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This month, in a study that has the potential to change the way we think about death, scientists revealed that they successfully restored some processes in the brains of dead pigs -- at least partially. What did the study actually tell us, and what do these findings mean?

Hosted by: Hank Green

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Sources:
https://www.nature.com/articles/s41586-019-1099-1
https://science.sciencemag.org/content/168/3929/375
https://www.sciencedirect.com/science/article/pii/0006899374904788
https://emj.bmj.com/content/24/7/511.short
https://www.nejm.org/doi/full/10.1056/NEJMoa1713973
https://www.fasebj.org/doi/10.1096/fj.01-0504com
https://www.nature.com/articles/d41586-019-01216-4
https://www.nature.com/articles/d41586-019-01168-9
https://www.nature.com/articles/d41586-019-01169-8


Image Sources:
https://www.flickr.com/photos/internetarchivebookimages/20119337634/in/photostream/
https://commons.wikimedia.org/wiki/File:Pig_Brain_in_a_Jar.jpg
https://commons.wikimedia.org/wiki/File:Identification-of-Injury-Specific-Proteins-in-a-Cell-Culture-Model-of-Traumatic-Brain-Injury-pone.0055983.s007.ogv
https://www.istockphoto.com/photo/brain-in-the-science-lab-gm1071399460-286714076
https://www.istockphoto.com/photo/neuron-system-gm937894966-256502519
https://www.istockphoto.com/photo/heart-beat-line-end-of-life-gm930392272-255081063
https://www.istockphoto.com/vector/pig-anatomy-vector-gm466368012-60398854
https://www.istockphoto.com/vector/spooky-zombie-pig-gm156797603-9524970
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Go to Brilliant.org/SciShow to learn more. [♪ INTRO]. There’s been an advancement in neuroscience that could eventually lead to changes in how we think about death.

In a study published on April 17 in the journal Nature, scientists revealed a method that successfully revived certain processes in the brains of dead pigs. While they didn’t restore consciousness or even recognizable brain activity, it’s a huge step that’s bringing up questions about what death really means and what’s ethical when it comes to reviving dead brains. Up until now, it’s been assumed that when the heart stops or the brain ceases activity for a relatively short period of time, there’s no going back.

That without oxygen, energy, or electrical activity, brain cells will quickly start to die. But even before this breakthrough, there have been hints that this assumption might not be true. Studies in cats and monkeys have demonstrated that the brain can fully recover after an entire hour without blood circulation.

There are also examples of people whose hearts have stopped or who suffered a stroke, leaving their brains without blood flow for hours at a time. But when doctors restored their circulation, those people made a full recovery. Even once cells have been removed from a brain, research has found they can be kept alive for weeks in culture.

So it’s possible that brains are tougher than we give them credit for. This new study sought to ask just how tough. They used the brains of pigs, which are big and complex like ours, and therefore very sensitive to any interruption in the flow of oxygen and nutrients.

And these pigs had already been dead for four hours. To revive the 32 brains, the researchers developed a system they called BrainEx, which kept them sealed in a specially designed chamber. It also pumped a specially formulated blood substitute into their blood vessels.

The blood substitute contained oxygen and nutrients to feed the brain cells, tiny particles to help it show up on an ultrasound and, importantly, chemicals designed to keep the neurons from firing. That was partly to protect the neurons from damage, and partly for ethical reasons: the researchers didn’t actually want to restart brain activity. These brains were detached from their bodies, and no one knows what it would be like for a disembodied brain to regain consciousness -- but they didn’t want to cause any distress, just in case.

And if the brains did become active, the researchers actually kept anesthetics on hand to stop them in their tracks. So they pumped the brains with this blood substitute for six hours. They could have gone longer -- the problem was actually with their control brains, which deteriorated too much to keep accepting saline instead of the blood substitute.

But while the cells of the control brains gave out, the cells of the test brains fared much better. They even performed a lot of their previous functions -- like metabolizing nutrients and mounting immune responses. The researchers even found that some neurons still fired when they applied electricity to a sample of the brain tissue.

Now, here’s what they did not do: They didn’t restore consciousness to a dead brain. They didn’t even see anything that could resemble coordinated neurological activity -- EEGs monitoring the brains were completely flat the whole time. It’s possible that if they hadn’t used the neuron-inhibiting chemical, they might have seen more, but the researchers have no plans to try again and see if they can trigger real brain activity.

And just because it needs to be said, they are nowhere near being able to keep conscious brains in jars like in Futurama, or transplant brains into new bodies like in Frankenstein. Right now, the biggest possibilities are in keeping brain tissue alive during experiments. Brain researchers do what they can with individual cells and tissue samples.

But studying them in context -- in an intact brain -- has the potential to be way more informative. Even though they didn’t restore consciousness, and even though this was only pig brains that had been removed from pig bodies, the breakthrough does bring up a whole lot of ethical and regulatory questions. Right now, regulations on animal research cover living animals and mostly exclude dead ones.

There are no guidelines for what to do with an animal that was dead but had its brain activity restored. What’s the best way to test for consciousness? Which animals should be off limits?

Should researchers be required to use neuron inhibitors and anesthetics in future studies? And then there are also questions about the meaning of death. Right now, physicians stop trying to resuscitate someone when they believe there’s no chance they’ll come back.

But if the human brain is viable for longer than we thought without blood flow, that changes things. It could affect when physicians and first responders actually decide when someone is and is not dead. Which, in turn, could affect things like organ donation.

This technology is extremely far from being ready to use in a healthcare setting. So we don’t have to answer all these questions right now. But the researchers behind the study, and others, are calling for the discussion to at least begin.

One thing is for sure though: this study changes a lot of what we thought we knew about our brains. It’s a big deal. Even though we did not make pig zombies.

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So no matter where you are -- you’ll be able to keep learning. And also the first 200 people to sign up at Brilliant.org/SciShow will get 20% off an annual Premium subscription, so get ready to learn something new! [♪ OUTRO].