Preserve the brain

The hope of mind uploading rests on the premise that much of the key information about who we are is stored in the unique pattern of connections between our neurons, the cells that carry electrical and chemical signals through living brains. You wouldn't know it from the outside, but there are more of those connections — individually called synapses, collectively known as the connectome — in a cubic centimeter of the human brain than there are stars in the Milky Way galaxy. The basic blueprint is dictated by our genes, but everything we do and experience alters it, creating a physical record of all the things that make us US — our habits, tastes, memories, and so on.

It is exceedingly tricky to transition that pattern of connections, known as the connectome, into a state where it is both safe from decay and can be verified as intact. But in recent months, two sets of scientists said they had devised separate ways to do that for the brains of smaller mammals. If either is scaled up to work for human brains — still a big if — then theoretically your brain could sit on a shelf or in a freezer for centuries while scientists work on the rest of these steps.

Both start by “fixing” the structure of a brain in place with a chemical similar to that used in funeral homes for embalming.

The first method involves soaking the brain both in osmium, a heavy metal that stains the outlines of all the neurons so they can be seen under an electron microscope, and a special-sauce solvent that allows the stain to penetrate evenly. Water is drained from the brain, which is then embedded in a hard plastic resin so that the brain’s connections can be scanned later on.

The potential problem is that all the staining and draining will obscure the molecular identity of each neuron and synapse — another critical piece of information likely necessary for a brain simulation.



The second method involves storing a brain at cryogenic temperatures (that is, really, really, really cold). Historically, the problem with that has been that it allows the formation of ice crystals that can slice through neurons and shatter synapses. A kind of antifreeze or “cryoprotectant” can help prevent ice from forming, but that in turn can lead to dehydration, shrinking the connectome so that it cannot be seen under an electron microscope, and potentially causing it to tear.

Scientists seem to have found a way around that — at least in pig brains — by fixing the structure in place and adjusting the cocktail of chemicals pumped through the brain. This method is far more likely to preserve the molecules. But how to stain and embed the brain in plastic would still need to be figured out before moving on to the next step.