In a breakthrough study, researchers have managed to restore some brain function in pigs as long as four hours after death. Using a system that pumps preserving chemicals through the brain's circulatory system, the team not only staved off cell death but actually restored some functions like synaptic activity. The astounding discovery raises some ethical questions and may spark new debate about the very definition of death.

The general consensus holds that when the brain is deprived of oxygen, neurons die within minutes. But the researchers reported that they managed to reduce cell death even several hours postmortem, as well as restore certain cellular functions. The tissue responded to drugs given to provoke a response, some metabolic processes returned and synapses even began to spontaneously fire again.

It's important to note that the team didn't observe the kind of global brain activity that would constitute consciousness or awareness, but chillingly, the researchers did actually prepare for that possibility.

"In the event that this were to occur, we were ready to swiftly implement countermeasures, including, but not limited to, reducing the temperature of the brain in order to diminish metabolic activity, and/or administering general anaesthetic agents," the researchers write.

The technology behind this incredible feat is a system called BrainEx, which pumps a specially-designed fluid through the brain's circulatory system at body temperature. The team tested it out on the brains of 32 pigs, which were sourced from food-processing facilities that would normally discard them. These brains were removed from the skulls and hooked up to the BrainEx system four hours after death. They managed to keep the system running for six hours at a time, so 10 hours after death.

While it sounds like the kind of headline that might flash up during the opening montage of a zombie movie, the researchers aren't exactly trying to bring the dead back to life. Their focus is more about helping brains recover after traumatic injuries such as strokes, or preserving dead brains for longer so scientists can study them more accurately.

"This line of research could lead to a whole new way of studying the postmortem brain," says Andrea Beckel-Mitchener, Ph.D., BRAIN Initiative Team Lead at the National Institute of Mental Health. "The new technology opens up opportunities to examine complex cell and circuit connections and functions that are lost when specimens are preserved in other ways. It also could stimulate research to develop interventions that promote brain recovery after loss of brain blood flow, such as during a heart attack."

But of course, it does raise some new questions that aren't easy to answer. Declaring a person legally dead is already a complex problem, but this new finding could complicate it even further. If resuscitating a brain feels closer – even if it still isn't viable – then people might be more reluctant to let go of loved ones on life support. That in turn could reduce a major source of organ donations for transplants, straining a situation that's already under pressure.

The main takeaway from the study is that the brain may be more resilient to damage than previously thought. It's a fascinating area of research that will no doubt continue to push the boundaries of what separates life and death.

The study was published in the journal Nature.

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