The idea of chemical brain preservation has its origins in late 1980’s and was proposed simultaneously by Drexler and Olson [16, 17]. To understand chemical brain preservation it helps to first examine the use of cryonics as there are many parallels between the two technologies. The idea of using cryonics for life extension has been around for at least two centuries. In 1826, Mary Shelly, the author of Frankenstein, wrote a short story entitled ‘Roger Dodsworth: The Reanimated Englishman’ about a man being revived about being frozen in the Alps [1]. The concept behind cryonics is to preserve the body or brain at or before death and then to revive the person when medical technologies advance to the point where the person can be cured of whatever illness they had at the time of suspension.
To understand how cryonics or chemical brain preservation can preserve life, we need a more sophisticated understanding of death than cardiac arrest (cessation of a heartbeat) or the current medical definition of death as the cessation of electrical activity in the cerebral cortex [18, 19]. Definitions of death tend to change with technology and the current definition of death is becoming outdated with improvements in neurology and neurosurgery [20]. The ultimate definition of death is based on the destruction of the information contained in the brain and is termed the information-theoretic definition of death. In his discussion of cryonics, Merkle [21] gives an excellent summary of this concept:
If the structures in the brain that encode memory and personality have been so disrupted that it is no longer possible in principle to recover them, then the person is dead - (Merkle [21], p. 9).
The information-theoretic definition of death is thus the foundation of modern cryonics. A person is not dead until the information in their brain is irreversible lost and cryonics aims to preserve this information until a person can be revived. Therefore cryonics should be viewed as a rational life-saving procedure. From this perspective, cryonics needs to be held to the same standards as any other medical procedure. Under this scrutiny the main limitations of cryonics are clear. First, it is unclear whether the information in the brain is actually preserved. This is the at least partly due to the unjustified abandonment of cryonics by the scientific community.1 The lack of government funding for cryonics has preventing the research needed to improve the protocols and fund the electron microscopy studies needed to examine the integrity of the brain after preservation. The second limitation of cryonics is that it depends on miraculous future nanotechnology to revive and cure the frozen brain. Nonetheless, there is indirect evidence that cryonics as currently practiced may preserve the information in the brain which could then be theoretically recovered. Given the alternative to cryonics is permanent death, Meon [14] has convincingly argued that even if the chances of success are low, cryonics is still a rational choice that individuals should be allowed to make.
The Connectome
Starting in the mid nineteenth century systematic brain lesion studies have convincingly shown that the brain is completely responsible for the mind. The last two decades have seen a revolution in our understanding of how this is achieved. It turns out that identity is completely defined by anatomy, i.e. brain connectivity [23-28]. All our memories and personality are completely captured in the synaptic and dendritic connections in the brain, what is referred to as the connectome. The connectome contains all the information that matters for identity and consciousness [23-28]. Each night during dreamless sleep the specific nerve impulses that generate the stream of consciousness stop and you are stored as physical structure! Each morning the connectome reboots and the stream of consciousness and identity continues. Cases of revival after hypothermia (which is also now intentionally induced in trauma patients and stops all electrical activity in the brain) counter arguments that there is always some low level of consciousness occurring even during deep sleep and which is required for identity [18, 30]. These cases also challenge the often unarticulated assumption that some kind of continual material or electrical circulation is required for identity to continue. Together the information-theoretic definition of death and an understanding of the connectome imply that death does not occur until the connectome is destroyed.
Chemical Brain Preservation
Once the information-theoretic definition of death and the fact that a person is their connectome are accepted, any technique that can preserve the information in the brain has the potential for life extension. In chemical brain preservation, rather than using low temperatures to lock the brain in place as is done cryonics, the brain is placed in stasis by chemical bonding [16, 17], a procedure also known as plastination [23, 29]. However, the difference between cryonics and chemical brain preservation is no absolute. Newer forms of cryonics use a process called vitrification [30, 31]. Vitrification uses low temperatures and cryoprotectants to turn tissue into a glass like state where decay is extremely slow. Therefore it may be possible to develop hybrid procedures involving elements of both cryonics and chemical brain preservation.
The current protocols used for chemical brain preservation were originally developed to preserve tissues for electron microscopy [17,23,32,33]. Electron microscopy requires tissues to be cut extremely thin. This in turn requires that the inter- and intra-cellular structures be strongly chemically bonded in order to avoid the breakup of tissue when microscopic slices are cut with a diamond knife. The first step in chemical preservation is to infuse the tissue with paraformaldehyde and glutaraldehyde. These aldehydes have bonding sites on each end of the molecular which fix cellular proteins in place by crosslinking. The second step is to link the lipids in place by infusing the tissue with osmium tetroxide. In the final step the tissue is immersed in a plastic resin [23, 32].
At the end of these three steps the tissue is essentially embedded in plastic (think of insects trapped in amber). Electron microscopy studies have shown that current protocols of tissue plastination do a remarkable job of preserving brain tissue [23, 29]. In fact, modern chemical preservation does such a good job preserving the cellular and molecular structure of neurons that if an entire brain were preserved this way it could be claimed that life can truly be frozen in this state. The chemically preserved tissue can be stored at room temperature without degradation and presumably could be preserved intact for millions of years. The main limitation of current brain preservation protocols is that they can only preserve a small section of the brain [23]. However, the protocols are rapidly advancing and there is an incentive price to scale up the preservation protocols to allow the chemical preservation of a large mammalian brain [23, 34].
Whole Brain Emulation
Suppose that chemical brain preservation is successful in preserving the connectome. In the past it was only science fiction that somehow these brains could be resuscitated by means of some unknown nano-technology:
In the distant future (e.g., 100 centuries form now), technology may advance to the state where the information of an individual’s brain design can be extracted from his or her preserved brain and implanted in a new machine – the new brain of the individual - (Olson [17] , p. 79).
It is a testament to the exponential growth of technology that in contrast to Olson’s prediction of a 100 centuries, the technology now exists to extract the information from a preserved brain. It turns out that not only is electron microscopy a key tool to verify the preservation of the connectome, it is also a key part of the technology for extracting the information. The best current methods of brain mapping involve scanning thin slices of a chemically preserved brain with an electron microscope. Standard resolution is around 50 nm when the slices are created with a diamond knife [35]. However, the newer technique of Focused Ion Beam Scanning Electron Microscopy (FIBSEM) is able to scan tissue at resolutions approaching 5 nm [23, 36]. The detail of all the synaptic and dendritic connections and their strengths can be captured at a resolution between 40 and 10 nm [23, 29]. Even if the details at the molecular level (neurotransmitter and receptor levels) were necessary, this information is stored in the chemically preserved brain and there is ongoing research and a variety of promising techniques in development that can provide molecular level scanning resolution [37]. The continued progress in automated brain mapping techniques should allow the complete connectome to be obtained from preserved brains [38, 39].
Once the connectome is mapped, the next key piece of technology in making chemical brain preservation a life-saving procedure is known as whole brain emulation (WBE) (also known as brain uploading). WBE involves replicating the informational structure of the brain in software that could then be run in a computer [37, 40, 41]. Rather than being science fiction, WBE is now big science [42-44]. Knowledge of the connectome should allow for a complete emulation of brain function and the technologies for mapping the connectome and for WBE have been rapidly advancing [38,39,42,45-49]. The development of WBE and the computer technology to implement it is now a flagship science initiative of the European Union known as the Human Brain Project [44]. The Human Brain Project aims to develop a complete emulation of a mouse brain within five years [50]. Other than scale there is no in principle difference to human WBE. The Human Brain Project aims to begin this process with a goal to scan and upload a significant portion of the human brain within ten years [51]. Estimates vary but we may be within 50 years of human WBE [3, 37, 40]. One important concern remains: will brain preservation followed by WBE preserve identity or even consciousness? These philosophical questions are outside the main scope of the current paper but there are good arguments that WBE does preserve identity and consciousness [52-57].
Why Brain Preservation?
It may seem obvious to some, but we need ask the question of why would anyone pursue brain preservation? Assuming it works, the obvious answer it that the person wishes to continue living. Many bioethicists argue it is wrong to “unnaturally” extend life and that we need to accept death [4-8]. This may be good advice if there is nothing we can do about death, but it rings hollow when something can be done. After all, no one argued about refusing public health measures beginning in the late nineteenth century which was arguably the first case of significant life extension. There are also strong arguments for brain preservation that go beyond individual self-preservation. Ken Hayworth, president of the Brain Preservation Foundation and a leading scientist investigating brain preservation, gives an excellent account of the altruistic motivation for brain preservation:
The Great Library of Alexandria, constructed in the third century BC, was the center of science and learning in the ancient world. Its collection of tens of thousands of scrolls contained the hard-won knowledge of the ancient world and a priceless trove of human history. But with the destruction of the library almost all of this knowledge was lost. “The burning of the Great Library of Alexandria” has become a metaphor for any reckless destruction of unique knowledge –an inexcusable insult to both the original author and to future generations.
Considering today’s obsession with digital archiving we might think that future generations will thank us for our careful conservatorship. But in fact it is much more likely that they will look back at the early 21stcentury and view it as ‘another burning of the Great Library of Alexandria!’ To understand why, envision the world a few centuries from now. A world whose technological advancements and material prosperity is as far beyond us today as we are beyond the ancient Greeks. Today’s neuroscientific theories have led us to deep learning neural networks which allow our apps to understand speech and recognize faces, and neuroscience imaging technology is preparing to map entire insect and small mammal brains at the nanometer scale using ultrafast electron microscopes, with the near-term goal of reading memories.
If the world continues this accelerated pace there is every reason to expect that in a few hundred years we will have a complete science of how the brain gives rise to mind, and the technological prowess to routinely upload memories and minds. Citizens of that future world will have conquered disease and death and overcome countless other biological limitations. And they will viscerally understand what today’s neuroscience textbooks try to convey: The mind is computational, and a person’s unique memories and personality are encoded in the pattern of physical connections between neurons.
From that vantage point, future generations will ask:
“Why didn’t humanity preserve its most priceless possession –the human brain?”
Coming back to our analogy: We are the scrolls in today’s Library of Alexandria. Each of us has spent decades honing our unique identity and accumulating our unique memories. Our memories weave the thread of our life together with the lives of our loved ones and, in turn, with the rest of humanity. As fragile biological creatures, we have learned to accept that we all age and die, and with death our particular thread is ripped out of the tapestry of humanity -our scroll is set ablaze. But with the ever quickening pace of science and technology more of us are realizing that death will not be a part of the human condition forever. Our great-grandchildren may not know traditional death at all; ours may be one of the very last generations to cower under its looming shadow. The perfection of brain preservation technology represents today’s best chance at reaching that future world. [58].
Regarding the question of whether anyone today would actually choose brain preservation, Hayworth continues:
Would anyone really elect to undergo such a brain preservation procedure? For at least a small minority of the population the answer is an emphatic yes. Since its inception, the Brain Preservation Foundation has attracted a diverse group of volunteers, advisors, and donors many of which not only support the development of such technology but hope that the option will be available to them when they need it. Informal surveys imply that a significant percentage (>10%) of the (online, technologically-savvy) population would desire the option for themselves, especially if friends and loved ones did so as well. Cryonics has never attracted significant numbers despite decades of trying, but in our experience most people rationally refuse to consider cryonics because they have no real proof of the quality of preservation. This new field of scientifically-verified brain preservation we are witnessing today may fundamentally change that calculus. [58].
So far, we have seen that there is good scientific evidence that chemical brain preservation may serve as a lifesaving technology in the future. We have also seen that many people would likely choose this procedure and there are good reasons for doing so. Now we need to ask whether it is ethical to do so.
Brain Preservation and the Individual
Before talking about the ethical arguments for or against brain perseveration we need to clear up some confusion in terminology. The terms radical or extreme life extension have been used in the past to describe a major increase in the human lifespan [8,59,60]. These terms are unsatisfactory as they clearly come with a negative connotation. Considerable life extension is another proposed term [61]. While lacking the negative connotation of the previous terms it seems too vague; after all, some would consider 5 years of life extension considerable. Therefore I propose the term exponential life extension. Exponential life extension can be defined as increases in life expectancy and/or life span by 50% or more. Any discussion of exponential life extension also needs to touch on the common mistake of equating this with immortality [1, 11, 12]. Immortality is a mythological concept and is not something that can be achieved with life extension technologies [12]. Discussion of immortality have no relevance in serious discussions of life extension technologies. With these two points cleared up, we can now begin a discussion of the ethics of exponential life extension by chemical brain preservation. This discussion will be divided into two parts. In the first section we will at the ethical issues involving the individual, and in the next section we will examine arguments from a societal perspective.
Is it is ethically acceptable for an individual to chemically preserve their brain? Currently this isn’t even a possibility, so we can rephrase this question as is it ethical for an individual to preserve their brain in the future when this becomes possible? A related question is whether it is ethical for individuals to research and support research on brain preservation? We will assume for this discussion that the protocol used for brain preservation has been shown to preserve the connectome. We will also assume that the individual who chooses brain preservation is convinced that brain preservation followed by WBE will allow for the continuation of personal identity and consciousness. In this case the individual correctly views brain preservation as a life-saving medical procedure. The option to choose or refuse medical procedures is a fundamental right of current medical ethics [62,63]. Thus the default position should be to allow people to choose chemical brain perseveration. To refuse to allow a person to choose this procedure would be a major affront to the principle of autonomy. The autonomy to choose brain preservation extends to the right to pursue and fund research into brain preservation. Standard medical ethics suggest that only evidence of serious harm to society could override a person’s autonomy to pursue chemical brain preservation [62, 63]. Therefore we need to examine arguments that brain preservation could be harmful to society and this will be the focus of the next section
Brain Preseveration and Society
Medical ethics clearly supports a person’s right to have or refuse a medical procedure that is deemed scientifically sound. Therefore we need to examine what potential harms brain preservation could have on society and determine if these harms are enough to over-ride a person’s autonomy. The greatest ethical challenges to brain preservation concern issues of justice: will everyone be allowed to access these technologies or will they only be for the rich? One worry is that society will be dominated by a new oligarchy of those rich enough to afford brain preservation. However, this scenario seems very unlikely. The procedure to chemically preserve the brain is relatively straightforward and unlikely to cost more than that of a minor medical procedure (cost is in fact part of the requirement to win the brain preservation prize [34]). The goal of those working on brain preservation is to have it recognized as a legitimate medical procedure that should be covered by both public and private insurance.
The second step of WBE will likely be much more expensive. Yet WBE is an information technology that should follow the economics of scale. A good parallel is the history of the human genome project, another information technology. To sequence the first genome took 13 years and 3 billion dollars to complete [64]. However, gene sequencing technology gets cheaper every year and it may soon be possible to sequence individual genomes for a few hundred dollars [64-67]. There will likely be a point where the cost of WBE will be too great for most people. Yet the early pioneers will help reduce the cost of WBE. Time is one thing those chemically preserved have plenty of and they can wait for the economics of scale to reduce costs. Society also has the option to delay WBE until the cost is available to all.
A related concern about the justice of brain preservation is the worry about limited resources. Is it right for people to continue to live past the “normal” life expectancy and take up resources that may not be available for the young? First, it should be noted that brain preservation could also be used on the young who would otherwise have died early. In this case it is hard to see why the why the genetic lottery is a better way to decide who lives 20 years and who lives 90 years. Yet it is true that most people will likely be older when they choose brain preservation and there is a concern that there will a population explosion if the human life span is increased [68-71]. To a large extent these are open empirical questions. The world population is slowing, and the industrialized nations (including China, Europe, The United States, and Japan) are facing severe population decline [72-74].
There is a major economic crises looming due to the rapid decrease in population of these nations, and this will likely be true of the rest of the world as it increases in development [71, 72]. Life extension technology is rapidly needed to help the aging population continue to be productive [74, 75]. Thus brain preservation and WBE, rather than being a drain on society, may be part of keeping future economies viable. Even if population trends change, society can always choose to delay the revival of preserved brains until such times as economic conditions allow. If these conditions never arrive, the outcome for the individual is no worse than not choosing brain preservation in the first place and anyone pursing brain preservation should understand these risks. It is also worth mentioning that those revived with WBE need not take up any significant resources or space: if necessary WBEs could be run in underground computing facilities in a location that allows cheap solar power (i.e. unwanted space in a desert).
Another concern is that there will be undue pressure on people to choose brain preservation. First, it is important to recognize that those developing the technology for brain preservation take it is as fundamental that people have a right to refuse such procedures (this is ingrained in the Brain Preservation Foundation Bill of Preservation Rights [76]). There is no reason to suppose that if brain preservation is allowed society would lose all respect for the autonomy and freedom of medical consent that we have now. There is still a legitimate worry that if brain preservation was widespread then many people would indeed feel great pressure to choose this option. We can safely assume this will not be a concern early on based on the limited number of people who have pursued cryonics. As more evidence builds up that brain preservation and WBE does preserve identity (i.e. as it shown that WBE of larger mammals captures behavior and thus identity), more people will likely choose brain preservation.
When the first human is successfully emulated and reports being the same person, most people will likely recognize brain preservation as preserving identity [3]. At this point people may indeed feel pressure from family and friends to also sign up for brain preservation when they die. However, this argument seems to have little force. Most of the pressure will arise because people believe the technology works and this can hardly be held against brain preservation. There are those today who refuse evidence-based medical care and their wishes are respected; there is no reason to believe the development of brain preservation will alter this freedom to opt out of medical care.
Finally, there is the worry that exponential life extension of any kind will not give the young their chance [68]. As discussed previously, however, empirical evidence is suggesting just the opposite. Life extensions technologies are needed to give the young the same opportunities as the previous generation by avoiding the economic burden of sustaining a working/retired ratio that is rapidly approaching one to one in industrial nations [74]. A related worry is the lack of distribution of wealth created by inheritance. This concern is more political than ethical and can easily be addressed. Currently cryogenically frozen human beings are treated as anatomical donations and have no rights. Clearly this will become increasingly unacceptable as the evidence for brain preservation grows and the feasibility for WBE increases. This does not mean we must treat those in suspension as if nothing has changed legally. It has proposed that we could legislate just how much wealth those in a preserved state could choose to have in a trust fund for when they are revived while the rest of their money could be treated as inheritance [77]. Thus these issues do not seem unsurmountable.
Conclusion
We have seen that there is little reason to fear progress in brain preservation technologies; rather there is every reason to be optimistic. Currently chemical brain preservation is not an option, but it is extremely likely that within only a few years whole brain preservation protocols with strong scientific support in favor of connectome preservation will be available for large mammalian brains. When this happens chemical brain preservation should be viewed as life-saving medical procedure. In another decade, if whole brain emulation is successfully demonstrated in mice, then there will be overwhelming evidence that chemical brain preservation is a reversible and life-saving medical procedure. It would require an extraordinary amount of evidence showing harm to society to outweigh an individual’s autonomy to choose this procedure, and no such evidence exists. The public is becoming more and more sophisticated in understanding these technologies and the old arguments against life extension are becoming increasingly stale. In his struggle to gain acceptance for anti-aging research Aubrey de Gray noted:
I mean only that the evolution of our morality over time seems—for whatever reason—reliably to follow a course of increasing internal consistency, and, in particular, when deviations from this consistency become too stark to ignore, ethical opinions that are more central tend to survive at the expense of less central ones - (de Grey [11], p. 660).
Thus with ever increasing advances in science, anti-aging research and life extension will be seen as increasingly acceptable by the public. The acceptance of brain preservation and whole brain emulation will likely take longer to become widely accepted, yet once whole brain emulations become routine in animals it will become increasingly inconsistent to argue against the use of these technologies to preserve life.
The hypothesis that we are out connectome is a revolutionary idea that will take time to assimilate. Yet each day our scientific understanding of the brain grows and there is no turning back from this knowledge. We need to learn from the tragedy of mainstream science’s abandonment of the cryonics community. Brain preservation and whole brain emulation need to remain respected domains of mainstream scientific research and organizations like the Brain Preservation Foundation have recruited a wide range of highly respected scientific advisors to insure the scientific community’s involvement [78]. It would be a great tragedy to not take advantage of these technologies when they become available. It is time to remove the taboo from brain preservation technologies (including cryonics) and support a major research investment in these procedures.
Footnotes:
1The story of modern cryonics is a tragic story of a legitimate scientific endeavor being abandoned by the scientific community [1, 22]. A few brave souls continue to pursue cryonics and this medical procedure is available today through two institutions: Alcor and Cryonics Institute.
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