In a study that raises profound questions about the line between life and death, researchers have restored some cellular activity to brains removed from slaughtered pigs.

The brains did not regain anything resembling consciousness: There were no signs indicating coordinated electrical signaling, necessary for higher functions like awareness and intelligence.

But in an experimental treatment, blood vessels in the pigs’ brains began functioning, flowing with a blood substitute, and certain brain cells regained metabolic activity, even responding to drugs. When the researchers tested slices of treated brain tissue, they discovered electrical activity in some neurons.

The work is very preliminary and has no immediate implications for treatment of brain injuries in humans. But the idea that parts of the brain may be recoverable after death, as conventionally defined, contradicts everything medical science believes about the organ and poses metaphysical riddles.