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categories: ["minds", "longevity"]categories: ["minds", "longevity"]tags: ["cryopreservation", "connectome", "uploading", "neuroscience", "vitrification", "death"]tags: ["cryopreservation", "connectome", "uploading", "neuroscience", "vitrification", "death"]summary: "Preserving the structural information in a brain well enough that a future technology could reconstruct its memories, rather than revive the tissue itself."summary: "Preserving the structural information in a brain well enough that a future technology could reconstruct its memories, rather than revive the tissue itself."updated: "2026-07-27"updated: "2026-10-29"humanEvidence: "Verification is from rabbit and pig brains only; no preserved human brain has been assessed the same way, and no preserved brain of any species has been scanned and shown to yield a working model."humanEvidence: "Verification is from rabbit and pig brains only; no preserved human brain has been assessed the same way, and no preserved brain of any species has been scanned and shown to yield a working model."access: "Offered after death by a small number of organizations, at lower cost than liquid-nitrogen cryonics; no provider is known to perform the premortem perfusion the published protocol assumes."access: "Offered after death by a small number of organizations, at lower cost than liquid-nitrogen cryonics; no provider is known to perform the premortem perfusion the published protocol assumes."reversibility: "irreversible"reversibility: "irreversible"lines 29–39 → 29–3914 unchanged lines not shown
}}`````` **Brain preservation** is the storage of a brain in a state that retains the structural information thought to encode memory and personality, on the assumption that this information — not the living tissue — is what would have to survive for a person to be recoverable. It differs from [[cryonics]] in an important respect: the leading method is chemically irreversible and makes no attempt to keep the brain biologically viable. It is a bet on scanning, not on resuscitation, and it is taken up mainly by people who do not expect [[longevity-escape-velocity]] to arrive in time for them.**Brain preservation** is the storage of a brain in a state that retains the structural information thought to encode memory and personality, on the assumption that this information, rather than the living tissue, is what would have to survive for a person to be recoverable. It differs from [[cryonics]] in an important respect: the leading method is chemically irreversible and makes no attempt to keep the brain biologically viable. It is a bet on scanning rather than resuscitation, and it is taken up mainly by people who do not expect [[longevity-escape-velocity]] to arrive in time for them. ## What is being preserved## What is being preserved The premise is that a person's memories and character are physically instantiated in the arrangement of their neurons and synapses, together with molecular details such as receptor composition and synaptic strength. If that arrangement can be frozen in place — literally or chemically — then in principle it can later be read out, whatever the state of the tissue.The premise is that a person's memories and character are physically instantiated in the arrangement of their neurons and synapses, together with molecular details such as receptor composition and synaptic strength. If that arrangement can be frozen in place, literally or chemically, then in principle it can later be read out, whatever the state of the tissue. This shifts the success criterion. Cryonics asks whether damage can be repaired; brain preservation asks whether information has been destroyed. The two lead to different procedures. A method that crosslinks every protein in the brain into an immobile mesh would be catastrophic for revival and excellent for structural preservation, and that is roughly what the field's leading technique does.This shifts the success criterion. Cryonics asks whether damage can be repaired; brain preservation asks whether information has been destroyed. The two lead to different procedures. A method that crosslinks every protein in the brain into an immobile mesh would be catastrophic for revival and excellent for structural preservation, and that is roughly what the field's leading technique does. lines 42–52 → 42–522 unchanged lines not shown
## Aldehyde-stabilized cryopreservation## Aldehyde-stabilized cryopreservation Aldehyde-stabilized cryopreservation (ASC) was published in 2015 by Robert McIntyre and Greg Fahy, whose earlier work produced the low-toxicity vitrification solutions that [[cryonics]] organizations use.[^mcintyre2015] The procedure perfuses the brain's vasculature with glutaraldehyde, which crosslinks proteins within seconds and halts decay, then introduces a high concentration of a cryoprotectant — ethylene glycol in the published protocol — and cools the brain below its glass transition, around −135 °C, where it can be stored without ice formation or further chemical change.Aldehyde-stabilized cryopreservation (ASC) was published in 2015 by Robert McIntyre and Greg Fahy, whose earlier work produced the low-toxicity vitrification solutions that [[cryonics]] organizations use.[^mcintyre2015] The procedure perfuses the brain's vasculature with glutaraldehyde, which crosslinks proteins within seconds and halts decay, then introduces a high concentration of a cryoprotectant (ethylene glycol in the published protocol) and cools the brain below its glass transition, around −135 °C, where it can be stored without ice formation or further chemical change. Fixation solves the problem that limits conventional vitrification. Because the tissue is already stabilized, cryoprotectant can be introduced slowly and at concentrations that would be fatally toxic to living cells, and osmotic damage no longer matters. Fixation also stops the clock immediately, whereas a purely cryogenic protocol must race cooling against ischemia.Fixation solves the problem that limits conventional vitrification. Because the tissue is already stabilized, cryoprotectant can be introduced slowly and at concentrations that would be fatally toxic to living cells, and osmotic damage no longer matters. Fixation also stops the clock immediately, whereas a purely cryogenic protocol must race cooling against ischemia. The published demonstrations used a rabbit brain and later a whole pig brain, with electron micrographs sampled across the specimen showing intact cell membranes, synapses and synaptic vesicles. Verification was the point: earlier preservation claims had rested on gross appearance rather than on ultrastructure at synaptic resolution.The published demonstrations used a rabbit brain and later a whole pig brain, with electron micrographs sampled across the specimen showing intact cell membranes, synapses and synaptic vesicles. Verification was the purpose: earlier preservation claims had rested on gross appearance rather than on ultrastructure at synaptic resolution. ## The Brain Preservation Prize## The Brain Preservation Prize lines 60–70 → 60–707 unchanged lines not shown
]]`````` The prize's design mattered more than its money. By fixing the evaluation criterion in advance — uniform preservation of synaptic ultrastructure across an entire brain, judged by independent electron microscopists — it forced a field that had traded in assertion into producing checkable images. It also, by its own terms, said nothing about whether a preserved brain could ever be read.The prize's design mattered more than its money. By fixing the evaluation criterion in advance (uniform preservation of synaptic ultrastructure across an entire brain, judged by independent electron microscopists), it forced a field that had traded in assertion into producing checkable images. It also, by its own terms, said nothing about whether a preserved brain could ever be read. ## The connectome criterion## The connectome criterion The argument that structural preservation suffices runs through [[connectomics]]. If memory is stored in the pattern and strength of synaptic connections, then a preserved connectome plus enough molecular annotation is the person in storage, and the remaining work is scanning and simulation — the pipeline described in the [[whole-brain-emulation]] roadmap by [[anders-sandberg]] and [[nick-bostrom]].[^sandberg2008] Nothing in the method requires the [[medical-nanorobots|cell-by-cell repair machinery]] that biological revival scenarios depend on, which is the main reason its advocates consider it the more tractable bet.The argument that structural preservation suffices runs through [[connectomics]]. If memory is stored in the pattern and strength of synaptic connections, then a preserved connectome plus enough molecular annotation is the person in storage, and the remaining work is scanning and simulation, following the pipeline described in the [[whole-brain-emulation]] roadmap by [[anders-sandberg]] and [[nick-bostrom]].[^sandberg2008] Nothing in the method requires the [[medical-nanorobots|cell-by-cell repair machinery]] that biological revival scenarios depend on, which is the main reason its advocates consider it the more tractable bet. The objections are substantial and not resolved.The objections are substantial and not resolved. lines 82–88 → 82–8811 unchanged lines not shown
Because good perfusion requires intact circulation, the ideal application of ASC is to a patient who is anesthetized and alive at the moment fixation begins. That makes the procedure a cause of death rather than a response to one, and places it squarely inside the [[right-to-die-and-right-to-live|assisted-dying]] debate rather than beside it. Advocates ground the claim in [[morphological-freedom]] and the right to dispose of one's own body; opponents note that no other elective procedure is both irreversible and immediately lethal, and that consent to it is being sought on the strength of a technology nobody can demonstrate.Because good perfusion requires intact circulation, the ideal application of ASC is to a patient who is anesthetized and alive at the moment fixation begins. That makes the procedure a cause of death rather than a response to one, and places it squarely inside the [[right-to-die-and-right-to-live|assisted-dying]] debate rather than beside it. Advocates ground the claim in [[morphological-freedom]] and the right to dispose of one's own body; opponents note that no other elective procedure is both irreversible and immediately lethal, and that consent to it is being sought on the strength of a technology nobody can demonstrate. The startup Nectome ran into this directly. Founded by McIntyre to commercialize ASC, it attracted attention in 2018 for a service described in press coverage as "100 percent fatal", accepted refundable deposits from a waiting list, and lost its research subcontract with MIT shortly afterward.[^regalado2018] The scientific objection raised at the time was not that the preservation failed but that selling it implied a claim about future revival that nobody could support.The startup Nectome ran into this directly. Founded by McIntyre to commercialize ASC, it attracted attention in 2018 for a service described in press coverage as "100 percent fatal", accepted refundable deposits from a waiting list, and lost its research subcontract with MIT shortly afterward.[^regalado2018] The scientific objection raised at the time did not concern the quality of the preservation; it was that selling the service implied a claim about future revival that nobody could support. A smaller practice has continued. Some organizations offer chemical fixation with storage at higher temperatures, which is far cheaper than liquid-nitrogen maintenance and may be adequate if the goal is structure rather than viability. A few well-funded startups, including one founded by the longevity investor Laura Deming, have taken the opposite tack and are pursuing genuinely reversible brain cryopreservation, which if achieved would make the fixation trade unnecessary.A smaller practice has continued. Some organizations offer chemical fixation with storage at higher temperatures, which is far cheaper than liquid-nitrogen maintenance and may be adequate if the goal is structure rather than viability. A few well-funded startups, including one founded by the longevity investor Laura Deming, have taken the opposite tack and are pursuing genuinely reversible brain cryopreservation, which if achieved would make the fixation trade unnecessary. lines 93–99 → 93–994 unchanged lines not shown
Brain preservation occupies an unusual position: its central technical claim is verifiable and largely verified, while its central practical claim is not testable at all with present knowledge. The bottleneck has moved to the read-out side, where progress depends on the throughput of volume electron microscopy and on whether models built from [[neural-decoding|decoded]] structure can reproduce function.Brain preservation occupies an unusual position: its central technical claim is verifiable and largely verified, while its central practical claim is not testable at all with present knowledge. The bottleneck has moved to the read-out side, where progress depends on the throughput of volume electron microscopy and on whether models built from [[neural-decoding|decoded]] structure can reproduce function. The field's honest position is that it preserves an option rather than delivering a result, and that the option's value depends on premises — [[substrate-independence]], the sufficiency of structure, the eventual existence of the scanning pipeline — that are argued rather than demonstrated. Whether preserving that option is worth doing, given that it must be exercised at the cost of a life that would otherwise have ended slightly later, is a question the technical results cannot settle. It is the same question [[mind-uploading]] raises, arriving decades earlier because the preservation half is already available.The field's honest position is that it preserves an option rather than delivering a result, and that the option's value depends on premises ([[substrate-independence]], the sufficiency of structure, the eventual existence of the scanning pipeline) that are argued rather than demonstrated. Whether preserving that option is worth doing, given that it must be exercised at the cost of a life that would otherwise have ended slightly later, is a question the technical results cannot settle. It is the same question [[mind-uploading]] raises, arriving decades earlier because the preservation half is already available. ## See also## See also removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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