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Assuming that someone or something created a human with the ability to regenerate most organs, including their head and brain. What might be a way for this human to retain their memories even after having there head cut off or destroyed? Perhaps something like a backup brain?

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    $\begingroup$ What happens to the chopped off pieces, do they become a clone of the regenerator. If not, how is it determined which piece regenerates? $\endgroup$
    – lijat
    Feb 26 at 14:47
  • $\begingroup$ Related from our science fiction and fantasy stack regarding prior art involving Deadpool. $\endgroup$ Feb 26 at 14:52
  • $\begingroup$ Does s/he keep a diary? sorry it's social media nowadays. $\endgroup$
    – user6760
    Feb 27 at 7:07
  • $\begingroup$ When you said your human had the ability to regenerate 'most organs, including head and brain…' did you mean to imply the memory was stored in the head and brain, or what? Even without lijat's clearly obvious contribution, why would beheading be any problem for a regenerator? $\endgroup$ Feb 28 at 22:02
  • $\begingroup$ In the anime "Attack on Titan" the "Titans" are humans who change in to giants at will and have the ability to regenerate and rebuild limbs etc.. and the Titan Reiner manages to transfer his mind in to the rest of his central nervous system when he takes a blade to the spine by an attacker trying to incapacitate him. So it's kind of like your back-up brain idea - guess would only work so long as a percentage of the nervous system remains, though could be a good way for someone to lose memories until they find their old head again... $\endgroup$ Feb 29 at 4:08

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There's a big difference between a head injury and having your head chopped off

Truth be told, we still know very little about how memory works. But we're working on it! Let's look at some recent research:

The researchers recorded the brain activity of participants as they watched the videos, and they noticed two distinct groups of cells that responded to different types of boundaries by increasing their activity. One group, called “boundary cells” became more active in response to either a soft or hard boundary. A second group, referred to as “event cells” responded only to hard boundaries. This led to the theory that the creation of a new memory occurs when there is a peak in the activity of both boundary and event cells, which is something that only occurs following a hard boundary.

...

The researchers next looked at memory retrieval and how this process relates to the firing of boundary and event cells. They theorized that the brain uses boundary peaks as markers for “skimming” over past memories, much in the way the key photos are used to identify events. When the brain finds a firing pattern that looks familiar, it “opens” that event.

...

The second test involved showing pairs of images taken from film clips that they had just watched. The participants were then asked which of the two images had appeared first. It turned out that they had a much harder time choosing the correct image if the two occurred on different sides of a hard boundary, possibly because they had been placed in different “events.” (Source)

What's important to realize (and this helps with your story immensely) is that the brain does not appear to just store "video frames." If it did, then damage that resulted to a "frame" being lost would mean it's lost forever. Instead, it appears to be highly associative and, for lack of a better word, efficient. Perhaps (and I stress that, perhaps) using a method reminiscent of how early game programmers created video on hugely limited computers. One technique that reflects what I'm talking about is that the common, basically unchanging parts of a series of images were stored as a single reference image and only those parts that were changing were stored as separate images. Thus, the memory needed for the whole of the video segment was minimized.

BUT! what that means if that if you lost one of the motion frames, it could be reasonably rebuilt by examining the frames around it.

Solution for head trauma...

Your amazing juju tech is able to restore memories lost to head trauma by scanning memories that physiological connections within the brain suggest are related to the memories lost to the damaged area. By examining those areas, most if not all of the lost areas can be reconstructed and, as part of the healing process, new synaptic connections are made that would restore most, if not all, of the memories.

If you think about it, even if in your story you presented this idea as not being perfect, it would reflect what we humans recognize anyway. Your average human can usually bring back the "image" of an early event if properly prompted. We call this "jogging the brain." On the first moment, it's a blank. But if we're reminded of the circumstances, or a smell, etc., then the memory returns.

More often what we have is an instinct or a reaction that's the "summary benefit" of the memory. We jump away from an unexpected heat source due to early childhood memories of being burned touching hot things. We might not be able to recall those memories clearly (and it's not uncommon that we can't), but the reaction remains. If all that was restored due to the healing process was that reaction, the core benefit of the restoration would be achieved.

OK, but what if I chop your head off, Highlander?

That's the more recognizable Sean Connery movie, but the better reference is Sword of the Valiant where Connery plays the Green Knight at King Arthur's court who challenges Arthur's knights to kill him. Decapitation doesn't bring home the proverbial bacon. It's a great C-grade popcorn movie, but it offers one way to solve the chop-your-head-off problem...

...create technology, perhaps implanted at birth... that preserves the flesh and function of the head until it can be reattached. Think of it this way: biotechnology is implanted below the skull that, if it detects a mortal drop in blood pressure, automatically shunts the various carotid arteries with a miniature oxygenator drawing from, oh, let's say a small grill located just inside each ear, resulting in the ability to keep oxygenated blood flowing through the brain until someone can solve the bigger problem.

Of course, we'll ignore the insanity that might just occur due to (a) the unbelievable pain having one's head severed might cause and (b) the psychological burden caused by looking around and knowing your head has been severed. (To be fair, the solution you're looking for might solve the mechanical problems with restoring memory, but won't solve at all the psychological problems.)

So, Connery picks his head up off the floor and we all think the maniacal laugh is because he's played King Arthur's knights! It's really because he's stark raving mad. Might not be much of a difference in the movie's plot, though.

Anyway, that's a solution that preemptively solves the problem. You're not really restoring memories, you're making sure they're not lost in the first place. On the other side of the coin is the solution used by Bob Mayer writing under the pseudonym Robert Doherty (or was it the other way around?) in his Area 51 books: all memory is stored on a MacGuffin hanging around the alien's necks. When they die, the contents of the MacGuffin are used to inform a clone replacement so there's a more-or-less continuous memory. Destroy the MacGuffin and you really do destroy the alien.

Another solution is to "scan the head before X hours have passed." In that way a memory map is created and can be re-imprinted on the new head after it's grown. That solution could also be used for the preemptive keep-the-head-alive solution such that the map is then transferred to the new head, psychological shock and all.

In the case that you don't have a MacGuffin and have lost the opportunity to map the memories from the original head (say, the head was crushed under a falling stone, destroying the brain), you're stuck. There's no way to restore something from nothing.

And if you're willing to consider something completely different...

Your regenerator isn't entirely human. There's extra brain tissue located throughout the body. It's useless for controlling the body, even useless for active memory, and thus can exist in much lower quantities while still providing the solution.

Think about RAID memory:

RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure.

So let's put all that I've said together and say this:

The state of modern memory regeneration can be attributed to the pioneering work of Dr. Althea Nurminen of the University of Iceland at Reykjavík in the early 2050s. She coined the term "re-associative memory" to describe her method of developing pseudo-brain tissue that could be grown artificially in the spaces between layers of muscle or flesh. Connected neurologically to the brain using modulated signals in the existing nervous system and with the benefit of a small demodulating controller at the cauda equina nerve cluster, a person's memory can survive major head trauma due to associative duplication throughout the body.

NOTE: My thanks to @ChthonicOne for pointing out something I had no idea about: There is already brain matter in our intestines! "The enteric nervous system that regulates our gut is often called the body’s 'second brain.' Although it can’t compose poetry or solve equations, this extensive network uses the same chemicals and cells as the brain to help us digest and to alert the brain when something is amiss. Gut and brain are in constant communication." (Source) That is so cool! There's already a Real World concept that can be used to rationalize the idea that the brain has a backup.

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    $\begingroup$ +1 Very altered-carbon. $\endgroup$
    – jdunlop
    Feb 26 at 21:45
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    $\begingroup$ There already is extra brain matter elsewhere in the human body, not inside the head. It's the reason why gut wounds are so traumatic. Our intestines are lined with brain matter. The exact purpose of it is not entirely known at this point, but it's not out of place to believe that some memory could be kept there as a backup in your scenario. We have many many yards of intestine. $\endgroup$ Feb 27 at 19:39
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    $\begingroup$ @ChthonicOne That is so honking cool! Thanks for bring that up! I found a relevant link and included the data in my answer. Cheers! $\endgroup$
    – JBH
    Feb 27 at 20:34
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    $\begingroup$ Puts the phrase "Thinking with your stomach" in a new light, eh? $\endgroup$ Feb 27 at 21:23
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If you're willing to indulge in a little more fantasy (or at least very soft sci-fi) in your setting, it might be that it was discovered that memory isn't actually stored in the brain at all, but rather in something else more loosely associated with the body than its direct parts -- i.e. a "soul" (or technobabble equivalent).

In most people, damaging the brain damages the ability to access the information in the soul, or actually does damage the soul itself; but the regenerator (or their creator) has discovered how to keep the soul intact during physical damage, and to perfectly reform the mechanisms used to access it when those are damaged.

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Since we're talking about intelligent design here, we can do all sorts of things that just straight-out couldn't ever evolve.

That said, we could easily design in a full redundant back-up system mediated by nanites that are regularly taking a copy of the person's brain state, and in the event of a loss of the brain, they could take over operating the remaining parts of the body until a new brain could be regrown and its pre-injury state restored.

In effect, the nanites would be maintaining multiple copies of the state of the brain and body so that if any were lost due to injury, the remainder would still be able to compile a full copy. The brain state would be the most complex part, restoration of the body's state would be relatively easy.

Given the potential for atomic-scale computing to store and process data, these nanites are certainly not beyond the bounds of possibility, and could conceivably each hold a full copy of the body state.

So... get your head blown off, and the nanites could take over thinking for you as they helped regrow your head, until your brain was restored. You might not even notice the difference... or at least you probably wouldn't want to.

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    $\begingroup$ This is the only technologically feasible, hard-science answer on here in my opinion. Nanobots are the only thing with the information density high enough to store a copy of the brain while co-existing with it and the body. $\endgroup$ Feb 27 at 17:39
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(r)DNA backup memory

Memory is complex

Let's preface this with a big asterisk. Memory is poorly understood, and what we understand is still subject to change. Currently the best thing we can say is that the neurons make connections. Each neuron is agitated to a certain degree by other neural connections, as well as modulated in the synaptic cleft, which causes the neuron to fire. The neuron can fire in different rhythms. One idea is that a memory is dependent on the current connections, modulation of a signal, and pattern of a signal. If one of these changes, they get a different effect. To make a related example, seeing a cheeseburger would normally trigger barely any response. For someone starving, just the faintest glimpse of the same cheeseburger results in a wholly different response.

In short, the brain and memory by extension is complex.

Teleportation and memory

The problem is shown by the teleportation problem. Say we want to copy you, destroy you, and rebuild you on another place. How much information do we need? The answer is 'too much'. We do not just need each exact position, bit also the laste state of each molecule. Spin, direction, the weird quark things they theorise. The data becomes more and more. Facing this problem, you can question yourself the following: when is close enough?

Memory is much the same. The amount of data required to have an exact match is nigh impossible. Instead, we should look at what is close enough. We forget or change memories and learned skills anyway, so that won't harm Headless Nick much.

With our scope determined, we must find a way to store the memories well enough to regenerate.

Memory backup in DNA

Let's first look at how to store memories. Regeneration means we grow it, so let's look at the building blueprints of our body to see if these can store memory.

Given the idea of connections, modulation and patterns above, we can see that at least the connections are plausible. The modulation can be ignored if we don't look too close. Being hungry or happy are states that modulate the memories and do not need to be stored. The patterns is more difficult, but let's assume that if the connections are correct, then the patterns will work. So the DNA only needs to make the right connections for this to work. Is DNA up to the task?

Sure it is. DNA forms many much more complex structures in the brain. The cerebellum organises many basic bodily functions in a tightly woven neural network. Breathing or artery constrictionfor example.

Humans come pretty blank in the world, but horses can stand and walk quickly after being born. So skills can be grown before ever doing them.

We also recognise other humans as humans, making recognition available as well. Other forms of memory should all be able to grow by DNA instructions. Theoretically of course, but we'll give some leniency for your sci-fi regenerator.

rDNA for storage

DNA can store it, but we do need a way to store it into DNA. We know DNA can be copied, but we are looking for a way to generate it for storage. rDNA is a great way to do this. DNA can copy tiny parts of itself to use as messengers. This is rDNA. how fast is this process? If you go from a light environment to a dark environment, your eyes make rDNA to change your eye receptors sensitivity. That is pretty fast! If you use this to store the information, your memory could lead up to a few seconds before you got decapitated. As long as they reach the rest of the body via the blood/lymph nodes, it can be stored.

Mash it together

To get the full picture, imagine the following. Your memories and skills cause new connections. These new connections cause a few rDNA strings to be released with this change, which are then stored in special memory cells. Think the memory cells of the immune system, but with a huge transcription of how the brain has grown. These cells appear in a few places in the body, probably the lymph nodes, so theres a few backups. As DNA is pretty tiny while holding a boatload of information there is no conceivable human limit to how much memory it can store.

When a decapitation or trauma to the brain occurs, these cells replicate and spread the brain compendium. The brain then follows this blueprint to restore the brain and it's memories, after which the memory cells tone down and normal operations can resume.

Does this answer play fast and loose with the rules of the real world? Sure. But if we're having regeneration anyway it seems plausible enough. It uses current real life ways the body grows and sends information, which potentially can be stored and later spread.

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  • $\begingroup$ Reminds me of Assassin's Creed, which is whilly based on the premise that you can read DNA-based memory of life events with a proper computer interface. $\endgroup$ Feb 27 at 15:25
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    $\begingroup$ Number of conections in the brain is huge: estimation is 100 trillion. Our DNA has a little over 6 billion base pairs. It is impossible to code our memory into the DNA, even if DNA did nothing else. Having DNA as a memory storage is completely immersion breaking for anyone with basic understanding of biology. Much better to explain the memory thing by magic... $\endgroup$
    – Negdo
    Feb 27 at 15:42
  • $\begingroup$ @Negdo how many of those connections relate to long term memory though? The rest can be regrown the same way it was the first time. Not to mention that compression algorimths may be able to reduce that - possibly lossely) $\endgroup$ Feb 27 at 16:35
  • $\begingroup$ @Negdo Thanks for your concern! As we need a 100.000 times the DNA, we would need to find that space. A nucleus is generally about a 1000 times bigger than the DNA in width. If we then look at a cell, which is a 1000 times to several 1000 times bigger than a nucleus, we find the space in a specialised cell. In addition, a lightsaber is immersion breaking to anyone with a basic understanding of physics. Few times I heard people say their immersion was broken. $\endgroup$
    – Trioxidane
    Feb 27 at 18:02
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    $\begingroup$ A lightsaber is a glowing stick powered by magic crystals: perhaps immersion-breaking to someone with a basic understanding of physics, but not to someone with a deeper understanding. Your technobabble "find the space" explanation is, likewise, not immersion-breaking (or, no more immersion-breaking than the concept we have to explain). Paternally-heritable DNA memory that is explicitly non-magical violates the basic laws of information theory – at least, once you get past a hundred books' worth. $\endgroup$
    – wizzwizz4
    Feb 28 at 0:02
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We already have memories which survive the regeneration of organ which made them.

Think of the immune system: the cells which make the memory when you get a vaccine are very rarely the same which recall it when the infection for which you are vaccinated happens.

The brain of your humans can use a similar mechanism.

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  • $\begingroup$ Great idea: You could even one up it.. emergency memory liquification and duplication. In extreme stress, the brain just releases antibodies with copies into the whole body as a stress reaction. Any surviving parts then crawl away and try to become wholeSum. Imagine regenerating in the stomache of a beast, and you chestburst back to life- and you cant get rid of the flashbacks.. $\endgroup$
    – Pica
    Feb 27 at 16:33
  • $\begingroup$ To be honest, this seems to be a side-effect of basically immortality that nobody talks about. How often can you survive having your head split in two halves, being chewed up and spit out, sliced into pieces by artillery, before you become a clan of shivering hermits, that lifes in fear of any trigger-signal restarting the carnage. $\endgroup$
    – Pica
    Feb 27 at 16:35
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Extradimensional backup

This may be a higher level of technology than what you are thinking of, but you could set up your regeneration to work this way: the body observed by characters in the story is completely baseline human - within the 4 spacetime dimensions we can perceive. In reality, the creature also extends into an extra spatial dimension we cannot perceive or affect conventionally.

It's up to you what is kept in that dimension - whether just a backup of the state that the regenerator is "supposed" to be, to be used as a template for the regeneration via unilateral quantum entanglement, or a higher-order being that rebuilds the meat puppet like we might heal a patch of skin, or anything in between.

Of course, this means that there exist high-tech ways of disrupting a regenerator's memory (by tampering with this connection using cutting edge MacGuffium).

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Brain implant

The regenerating human has a brain implant that interfaces with the brain, and is capable of reading the brain's current state at any moment.

It also has access to wireless networks and is constantly backing up memories to someone else's computer the cloud. This will surely necessitate future technology for the required bandwidth to be available.

If the brain is damaged but the implant is not, let the brain regenerate and the implant can restore a backup from the cloud.

But if the implant is damaged, then the regenerating person needs to get a new one before they can access their old memories.

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    $\begingroup$ This is the approach taken by Cory Doctorow's Down and Out in the Magic Kingdom, except that backups there aren't constant (there's presumably not enough wireless bandwidth). $\endgroup$
    – wizzwizz4
    Feb 28 at 0:17
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    $\begingroup$ @wizzwizz4 also in TF2's Sniper's Dancing With Eternity. $\endgroup$ Feb 28 at 0:32
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Memory is not stored at all by some biological mechanism, but in the substrate of the atoms (ignoring quantum weirdness) - and your reborn self regains it, by returning to the corpse or plant and basically simulating a deterministic universe backwards, till it reaches the moment of death- and then reading the mind that it was back into itself. Which obvious has problems. Matter can be distributed far and wide and you need to know it all, from that tiger poo to those tree nutrients, were it went.

Without all, it gets lossy, sloppy, a xerox-copy of a copy with only the caricature and outlines remaining.

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    $\begingroup$ Suppose I chop something into 10 seemingly-identical pieces, and switch them around however I see fit. You'd need to know the state of my mind at the time, in order to wind back the clock and discover the original arrangement. But I might have been influenced by a message received from the other side of the world. Assuming a reversible, deterministic universe, you'd need to know the state of everything in the future light cone of the last known good configuration. // This idea has promise, but it should be based around something like sympathetic magic, or handwaving, imo. $\endgroup$
    – wizzwizz4
    Feb 28 at 0:11

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