Cryonics revival

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There are a number of planned and hypothetical methods around cryonics revival.

Overview

Possible necessary future technologies include:

Damage

The kinds of damage that need to be repaired have been slowly reduced over time, but at present, under the best conditions, the process of cryopreservation still causes severe damage to the Patients.

Cryoprotectant Toxicity

Cracking

There are two forms of cracking: That which is caused by thermal stress, and that which is caused by cooling below Tg. Cracks are generally few and large, which is far better than many smaller cracks; since from an information point of view they cause little damage.

If revival is attempted through Whole Brain Emulation, then fixing cracks is just a matter of adjusting the images. If it is attempted through some form of Biological Repair, this will require other methods to readjust the severed pieces of tissue.

Thermal Stress

Glass Cracks

When materials (Not only glasses) are cooled below their vitrification temperature, cracking occurs. Since the Tg of the cryoprotectant solutions is far above the temperature at which Nitrogen liquefies, cracking occurs during the cooling to this temperature, whether tissue has been vitrified or not. If cryoprotective Perfusion is not carried out properly or is compromised by severe ischemic injury, cracking can begin at temperatures as high as -90 ºC.

A solution for this (In properly perfused patients for whom cracking will only occur below glass transition) is Intermediate Temperature Storage.

Biological Repair

Whole Brain Emulation

See Whole Brain Emulation

File:Cryoultramicrotome.jpg
A cryoultramicrotome used to section tissue at low temperatures.
File:Spikes real and fake.jpg
One of these columns is a graph of the activity of a rat's pyramidal neuron under electrical stimulation. The other is an Izhikevich simulation of the same. This shows that reality and abstract models can have different internal behavior and foundations, but produce the same activity.

This approach to cryonics takes the ideas of information-theoretic death and the central tenets of Whole Brain Emulation (Memory and personality are stored in the brain, consciousness arises from material processes, et cetera) and proposes that cryonics patients may be revived by scanning the connectivity and properties of the cells in their brains (For example, with an ATLUM or some form of high-resolution tomography); and that an abstract, computer model of these properties will be very similar to the person who was cryopreserved.

Process

  1. The vitrified brain is extracted from the patient. Necessary extra fixatives are applied.
  2. The brain is segmented into as many pieces as needed.
  3. Each piece is laminated and scanned by a cryoultramicrotome, ATLUM or some other machine.
    1. Current technology is rather slow, but new massively-parallel electron microscopes are being, developed, primarily by the semiconductor industry. The speed of scanning depends on how many machines you have.
  4. A stack of electron micrographs is built, one for every slice.
  5. Noise is eliminated, different electron micrographs at the same height are pasted together by inferring edge connectivity.
  6. An edge detector traces the contours of neurites and cellular structures.
  7. Other algorithms detect intracellular structures of interest (Polyribosome complexes).
  8. This is done for every layer.
  9. Another algorithm joins the edges in different layers, creating a 3D model of the brain.
  10. Another algorithm uses that model to create a graph of the connectivity of the brain. Each node in this graph is a neuron, and the neuron data structure is supplied with all the necessary extra information acquired by step 7.
  11. After the scan is complete, the graph is stored in a neuromorphic computer; a machine where every processor is a hardware implementation of some model of neurons.
  12. The graph at the lowest level of the stem is joined with a species-generic graph of the connectivity of the spine, ie: Axons of the brain are matched to virtual nerve endings.
  13. The simulation of the body and brain, either connected to a robot or virtual avatar, is started.

Molecular Nanotechnological Repair

See Molecular Manufacturing

The approach of using Molecular Nanotechnology to revive cryonics patients dominated the discussions of the future of cryonics for over a decade since the publication of Engines of Creation, but has now mostly shifted to a historical curiosity.

Non-viable methods

  • Rehydrating like various animals do, e.g. Tardigrade, too much neuro/tissue damage to address first
  • Head transplants, just... no[1]

References