Scientists have managed to restore cell function in the brains of pigs hours after they died, in a breakthrough Wednesday that experts said threw into question the very notion of what makes animals - or even humans - alive.
The team from the NIH BRAIN initiative, a federally funded U.S. research programme, used the brains of 32 pigs that had been slaughtered for food and discarded, without blood or glucose flow, for four hours each. Also, electrical activity in the brain can reduce drastically as brain cells can quickly switch their charge from positive to negative.
"This is not a living brain, but it is a cellularly active brain", Sestan said during a briefing held by The National Institutes of Health, according to The New York Times.
The scientists behind the research claim the development could help in the study and treatment of brain disorders.
This line of research could lead to a whole new way of studying the post-mortem brain.
In the long term, scientists hope to find better ways of protecting the brain after traumas such as a stroke or being starved of oxygen at birth.
Researchers said they were anxious about ethical implications that could arise during the experiment - and during future similar experiments - and they monitored the brain activity to ensure the brains did not regain any level of consciousness. Coauthor Stephen Latham of Yale University says there may be cases where it is ethically justifiable, such as with testing drugs in studies of neurodegenerative diseases, reports Nature.
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The scientists also found no evidence of global network activity or full-brain function during the experiments.
Martin Monti, an associate professor in the Departments of Psychology and Neurosurgery at University of California Los Angeles, told Science Media Centre that "the advance here is that, with the right technology, we might now have more time to recover some molecular, cellular, and microvascular function before these are completely compromised in the non-human animal model".
Was the pig's brain conscious?
He stressed that the revivifying system the researchers developed, which they dubbed BrainEx, may not reverse cell death and restore brains to what would be considered a stable, living state.
The researchers found working synapses - the connections between brain cells that allow them to communicate. Previous experiments had already shown viable cells could be removed from brains hours after their owners were pronounced dead, but "once you do that, you are losing the 3D organization of the brain", Sestan pointed out.
However, it also leaves researchers "with a gaping gray zone, with nearly no guidance of how to proceed ethically", she added. For another six hours, the system pumped a solution of synthetic nutrients through the brains in a fashion meant to mimic what other organs in the body do. But the blocker also ensured the pig brain would not have any risk of awareness.
Farahany said the research field needs to be careful going forward to ensure that animals studied in laboratories - even dead animals by traditional definitions - do not suffer: "Given that there's this gray zone between dead and alive we need to divine what is the appropriate use of animals in that context, to ensure that there isn't pain or distress". Cut off from oxygen and a blood supply, the brain's electrical activity and signs of awareness disappear within seconds, while energy stores are depleted within minutes. "For now, the cautious interpretation of this work is that, with this technology, the window for rescuing from the process of death profoundly damaged neural tissue, in the pig model, might be larger than we thought". Bioethicist Nita Farahany, who has urged ethics guidelines for similar experiments in the future, said the study leaves a "gaping gray zone, with nearly no guidance of how to proceed ethically".