Or when you drop them, or bang them against something, or otherwise injure them.
Over the last couple years, scientists have grown blood vessels, skin, parts of organs, and even vaginas in the lab. But now, for the first time, they've managed to grow three dimensional, "brain-like" tissue (from rats)—with the express purpose of injuring it to see what happens.
Of course, that's not really the only purpose of doing this, but it's what's been done so far. In a paper published in Proceedings of the National Academy of Sciences, Tufts University researcher David Kaplan details a process that has allowed him and his team to make 3D brain tissue to study injury.
Until now, the only way to actually research brain injuries caused by concussions, bomb blasts, and even new drugs has been to do it with actual brains, in actual humans, rats, or other animals (unfortunately, usually postmortem). We've had no real in-vitro options for doing any of this research, because every brain scientists have tried to grow has died within a day of being created.
It's not, of course, a real brain (though I'm going to refer it as one for the rest of this article)—you can't just pop it into a living creature and expect it to function, and there's a lot more to a brain than a bunch of neurons. But these brains have both grey matter and white matter, organize themselves in a manner much like a brain, and apparently express a much higher number of genes than neurons do when they are simply grown on a two dimensional dish.
The brains grown at Tufts are also unlike the "mini brains" that have been grown before: Those were created using stem cells, and the lack of blood supply keeps them limited to just four millimeters in diameter. Tufts' brains shouldn't have that limitation, and they're able to survive for long periods in the lab, allowing longer-term growth and study.
"We show that, on injury, this brain-like tissue responds in vitro with biochemical and electrophysiological outcomes that mimic observations in vivo," Kaplan wrote in the study. "This modular 3D brain-like tissue is capable of real-time nondestructive assessments, offering previously unidentified directions for studies of brain homeostasis and injury."
How do they know that? Because they went and dropped the brains, then measured its activity immediately following.
"With the system we have, you can essentially track the tissue response to traumatic brain injury in real time," he said in a statement. "Most importantly, you can also start to track repair and what happens over longer periods of time."
The hope is that the brains can be used to study brain implants, the effects of electric brain hacking, brain responses to drugs, and the way the organ changes when it gets certain diseases.
The main breakthrough here is the method in which the brains were grown. Usually, neurons are grown on a 2D collagen plate. That's worked just fine in terms of making the neurons themselves, but anytime they were stimulated to grow in three dimensions, they degraded and died, often very quickly. But Kaplan and his team created a scaffolding for the neurons to grow on—made out of a silk protein—which seems to do the trick.
The brains grow and anchor themselves onto this scaffolding, then develop, more or less, into brains. So hey, even if we never get to the point where we can create full-scale human brains in the lab, maybe we can at least create a sustainable source of zombie food.