A team of neuroscientists at Yale School of Medicine, led by Nenad Sestan, last week reported that they had managed to revive brains from pigs that had been decapitated in an abattoir four hours earlier.
Well, “revive” in the sense of getting certain neurons to fire. This was no “brain in a vat” experiment. The brains were neither alive nor possessed consciousness.
The Yale team hooked 32 pig brains to a system that pumped in a blood substitute, delivering nutrients and oxygen to the cells. This helped preserve brain architecture, which would normally have collapsed. Many cells restarted normal metabolic functions, such as producing energy and removing waste. Some neurons even started firing. But there were no signs of the coordinated, brain-wide electrical activity indicating sentience. The team had anesthetics on hand in case brain activity did indicate consciousness. It never did.
Nevertheless, the study raises many scientific and ethical questions. How do we define consciousness in a brain unattached to a body? Is it possible to talk of consciousness in a disembodied brain? How would we know if the brain possessed consciousness?
Some have questioned whether the study challenges our conception of brain death in humans. So far, it doesn’t.
“The pigs were brain-dead when their brains came in the door, and by the end of the experiment, they were still brain-dead,” said Stephen Latham, a Yale University ethicist who advised the team. The study does, however, raise the possibility of innovative treatments for patients with brain injuries, and perhaps of reversing brain damage. All that is still a long way off.
We may need that time to grapple with fundamental questions of consciousness, life and death.
*This article was first published in the Guardian.