The pigs were dead for 10 hours, and then they weren’t: “The ethics of experimenting on partially reanimated brains is uncharted territory.”

So this is a study from Nature, but I like the way Vox covered it. Yale scientists, using a kind of artificial blood (and machine heart and kidney), have brought the brains of slaughtered pigs back to life hours after they died:

First, the researchers took 32 brains from pigs slaughtered for food and waited four hours. Then they hooked them up for six hours to a system called BrainEx, which pumped those brains full of oxygen, nutrients, and protective chemicals.

At the end of the 10 hours, the scientists found that the tissue of the pig brains was largely intact, compared to controls. Individual brain cells were up and running, performing their basic duties of taking up oxygen and producing carbon dioxide.

To be clear: The neurons in these brains were not communicating, so there was no consciousness. But the cells were alive — and that alone is a very big discovery.

“Previously, findings have shown that in basically minutes, the cells undergo a process of cell death,” Nenad Sestan, the Yale neuroscientist who led the effort, said during a press conference. “What we’re showing is that the process of cell death is a gradual step-wise process, and some of those processes can be either postponed, preserved, or even reversed.”

Four hours after slaughter, the pig brains were attached to the BrainEx device via the carotid arteries. You can think of the device as something like an artificial heart. It pumps a perfusate — a synthetic blood that delivers oxygen and nutrients — throughout the brain via the pig’s own arteries.

The perfusate also contains chemicals that stop the oxidation (i.e., breakdown) of body tissue, that stop apoptosis (cells bursting after death). It also contains a neural activity blocker, the purpose of which is twofold.

One was to halt excitotoxicity — a process by which neurons become damaged when they are left turned on, creating a chemical imbalance, also leading to cell death. The other was to make sure the brain didn’t “wake up” and regain any level of consciousness. If any consciousness was detected via EEG, the researchers said, they would have shut down the experiment immediately. They were even standing by with anesthesia to administer to the brain in case any widespread neural activity was detected.

After six hours on the BrainEx — 10 hours after slaughter — the researchers didn’t see signs of consciousness in the brains. But they did see signs of life. When hooked up to the BrainEx system, “we see the brains extract oxygen … they use glucose [sugar], and they produce CO2,” Zvonimir Vrselja, a Yale researcher and one of the study co-authors, told reporters.

Most compellingly: When the brains were dissected and the neural activity blocker was washed away, the researchers found the neurons retained their ability to communicate with one another. That means the cells retained the function they had when the body was alive.

Technically, this doesn’t fall into the category of animal research “because the brain comes to the researchers already from a dead animal,” from a slaughterhouse, [Yale bioethicist Stephen] Latham explains. That means the researchers don’t have to follow the ethical guidelines that come with animal research, namely that animals should not be subjected to unnecessary harm. But what about partially revived animal brains? There’s no guidance on that.

Here’s another. The researchers also used chemicals to block neural activity in the pigs’ brains to try to ensure they never became conscious. But what if the researchers hadn’t done this? They wouldn’t speculate what would happen then. They don’t know if some consciousness could ever be restored after death, and they say they don’t want to try to restore it.

But some other research group might take their results and try.

The original Nature study is available here, and Dr. Nenad Sestan’s lab page here.