Revival of icryonic Patients

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Reviving iCryonic’s patients from cryopreservation is fundamental to its mission. As the revival technology begins to come into focus, the process of planning patient revival can begin. At an abstract level, the revival process might use any of three primary means: in situ repair, scan-and-restore, or scan-to-WBE (Whole Brain Emulation). In situ repair will require the development of medical nanorobots capable of operating in cryopreserved tissues (“cryobots”), while scan-and-restore and scan-to-WBE could benefit from this technology. The cryonics community will likely have to play a major role in the development of cryobots. In addition, while it might not seem immediately obvious, the need to test any cryopreservation revival protocol on human subjects before it is used to revive cryopreserved patients, combined with the need to comply with basic ethical principles, will force the extensive use of computer simulations, WBEs, neurobots to monitor nerve impulses, and technologies to scan cryopreserved brains. WBEs, neurobots and scanning technologies are, therefore, of broad interest to all members of the cryonics community who seek to ethically evaluate cryopreservation revival protocols before they are used to revive cryopreserved patients.


iCryonic ’s mission has three major elements:

  • Maintain the current patients in biostasis.
  • Place current and future members into biostasis (when and if needed).
  • Eventually restore to health and reintegrate into society all patients in iCryonic’s care.

While acknowledging its importance, we have historically ignored the third major element of our mission: reviving our patients. The technologies that will allow us to carry out this component of our mission are finally becoming clear, and we can now begin the process of planning for the revival of iCryonic’s patients. In the following discussion, we will distinguish between those technologies that are likely to have such broad societal value that they will probably be developed without substantial input from the cryonics community, such as molecular nanotechnology and nanomedicine, and those technologies that might require support from the cryonics community, such as medical nanorobots capable of operating at cryogenic temperatures in cryopreserved tissues (i.e., “cryobots”). Identifying the critical tasks that will not happen unless we make them happen is crucial if the cryonics community is to revive our cryopreserved friends and loved ones as rapidly and reliably as possible.

What are these critical tasks? Horizon Mission Methodology is a method for making long term plans to accomplish major objectives that appear, upon initial examination, to be either very difficult or even impossible. We can apply Horizon Mission Methodology to the problem of reviving iCryonic’s patients. The core concept is to look back at the present from the perspective of a future in which the objective has already been successfully achieved. Reorienting one’s thinking to this new conceptual framework greatly facilitates the search for a solution and allows a clearer reexamination of previous assumptions that might otherwise have inhibited a clear understanding of possible answers. The assumption that the objective has been accomplished also significantly reduces the size of the search space, simplifying the search for a solution. Paradoxically, the more difficult the objective appears, the greater the reduction in the size of the search space and the more effective Horizon Mission Methodology becomes. Our conceptual framework is that we are looking back from the year 20xx2 (with the particular value of “xx” left unspecified), the year in which iCryonic ’s patients were revived. In looking back from the perspective of those who successfully revived iCryonic’s patients, the first thing we realize is that we almost certainly had to carry out repairs at cryogenic temperatures, at least in the early stages of the repair process, even if some less major components of the process were deferred until after the patient was warmed. We now can examine what these early stages of the repair process must have looked like.

Three methods for revival

The three primary methods by which revival from a state of cryopreservation might take place include in situ repair, molecular scanand-restore, and scan-to-WBE.


In situ repair uses the minimum repair methodology necessary for any given region of tissue. In this approach, any functional tissue, or tissue that can be restored to a state from which it can restore itself to a functional state, will be retained and repaired. In situ repair scenarios typically involve medical nanorobots called “cryobots” that enter the cryopreserved tissue at liquid nitrogen temperature by “tunneling” through the circulatory system, bringing them to within ~20 microns of every point in the patient’s brain and ~40 microns of every point in other tissue.


Cryobots might be about 2 microns in diameter and have robotic arms designed using rotary joints. Molecular rotary joints can have very low energy dissipation. Small onboard computers guide their actions, while more substantial computational power is provided externally. Onboard power dissipation must be limited to prevent undesired elevation of tissue temperature. External computation does not suffer from this constraint and guides overall repair activity. iCryonic need not develop the required molecular computers, nor the medical nanorobots that operate in liquid water. However, it is less clear that operation of cryobots at cryogenic temperatures for repair of cryopreserved tissue will be developed by mainstream organizations.

It seems more likely that the organization that develops cryobots will be founded by cryonicists, possibly with iCryonic’s help. In any event, we assume that cryobots are developed by an organization called Cryobotics, whose precise nature (for profit, non-profit, jurisdiction, source of funding, etc.) is left open. In situ repair will use cryobots. Cryobots operate in cryopreserved patients at cryogenic temperatures. Their first mission is to tunnel out the patients’ circulatory system. Their second mission is to assess the state of each region of tissue. The primary purpose of this assessment is to determine if the local tissue can be warmed to enable further repairs to take place in the liquid state. The expectation is that well cryoprotected regions that are minimally damaged (“good regions”) could be rewarmed until they are liquid, and repairs would continue in the liquid state. Regions where cryoprotectant did not penetrate, or which were otherwise subjected to significant damage (“bad regions”), would be processed at low temperature using in situ molecular scan-and-restore. Repair of fractures proceeds by taking a local molecular scan of the region near the fracture, and enough of the surrounding region to enable entry of cryobots into the extended fracture region, followed by rebuilding of the extended fracture region. On-site cryobots will report out to off-site computers, which will analyze the results of any regional molecular scans and develop a regional rebuilding plan for the bad regions compatible with the boundary conditions defined by the adjacent good regions. Cryobots will need to be able to communicate with external computational resources, as well as take local molecular scans. The primary requirement for correct functioning of cryobots is the ability to identify and tunnel through the circulatory system. For this to be possible, the circulatory system in the cryopreserved patient must be relatively intact and identifiable, especially the capillaries. If the circulatory system cannot be identified, or if it is not possible to create an appropriate network of tunnels without damaging the tissue, then it might be necessary to take a molecular scan of the cryopreserved patient as a whole. If, upon assessment, most of the tissue cannot be warmed to a liquid state but must be scanned in place, then a molecular scan of the cryopreserved patient as a whole would seem more appropriate. The level of damage that would prevent correct identification of the circulatory system, followed by tunneling into it by cryobots, would likely be severe.


We assume that the organization that develops cryobots is called Cryobotics. The primary charge of Cryobotics will be to develop those components of the technology that mainstream companies have not developed. We can safely assume that mainstream companies will have developed medical nanorobots able

to operate in patients at liquid-water temperatures as well as the nanofactories necessary to build these nanorobots. Cryobotics will have to develop the cryobots that carry out the cryogenic component of in situ repair. Once the tissue has been restored to a liquid state it is reasonable to expect that more conventional medical nanorobots will be able to deal with the patient. The specific questions raised by cryonics will be operation of cryobots at cryogenic temperatures: tunneling through the circulatory system, setting up the communications and power infrastructure, taking local molecular scans, restoring tissue at cryogenic temperature, and rapidly warming cryopreserved tissue to a liquid state. Cryobotics might also play a major role in the development of molecular scan technology, as local molecular scans are an integral component of in situ repair. Local molecular scans might be necessary in patients with imperfect cryopreservation in narrowly confined areas, even when the overall cryopreservation is excellent.


A few questions of great practical importance will include:
1. Who will fund Cryobotics and why?
2. Does funding have to come entirely from the cryonics community?
3. Must funding be in the form of donations, or are there commercial applications of cryobots?
4. Might Cryobotics be funded because cryobots could perform useful surgical procedures on patients who are beyond the ability of conventional surgical techniques? Might a conventional medical patient ever decide to be cryopreserved because certain treatment options are only available to cryopreserved patients?
5. Are there medical conditions that can be treated by cryobots, but whose treatment would be difficult or impossible by other means? If cryobots have applications in conventional medicine, then iCryonic and the cryonics community would not have to fund some or all of their development. A high-leverage activity would be to envision such applications, find those who would benefit from them, and explain to them the benefits thereof. Such beneficiaries might then be induced to provide significant funding for Cryobotics. However, it seems almost certain that the task of envisioning and identifying high-value applications of cryobots – and very likely the early developmental work as well – will fall to the cryonics community. If funding comes from donations, Cryobotics should be structured as a nonprofit. If funding comes from investors, Cryobotics should be structured as a forprofit. If funding comes from both, great care should be exercised with respect to intellectual property (IP) issues, as mixing non-profit and for-profit organizational structures can create legal issues. For-profit entities can legally donate IP to non-profit entities, although normally they would not wish to do so because this would mean lost profit opportunities. There are legal restrictions on the sale of IP developed and owned by non-profit entities to for-profit entities. Developing IP under the guise of being a non-profit and then using the fruits of that development work in a for-profit activity would violate the public purpose for which the non-profit status was granted. There is likely to be a very restricted market for IP in the early stages of development, and therefore difficulty in establishing that the sale was in fact an arm’s length transaction. The terms of any sale are likely to be subjected to intense legal scrutiny in hindsight, once the great monetary value of the IP is obvious and any early uncertainty has been forgotten. As a consequence, if a close working relationship involving both non-profit and for-profit components is anticipated for the structure of Cryobotics, then a careful legal review of that structure should be conducted to ensure that IP issues are handled in a way that will produce satisfactory results for all parties concerned throughout the life of the project. Identifying sources of funding for Cryobotics is critical for rapid development of the required technology. These sources might include:

wealthy members of the cryonics community who expect to be cryopreserved and who set up trusts or foundations able to fund Cryobotics;

living wealthy members of the cryonics community with cryopreserved loved ones who wish to fund Cryobotics; or

members of the cryonics community who can identify major value creation opportunities for Cryobotics, and then help to develop those opportunities.

Getting funding from outside the cryonics community

It would be highly desirable to obtain funding from outside the cryonics community. How to obtain this funding before successful revival of cryopreserved patients has been demonstrated is not entirely clear. Hopefully, there are reasons for pursuing research in this area that are unrelated to reviving cryopreserved patients.
The in situ scan technology used for a particular region of cryopreserved tissue might depend on the quality of its cryopreservation. The lower the quality of the cryopreservation, the more difficult it will be to accurately restore the tissue and the more important it will be to use a scan technology that provides as much information about the tissue as possible. The greatest amount of information would be provided by a molecular scan, which, by definition, produces exact information about the position and type of every atom and molecule in the scanned tissue. A molecular scan is therefore the most conservative type of scan technology, and would be preferred if there was any question about the type of scan technology that was needed. Should the quality of an entire cryopreservation be sufficiently poor that it becomes prudent to perform local molecular scans in essentially all regions of the brain, then the use of molecular scan-and-restore throughout the entire brain would be preferred. It would also be logistically simpler and more reliable. The precise level of damage at which it becomes reasonable to do this is unclear, but given that the quality of cryopreservation can vary widely, it seems likely that this will be the appropriate course of action for at least some patients. Molecular scan-and-restore should be effective even in cases of severe damage. It
consists of three steps:
(1) a molecular scan,
(2) processing of the scan, and
(3) physically restoring the patient from the processed scan. In this approach, the molecular scan gathers complete information about the molecular structure of the patient’s tissues, particularly including the brain. A molecular scan gives the position and type of every atom. It provides the raw information that could, after processing, serve as the basis for restoring the scanned patient. This approach should be applicable in cases that would, by any present-day criteria, be considered beyond hope.

What is a molecular scan?

A molecular scan is any method of scanning which provides the location, orientation and type of every atom and molecule in the cryopreserved tissue. If we assume that every molecule has one, or at most a few, stereotypical three dimensional shapes, then we can readily approximate the total number of bits required to store an exact description of the molecular structure of the scanned tissue. A molecular scan will literally give us the location and type of every atom in the cryopreserved tissue. To give a specific example, a single hydrogen atom might be encoded by four numbers: an X coordinate, a Y coordinate, a Z coordinate, and an atom type. Each coordinate might require 40 bits to specify, so that the three coordinates together might take 120 bits to specify. The atom type might take 6 bits to specify. A single atom would then take 126 bits to specify. A water molecule, consisting of three atoms, would require 372 bits. A more compact representation for a water molecule would specify its location (120 bits), the type of the molecule (perhaps 20 bits), and its orientation (roll, pitch, and yaw, perhaps 20 bits each), for a total of 200 bits. This is a more compact representation (200 is less than 372), especially useful in cases such as water where large numbers of them are present. This method of compressing the representation becomes more effective for bigger molecules and larger structures. A single molecule, no matter how big, can be specified with only 200 bits (provided it adopts only one functionally significant conformation during normal biological operations). For example, specifying the position and orientation of a ribosome specifies the positions and types of all the atoms that compose it. Those familiar with data compression methods will realize that a variety of methods for reducing the size of the data encoding the information about the molecular structure of the tissue are available. Molecular scans are generally divided into two types: destructive and non-destructive. Destructive scans, as their name implies, disassemble the cryopreserved tissue in the process of scanning it. Non-destructive scans preserve the tissue intact. Reliable methods for conducting destructive molecular scans that entirely disassemble the tissue are relatively easy to envision (e.g., “Backups Using Molecular Scans”). Such methods might be based on high resolution Scanning Probe Microscopy (SPM) methods. SPMs rely on the physical interactions between a molecular-sized tip and the surface being scanned. The mechanism positioning the tip can be large (as in today’s SPMs) or could be very small, even molecular, in scale, in future SPMs built using molecular nanotechnology (MNT). A parallel array of SPM tips spaced approximately 100 nm (10-7 m) apart seems feasible, and would allow the surface of the brain (or other tissue) to be rapidly scanned. Assuming a moderately fast scan rate of 10 MHz (10 million pixels per second per tip) and an atomic resolution of 0.1 nm (10-10 m, one angstrom), means each tip would be able to scan its 100 nm x 100 nm square region in 0.1 second. Assuming a rate of penetration into the tissue of 1 nm per 0.1 second yields a molecular scan rate of ~106 nm/day, or 1 mm/day. A 100 mm thick brain could be completed in ~100 days. Thus we can readily envision at least one future molecular scan technology able to scan an entire cryopreserved human brain in a few months or less. Partial molecular scans would require less time. There has not yet been published any detailed proposal for a non-destructive molecular scan technology able to scan a structure as large as a cryopreserved human brain. How this might be done is, at present, an open research question, although some intriguing research has been done in the area of high resolution MRI.

Processing molecular scan data

Once we have the raw scan data from the molecular scan, that data must be processed. In the most favorable case, the cryoprotection went well and the data is beautiful, crisp, and complete. As the data becomes increasingly distorted and as increasing amounts of noise are introduced from various sources, the inherent redundancy in the original structure will be increasingly called upon to allow an accurate reconstruction. Accurate reconstruction in the face of noise is initially computationally inexpensive when the amount of noise is limited, but becomes computationally increasingly expensive until, at some point, it becomes prohibitively difficult shortly before the ability to provide an accurate reconstruction becomes infeasible and the data becomes inherently ambiguous. Deep learning algorithms can be adapted to apply to the kind of data we’ll be able to generate from molecular scans: three dimensional high resolution atomically precise data. We’ll also have quite a bit of computer power available: at least 1012 GFLOPS/Watt. The cost of electrical power should then be at least 100-1000 times cheaper than today. That combination will give us quite a bit more computational power to apply to our image analysis. An object the size of the human brain has ~1027 voxels, assuming one angstrom voxels. We may be able to buy 1015 joules for as little as $10,000, giving us 1027 GFLOPS, or 109 FLOPS per voxel. That should be more than sufficient for most image analysis and deep learning purposes. The deep learning and image analysis algorithms will have been developed for other purposes, and their application to whole brain emulation and reconstruction might have been pursued by others. However, it seems likely that at least some of this development will need to be pursued by members of the cryonics community, and possibly by iCryonic. It will be useful to plan how the image analysis will integrate with the data produced by the molecular scan. We’ll likely have to start with “model systems”20 and incrementally work our way up to bigger and bigger systems.
The “image analysis” or “deep learning” or “AI software” is assumed to produce, as output, an atomically precise description (possibly in some compressed format) of a biological system, such as a human brain, along with the surrounding support structures and interface systems. This description could then be entered into a suitable atomically precise 3D manufacturing system (or “3D printer for atoms”) to fabricate the described structure. It seems reasonable to assume that manufacturing takes place at cryogenic temperatures and is followed by rapid warming. The algorithms for processing molecular scan data will need to be developed, and it would be helpful to have as clear an idea of what these algorithms will look like as possible. One strategy for doing this would be to generate synthetic molecular scan data. If we assume that molecular scans will provide us with atomically precise information about the cryopreserved structure, then it should be possible to generate synthetic molecular scan data by creating atomically precise descriptions of cellular structures based on our current understanding of such structures, then applying damaging transformations based on our current understanding of the transformations involved in present-day cryopreservation methods. The resulting synthetic molecular scan data could then be used as input to aid in developing and debugging the algorithms used in processing molecular scan data. Arguing against this approach is the likelihood that synthetic molecular scan data will deviate from actual molecular scan data in significant ways. While it would still be possible to test and debug the algorithms to be used in processing real molecular scan data on synthetic scan data, there would be a risk that the resulting algorithms, even if they performed well on the synthetic scan data, might still not perform well on real scan data. But developing and testing algorithms on synthetic scan data should speed development even if such testing was incomplete, and even if further testing and debugging on real scan data was still required. Of course, it is also possible that molecular scans might prove to be significantly more detailed than is required, and that some lesser scanning method will prove to be sufficient (see “Lower Resolution Scans”), rendering the need to analyze molecular scan data moot. Should it be possible to develop algorithms that are easily generalizable, then algorithm development could start today, with the understanding that any specific algorithm might not be used but that the general concepts developed could still form the framework within which the actual scan technology would be developed and the scan processing would take place.

A molecular scan is the best we can do

A molecular scan provides us with all the information about the cryopreserved tissue that it is possible to obtain. No further information can be obtained. A molecular scan puts us in the best possible position to restore the scanned tissue to a healthy state. If we can’t restore a person with their memories and personality intact after a molecular scan, then there’s too little information in their cryopreserved brain to do this. To put it another way, if someone has been cryopreserved and we pursue any other method for reviving them based on their cryopreserved tissues, we cannot, in principle, do any better than by starting with a molecular scan. In particular, if a cryopreservation went badly and we attempt to revive the person by warming them up and using some form of biological repair, such a biological repair process cannot, in principle, do a better job than a restoration process that started with a molecular scan. The reason for this is simple. After rewarming, the biologically oriented repair process must contend with the continuing deterioration of the damaged molecular and cellular structures. Ruptured membranes will continue to allow mixing of the contents of cellular compartments. Damaged molecular structures will continue to deteriorate and entropy will continue to increase. The biological repair processes, whatever they might be, will be fighting against extensive levels of damage and would have to move with implausibly great speed simply to limit the further spread of that damage, let alone to perform repairs.
By contrast, a molecular scan provides a snapshot of the system at the moment it was cryopreserved. There will be no further deterioration. Entropy is held in check. The computational processes that examine the digitized tissue can do so at leisure, mathematically restoring the digital representations of the structures to their appropriate state as though they were frozen in time. Only after the full digital restoration has been completed and every detail has been attended to would the whole digitally restored structure then be actually converted back into a physical structure. This conversion process could take place either by carrying out a series of lowtemperature repairs on the existing physical structure, using the digital restoration held in computer memory as a guide; or by using what would amount to a 3D printer for atoms that allows the exact three dimensional structure to be printed in atomically precise detail. If a non-destructive molecular scan technology can be developed, then it could be applied to every cryopreserved patient. It would provide valuable information that could be used to assist the repair process, whatever that repair process might be, and would cause no damage that might impair subsequent efforts to revive the patient. Further, it would provide an invaluable failsafe in case the repair process went awry. However, if only destructive molecular scan technologies are available, then their application to a specific patient would require weighing the benefits of the information they provide against the possibility that damage to the original structure might impair subsequent steps in the revival process. Some cryopreservation patients would prefer recovery of complete information about themselves through a molecular scan, regardless of whether or not it was destructive. Other cryopreservation patients might elect to have a destructive molecular scan only if it were necessary for their successful revival and only if there were no other options [Alexandre Erler, Brain Preservation and Personal Survival: The Importance of Promoting CryonicsSpecific Research, Cryonics magazine, November-December, 2017]. There may even be some cryopreservation patients who would forego a destructive molecular scan altogether, even if this meant failure of their revival. A destructive molecular scan is compatible with, and could be used as the starting point for, the biological restoration of a patient. A destructive molecular scan, followed by the use of a digital restoration algorithm, followed by the use of an atomically precise 3D printer to instantiate the resulting atomically precise digital restoration, might be effective at producing a high fidelity and biologically accurate reproduction of the original person, in cases where methods that did not involve digital restoration would produce unsatisfactory results. For these reasons, further research on a purely non-destructive molecular scan should be pursued. This technology could be used in all cases, by all people, regardless of their philosophical views.

Backups using molecular scans

At a deeper level, tissue is information: the two are interchangeable. Anyone who seeks a very long lifespan, and who acknowledges that accidents can happen, must at some point come to terms with the need for backups: sufficiently accurate descriptions of themselves from which they can be restored, should they suffer from a misfortune so catastrophically damaging that no recovery from that misfortune is otherwise possible. This is both feasible and obviously desirable. If a destructive molecular scan is taken of your cryopreserved self and the processed scan is used as the blueprint from which you are restored, this is philosophically similar to awakening from a backup after a catastrophic mishap. Can existing proposals for destructive molecular scans, based on SPM technology, be carried out reliably? In other words, if we disassemble tissue in the process of scanning it, as is called for by existing proposals for molecular scans, then the scan needs to be quite reliable, as the tissue will be gone when the scan is finished. If the scan is lost, and the tissue that was scanned is no longer available, then the person being scanned will be dead – clearly an undesirable outcome.

An SPM can scan the exposed surface of a block of tissue, characterizing it completely. After the surface has been completely characterized, but not modified, the information about the surface could be digitized and stored. All information from this surface scan can be continuously and redundantly transferred to stable storage media as the exploration of the tissue block proceeds. Only after information from the ongoing scan had been duplicated and stored redundantly, or even triplicated or quadruplicated, thus providing whatever level of reliability might be desired, need the scanning process proceed to the next step: removing the scanned surface layer to expose the layer beneath it. Very high reliability should be feasible. This method of analyzing tissue is both conceptually simple, and can be made highly reliable: 1. Analyze the tissue surface using SPM technology. 2. Redundantly and reliably store the results of the surface analysis. 3. Only then, after confirming storage of the analyzed surface, remove the analyzed surface and expose the next layer. 4. Repeat. While simple and reliable, and capable of providing molecular scans, this method does have the obvious disadvantage that is disassembles the tissue in the process of analyzing it. Is there a method of carrying out a molecular scan that does not require disassembly? The answer to this question is more difficult. There could well be a way of gaining molecularly and atomically precise knowledge of tissue without disassembly, but it is not immediately obvious how this might be done. Magnetic Resonance Imaging (MRI) using nanoscale devices operating from adjacent capillaries and performing indirect scans of the intervening tissue offer intriguing possibilities, but a molecular scan of something as large as the human brain still presents significant technical challenges. The options made available by MNT and complete access to the circulatory system have not been fully explored. Further studies are needed to understand the possibilities and to provide a reliable answer to this question.

Lower resolution scans

A question of some interest is whether molecular scans are actually necessary, and if lower resolution scans might be sufficient. While we can be confident that a full molecular scan will be sufficient if anything is sufficient, lower resolution scans that provide less information about the tissue being scanned might also be sufficient, depending on the type of scan and the use to which the data is being put. The question of what sort of information we need is one where neuroscience must inform our discussion. How much information is required to construct a satisfactory model of the human brain? While it’s rather obvious that we don’t need to know the location and orientation of every molecule in the brain (esp. the orientation of all the water molecules), how much information do we need to know? And what sort of scanning technologies might provide us with enough information at a sufficiently low cost? There are many existing research projects aimed at developing high resolution three dimensional images of biological tissues, including the human brain. At some point in the future, it should be possible to obtain funding to apply MNT to this problem. Again, further research is required.


A third alternative that some patients might explicitly request is to process the information from a molecular scan and use it to directly construct a whole brain emulation (WBE). This “scan-to-WBE” option might be simpler than the molecular scan-and-restore process, as it would eliminate the need for physically restoring a biological body. Scan-to-WBE would rely entirely on the information recovered from the cryopreserved tissue. It is possible that the technology for molecular scans and Whole Brain Emulations might become available before the technology for in situ repair. iCryonic members wishing to return to an active life as quickly as possible might want to take advantage of whatever technology arrives first. Of course, those members who wish to be revived as a WBE would have to communicate this wish to iCryonic before they are cryopreserved as, once cryopreserved, further communication will not be possible. This process could be facilitated if iCryonic provided forms enabling members to explicitly express their wishes in this regard. As will be discussed later, scan-toWBE will be an essential component of the process that we will use to ethically evaluate any proposed method of reviving a cryopreserved patient. As a consequence, methods for scanning-to-WBE are of interest to everyone in the cryonics community, not just those who are specifically interested in themselves becoming WBEs.

Technical considerations

What criteria should be applied in deciding whether to use in situ repair or molecular scan-and-restore? Some might argue that we should always employ in situ repair, relying on the fact that in situ repair will include local assessments of tissue damage and utilize local molecular scans on an asneeded basis. These local molecular scans might be performed on a larger and larger percentage of the tissue as the quality of the cryopreservation became poorer and poorer. Many patients in iCryonic ’s care have inevitably suffered extensive damage. Some have suffered such extensive damage that there are serious questions about the ability of any technology, no matter how advanced, to revive them with their memories and personality completely intact. In such cases, the use of a molecular scan followed by digital restoration prior to any attempt to carry out a biological restoration (guided by the digital restoration) would seem appropriate. While iCryonic seeks to comply with patient wishes, there might be two opposing wishes at work here. On the one hand, some patients may prefer to use in situ repair for philosophical reasons. On the other hand, some patients may want to get out of the dewar as quickly as possible. It is possible that fully developing the technology for in situ repair might take longer because it appears to be a more complex technology. There are plausible scenarios in which molecular scan-and-restore might turn out to be a simpler technology to develop and deploy. It is even possible that in some circumstances, scan-to-WBE might

be available before molecular scan-andrestore, which in turn might be available before in situ repair. Molecular scan-andrestore might also be less prone to residual damage than in situ repair, and more likely to correct all the damage incurred by both the cryopreservation and any preexisting medical conditions. For example, if an existing region of tissue is evaluated as “good” during the in situ repair process and is warmed without being scanned, then there is no backup for that region. Any failure during the revival process, or any undetected damage in that region, could result in a less-than-optimal revival. As an additional confounding variable, some iCryonic members might prefer being revived as a WBE living in a virtual world (if the technology is reliable). This arguably offers certain benefits, most notably the ability to make regular or even continuous backups and the opportunity to quite literally expand your mind. Patient preferences should be taken into account. The best course of action is probably to explicitly ask members what they prefer – before they are cryopreserved.

Did we do ir right?

An obvious and rather awkward question is this: once we revive someone, how do we know we did it right? We could, of course, ask them: “How do you feel?” If they say “Terrible! I don’t feel like myself!” we might naturally be concerned. But how do we know that’s not the right answer? There are people who say that kind of thing quite a bit. One solution is to conduct some sort of test before a person is cryopreserved, then test them again after we revive them, and compare the results. What sort of test might we conduct? How can we determine if we’ve done a high-fidelity cryopreservation and revival?

Evaluating an animal revival protocol

Perhaps the most detailed functional information we could acquire about an experimental animal’s brain would be a record of every nerve impulse for some period of time. Is this feasible? Certainly with MNT, the answer appears to be “yes”.
We consider one possible approach: building “neurobots”, a class of medical nanorobots, and locating them on, in, or near nerve cells. Neurobots detect and record passing nerve impulses and have an accurate time base (either built in, or based on a centrally transmitted clock). When a nerve impulse passes by, the neurobots note the time and record the associated small fluctuations in voltage or electric field on a polymer “tape”. The tape is extruded into the extracellular space and finds its way out of the body, where it and many others like it are later recovered and analyzed. Other methods of communicating the data recorded by the neurobots are also possible. We could record every nerve impulse in the brain by embedding a sufficient number of neurobots. A few back-of-the-envelope calculations show that the storage density of polymer tape is more than sufficient to hold all the data. Some specific proposals along these lines have already been advanced in the literature,30 though their effectiveness without MNT may be marginal. The objective is to record all neuronal activity within the test subject’s brain (or other volume of interest). This has been a long-standing goal of neuroscientists. The major limitation facing neuroscientists today is the relatively large size of the devices needed to record the voltages and electric fields. MNT will enable the manufacture of devices of sufficiently small size and precision to enable this long-sought goal. We could then record data from neurobots in the brain of an experimental animal before they were cryopreserved, cryopreserve them, revive them, and then record data from neurobots in the brain of the revived experimental animal, giving us two sets of neuronal data: “before” and “after”. Comparing the “before” and “after” data would let us tell if we had done a good job in cryopreserving and reviving the experimental animal. At a purely structural level, the connectome31 from “before” should be the same as the connectome “after”, except for those changes that took place because of learning, where we interpret “learning” broadly as “plastic changes in the brain caused by its normal functioning as a consequence of its interactions with a normal environment”.
To spell this out in more detail, if we wish to evaluate a protocol for cryopreserving a biological experimental animal and reviving them as a biological experimental animal, we would: (1) use neurobots to monitor all nerve impulses in a test subject, (2) construct a “before” WBE from the monitored nerve impulses, (3) cryopreserve the test subject while continuing to monitor their nerve impulses, (4) revive the test subject biologically, (5) use the neurobots to monitor all nerve impulses in the revived test subject, (6) construct an “after” WBE from the second set of data produced by the neurobots, and then (7) compare the “before” and “after” WBEs and see if there are any significant differences. If there are significant differences, then the cryopreservation and revival technologies are regarded as “not good enough”. If there are no significant differences, then the cryopreservation and revival technologies are regarded as “good enough”. We construct “before” and “after” WBEs and compare them because it’s difficult to compare the raw data generated by the neurobots from “before” and “after”. Merely knowing that a nerve impulse passed neurobot A at time t1 “before” and that a nerve impulse passed neurobot B at time t2 “after” is not going to tell us much without a great deal of analysis. Conceptually, the required analysis must convert the raw nerve impulse data into a picture of the neural connections of the test subject’s brain. This may be roughly likened to deriving the connectome, that is, the network of neural connections between the nerve cells in the brain, from the pattern of nerve impulses.32 The progression of a nerve impulse as it passes individual neurobots could be monitored, allowing the existence of a neuronal path winding along between those neurobots to be inferred. The generation of a new nerve impulse by the summation of several input nerve impulses could likewise be inferred from a sufficiently dense network of neurobots monitoring the nerve impulses in the brain. With a sufficient number of neurobots monitored for a long enough period of time, the entire connectome of the brain could be inferred. We can then use the connectome as a significant subset of the information required for a WBE.33

Injection of nerve impulses

A question that needs to be addressed is whether or not passive data collection by neurobots will be sufficient to allow reconstruction of the connectome. That is, is it sufficient if neurobots simply monitor the existing neuronal traffic for some reasonable period of time? One can readily imagine that a particular synaptic connection between two neurons only occasionally plays a role in the pattern of nerve impulses actually generated. Monitoring nerve impulses between those occasions when that synapse plays a role would reveal nothing about that synapse. A simple (but not necessarily realistic) example from computer science will serve to illustrate the point. A three-input MAJORITY gate has three inputs, input 1, input 2, and input 3. It will only fire if two of the three inputs take on the logical values of “1” at the same time. If we only knew the data values on the wires connecting the various logic gates, we might never realize that input 3 was connected if the actual pattern of data never had a logic “1” on input 3 at the same time there was a logic “1” on either input 1 or input 2. Thus, if there was a logic “1” on input 1 and input 2 at the same time, but never a pattern showing the gate firing when input 3 was at a logic “1” (because neither input 1 nor input 2 was at a logic “1” at that point in time), then we would conclude that the gate was a two-input AND gate, not a three-input MAJORITY gate. While we don’t yet know whether passive collection of nerve impulse data is sufficient to allow correct inference of an individual’s WBE, we’ll need to determine the full set of synaptic connections even if passive collection is insufficient. To this end, we might need to inject signals into the nervous system, allowing us to interrogate the cellular circuits with a sufficient number of possible inputs to ensure that we have accurately determined all of the synaptic connections. In our example of a MAJORITY gate that was incorrectly labeled as an AND gate, we would need to inject a “1” on input 3 at the same time that there was an input of “1” on input 1 or input 2. In this way, we could guarantee that we had enough data to deduce the nature of the MAJORITY gate, and correctly distinguish it from an AND gate. Whether this will be necessary or not is unclear at the present time. If it is not necessary, then the neurobots will not need to inject signals into the nervous system, which could potentially simplify their design. If it is necessary, then the neurobots will need to be able to inject signals (nerve impulses, selective depolarization of the cell membrane) into the nervous system. A variety of methods for carrying out this task are possible. Such an ability would, in any event, be desirable for other reasons, both in terms of treating a variety of medical conditions and in terms of diagnoses.

Comparison of WBES

Once we have constructed a WBE from the raw data gathered by the neurobots, then it would become possible to compare two such WBEs to each other in a meaningful way, as we expect that information like the connectome of a primate before and after they have been cryopreserved should remain the same. Changes in the WBEs would either be the result of damage caused by the cryopreservation-and-revival process, or would be the result of learning that took place between the “before” and “after” WBEs. Assuming the neurobots remained in place during the cryopreservation, recording nerve impulses before and during the cryopreservation, and then later recording nerve impulses immediately following revival, there would be no loss of neuronal information. It should be possible to more directly compare the “before” and “after” WBEs with less concern about unaccounted-for changes that took place because of learning between the time the “before” WBE was taken and the “after” WBE was taken. The only unaccounted changes would then be those caused by damage due to the cryopreservation and revival process. While this protocol works for experimental animals, we shall see later that it is ethically inappropriate to apply it to human test subjects. After some analysis of the ethical principles that must be followed, we derive a different protocol for evaluating a revival protocol that should be ethically acceptable for human use.

When is a scan technology good enough?

In the previous Section, we discussed how to evaluate a method for biologically reviving a cryopreserved experimental animal: gather data from the brain of the experimental animal before it is cryopreserved, and gather data from the brain of the experimental animal after it has been revived. In this Section, we discuss how to evaluate a method for scanning a cryopreserved test subject and constructing a WBE. That is, if our objective is not to biologically revive the test subject, but to construct a WBE directly from a scan, how might we evaluate the result? The scan might be a molecular scan, or it might be a lower resolution scan. We will also need to evaluate the algorithm used to construct the WBE from the scan data. We will be using the same basic principle as before: constructing a “before” and “after” WBE and comparing them. However, while the “before” WBE will be constructed from neurobot data, the “after” WBE will be constructed directly from the scan data. Again, we use neurobots to monitor all nerve impulses in a test subject, either a non-human test subject or, eventually, a human test subject. We construct a WBE from the recorded nerve impulses. We then cryopreserve the test subject. We then scan the test subject’s brain using the scan technology under investigation. We then do the scan-to-WBE using the algorithm under investigation. We then compare the two WBEs and see if there are any significant differences. If there are, then the scan technology in combination with the scan-to-WBE algorithm is judged “not good enough”. If there aren’t, the scan technology in combination with the scan-to-WBE algorithm is judged “good enough”. It is worth emphasizing that in this case, the “after” WBE is constructed from scan data, not from neurobot data. That is, the existence of a neuron that carries nerve impulses is deduced from scan data, not from the pattern of nerve impulses. The manner in which a dendritic network processes incoming nerve signals and produces an outgoing nerve signal along the outgoing axon is deduced by examination of the scan data rather than from the incoming and outgoing nerve impulses recorded by neurobots. That is, we are deducing the existence of a neuron by examination of the scan data. The better the quality of the cryopreservation and the better and more accurate the quality of the scan, the easier it will be to determine the connectome of the test subject, and the easier it will be to build an accurate WBE of the test subject’s brain from the scan data. As the quality of the cryopreservation gets worse, and as the quality of the scan gets worse, the ability of the scan-to-WBE algorithm to recover the connectome information with high fidelity will become increasingly difficult, and will require increasingly sophisticated algorithms that are increasingly computationally intensive.
This comparison of before and after WBEs appears to be the best we can do in terms of evaluating the quality of the combined cryopreservation and revival technology, whether we are considering biological revival, or revival as a WBE. It certainly appears to be the kind of testing that iCryonic and future physicians will have to carry out before reviving any patients. Regardless of the specifics of how the before-and-after comparison is performed, the critical insight is that detailed information gathered from the entire brain, both before cryopreservation begins and after revival is complete, will be required to assess the quality of the overall process. Neurobots can gather this detailed information that is required for the “before” WBE, and neurobots can gather the same information for the “after” WBE when biological revival of animals is being evaluated, as they’ll be able to quite literally record every nerve impulse in the animal brain. If the objective is to construct a WBE without biological revival, then the “after” WBE can be constructed directly from the scan data of the experimental subject’s brain, whether that experimental subject is animal or human.

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