I can’t see how a brain’s electrical impulses and ongoing chemical reactions would be preserved and restarted, if they were ceased.
I don’t see why you think there would be a problem. Raising the temperature restarts chemical reactions. Shine a light in the eyes or tickle the feet—that is all it takes to start nerve pulses flowing if the metabolic support is working. Restarting the heart is going to be more difficult than restarting the brain. That is to say, not difficult at all.
This is slightly misleading, since the difficulty is not in restarting the reactions, but in repairing the damage sustained between death and preservation, repairing damage caused by the preservation process, and undoing the vitrification itself. These are hard problems, but they are well enough understood that we think we can predict which research paths will eventually lead to solutions, and what those solutions will look like in broad terms.
The original comment didn’t say anything about structural damage or toxicity, just electrical activity and ongoing chemical reactions, which are non-issues.
Yes, cryonics is a much more complex subject than many people give it credit for and many aspects get confused. Whenever someone mentions the brain’s electrical activity being switched off as a sign of irreversible death I think they must be a newbie to the topic. Hypothermia patients frequently lose electrical activity and recover just fine. Structure is the key.
There is in reality a spectrum of cryonics. On the “soft” side would be a future invention (e.g. a very nontoxic cryoprotectant, or a means of rapid perfusion that lets you lower temperatures quickly enough) that permits zero chemical and structural damage, much like is currently only achievable in thin slices. On the “hard” side there are sub-ideal vitrifications and hard freezes.
There’s a spectrum of probabilities of success. Zero damage would be about 100% likely to succeed, whereas hard freeze is probably less than 1%. (Perhaps the chance is higher than that, but the person would be almost completely amnesiac—like a clone but with macroscopic features of the brain preserved.) Ideal conditions achievable today have a significantly higher probability (or percentage of memories preserved) than hard freezing. Unfortunately the unpopularity of cryonics means there’s hardly any infrastructure for it, which means an ideal case is relatively unlikely to actually occur.
I don’t see why you think there would be a problem. Raising the temperature restarts chemical reactions. Shine a light in the eyes or tickle the feet—that is all it takes to start nerve pulses flowing if the metabolic support is working. Restarting the heart is going to be more difficult than restarting the brain. That is to say, not difficult at all.
This is slightly misleading, since the difficulty is not in restarting the reactions, but in repairing the damage sustained between death and preservation, repairing damage caused by the preservation process, and undoing the vitrification itself. These are hard problems, but they are well enough understood that we think we can predict which research paths will eventually lead to solutions, and what those solutions will look like in broad terms.
The original comment didn’t say anything about structural damage or toxicity, just electrical activity and ongoing chemical reactions, which are non-issues.
Right. I was assuming essentially no damage between death and preservation. Current practice is far from this ideal, as I understand it.
Yes, cryonics is a much more complex subject than many people give it credit for and many aspects get confused. Whenever someone mentions the brain’s electrical activity being switched off as a sign of irreversible death I think they must be a newbie to the topic. Hypothermia patients frequently lose electrical activity and recover just fine. Structure is the key.
There is in reality a spectrum of cryonics. On the “soft” side would be a future invention (e.g. a very nontoxic cryoprotectant, or a means of rapid perfusion that lets you lower temperatures quickly enough) that permits zero chemical and structural damage, much like is currently only achievable in thin slices. On the “hard” side there are sub-ideal vitrifications and hard freezes.
There’s a spectrum of probabilities of success. Zero damage would be about 100% likely to succeed, whereas hard freeze is probably less than 1%. (Perhaps the chance is higher than that, but the person would be almost completely amnesiac—like a clone but with macroscopic features of the brain preserved.) Ideal conditions achievable today have a significantly higher probability (or percentage of memories preserved) than hard freezing. Unfortunately the unpopularity of cryonics means there’s hardly any infrastructure for it, which means an ideal case is relatively unlikely to actually occur.