Science has given us some pretty great images of the brain over the years thanks to fMRIs, CT scans, and the like. But we’ve never seen anything quite like this: A “thought,” however simple, captured in real time in the brain of an animal doing what animals do naturally—looking for a bite to eat.
A group of Japanese scientists led by Akira Muto chose larval zebrafish for their thought-capturing experiment, in part because they are transparent in the embryonic and larval stages and already able to recognize prey. Using new gene expression technology, the scientists were able to re-engineer the baby fish’s genetics so the neurons in its optic tectum flashed with fluorescent light whenever they fired.
Researchers then tested the zebrafish in several scenarios to stimulate its optic tectum. In the first experiment, they attracted the baby fish’s attention with a moving spot of light. In the second experiment, they stimulated the baby fish using a paramecium—a single-celled organism that is the larva's natural prey.
What you see above is a close-up of the neurons firing during the first experiment while the fish is visually stimulated with a light.
Below is a video documenting the second experiment, from a wider perspective so we can see how the neurons fire in relation to the object stimulating them. The little dot jerking around is the paramecium. The neuronal firing patterns conformed to what we’ve long known about the relationship between eyes and brains, but were never able to see on such a minute scale in real time. Muto, et al., call it a “functional visuotopic map.”
Watch how the optic tectum fires in opposite relation to where the paramecium is. When the paramecium is on the left, the optic tectum fires on the right:
In a third experiment, the scientists left the larval zebrafish free to pursue and devour the paramecium. By watching them actually complete their hunting task, the researchers found that pre-capture behavior was always marked by activity in the anterior part of the optic tectum—signaling a neuronal difference between the hunt and the catch.
The study, published yesterday in the journal, Current Biology, is unavailable to readers without a subscription. But the journal provided this video abstract, below, in which you can see footage of the third experiment, as get a more in-depth explanation of the science directly from the researchers. It's as worth your time to watch in its entirety as any five-minute video in recent memory.
As the researchers note, this kind of technology can't be used on humans—for starters, our heads aren't see-through. But our brains and fish brains work according to many of the same basic principles. Over time, these kinds of experiments could grant us ever keener insight into our own cognition.