In a paper published in Cell Biology, a team of researchers from Japan's National Institute of Genetics have outlined how they managed to record a video of a thought forming in a zebrafish's brain.
Why a zebrafish? They make popular research fish as their embryonic bodies are transparent, which makes recording florescence easier. To see the "thought," the scientists inserted a special gene called GCaMP into the zebrafish. GCaMP essentially causes the fish's brain neurons to glow, which can then be captured on video using a fluorescent probe.
But first the scientists devised a test to see which neurons would glow when stimulated: the zebrafish followed a dot across a screen, and the researchers observed to see what lit up. As expected, the fish's neurons moved from one side of the brain to the other, in reverse, as it followed the dot.
With those neurons noted, the scientists placed a single-celled paramecium for the zebrafish to gobble up. As the fish tracked the paramecium, the same exact neurons lit up, indicating they were the ones directly related to thoughts.
Although the same technology can't be used to follow a person's thoughts, researcher Koichi Kawakami thinks monitoring neuron patterns may lead to a better understanding of animal behaviors and better psychiatric medications.
In release, Kawakami said:
“We can make the invisible visible; that’s what is most important… 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."
Embedded below is a black and white video of neurons in a zebrafish going off. For a color video, check out the one from the Smithsonian here.