Scientists in Japan have recorded the neuronal activity of a fish as it eyes its dinner, the first live recording of the brain processes behind a natural behavior. The study was published online in Current Biology on Thursday.

“Our work is the first to show brain activities in real time in an intact animal during that animal’s natural behavior,” said Koichi Kawakami of Japan’s National Institute of Genetics, according to a released statement. “We can make the invisible visible; that’s what is most important,” he said.

Just five days after fertilization, a zebrafish larva can go hunting for its food— in this case, a tasty paramecium (a single-celled organism). To see how visual cues map to the brain, the scientists genetically engineered a strain of zebrafish in which neurons in the animal’s visual-perception region of the brain glow when activated.  The team then watched the tiny predator watch its prey.

In this video, you can see a paramecium whipping around the head of a baby zebrafish (bottom of screen) that has been trapped in a gel so the scientists can monitor it’s brain it through a microscope. The little fish’s eyes can still move, and they track the movements of the paramecium while its neurons light up in a pattern that matches the movements of its food, say the authors.

The technique could help researchers figure out which brain circuits are involved in complex behaviors.

“In the future, we can interpret an animal’s behavior, including learning and memory, fear, joy, or anger, based on the activity of particular combinations of neurons,” Kawakami said.

If you want to learn more, there’s a nice video abstract of the study on Current Biology’s website, in which you can learn more about the awesome power of genetics and what a room with more than 1000 kinds of transgenic fish looks like.