A big leap towards reanimation after death because the mammal’s brain is preserved

An entire mammalian brain has been successfully preserved using a technique that will now be offered to people who are terminally ill. The idea is to preserve all the neural information deemed necessary to one day reconstruct the mind of the person it once belonged to.

“They would have to donate their brains and bodies for scientific research,” he says Boris Wrobel at Nectome in San Francisco, California, a memory research company. “However, as a society we are offering their body and brain to be preserved essentially indefinitely in the hope that at some point in the future the information from the brain can be read and the person can be reconstructed … allowing them to basically get on with their lives.”

When it comes to preserving the tiny architecture of the brain, timing is critical. Within minutes after the blood has stopped circulating, enzymes break down the neurons and the cells begin to digest themselves.

Cryonics typically involves storing human bodies at sub-zero temperatures in the hope that they might one day be revived if a treatment or cure for their medical condition becomes available. Traditionally, the goal is to preserve the brain quickly after natural death by cooling it and adding fixatives, but unless a cryonics team is at the person’s bedside, deterioration has already begun before that happens.

To avoid this problem, Wróbel and his team developed a protocol that is compatible with physician-assisted death, in which a terminally ill person chooses the time of their death. The idea is that by intervening immediately, scientists may have the best chance of preserving the brain in a state that accurately reflects living conditions.

Wróbel’s team tested the protocol on pigs, which have brain and cardiovascular anatomy comparable to humans. First, they inserted the cannula into the heart about 1 minute after the cardiac arrest, before flushing the blood and injecting preservation solutions into the brain. These fluids contain aldehyde chemicals that form molecular bridges between cells and essentially block cellular activity in place.

They then introduce cryoprotectants, which replace water in the tissue and prevent the formation of ice crystals during cooling that would otherwise damage the cells. Next, the brain was cooled to approximately -32 °C, at this temperature cryoprotective substances form a glassy state. The structure of the brain can then be preserved indefinitely.

To assess how well it worked, the team took samples from the outermost layer of the brain and examined them under microscopy. Early experiments, when perfusion began approximately 18 minutes after death, showed clear signs of cell damage. After shortening this delay to less than 14 minutes, the tissue showed excellent preservation of tiny structures, including neurons, synapses and the molecules that make them up.

Wróbel says that in theory they could use this protocol “to reconstruct the three-dimensional structure of neurons and the connections between them.” This is known as the connectome, and by mapping it we hope to help us understand how the brain produces our thoughts, feelings and perceptions. So far, scientists have succeeded map only a small part of the mouse brain in this way, which took seven years to complete.

Despite advances in cryopreservation and computing, “resuscitation” is not yet an option. “This approach is essentially a form of fixation using toxic chemicals that preserves the structure of the brain and neurons, but without the expectation of biological viability,” he says. Joao Pedro de Magalhaes at the University of Birmingham, UK. “Currently, there is no way to revive an organ preserved in this way because it is a type of embalming.”

De Magalhaes is also not convinced that one can “live on” by reconstructing one’s connectome. “Even a perfect copy of my mind would still be a different entity, although I appreciate that some people see this as a potential path to some kind of ‘virtual immortality,'” he says.

Nevertheless, Wróbel’s team thinks that the human mind could one day be recreated, digitally or biologically. “Although we are agnostic about the type of recovery methods, we think we might be able to preserve all the information needed for recovery,” says Wróbel.

He says the team at Nectome is preparing to invite terminally ill people to Oregon, where they can spend a few days with their family before engaging in the new protocol. “They would come to us, take the medication—which would have to be prescribed by an independent doctor, not us—and then, once it was legal, we would start the surgery,” says Wróbel.

Regardless of hypothetical futures, this work raises deep philosophical questions about our definition of death. “It has long been known that the declaration of death by circulatory arrest is a formalized prognosis of futility, not a metaphysical event,” he says Brian Wowk at the biotech company 21st Century Medicine in Fontana, California.

“The ability to preserve the detailed structural and molecular makeup of the brain, perhaps even to preserve what makes a person who they are at the most basic level—even after significant periods of circulatory arrest, as this study does—highlights that the difference between life and death is more complex than simply stopping vital functions,” he says.

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