To answer this question we should talk to lots of neuroscientists. Here's one:
There's a burden of proof issue here: If there is a small group making a scientific claim that the larger scientific community finds ludicrous, skepticism should be the default position. I'm not aware of any peer-reviewed publication explicitly debunking cryonics. Probably the reason is that practicing lab scientists aren't inclined to write up a refutation of an particular idea when all you need to see it's bullshit is an undergraduate-level understanding of biology. So, since I can't point you to a systematic refutation, I'll give you this in the way of citation: http://jcb.rupress.org/content/188/1/145.full
This is a technically impressive study, they get really pretty and informative EM results. Excepting minor advances in the few years since it was published, this is close to state of the art as far a vitrification of brain tissue goes. If what the cryonics huckster companies were offering provided THIS level of preservation in a whole brain, then maybe we could have an interesting conversation. Cryonics would still be hopeless and vapid for other reasons, but at least you could count on fine membrane structure in synapses being preserved.
But in order to GET such good preservation, they had to take a slice of brain 400 micrometers thick and 1mm in diameter and vitrify it at 2000 bar. The high pressure required would damage an entire brain, and this works specifically because you're dealing with a small volume of tissue. Slicing an entire MOUSE brain and reconstructing it at this level is a major goal of connectomics, pretty far off. But I promise you (my lab does this kind of freezing for EM fairly routinely, it's time-consuming and the sectioning is artifact-prone), what the huckster companies are offering to do to your head is NOT going to give the kind of preservation that maintains synaptic structure. Thinking that in the early 21st century you're going to pay a company to freeze your brain in a way that it could be "reanimated" is insane, and shows a stunning naivete of the underlying biological complexity. The service you are paying for is "please destroy my already-dead brain in a way that involves chemicals and coldness". -- David Ruhl on facebook:LessWrong
There was also a discussion with another neuroscientist, kalla724, here a year ago.
Do people know of other places where a neuroscientist who knows about vitrification gives their opinion?
"When all you need to see it's bullshit is an undergraduate-level understanding of biology" is an extremely clear cue that the speaker does not understand the current state of the cryonics debate and cannot be trusted to summarize it. Anyone who does not specifically signal that they understand the concept of information-theoretic death as mapping many cognitive-identity-distinct initial physical states to the same atomic-level physical end state is not someone whose summaries or final judgment you can possibly reasonably trust. If they cite sources you might look at those sources, but you're going to have to figure out on your own what it means.
In June 2012, Robin Hanson wrote a post promoting plastination as a superior to cryopreservation as an approach to preserving people for later uploading. His post included a paragraph which said:
This left me with the impression that the chances of the average cryopreserved person today of being later revived aren't great, even when you conditionalize on no existential catastrophe. More recently, I did a systematic read-through of the sequences for the first time (about a month 1/2 ago), and Eliezer's post You Only Live Twice convinced me to finally sign up for cryonics for three reasons:
I don't find that terribly encouraging. So now I'm back to being pessimistic about current cryopreservation techniques (though I'm still signing up for cryonics because the cost is low enough even given my current estimate of my chances). But I'd very much be curious to know if anyone knows what, say, Nick Bostrom or Anders Sandberg think about the issue. Anyone?
Edit: I'm aware of estimates given by LessWrong folks in the census of the chances of revival, but I don't know how much of that is people taking things like existential risk into account. There are lots of different ways you could arrive at a ~10% chance of revival overall:
is one way. But:
is a very similar conclusion from very different premises. Gwern has more on this sort of reasoning in Plastination versus cryonics, but I don't know who most of the people he links to are so I'm not sure whether to trust them. He does link to a breakdown of probabilities by Robin, but I don't fully understand the way Robin is breaking the issue down.