The Brain Preservation Foundation’s mission to validate structural preservation of the brain has been very successful but the link with mind uploading as a means of personal survival raises some important questions. Alexandre Erler makes the case for a distinct cryonics research program based on biological survival.

INTRODUCTION: CRYONICS AND THE BRAIN PRESERVATION FOUNDATION

As someone who is fully supportive of the ultimate goals of the cryonics enterprise, but still views the current state of the practice with some degree of skepticism, I make a point of acquainting myself with the latest evidence regarding the quality of cryonics procedures and their ability to preserve the foundations of a person’s identity through time. Over the past two years or so, I have increasingly seen a recent achievement by 21^st-Century Medicine (21CM) cited by some cryonics supporters as demonstrating the scientific validity of those procedures: namely 21CM’s research on aldehyde-stabilized cryopreservation (ASC). This new technique has allowed them to win, in 2016, the Small Mammal Prize, and just this year, the full Technology Prize awarded by the Brain Preservation Foundation (BPF), by demonstrating excellent preservation of the ultrastructure in, respectively, a whole rabbit brain (McIntyre and Fahy, 2015) and a whole pig brain (The Brain Preservation Foundation, 2018). Were I to follow this line of reasoning, I could happily set aside my concerns about the adequacy of today’s cryopreservation procedures, which had now been verified by scientific experts; the proper focus would now need to be on how to responsibly introduce those procedures into a clinical setting, for patients at the end of their lives who might request them.

It turns out, however, that things are not so simple. ASC is no doubt a step forward for the field of brain banking, and as its name indicates, it it is indeed a form of cryopreservation, since it involves vitrification of the brain at -135 °C. Nonetheless, ASC does not count as cryonics, insofar as it uses a fixative solution prior to vitrification and cooling, which could potentially preclude revival of the original biological brain (an essential part of cryonics as traditionally understood). And indeed, biological revival with the help of future technology is not a priority for the BPF’s president, Dr Kenneth Hayworth. Rather, he envisages brain preservation as conducive to life extension via mind uploading: a process that would involve cutting the preserved brain into thin slices, scanning each slice, and feeding the resulting data to an advanced computer that would thereby be able to map out the entire network of neural connections in the person’s original brain, and ultimately to emulate that person’s mind (Hayworth, 2010). This is quite different from cryonics.

Assuming that a technique like ASC is compatible with mind uploading, but not with the revival of the original brain, it should not be treated as a landmark in cryonics research. Admittedly, there is some uncertainty about the truth of that assumption. It seems at least conceivable that the chemical cross-links created by the fixation process could be reversed, and the original brain revived, using future technology. Nonetheless, ASC introduces empirical and philosophical uncertainties (e.g. could we really restore, as opposed to recreating, the original neural structure following the various molecular changes involved?) to a much greater degree than traditional cryonics does.

But why, it might be asked, should one remained fixated on pursuing biological revival via cryonics, if the evidence in favour of good ultrastructure preservation is better for ASC than it is for contemporary cryonics procedures? It is for instance known that, up to now, 21CM’s cryonics protocol involving the use of cryoprotectant M22 has been causing the brain to shrink to almost 50% of its natural size due to osmotic dehydration, hindering our ability to establish the quality of ultrastructure preservation using electron microscopy (The Brain Preservation Foundation, n.d.; De Wolf, 2017). If so, why not join the BPF in focusing simply on the type of brain preservation that seems to yield the best evidence of success, even if this means turning away from cryonics towards mind uploading?

In what follows, I will argue that, given the current state of our scientific and philosophical knowledge, doing so would be irresponsible. The BPF’s commitment to holding brain preservation research to the highest standards of scientific rigour is laudable, and worth emulating. Nonetheless, for those interested in brain preservation with a view to enabling life extension, supporting cryonics-specific research remains the safer bet. We should not simply rely on the BPF’s approach if our goal is to try and save those whom medicine in its current state cannot restore to life and health.

TWO DIFFERENT VIEWS ABOUT PERSONAL IDENTITY AND SURVIVAL

To see why this is so, let us begin by noting the two main philosophical theories of personal identity through time that are relevant when discussing the respective merits of cryonics and mind uploading in this context. The first one, which we can call the “Physical Continuity” (PhyCon) theory, asserts that a person is identical with the physical substratum from which her mind emerges: that is to say, her brain, with its intricate web of neurons and synaptic connections. (For a good exposition of the theory, see e.g. McMahan, 2002.) According to this theory, saving a person from destruction after she has been pronounced dead requires preserving enough of her brain, in a state in which that brain retains at least its potential for viability. What exactly counts as “enough” of the brain is of course a difficult question that would deserve much more discussion. While we can safely say that, all else being equal, it is always preferable to preserve as much of the original brain as we can, the survival of the person arguably does not require perfect preservation. Intuitively, people can survive limited forms of brain damage, such as those caused by strokes. What is more, as cryonicists have pointed out, brain damage that causes significant disability today might no longer be a serious problem (as long as it is limited enough not to undermine personal identity) in a future where cryonic revival has become possible, as the technological means will then likely exist to fully repair that damage, e.g. based on inferences from the state of the person’s brain prior to repair.

The second relevant theory can be referred to as the “Psychological Continuity” (PsyCon) theory. Roughly speaking, it says that you are to identical with the set of psychological features (memories, beliefs, desires, personality traits, etc.) that constitutes your mind. On this view, preserving you after you have been pronounced dead requires ensuring the persistence of enough of those psychological features, in an embodied mind of some sort (but one that need not be embodied in your current biological brain). One variant of PsyCon, endorsed by many supporters of mind uploading including Hayworth, states that preserving a person after legal death requires preserving her connectome, understood as the mapping of neural circuitry encoding one’s memories, skills, and other psychological features – that is to say, the connectome as an informational entity rather than a physical one (Hayworth, 2010), even though the information in question will by necessity be stored in some physical substratum, whether a brain or a computer.

Like virtually all philosophical theories, both the PhyCon and PsyCon theories have their partisans and detractors. PhyCon, for instance, has been said to imply that there is a fundamental difference between a scenario in which a person had her brain suddenly destroyed and replaced by an exact copy of it, perhaps produced via scanning and 3D printing using neurons as basic material; and a scenario in which the person’s brain cells were gradually replaced by new ones over an extended period of time, in the same way as the rest of the human body regularly regenerates itself. While most PhyCon theorists would agree that the second scenario is compatible with the preservation of the person’s identity through time, they will deny that the first is – if the original brain gets destroyed, they will say, so must the person as well, and the new replica brain must belong to a new person not numerically identical with the first one. Some find this difference of treatment between the two scenarios arbitrary (e.g. Parfit, 1984).

Some versions of PsyCon, on the other hand, imply that multiple copies of yourself could all be you. Indeed, suppose that after scanning your brain to obtain a map of your connectome, we then created two identical copies of your mind running on two different computers. Since both copies would demonstrate the same degree of psychological continuity with your previous self, we would have to conclude that both are you – something many find intuitively unacceptable. Other versions of PsyCon strive to avoid that implication by stipulating that you are only identical with an upload of your mind if no more than one copy of it has been created, yet this move leads to other philosophical problems. Hayworth, however, happily endorses the implication that multiple copies of a single individual can co-exist at the same time, and contends that those who object to that implication are simply confused (Hayworth, 2010).

HOW TO MAKE A PRUDENT CHOICE UNDER (PHILOSOPHICAL) UNCERTAINTY

For the record, I personally find PhyCon more plausible than PsyCon (although I also agree that the preservation of one’s psychological features after cryonic revival is highly desirable, regardless of its significance for sheer survival). On that basis, I do not support further animal research targeted exclusively at the development of mind uploading technology. However, my personal opinion on the matter can be set aside for the sake of the present discussion. The important fact is that there are reasonable, honest and intelligent people on both sides of that debate, and that neither side has so far managed to present arguments that would convince all reasonable people on the other side. In such a situation, the intellectually responsible path to take is surely to eschew certainty, and acknowledge that the other side could be right, even if one thinks that this is unlikely and that the arguments favoring one’s own position are very strong.

If that is the case, what is the prudent choice to make for those who wish to promote life extension through brain preservation? I submit that traditional cryonics is the more prudent option to pursue. (This remark could be extended to ASC if one could show that it is in principle compatible with the revival of the original brain, and provided that it is not combined with destructive mind uploading.) This can be demonstrated using a simple argument that considers what the implications are if we assume that PhyCon and, respectively, PsyCon are true.

Suppose first that PhyCon is true. If so, a cryonics procedure carried out properly will save a person’s life, whereas using a technique like ASC that compromises the brain’s potential for viability, followed by destructive scanning and uploading, will kill that person. If PsyCon is true, on the other hand, both methods can ensure survival. Indeed, adequate cryonic preservation of a person’s brain would also preserve the ultrastructure grounding the various psychological features that defined that person. Insofar as traditional cryonics (at least once sufficiently perfected) can secure survival whether PhyCon or PsyCon is true, whereas mind uploading of the kind envisaged by the BPF can only do so if PsyCon is correct, traditional cryonics is the safest bet.

This conclusion is reinforced by the fact that the success of mind uploading at securing personal survival might depend on an additional factor, namely the possibility of creating conscious or sentient machines. If, for whatever reason, computers – which, unlike biological brains, rely on hardware rather than “wetware” – happen to fundamentally lack the capacity for consciouness, regardless of how powerful and sophisticated they might be, then uploads turn out to be no more than computer “zombies” mimicking now deceased people. It’s unclear that someone could “survive” as such an entity. And even if we assume that they could, the value of such survival, devoid of the conscious experiences that make our lives worth living, would be dubious, somewhat like the value of surviving with only a brain stem. This point about machine consciousness equally applies to the idea of a “Moravec transfer”, i.e. a procedure involving gradually uploading a person’s mind to a computer (neuron by neuron if necessary), unlike the BPF’s proposed method (Moravec, 1988). Traditional cryonics, by contrast, can succeed at preserving a person regardless of whether or not computers can be conscious.

Hayworth would presumably deny that any such doubts about the possibility of machine consciousness are legitimate. Indeed, he seems to confidently embrace the so-called computational theory of consciousness, according to which consciousness is fundamentally the product of – highly complex – computation, which we know computers to be capable of at least in principle (e.g. Hayworth, 2015). However, there is currently no general agreement among philosophers of mind or neuroscientists that the computational theory of consciousness is correct, and Hayworth does not demonstrate that it is (although he dogmatically equates the idea that there might be physical properties required for the production of conscious experience which are found in wetware, but not computer hardware, with invoking “magic”).

Furthermore, even if taken for granted, the computational theory of consciousness cannot, absent additional philosophical arguments, show mind uploading to be consistent with personal survival. Assuming that R2-D2 from Star Wars is conscious does not commit us to accepting that a perfect replica of R2-D2 built from fresh parts, after – let us assume – it was destroyed by the Empire’s forces, is numerically identical with the original robot. In response, Hayworth could perhaps abandon PsyCon and instead invoke the claim, famously defended by philosopher Derek Parfit, that personal identity does not actually matter in the way many of us tend to think – rather, psychological continuity is what really matters (Parfit, 1984). (In his reply to an article by neuroscientist Michael Hendricks critical of cryonics, Hayworth actually appears to move in that direction: see Hayworth, 2015.) However, besides the fact that this is again a controversial philosophical view, it notably led Parfit to dissociate psychological continuity from personal survival, and to conclude that the latter was, in itself, also overrated. This position is very much at odds with the life extension project, which the BPF claims to be pursuing.

I cannot but see some irony in the fact that Hayworth, the author of an essay titled “Killed by Bad Philosophy”, should show a degree of overconfidence in his philosophical views that might potentially lead his followers to experience the very same outcome his essay is warning against.

The differences previously highlighted between traditional cryonics and the BPF’s approach are summarised in the table below:

(*It is assumed that the relevant procedures are performed in accordance with the highest standards of quality)

WHAT THE CRYONICS MOVEMENT CAN LEARN FROM THE BPF

None of this is meant to imply that the work of the BPF is without merit. On the contrary, the Foundation’s approach demonstrates a number of virtues that can provide a model for the cryonics movement to follow. These include a commitment to rigorously and impartially evaluating the quality of brain preservation procedures, in accordance with the standards of scientific peer-review. Another example is the BPF’s successful effort at crowdfunding its incentive prizes for brain preservation research, such as the two prizes won by 21CM. For those seeking to promote life extension through brain preservation, who I have argued need to prioritize cryonics-specific research, this suggests two main paths worth pursuing in the future:

(a) Incentive prizes. Such prizes are a powerful tool for stimulating research, particularly in neglected areas of science. Unfortunately (and perhaps unsurprisingly, given Hayworth’s philosophical beliefs), the BPF does not at this point appear inclined to set up any new prize that would include a requirement to preserve the brain’s potential for viability. On the basis of the arguments I have provided so far, I submit that the institution of a prize (possibly crowdfunded) incorporating that requirement would be highly desirable.

How demanding such an incentive prize should be with regards to the winning entry is a matter for further debate. A relatively modest version would require demonstrating adequate ultrastructure preservation in a small mammalian brain, but using a procedure that could in principle be reversed by future technology, making it possible for the original brain to eventually be “re-started”. However, based on a recent talk by Dr Greg Fahy from 21CM, which I attended in May 2017 at the International Longevity and Cryopreservation Summit in Madrid, such a goal may soon be achieved. Indeed, Dr Fahy reported having found a way to largely overcome the abovementioned problem of dehydration and shrinking that has so far prevented a proper assessment of the quality of ultrastructure preservation offered by traditional cryonics protocols (e.g. using M22). Assuming Fahy has now reached that milestone (and I look forward to the publication of his paper on the topic), one could set up a prize with a more ambitious goal: for instance, one could add that besides showing good ultrastructure preservation and retaining the preserved brain’s potential for viability, one should also demonstrate actual viability, say via measurable electrical activity, either at the level of the whole brain or in slices obtained from that brain. Ultimately, the details of such a prize should be worked out by scientists with the relevant expertise (as long as the constraints I have outlined here are respected).

Those who believe that ASC holds greater promise could support a prize rewarding the first team who found a way to reverse the fixative process involved in that procedure, and restore the original neural structure.

(b) Research funds. Such a fund, which could also be crowdfunded, would be managed in a transparent manner by an organization committed to promoting cryonics-specific research. In accordance with standard practice when it comes to funding scientific research, project proposals would be solicited from active researchers in cryobiology (and other relevant fields), and a committee of experts would select the proposals that it deemed most worthy of funding. The organization would then help disseminate the results of the completed projects (e.g. as laid out in peer-reviewed publications).

The scientific experts tasked with evaluating the submissions for either an incentive prize or a research fund should ideally be publicly identified, and sufficiently independent of both the authors of the submissions and of cryonics companies (e.g. they should not be receiving research funding from those companies). Furthermore, while an organization that might implement solution a) or b) could be created de novo, existing institutions might already be able to fulfill that role. One example would be the UK Cryonics and Cryopreservation Research Network (http://cryonics-research.org.uk), led by Dr João Pedro de Magalhães, who has connections with other scientific experts, including Ken Hayworth. Despite the scientific rigour with which it approaches the issue of cryonics, the network is currently underfunded.

While most people may understandably not be able to commit substantial amounts of resources to supporting cryonics research, the success that the BPF has enjoyed so far with its incentive prizes demonstrates that large numbers of even small donations can foster impressive technical breakthroughs and help strengthen the credibility of research projects of the most audacious sort. I believe it is now time to apply a similar approach to the safer bet of cryonics-specific research. Further raising the public profile of such research, and improving its status in the eyes of the mainstream scientific community, can help promote a virtuous cycle leading in turn to more funding and greater professionalization. The sooner we can make this happen, the better.

An earlier version of this article appeared in Cryonics magazine, November-December, 2017.

REFERENCES:

DE WOLF, A. August 21 2017. Cryonics Without Cerebral Dehydration? Evidence-Based Cryonics [Online]. Available from: https://www.biostasis.com/2017/08/21/cryonics-without-cerebral-dehydration/.

HAYWORTH, K. 2010. Killed by Bad Philosophy: Why Brain Preservation Followed by Mind Uploading Is a Cure for Death. Available: http://www.brainpreservation.org/content-2/killed-bad-philosophy/.

HAYWORTH, K. September 16 2015. Ken Hayworth’s Personal Response to MIT Technology Review Article. Brain Preservation Foundation [Online]. Available from: http://www.brainpreservation.org/ken-hayworths-personal-response-to-mit-technology-review-article/.

MCINTYRE, R. L. & FAHY, G. M. 2015. Aldehyde-Stabilized Cryopreservation. Cryobiology, 71, 448-58.

MCMAHAN, J. 2002. The Ethics of Killing : Problems at the Margins of Life, Oxford, Oxford University Press.

MORAVEC, H. P. 1988. Mind Children : The Future of Robot and Human Intelligence, Cambridge, Mass., Harvard University Press.

PARFIT, D. 1984. Reasons and Persons, Oxford, Clarendon Press.

THE BRAIN PRESERVATION FOUNDATION. n.d. Overview of 21st Century Medicine’s Cryopreservation for Viability Research [Online]. Available: http://www.brainpreservation.org/21cm-cryopreservation-eval-page/.

THE BRAIN PRESERVATION FOUNDATION. 2018. Aldehyde-Stabilized Cryopreservation Wins Final Phase of Brain Preservation Prize [Online]. Available: http://www.prweb.com/releases/prweb15276833.htm.

There is little disagreement among cryobiologists that the biggest limiting factor to reversible organ cryopreservation is cryoprotectant toxicity. It is actually not that hard to create vitrification solutions that completely inhibit ice formation at even the slowest cooling rates. The problem is that such highly concentrated vitrification solutions are too toxic to permit recovery of complex organs. The least toxic vitrification solution for complex mammalian organs as of writing is M22. M22 is the culmination of many years of experimental and theoretical work by cryobiologist Greg Fahy and colleagues.

Studying cryoprotectant mixtures on rabbit kidney slices, Fahy and colleagues came to the following conclusions:

1. High concentrations of a cryoprotective agent (or a mixture of different cryoprotective agents)
can prevent ice formation during cooldown and warming.

2. The toxicity of some cryoprotectants can be neutralized by combining them with other cryoprotectants.

3. The non-specific toxicity of a cryoprotectant solution can be predicted by calculating a quantity (“qv*”) which is intended to measure the average hydrogen-bonding strength of the cryoprotectant polar groups with the water molecules in the solution.

4. Within limits, non-penetrating agents can reduce the exposure of cells to toxic amounts of cryoprotectants without reducing vitrification ability.

5. Synthetic “ice blockers” can be included in a vitrification mixture to reduce the concentration of toxic cryoprotective agents necessary to achieve vitrification.

While M22 is a low toxicity solution, its toxicity profile still necessitates minimizing exposure time and introduction and removal at low (subzero) temperatures. If we had a better understanding of the mechanisms of cryoprotectant toxicity, vitrification solutions with no toxicity at all could be introduced at higher temperatures and exposure times could be increased to optimize complete equilibration of the tissue with the cryoprotectant.

Two major reviews of cryoprotectant toxicity were published in the last 5 years; Gregory Fahy’s“Cryoprotectant Toxicity Neutralization” (Cryobiology, 2010) and Benjamin Best’s “Cryoprotective Toxicity: Facts, Issues, and Questions” (Rejuvenation Research, 2015).

Greg Fahy’s paper is a rigorous exposition of experimental results concerning the phenomenon of cryoprotectant toxicity neutralization. The paper is mostly limited to the discovery that DMSO can block the toxic effects of amides such as formamide. The combination of DMSO and formamide (or other amides such as urea and acetamide) is indeed one of the building blocks of M22 but this combination cannot be used without limit and the paper includes data that indicate the maximum molar concentrations (and ratios) that still permit full viability. In theory, if two (or more) cryoprotectants would completely neutralize each other’s toxicity they could be the sole components of a vitrification solution. But as the formulation of M22 shows, it is still necessary to add weak glass formers such as ethylene glycol, extracellular CPA’s, and “ice blockers” to supplement the toxicity neutralization obtained with formamide and DMSO. An important finding in Fahy’s paper is that n-methylation abolishes toxicity neutralization for amides and combining methylated amides also does not lead to toxicity neutralization between
them. In fact, Fahy found that the presence of n-methylated compounds renders even small amounts of DMSO toxic. The remainder of the paper discusses the mechanisms of cryoprotectant toxicity and Fahy now favors protein denaturation as a plausible mechanism of (non-specific) toxicity. While other cases of toxicity neutralization have been reported in the literature, no rigorous studies have been done to produce a body of knowledge that is comparable to what we know about amide-DMSO interactions.

Benjamin Best’s paper is more general in scope but discusses a lot of experimental data from other papers and also critically discusses Fahy’s work on cryoprotectant toxicity. As Ben Best points out, different (and seemingly contradictory) results do not necessarily mean that cryoprotectant toxicity is a species or cell-type dependent phenomenon. One could imagine a meta-analysis of cryobiology data in which variables such as concentration, loading and unloading protocols, exposure temperature, exposure time, and the type of viability assay are matched to ensure methodological consistency. It is also important to compare cryoprotectants at their minimum concentration to vitrify to make meaningful toxicity comparisons.

If the work at 21st Century Medicine is an indication, universal low-toxicity cryoprotective solutions should be feasible. Perhaps the most interesting part of the paper is where Best offers a critique of Greg Fahy’s “qv* hypothesis of cryoprotectant toxicity,” which aims to show that non-specfic toxicity concerns the degree to which cryoprotectants leave water available to hydrate macromolecules. This discovery allowed for the substitution of ethylene glycol for propylene glycol in Fahy’s lower toxicity vitrification solutions, despite the resulting higher CPA concentrations. Best observes, “it seems contradictory that water remains available for hydration, but not available for ice formation.” A potential rejoinder to this observation is that so called “bound water” does not participate in ice formation but can be disturbed by strong glass formers. Best also suggests a potential refinement of qv* that allows for more precise calculation of the hydrogen bonding strength of the polar groups that are used to calculate qv*. It is conceivable that such a refinement would eliminate the few remaining outliers in the data that support the qv* hypothesis. The paper also draws attention to the possibility of kosmotropic co-solvents and changes of pH and microenvironment polarity to mitigate cryoprotectant toxicity.

Neither of the papers discusses cryopreservation of the mammalian brain, but there is good reason to believe that in the case of this organ, modification of low-toxicity vitrification solutions is required. Conventional cryoprotective agents such as PG, EG, and DMSO have poor blood brain barrier (BBB) penetration and the brain may not tolerate the CPA exposure times that other organs do. For example, while M22 can be used for cryopreservation of the brain, many of its component have poor BBB penetration and PVP and the ice blockers (X-1000 and Z-1000) are assumed not to cross the (non-ischemic) BBB at all. One potential solution is to (reversibly) open the BBB with so-called BBB modifying agents like detergents or perhaps to search for cryoprotective agents that can cross the BBB.

The most fundamental question in the design of vitrification solutions remains whether it is possible at all to introduce high concentrations of cryoprotectants without creating any kind of irreversible molecular and ultrastructural adverse effects. Understanding what specific and nonspecific cryoprotectant toxicity exactly is should enable us to answer this question.

Originally published as a column in Cryonics magazine, August-September, 2016

A cryonics advocate makes an eloquent case for cryonics. Then a scientist is called upon to dismiss the idea of cryonics because there is “no proof” for it. Unfortunately, such a statement reveals that the “scientist” in question does not know the difference between empirical science and logic, and also does not understand the difference between cryonics and suspended animation.

As the evolutionary biologist Satoshi Kanazawa writes in a November 16, 2008 column for Psychology Today “The knowledge that there is no such thing as a scientific proof should give you a very easy way to tell real scientists from hacks and wannabes… Proofs exist only in mathematics and logic, not in science. Mathematics and logic are both closed, self-contained systems of propositions, whereas science is empirical and deals with nature as it exists. The primary criterion and standard of evaluation of scientific theory is evidence, not proof.” He goes on to write that “all scientific knowledge is tentative and provisional, and nothing is final. There is no such thing as final proven knowledge in science.”

What is the proper role of science in cryonics? Let’s say that a person proposes that if we freeze a person after clinical death there is a reasonable expectation that more advanced medical technologies can reverse the freezing damage, the medical condition that gave rise to this person’s critical condition, and also the aging process that caused this medical condition in the first place. We can respond to this proposal by asking a number of questions. What will freezing do to the fine structure of the brain? How will future medical technologies infer the original state of the brain from the frozen state? What kind of technologies are required to repair the brain and restore the person to a healthy and youthful state?

These are the kinds of questions where science (and reasonable extrapolations of where science will be heading) is important in evaluating the idea of cryonics. And we are not limited to just consulting existing science, we can also push science in the direction of minimizing the damage incurred during cryopreservation so the odds of revival for the typical cryonics patient will increase. For example, in 2000 Alcor changed its protocol from limiting freezing to eliminating it through a technology called vitrification. Advances in gene editing, virus modification, and nano-scale 3D printing can make the idea of cell repair more plausible. Advances in science and technology of this nature can make people update their prior (subjective) estimates about the probability of cryonics being successful.

What such advances in science cannot do is to provide “proof ” that cryonics will work. They cannot do this because all scientific knowledge is “tentative and provisional,” but it also cannot do this for a more fundamental reason. Cryonics is not suspended animation. Cryonics concerns
stabilizing people for whom no successful medical treatment is available to permit them to benefit from future advances in medicine. By definition, it is not possible to prove that these technologies will become available.

What people who insist on “proof ” for cryonics want to see is evidence of reversible cryopreservation. Human suspended animation is indeed a research- and clinical objective that a credible cryonics organization should aim for. But it cannot be emphasized enough that while “proof ” of suspended animation would provide strong support for the practice of cryonics is it is not necessary for the cryonics idea to be plausible. What is necessary for cryonics to work is that the brain (and rest of the body) of a person are preserved to a degree that the original, healthy, state of the brain can be inferred from the preserved state. Perhaps future “neurological archeology” technologies will reveal that even freezing of the brain without cryoprotectant allows for complete revival.

A proper understanding of cryonics requires that scientists recognize the difference between providing proof and updating expectations based on empirical evidence. But it also requires the scientist, as the great cryonics writer Thomas Donaldson once recognized, to make peace with the unknown because the capabilities of future science remain a matter of debate and we cannot say for certain when a person is dead by information-theoretic criteria.

Originally published as a column in Cryonics magazine, July-August, 2016

On February 9, 2016 the Brain Preservation Foundation announced that the cryobiology company 21st Century Medicine had won their small mammal brain preservation prize. The team at 21st Century Medicine used a procedure named Aldehyde-Stabilized Cryopreservation (ASC) to preserve the ultrastructure of the brain in a “near-perfect” condition. It is important to understand how ASC differs from both conventional cryopreservation and other human biostasis alternatives to understand its merits and limitations.

In conventional cryopreservation (which is the procedure Alcor currently uses) the blood (and cell water) in the brain is replaced with a vitrification agent that permits long term storage at liquid nitrogen temperature without further degradation. The advantage of this method is that it seeks to both preserve viability and the fine ultrastructure of the brain. Currently, the disadvantage of this method is that it produces (severe) cerebral and cellular dehydration, which alters the ultrastructure of the brain and renders some components of the brain difficult to observe in electron micrographs.

A radically different alternative to cryopreservation is to chemically fix the brain with aldehydes (formaldehyde, glutaraldehyde) and store the brain at room temperature or in a fridge in the liquid state. While some people consider such a procedure “better than nothing”, Alcor does not support this kind of “chemopreservation” as a long term care option due to concerns about long-term degradation and  sub-optimal preservation in ischemic cases. An extensive critique of liquid state chemopreservation can be found in my article ‘Chemical Brain Preservation and Human Suspended Animation.’

What is notable about the procedure that won the small mammal brain preservation prize is that it combines both aldehyde fixation and vitrification. In short, first the brain is perfused with glutaraldehyde, followed by perfusion of a high concentration of cryoprotectant to protect the brain against ice formation during long term care. This idea is actually not new and was discussed in in the mid-1980s in Eric Drexler’s book Engines of Creation. The renewed popularity
and technological development of this idea was recently triggered by the formation of the Brain Preservation Foundation and its emphasis on ultrastructural preservation. The protocol that won the small mammal brain cryopreservation prize has shown indeed a degree of ultrastructural preservation that has not yet been achieved with conventional brain cryopreservation.

Alcor’s biggest concern with aldehyde-stabilized cryopreservation is that it renders the tissue completely dead by contemporary viability criteria by creating irreversible crosslinks between bio-molecules. Despite claims to preserve the “connectome”, at the molecular level structure is fundamentally altered. In terms of research aimed at reversible biopreservation, this is a dead end.

Conventional cryo, conventional chemo, and a combination of the two are the three most discussed options of human biopreservation. Other, hypothetical possibilities include (a) vitrification with agents with much higher glass transition temperatures that permit warmer storage such as at dry ice temperature (b) poly-vitrification, in which high molecular weight polymers are used to stabilize the patient near or at room temperature, and (c) the use of molecular nanobots to induce reversible biostasis (an idea originally proposed by Robert Freitas).

The current position of Alcor is to keep researching and offering conventional cryopreservation without the use of chemical fixatives. The research emphasis of the organization and associated labs this year will be to produce better electron micrographs of cryopreserved brains and the validation of blood brain barrier modifying agents to eliminate the severe dehydration that is currently observed in “good” cryonics cases.

Originally published as a column in Cryonics magazine, March-April, 2016

On September 15, 2015, the MIT Technology Review published an article named “The False Science of Cryonics” that revealed how much ignorance about cryonics still exists among those that should know better (scientists, medical professionals, etc.). First of all, cryonics is not a “science” but an experimental medical procedure that is informed by scientific developments in disciplines such as cryobiology and neuroscience.

Semantics aside, a major flaw in the article is that it conflates mind uploading and cryonics. While some of our members may favor the possibility of “substrate-independent minds,” in its most “conservative” incarnation resuscitation will occur through repair of the same biological brain (or whole body) that was preserved. Complicated philosophical issues about whether a copy is “you” do not come into play in this repair scenario at all. So when Alcor was asked by a reporter to comment on the article, we submitted the following response:

The article in the MIT Technology Review rests on several mistaken assumptions. First of all, cryonics does not require or imply mind uploading. While some of our individual members are interested in this topic, the default resuscitation scenario for cryonics patients involves molecular repair of the patient’s biological brain (and body). While we are encouraged by the rise of connectomics, the aim at Alcor is to cryopreserve all the fine details of the brain and even secure viability of the brain as well as we can. In fact, in our stabilization procedures we aim to keep the brain viable by contemporary medical criteria and collect data to evaluate the efficacy of our procedures.

Alcor is a charitable, non-profit, organization and we do not make a profit when we place our patients in biostasis. Also helpful to understanding the ethics and financial feasibility of cryonics for persons of ordinary means is that most people fund cryonics through an affordable, dedicated, life insurance policy, making cryonics an accessible personal choice.

We strongly disagree that without proof of human suspended animation or flawless ultrastructural preservation it is not ethical to practice cryonics. Our organization challenges the mainstream definitions of death, and we believe that perfected cryopreservation is a sufficient but not necessary condition for cryonics to succeed. As long as we have good reasons to believe that the original state of the brain can be inferred from the damaged state, making cryonics arrangements can be a rational choice to make. To our knowledge, there are no rigorous, scientific, studies that demonstrate that today’s cryonics procedures produce irreversible destruction of identity-critical information.

Information about the ultrastructural effects of the vitrification solutions we use to inhibit ice formation can be found here: http://www.alcor.org/Library/html/newtechnology.html

It is disappointing that scientists and professional writers put so little effort into understanding what cryonics entails and what the real technological challenges are. Unfortunately, there is essentially no cost to being factually wrong about cryonics. In fact, when professional cryobiologists comment on cryonics they often make claims about their own field that are factually incorrect, such as that cryonics produces intracellular freezing, or that ice-free cryopreservation of complex organs is not yet possible.

We may not be able to persuade everyone that cryonics is the prudent, conservative choice to make, but we might benefit from giving more thought to how to prevent and counter factually erroneous articles such as the one in the MIT Technology Review.

Originally published as a column in Cryonics magazine, November 2015

Evidence in cryonics is a complicated concept. For starters, it is not possible to “prove” cryonics will work, here and now, because the fundamental idea of cryonics is to stabilize critically ill patients (people considered “dead” by less rigorous criteria) in anticipation of more advanced future medical technologies. What we can do is validate cryonics technologies with reversible cryopreservation (“suspended animation”) as a benchmark. As a general rule, we can state that we make progress in cryonics when stabilization, cryopreservation, and maintenance (“storage”) technologies cause less damage than the technologies that preceded them. But how do we know if this is the case?

The most rigorous form of validation, human clinical trials, is usually not available in cryonics. There are often new (approved) emergency medical technologies, however, that can be modified to be used in cryonics procedures. A major advantage of adopting such technologies is that the validation has already been done by other organizations or companies. Examples of such technologies will often fall under the rubric of emergency medicine. For example, an FDA-approved technology that improves blood flow during cardiopulmonary resuscitation can be added to Alcor’s stabilization equipment to improve stabilization procedures.

One step down from rigorously designed human clinical trials are animal studies. In cryonics we often make a distinction between small animal studies (e.g., mice, rats) and large animal studies (e.g., pigs, dogs) etc. It seems common sense to think that large mammals provide stronger evidence for a technology than smaller animals but the real issue at stake here is not how large an animal is but how closely an animal model tracks what happens in humans. For example, if cat brains have an uncharacteristically high tolerance for cerebral ischemia, the (smaller) rat may actually be a more realistic model for validating neuroprotective strategies in humans.

One area where choosing the correct animal model has proven itself to be of crucial importance concerns the effect of cryoprotectants on the brain. Most mammalian species experience dehydration of the brain after equilibration with a vitrification agent. Because it is reasonable to assume that severe dehydration adversely affects brain viability it is tempting to select an animal model that experiences little cryoprotectant-induced dehydration. But one thing that we have learned from burhole measurements and CT scans in human cryonics patients is that under optimal conditions cryoprotective perfusion with both glycerol and the modern vitrification agents produces severe shrinkage of the brain. So if we want to validate strategies to eliminate this dehydration the most important consideration is not how “large” the animal is but how well the animal tracks the effects of cryoprotectants on the human brain.

Most technologies in cryonics need to be evaluated with ultrastructure and/or viability as an endpoint. But there are also new developments in cryonics where such a benchmark would not make a lot of sense. For example, if we build a new patient enclosure to keep the patient cold during cryoprotective perfusion we can just measure the core temperature of the patient to see if we have done a satisfactory engineering job. Another example is the design of new dewars where we can look at variables like the boiloff rate and long-term durability of the design.

In conclusion, there are a number of ways to validate new technologies in cryonics. If a new technology has undergone human clinical trials we often can just adapt that technology for cryonics without designing new experiments. In the case of more cryonics-specific technologies animal studies can be conducted and the choice of animal model will be dictated by how close a model tracks what we know to occur in humans (among other considerations like ethics and cost). Finally, when a new development in cryonics is mostly an engineering challenge, validating its efficacy is often just an issue of doing basic physiological measurements or practical tests.

Originally published as a column in Cryonics magazine, August, 2014

There is little disagreement among cryobiologists that the biggest limiting factor to reversible organ cryopreservation is cryoprotectant toxicity. It is actually not that hard to create vitrification solutions that completely inhibit ice formation at even the slowest cooling rates. The problem is that such highly concentrated vitrification solutions are too toxic to permit recovery of complex tissues. The least toxic vitrification solution for complex mammalian organs as of writing is M22. M22 is the culmination of many years of experimental and theoretical work by cryobiologist Greg Fahy and colleagues using rabbit kidney slices. Studying selected cryoprotectant mixtures on rabbit kidney slices, Fahy and colleagues came to the following conclusions:

1. High concentrations of a cryoprotective agent (or a mixture of different cryoprotective agents) can prevent ice formation during cooldown and warming.

2. The toxicity of some cryoprotectants can be neutralized by combining them with other cryoprotective agents.

3. The non-specific toxicity of a  cryoprotectant solution can be predicted by calculating a quantity (“qv*”) which is intended to measure the average hydrogen-bonding strength of the cryoprotectant polar groups with the water molecules in the solution.

4. Within limits, non-penetrating agents can reduce the exposure of cells to toxic amounts of cryoprotectants without reducing vitrification ability.

5. Synthetic “ice blockers” can be included in a vitrification mixture to reduce the concentration of toxic cryoprotective agents necessary to achieve vitrification.

While M22 is a low toxicity solution, its toxicity profile still necessitates minimizing exposure time and introduction and removal at low (subzero) temperatures. If we had a better understanding of the mechanisms of cryoprotectant toxicity, vitrification solutions with no toxicity at all could be introduced at higher temperatures and exposure times could be increased to optimize complete equilibration of the tissue with the cryoprotectant. It would also allow safer storage at intermediate temperature temperatures (around -130 degrees Celsius) because ultra-stable vitrification solutions could be used that are less prone to de-vitrification upon re-warming. This would be of particular interest for the cryopreservation of large organs or even whole organisms (with applications such as suspended animation and cryonics).

Two major reviews of cryoprotectant toxicity were published in the last 5 years; Gregory Fahy’s “Cryoprotectant Toxicity Neutralization” (Cryobiology, 2010) and Benjamin Best’s “Cryoprotective Toxicity: Facts, Issues, and Questions” (Rejuvenation Research, 2015).

Greg Fahy’s paper is a rigorous exposition of experimental results concerning the phenomenon of cryoprotectant toxicity neutralization. The paper is mostly limited to the discovery that DMSO can block the toxic effects of amides such as formamide. The combination of DMSO and formamide (or other amides such as urea and acetamide) is indeed one of the building blocks of M22 but this combination cannot be used without limit and the paper includes data that indicate the maximum molar concentrations (and ratios) that still permit full viability. In theory, if two (or more) cryoprotectants would completely neutralize each other’s toxicity they could be the sole components of a vitrification solution. But as the formulation of M22 shows, it is still necessary to add weak glass formers such as ethylene glycol, extracellular CPA’s, and “ice blockers” to supplement the toxicity neutralization obtained with formamide and DMSO. An important finding in Fahy’s paper is that n-methylation abolishes toxicity neutralization for amides and combining methylated amides also does not lead to toxicity neutralization between them. In fact, Fahy found that the presence of n-methylated compounds renders even small amounts of DMSO toxic. The remainder of the paper discusses the mechanisms of cryoprotectant toxicity and Fahy now favors protein denaturation as a plausible mechanism of (non-specific) toxicity. While other cases of toxicity neutralization have been reported in the literature, no rigorous studies have been done to produce a body of knowledge that is comparible to what we know about amide-DMSO interactions.

Benjamin Best’s paper is more general in scope but presents a lot of experimental data and also critically discusses Fahy’s work on cryoprotectant toxicity. As Ben Best points out, different (and seemingly contradictory) results do not necessarily mean that cryoprotectant toxicity is a species or cell-type dependent phenomenon. One could imagine a meta-analysis of cryobiology data in which variables such as concentration, loading- and unloading protocols, exposure temperature, exposure time, and the type of viability assay are matched to ensure methodological consistency. It is also important to compare cryoprotectants at their minimum concentration to vitrify to make meaningful toxicity comparisons. If the work at 21st Century Medicine is an indication, universal low-toxicity cryoprotective solutions should be feasible. Perhaps the most interesting part of the paper is where Best offers a critique of Grag Fahy’s “qv* hypothesis of cryoprotectant toxicity”, which aims to show that non-specfic toxicity concerns the degree to which cryoprotectants leave water available to hydrate macromolecules. This discovery allowed for the substitution of ethylene glycol for propylene glycol in Fahy’s lower toxicity vitrification solutions, despite the resulting higher CPA concentrations. Best observes, “it seems contradictory that water remains available for hydration, but not available for ice formation.” A potential rejoinder to this observation is that so called “bound water” does not participate in ice formation but can be disturbed by strong glass formers. Best also suggests a potential refinement of qv* that allows for more precise calculation of the hydrogen bonding strength of the polar groups that are used to calculate qv*. It is conceivable that such a refinement would eliminate the few remaining outliers in the data that support the qv* hypothesis. The paper also draws attention to the possibility of kosmotropic co-solvents and changes of pH and microenvironment polarity to mitigate cryoprotectant toxicity.

Neither of the papers discusses cryopreservation of the mammalian brain, but there is good reason to believe that in the case of this organ modification of low-toxicity vitrification solutions is required. Conventional cryoprotective agents such as PG, EG, and DMSO have poor blood brain barrier (BBB) penetration and the brain may not tolerate the CPA exposure times that other organs do. For example, while M22 can be used for cryopreservation of the brain, many of its component have poor BBB penetration and PVP and the ice blockers (X-1000 and Z-1000) are assumed not to cross the (non-ischemic) BBB at all. One potential solution is to (reversibly) open the BBB with so- called BBB modifying agents like detergents or perhaps to search for cryoprotective agents that can cross the BBB.

The most fundamental question in the design of vitrification solutions remains whether it is possible at all to introduce high concentrations of cryoprotectants without creating any kind of irreversible molecular and ultrastructural adverse effects. Understanding what specific and non-specific cryoprotectant toxicity exactly is should enable us to answer this question.

Originally published as a column (Quod incepimus conficiemus) in Cryonics magazine, September-October, 2016