A few months ago, I wrote about a flashy study from the Howard Hughes Medical Institute’s Janelia Farm Research Campus: researchers reported that they were able to watch the individual activity of nearly all the neurons in a fish’s brain at the same time (see “A Near-Whole Brain Activity Map in Fish”).

Now, HHMI has put together a video about the work, and it’s worth a look. Neuroscientist Philipp Keller explains how some of the technology behind the experiment works. Best of all, we get to see more of the complex flickering constellations of brain cells—fish thoughts in action. This work is the first time researchers have been able to look at the activity of nearly all neurons in a vertebrate brain.

The meaning of the complex patterns seen in the fish brains remains a mystery for the most part. Solving that mystery is an important goal of the U.S. government’s BRAIN initiative, an ambitious, well-funded project to better understand how the brain works that was announced earlier this year (see “Why Obama’s Brain-Mapping Project Matters”). The HHMI technology could help by giving researchers a way to watch how neurons in different brain regions work together.

That may be best achieved with an upcoming experiment mentioned in the video. HHMI neuroscientist Misha Ahrens says that the brain activity mapping technology will be combined with a zebrafish virtual reality set up so the fish can “respond” to its environment (the fish is actually tethered, but with VR, the little swimmers think they are moving) while its brain activity is recorded. Other researchers have captured video of a tethered fish watching its prey (see “Watching Fish Thoughts Form”), but this new experiment promises even greater details of the inner workings of the vertebrate mind.