The Scientific Basis of Cryonics(technologyreview.com)
technologyreview.com
The Scientific Basis of Cryonics
http://www.technologyreview.com/view/542601/the-science-surrounding-cryonics/
4 comments
> Yeah, I freeze and thaw cells constantly without much trouble--just plop those suckers in a solution of 10% DMSO and a serum-containing isotonic liquid then throw into the freeze-assist device, then put that into the -80C freezer and transfer it to the liquid nitrogen freezer the next morning. Everyone does it this way, and has for years. I've always wondered if the freezing and thawing process subtly changes cell functioning (beyond the time given to cells to rest after being thawed), but I'm guessing if it were the case someone would have noticed it by now.
Has anyone tested this on a macroscopic creature? In particular, one complex enough to demonstrate memory, which could be tested afterward?
I've seen one or two reports of such tests, but nothing going into detail about the degree of function afterward.
Has anyone tested this on a macroscopic creature? In particular, one complex enough to demonstrate memory, which could be tested afterward?
I've seen one or two reports of such tests, but nothing going into detail about the degree of function afterward.
I believe that certain model organism worms can be frozen and thawed without consequences, and likely certain amphibians. The main features that allow freezing traditionally in these creatures is that they're small (easy to quickly permeate completely with cryoprotectant, assuming they're using that method) and already live in an aqueous environment. It's important to remember that these animals are much smaller than typical human organs, which (correct me if I'm wrong) we are yet to successfully freeze, re-thaw, and implant functionally.
Won't work so smoothly on most living creatures or organ structures for a few reasons. First, for cells in a liquid media solution or very small/simple animals, you can guarantee that the cryoprotectant is going to permeate into all the proper places, preventing destructive ice crystals from forming inside of the cells. For an entire living creature, there's a bunch of barriers-- rate of seeping of cryoprotectant through tissues, large internal solid and liquid volumes, and difficult-to-permeate epithelial tissue or fur. The cryoprotectants can seep through outer skin without additional help, but there are likely to be some spots where they can't or don't get to. It's important to remember that this process would have to occur in a race against two separate death clocks: race one is against irreversible damage as a result of stalled metabolic output (death of neurons or other irreplaceables from lack of oxygen or nutrients) and race two is against the toxicity of the cryoprotectant/freezing process causing irreversible damage in the first-permeated tissues before metabolic activity is completely stopped by freezing temperatures. I have no idea if these spots are understood or identified.
Second, the far larger problem is removing the toxic cryoprotectant once metabolic activity has resumed during thawing. For cells in a liquid media solution, you can pellet cells to the bottom of a test tube in a centrifuge, then suction off the cryoprotectant. For an entire living creature, I don't even know where you'd begin, or how you'd guarantee all the cryoprotectant was flushed out. For cells in liquid media, you have about a 30 minute time window to remove the cryoprotectant before your cells are kaput.
Won't work so smoothly on most living creatures or organ structures for a few reasons. First, for cells in a liquid media solution or very small/simple animals, you can guarantee that the cryoprotectant is going to permeate into all the proper places, preventing destructive ice crystals from forming inside of the cells. For an entire living creature, there's a bunch of barriers-- rate of seeping of cryoprotectant through tissues, large internal solid and liquid volumes, and difficult-to-permeate epithelial tissue or fur. The cryoprotectants can seep through outer skin without additional help, but there are likely to be some spots where they can't or don't get to. It's important to remember that this process would have to occur in a race against two separate death clocks: race one is against irreversible damage as a result of stalled metabolic output (death of neurons or other irreplaceables from lack of oxygen or nutrients) and race two is against the toxicity of the cryoprotectant/freezing process causing irreversible damage in the first-permeated tissues before metabolic activity is completely stopped by freezing temperatures. I have no idea if these spots are understood or identified.
Second, the far larger problem is removing the toxic cryoprotectant once metabolic activity has resumed during thawing. For cells in a liquid media solution, you can pellet cells to the bottom of a test tube in a centrifuge, then suction off the cryoprotectant. For an entire living creature, I don't even know where you'd begin, or how you'd guarantee all the cryoprotectant was flushed out. For cells in liquid media, you have about a 30 minute time window to remove the cryoprotectant before your cells are kaput.
There are a number of amphibians that freeze during winter as part of their natural life cycle. They seem to be fine.
https://www.youtube.com/watch?v=UuhEHNey37Q
The above video is a short demonstration of one such amphibian
The above video is a short demonstration of one such amphibian
Did you read the article we're commenting on? It stated roundworms have been frozen and illustrated learned behaviors to certain scents afterwards. It also stated rabbit brain tissue retained long term memories.
The article mentioned tests on brain tissue, subsequent analysis of which suggests it wouldn't have affected memory, but not actual tests of a living organism in practice.
> This is completely fine if you're tooling around in a research lab or industrial lab, but even a 1% loss is probably too much for a human brain to bear and remain the same as before.
You probably lose at least that many neurons over a lifetime; consider the shrinking volume of the brain with age. And losses definitely easily exceed 1% in early Alzheimer's or dementia, but while not fun, people with early Alzheimer's clearly have not died or ceased to exist!
(And anyway, the real question about the dead cells is whether they still have the information about their synaptic weights and other functional information. Being able to revive the cell is overkill; the focus on revival is as an _a fortiori_ argument, since any revival proves that, even in the absence of future scanning advances, it must be possible.)
You probably lose at least that many neurons over a lifetime; consider the shrinking volume of the brain with age. And losses definitely easily exceed 1% in early Alzheimer's or dementia, but while not fun, people with early Alzheimer's clearly have not died or ceased to exist!
(And anyway, the real question about the dead cells is whether they still have the information about their synaptic weights and other functional information. Being able to revive the cell is overkill; the focus on revival is as an _a fortiori_ argument, since any revival proves that, even in the absence of future scanning advances, it must be possible.)
(Not a biology guy)
It would seem like there should be a difference between an operational brain losing neurons and a suspended brain losing neurons?
I'd assume that if inter-neuron communication speed is anywhere on the same order as the time-between-individual-neuron-loss, then that would alleviate the effect somewhat, no? My understanding was there was a lot of redundancy up there, so it would make sense that the brain would resilver itself in certain scenarios.
It would seem like there should be a difference between an operational brain losing neurons and a suspended brain losing neurons?
I'd assume that if inter-neuron communication speed is anywhere on the same order as the time-between-individual-neuron-loss, then that would alleviate the effect somewhat, no? My understanding was there was a lot of redundancy up there, so it would make sense that the brain would resilver itself in certain scenarios.
> I'd assume that if inter-neuron communication speed is anywhere on the same order as the time-between-individual-neuron-loss, then that would alleviate the effect somewhat, no? My understanding was there was a lot of redundancy up there, so it would make sense that the brain would resilver itself in certain scenarios.
The brain is remarkably resilient and adaptive; people manage to recover at least partial function even after major strokes. And, quite frankly, I'd take "functioning like a stroke victim" over "dead" any day.
The brain is remarkably resilient and adaptive; people manage to recover at least partial function even after major strokes. And, quite frankly, I'd take "functioning like a stroke victim" over "dead" any day.
See also the scientists' open letter on cryonics, which is old enough to have had many homes online over the years, but is now here:
http://www.evidencebasedcryonics.org/scientists-open-letter-...
You might also look at the Alcor FAQ for scientists:
http://www.alcor.org/sciencefaq.htm
Some of the ongoing information generated by the Brain Preservation Foundation's technology prize competition is also interesting.
http://www.brainpreservation.org/competitors/
The perspective of the BPF folk is perhaps a useful calibration point for those coming into this as a new topic; they are critical of cryonics for some detailed technical reasons, with plenty of room for debate, think that plastination should be developed as an alternative technology, but are firm supporters of the concepts of brain preservation and the evidence to date for fine structure preservation. For example, see this response to an earlier and very shoddy article critiquing cryonics at the Technology Review:
http://www.brainpreservation.org/ken-hayworths-personal-resp...
http://www.evidencebasedcryonics.org/scientists-open-letter-...
You might also look at the Alcor FAQ for scientists:
http://www.alcor.org/sciencefaq.htm
Some of the ongoing information generated by the Brain Preservation Foundation's technology prize competition is also interesting.
http://www.brainpreservation.org/competitors/
The perspective of the BPF folk is perhaps a useful calibration point for those coming into this as a new topic; they are critical of cryonics for some detailed technical reasons, with plenty of room for debate, think that plastination should be developed as an alternative technology, but are firm supporters of the concepts of brain preservation and the evidence to date for fine structure preservation. For example, see this response to an earlier and very shoddy article critiquing cryonics at the Technology Review:
http://www.brainpreservation.org/ken-hayworths-personal-resp...
Consider what will happen a hundred years from now, if the technology to restore cryopreserved people is developed and used. Our descendants will look back on our failure to do cryopreservation on any significant scale, and I think they will judge us harshly. We, humanity, should have a billion-dollar research project to learn how to do cryopreservation well, to improve the odds that the brains we preserve will be repairable and to get the cost down low enough to offer to everyone. Instead, we are condemning literally everyone to inevitable, permanent death, not even trying to save them.
It is, without exaggeration, the greatest tragedy in the world, and it's happening because superstition and our society's anti-superstition memetic immune system misfired simultaneously.
It is, without exaggeration, the greatest tragedy in the world, and it's happening because superstition and our society's anti-superstition memetic immune system misfired simultaneously.
> We, humanity, should have a billion-dollar research project to learn how to do cryopreservation well, to improve the odds that the brains we preserve will be repairable and to get the cost down low enough to offer to everyone. Instead, we are condemning literally everyone to inevitable, permanent death, not even trying to save them.
Agreed. Though I would argue we should be spending even more effort and funding on anti-aging research and AI, the two routes to what people will need at the other end of cryopreservation. (The latter being much more comprehensive than the former.)
Agreed. Though I would argue we should be spending even more effort and funding on anti-aging research and AI, the two routes to what people will need at the other end of cryopreservation. (The latter being much more comprehensive than the former.)
I've suggested to a few people the idea of cryopreservation and I've yet to find someone who wants it. The consensus is one life is enough. I quite like the idea of living on but seem to be in a minority. Rather than billion-dollar research maybe the government might be better funding a big freezer. People might be more inclined to do it if it was a no cost option compared with cremation / burial.
It's not just a matter of putting people in a freezer; if you do that, ice crystals will form and totally destroy the brain structures you're trying to preserve. The actual procedure involves pumping cryoprotectants into arteries very shortly after death (it has to be quick). Nearly all of the cost is in the procedure performed at time of death; once that's done, long-term refrigerated storage is trivial by comparison.
Interesting, but I think that the psychological basis of the belief in cryonics (to the point of paying for/investing in it) is far more so.
I was asked a while ago by a non-geek, wouldn't you have to be crazy to believe in cryonics? My answer was, you would have to be crazy to believe there was a one hundred percent chance it was going to work, but you wouldn't have to be crazy to believe there was, say, a five percent chance. And that's a lot better than the zero percent you get in a hole in the ground.
Yeah but that hole in the ground doesn't cost you nearly as much, and you don't risk the chance of waking up a brain-in-a-jar.
The bugger that haunts human cryonics is that thawing is never perfect because the cryoprotectants used to prevent ice-crystals within the cells are usually toxic. If you freeze cells that are measured to be 100% viable/alive at the time (very common) then thaw them using best practices, you're going to have some cell death-- maybe 1-5% if you're fast (less time spent in toxic cryoprotectant) and lucky. If you're unlucky or slow, you can look at 25-45% of your originally healthy cells being dead upon completion of the thawing process. The remaining cells are usually extremely discombobulated, and can take days to return to their baseline. This is completely fine if you're tooling around in a research lab or industrial lab, but even a 1% loss is probably too much for a human brain to bear and remain the same as before.
I suppose that if you work under the assumption that the future technology cryonics relies on for thawing will exist, cell loss during thaw will not be a problem; I find this possibility to be fairly likely over a long time span. Alternatively, you could assume that there will be advanced ways of restoring brain function or generating fresh neurons after systemic damage-- quite a stretch if you ask me, but it's conceivable. I think that ultimately the goals of cryonics will be scientifically realizable for those who were most recently preserved.