There is a contingent of cryonics supporters who want more iron-clad evidence beyond that which already exists to demonstrate that the process of vitrification of tissue does work to preserve the fine structure of the brain, and thus the data of the mind. Everyone has a different threshold of comfort for proof, and some people have the luxury of time when it comes to watching the evidence accumulate over the years. There will always be those who will be uncomfortable with all uncertainty and wish to wait until the first preserved individual is revived, for example, but that is distant in time and technology; many decades, or possibly longer. Decisions on whether to sign up and whether to be preserved must be made before that point arrives for most of us.
There is also a contingent of cryonics supporters who see the ultimate destination for a preserved individual as scanning in order to run a mind in emulation in software. The original tissue would be discarded, and some folk are just fine with that. This is not appealing to me, and I see the primary purpose of preservation as being to offer the chance of restoration of the original - a copy of you is not you. Identity is not just a pattern, but also bound up in the particular matter that encodes that pattern. Restoration of vitrified brain tissue to a living, repaired status in a new body will probably be a more challenging task than scanning and emulation for the technology of the late 21st century, even though reversible vitrification of organs other than the brain is fairly close to realization as a practical technology for use in the organ transplant industry. Still, it is the only option if you, yourself, the original individual, wish a chance at a renewed life in the future.
Though no frozen humans have yet been revived, cryonics has been an industry for over fifty years. In that time, focus has shifted slightly. Lately, the emphasis has been more on brain emulation: mental maintenance as opposed to physical resurrection. The body and the self have been, in a sense, decoupled. Michael Cerullo, a neuroimaging specialist, moonlights as a cryonics pioneer. He spends a lot of time working with the Brain Preservation Foundation, an organization devoted to pushing cryonics toward the mainstream or, barring that, the mainstream towards cryonics. Because he's a doctor, Cerullo thinks of the freezing procedure as fundamentally medical in nature. More specifically, he and the BPF consider it an issue of brain health, which is why they awarded scientist Robert McIntyre a prize in February for his pioneering work with Aldehyde Stabilized Cryopreservation. McIntyre's technique allowed him to preserve a rabbit's connectome for, in theory, thousands of years. Cerullo says this is the sort of procedure he hopes will someday happen in hospitals.
What makes Cerullo a particularly compelling advocate for cryonics is that he's not a true believer - not exactly. He's an associate member of Alcor, the most recognizable name in the field, but he hasn't signed up to be preserved: evidence is lacking that current technology actually works. He's a man who wants proof and, more specifically, he's a man who wants proof that his identity can be preserved. He's open to experimentation with machine-neuron interfaces and emulation, but if he comes back, he wants to come back as himself. And that's the rub. We can't know if self-identity can be preserved until the technology starts working. Cerullo gives it twenty years, but points out that current dead bodies are stored as donated organs. If they still contain selves, we'll need to seriously reconsider our relationships with the frozen and the passed on.
If the brain turns off, are we the same people when it turns back on? That's the challenging question. Right away there are two schools of thought. A lot of the cryonics people want to be brought back biologically. They're hoping for a technique that they can be thawed out and continue in the same brain and same body. The challenge with that, though, is that a lot of the procedures, like the Aldehyde Cryopreservation, are not reversible. The first step is infusing the brain with glutaraldehyde, which is about the deadliest substance known. So you're never going to be able to revive that. What you're hoping is that, since you've got all the information there, with improvements in large-scale scanning techniques, you could get all the information uploaded. Let's say you do something like this new procedure, where there's no hope of biological revival. Then you upload the brain. There are still a couple of options: there's destructive and nondestructive uploading. One possibility would be that you could noninvasively scan the brain and get all the information. More likely, it would be destructive uploading, where you slice the brain in billions and billions of little nanometer thick slices, and map the whole connectome. Let's say you do that. Then, you emulate it in a computer in fifty, a hundred years, when the technology is there.
Does identity continue? Ultimately, we don't know the answer. No one has the full answer. A lot of people, though, assume that, you know, 'Okay, well this is just a simulation or a copy, and so of course it's not you.' I think that's the default answer. That seems to be the safe answer, because it doesn't really challenge a lot of things. But, what I think is more interesting, though, is that either way you answer that question - whether you say yes, the person is the same, or no, it's just a copy - either way there are a lot more implications than people realize. Either way, consciousness is a lot more complicated than we think. I don't think there's any easy answer. Either answer you take leads to paradoxes and just bizarre consequences that we really don't have great answers to. A lot of the scientists that I talk to are very gung-ho: 'Yes, this preserves the pattern, the information, and that's all we are.' I have a lot of sympathy for that view, but I think there are still a lot of deep questions that you really need to think about. But, I think that's the strongest answer, because the more we learn about the brain, and the more neuroscience advances, there really doesn't seem to be anything left out. The brain is the neurons and the information, and if that pattern's still there, then the person is still there.