This recording lets us see 77 of the nematode's 302 neurons light up like a Christmas display as the worm freely wriggles around on a plate. This is amazing. We're watching an animal's mind at work. This recording, made by researchers at Princeton University, and supplemented with a recent paper in the Proceedings of the National Academy of Sciences, lets us see nearly the entire brain of a nematode in action. The system relies on the fact that neurons vary their calcium levels, depending on whether or not they're communicating with other neurons. Scientists got the nematode to create a protein which fluoresces in response to calcium. When the neurons go to work, they light up.
Once the neurons lit up, the researchers took several simultaneous images of the worm. On the upper left panel of the video, we see a close-up of the location of the neurons, while the upper right panel shows us the calcium lighting up inside the worm as it moves.
For the lower panels we zoom out. On the lower right panel we see the location of the worm's brain, while on the lower left panel, we see the worm itself, going about its business.
The technology lets scientists see not only how single or small groups of neurons control an animal's behaviour, but how large groups of neurons all work together. The researchers hope to create a mathematical model, and use them to stimulate the worm's neurons in order to control -- not just observe -- how it behaves.