Ken Hayworth’s idea of promoting a fixation-based alternative to brain cryopreservation is something I am highly sympathetic to overall, and I hope some progress in this direction results from the work he is doing and trying to induce others to do. That said, I wanted to comment on Hayworth’s remarks about straight freezing of brain tissue.

Figure 1B shows the horrific damage (destroyed cells) that occurs when such a slice is “preserved” using a freezing technique typical of those employed early in cryonics. Such damage is clearly irreversible by any future technology and it should come as no surprise that such techniques were flatly rejected by the scientific and medical community.

While it’s true that straight-frozen tissue as shown looks pretty awful I think it’s too strong a statement to say that “such damage is clearly irreversible by any future technology” unless you have further supporting arguments. To invoke a relevant analogy, we could run a phone book through a garden-variety shredder found in many offices, and still be able to reconstruct it from the resulting debris. The fact that there is debris remaining with the frozen tissue (as opposed to the cases of decay or burning) means we cannot, without further argument, rule out some sort of reconstructive process using future technology, including nanotechnology. It is also worth noting that with imperfect chemical fixation you run a risk of tissue loss over time that does not occur with cryopreservation; even debris resulting from straight freezing will remain as-is so long as cryogenic temperatures are maintained.

I also note that Hayworth says his proposed plastination could only be done properly if you start with a living patient with still-beating heart to distribute the initial fixative.

It is important to understand that the standard fixation and plasticization protocol is started while the animal is still alive. If the animal’s heart is allowed to stop for even a few minutes before the glutaraldehyde is perfused into the vasculature, then the quality of the preservation is markedly reduced. This fact will also be true for any whole brain protocol based on perfusion.

This of course would be problematic for any procedure to be used on humans; you’d have to treat it as some form of euthanasia.