fields to record the activity of individual atoms.

neuroscientist: Someone who studies the structure or function of the brain and other parts of the nervous system.

reward: (In animal behavior) A stimulus, such as a tasty food pellet, that is offered to an animal or person to get them to change their behavior or to learn a task.

scanner: A machine that runs some sort of light (which includes anything from X-rays to infrared energy) over a person or object to get a succession of images. When a computer brings these images together, they can provide a motion picture of something or can offer a three-dimensional view through the target. Such systems are often used to see inside the human body or solid objects without breaching their surface.

subtle: Adjective for something that may be important, but can be hard to see or describe. For instance, the first cellular changes that signal the start of a cancer may be only subtly different — as in small and hard to distinguish from nearby healthy tissues.