Sparks Brain Preservation
A Non-profit Organization
This page describes some of the challenges involved in biological revival. The details apply equally to both our standard fixation patients as well as Traditional Cryonics patients. Regardless of whether traditional cryonics or fixation is used, biological revival is equally possible.
The repairs would all involve extensive inference. This means that AI would need to try to extrapolate what the original structure looked like in spite of different kinds of damage.
Each cell is surrounded by a membrane. This is the most fundamental repair that would need to be made because the exact shape of a neuron is defined by its membrane. The membrane is somewhat fragile, but it's held in place by a cytoskeleton. Here's what a cytoskeleton looks like. Even if a membrane was torn or missing, the cytoskeleton could be used to infer where the membrane was supposed to be and it could then be repaired.
Neurons have long delicate axons and dendrites. For example, it's common for a single neuron to span the entire brain. It's very important to maintain this continuity, but damage could make that difficult. There could be ambiguity about which two ends need to be matched up. The solution to this problem would be to read all of the molecules. Each neuron has a molecular fingerprint of sorts which would allow tracing neurons with higher accuracy than our current technology. This molecular fingerprint could allow matching up two ends in a damaged area. As the cell membranes get repaired, we would end up with what we call a connectome. But this is just the membrane repair step.
In our standard fixed brains, 100% of the proteins would need to be repaired by removing the aldehyde molecules (shown in red below). In a cryonics case, there would be protein damage between about 5% and 90%, depending on the level of cryoprotectant in a given area. If 20% of proteins were damaged, that would translate to 10 million proteins per cell that would require repair. So while the percentages may be different between fixed and cryopreserved brains, the same fundamental repairs would be needed in both cases. Both fixation and cryopreservation would require the exact same very high technology.
Eric Drexler has been called “the godfather of nanotechnology.” His influential book Engines of Creation laid out the theoretical foundations for machines capable of molecule-by-molecule biological repair. The method of long-term preservation that Drexler proposed in his book was aldehyde fixation and cryopreservation, reasoning that molecular nanotechnology could identify and undo the aldehyde bonds that this introduces. Aldehyde bonds between molecules are not exotic chemistry. They occur naturally in our cells from metabolic byproducts like formaldehyde, and living cells have already evolved repair enzymes that detect and respond to them. The challenge is performing such repairs at scale across an entire brain. This is what molecular nanotechnology is proposed to allow for.
Ice damage would only be present in cryonics cases. Perfusion quality is never good in traditional cryonics cases and perfusion is frequently impossible. This means that there would either be some ice or extensive ice. This image show ice crystals in white and highly compressed tissue in black. It's likely that this damage could not be repaired at all.
This would be far easier than any of the repairs above. From any cell, you could grow an entire new body. Each cell already has all the programming to grow a new body if we can provide it the right conditions. Growing a new body from the preserved person's DNA and epigenetic biomolecules would be straightforward long before brain repair becomes feasible. The new body could (and would need to be) grown without brain development to avoid ethical problems. This is not repairing molecules as above. It's much easier. The technology does not need to operate inside the cell at all. This will have been routine for many decades before we even start to think about repairing brains.
If it ever becomes possible, any revival process will need to be highly regulated to protect the interests of revived individuals. We expect that revival would involve medical teams operating within a framework of rights for preserved patients. Those rights would include independent oversight from judges, lawyers, ethicists, and others who will help determine what course of action best serves each patient's interests based on their own goals and values. At SBP we are committed to advocating for our patients throughout this process to ensure that their preferences for revival are respected.