Sometimes science catches up

That’s a quote from Rick Rubin.

When I speak to a general audience, I sometimes show this clip (start at 2:52) from Fantastic Voyage and say:

How can we study the brain? What does it even look like in action? Here’s how some people have imagined it. This is a clip from the movie “Fantastic Voyage”. Our heroes, played by Stephen Boyd, Raquel Welch, and colleagues, are shrunk down to microscopic sizes and swimming through a person’s brain. Notice the individual neurons are lighting up when they spike. Like twinkling stars. How convenient! All we have to do is take microscopic pictures of the brain and the neurons will light up when they’re spiking.

Of course, that was science fiction. But it was science fiction written by Isaac Asimov, and he had some good ideas.

Fifty years after that film, technology has caught up with science fiction, and we can now genetically engineer mice so that their neurons light up when they spike. I’m not kidding. It took a bunch of Nobel prize winning work, plus a bunch more work of similar caliber, but humankind did it.

During an action potential (aka spike), the concentration of calcium ions briefly increases about 1000 times. Just for a fraction of a second. Molecular biologists created a new protein that is partly the fluorescent protein found in jellyfish and partly a calcium binding protein. When this new hybrid protein is not bound to calcium, it is not very fluorescent. It is dark. And then, when an action potential happens, the calcium concentration goes up, it binds to the protein, and the protein changes shape a bit and briefly becomes fluorescent. We use mice that have been genetically engineered to express this protein in their neurons. So when we shine light on the neurons, they fluoresce with flashes of green light when they’re spiking. It’s not far off from what this old science fiction film imagined.