I am creating an alternate history world that leads to modern Earth having many different nations & cultures than it has in real life. One country is big on funding many extreme experiments to find out more about the human brain and body. Vitruvia (the country name) wants to research & develop drugs and gadgets like truth serums, love potions, and memory destroyers.

Vitruvia essentially wants to create the Neuralyzer from Men In Black. A machine or mechanism that can be used to cause retrograde amnesia in any number of humans. Is such a gadget constructible with 21st Century Technology (without severely damaging/killing the victim)?

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    $\begingroup$ Why does it matter whether such a device can or cannot be built with the technology of our 21st century? Your story is not set in our world, it is set in a world with a very different history. (How do I know that your world has a very different history from ours? Because there are so many more nations and cultures. Specifically, in our real world if such advanced technology would be developed by one country, that country could only be Russia, India, or China. Everybody else is either not capable of such development, or else is working in a framework of wide international of cooperation.) $\endgroup$
    – AlexP
    Commented Nov 16, 2023 at 21:28
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    $\begingroup$ > without severely damaging the victim I'd argue that erasing someone's memories is an act of tremendous violence and irreparable damage. $\endgroup$
    – Daniel B
    Commented Nov 16, 2023 at 21:39
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    $\begingroup$ @AlexP It matters as it is the basis from which we can describe the requested technology, or the possibilities thereof. Specifically to prevent comments like "we cannot answer the technology of your unknown world". Our current technology is the pinnacle of understanding of the real world, which seems like a good basis to start an imaginary story and it's technology from. $\endgroup$
    – Trioxidane
    Commented Nov 16, 2023 at 22:23
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    $\begingroup$ Modern science don't really know how human memory works at a granular level. There's a reason why we don't have devices to store our memories. $\endgroup$
    – Nelson
    Commented Nov 17, 2023 at 2:41
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    $\begingroup$ A baseball bat "causes memory loss" and is without a doubt "created with near-modern technology". $\endgroup$
    – RonJohn
    Commented Nov 18, 2023 at 0:46

10 Answers 10


You could go with a technique called Trans-cranial Magnetic Stimulation or TMS. But you'd also have to 'play around' with the science a bit and assume a couple of breakthroughs in neuroscience that may never really be possible.

TMS is being used for the treatment of metal health conditions such as PTSD and depression etc and one of the side effects of TMS that have been reported is disruption of working (short term memory). There are different types of TMS. See link here.


The other relevant technology is MRI particularly fMRI. These technologies are working towards the mapping of individual neural circuits in the central nervous system and this is an area of technology that is developing rapidly. See link here.


For the purposes of your story you can assume a 'breakthrough' has been made in both technologies. Very accurate fMRI lets you scan a brain to identify the circuits active in particular memories. Very accurate TMS lets you alter those networks to remove the memory.

The only problem is your 'Neuralizer' is going to be more like the one from MIB 3 not the ones in the other movies. At the least you'd have to have the 'patient' seated in a chair with something the size of a hair salon style professional dryer pushed down over their heads or alternatively they're are laid out horizontally and their heads are placed inside a compact MRI/TMS head scanning device. (Maybe all the victims mysteriously wake up in their apartments or whatever with no memory of how they got there and a nice perm!) :)

As a side bonus though the same tech might also give you a very effective lie detector. So you get two for one. This last is important by the way. Because questioning your victims about whatever it is you want them to forget while they are being scanned could, for plot purposes help identify the brain areas to be 'neuralized'.

  • $\begingroup$ Electroconvulsive Therapy has had memory loss as a side effect. psychologytoday.com/us/blog/the-superhuman-mind/202109/… $\endgroup$
    – David R
    Commented Nov 17, 2023 at 15:20
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    $\begingroup$ @DavidR, so does hitting someone on the head with a hammer. The trick here is targeted memory loss. $\endgroup$
    – Mark
    Commented Nov 17, 2023 at 23:03
  • $\begingroup$ I can't give you any references, but TMS is woefully underpowered and consider near witch-craft in some circles. $\endgroup$ Commented Nov 20, 2023 at 1:26
  • $\begingroup$ @Mon in some circles sir. In some circles. $\endgroup$ Commented Nov 22, 2023 at 1:41

This is unanswerable

I mean this in a technical sense - we do not know how Memory works, how it is stored etc.

And as such, we do not know what is needed to impact it.

What do I mean by this:

Go back 10,000 years - the fungi "Penicillium chrysogenum" exists - it was possible, with 10,000 year old technology to make Penicillin and therefore an antibiotic.

But - without all the surrounding knowledge, it's impossible to do so.

It might be that we have all the materials, manufacturing techniques and equipment that could build such a device - but without sufficient knowledge of how Memory works - we cannot answer.

  • 5
    $\begingroup$ Your penicillin comment is interesting, because the healing properties of bread mold were known in ancient times, such as Egypt or Greece. And getting the penicillin itself is just a filtration process, so it's not impossible. But memory is a much more difficult thing, unless the story provides a similar history of happenstance to allow discovery of the method. $\endgroup$
    – Brianorca
    Commented Nov 16, 2023 at 22:27
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    $\begingroup$ The issue is not the tech, but how that knowledge even came into being. The very idea that you can "filter out bad stuff" from something that will kill you is completely foreign. If you saw someone eat a fruit and drop dead, you're not going to think "Hmm, maybe if I eat this bit after I squeeze it through some leaves would make it safe". You wouldn't even think to eat less and maybe it'll be good. You're going to tell everyone that the fruit kills you and not touch the damn thing. $\endgroup$
    – Nelson
    Commented Nov 17, 2023 at 6:43
  • $\begingroup$ @Brianorca Except bread mould doesn't contain penicillin. This is an unfortunate case of popular myth extrapolating at least 4 steps too far: first assuming that any mould will do; second assuming that any mould in situ on the bread can be used as-is (ignoring yeast and other microorganisms also in the mouldy bread); third assuming that they had the technology to do this (you need a sterile starting point, which is hard for a pre-industrial setting); and fourth that what they "knew" back then had any basis in fact (look at all the other bizarre remedies back then). $\endgroup$
    – Graham
    Commented Nov 17, 2023 at 15:25
  • $\begingroup$ @Brianorca ... Which really illustrates the answer's point. Even though some medical things are possible now, they've built on a level of knowledge and sophistication which is far more than a regular civilian (like you or me) has. If we can't even answer this well for a century-old technology, good luck trying to do it for something we don't even understand yet, even with all our MRIs and stuff. :) $\endgroup$
    – Graham
    Commented Nov 17, 2023 at 15:28
  • $\begingroup$ "as such, we do not know what is needed to impact it." We know full well that a baseball bat to the forehead impacts (pun intended) memory recall. $\endgroup$
    – RonJohn
    Commented Nov 18, 2023 at 0:47

We have this device. Its aanesthetic. Many are not aware, but the medicamentation cocktail you receive, constantly monitored on the operating table is composed of substances with different effects.

Some just reduce/prevent movement. Some prevent pain signals from travelling. And some supress conciousness - or prevent memory formation.

As in the substance prevents the encoding from shortterm to longterm memory. https://en.wikipedia.org/wiki/Benzodiazepine#Cognitive_effects

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    $\begingroup$ +1 I think a chemical gas might be feasible, which prevents encoding from short term to long term memory for all that inhale it. You could spray it across a group of people right after they saw something they shouldn't see. It could easily work good enough. $\endgroup$
    – Falco
    Commented Nov 17, 2023 at 14:03

Sure, why not?

We currently have the technology to cause anterograde amnesia: specifically, drugs that basically prevent the transfer of short-term memories into long-term storage. Outside certain medical contexts, these are very illegal and mostly used as a "date rape drug".

The most common/notable of these is Flunitrazepam also known as Rohypnol, a type of Benzodiazepine where, quote Wikipedia:

If enough of the drug is taken, a person may experience a state of automatism or dissociation. After the drug wears off, users may find themselves unable to remember what happened while under its influence

The drug is used to treat insomnia or act as an anesthetic, but has some rather out-there side effects.

Additionally, it doesn't case retrograde amnesia: people who take it don't forget what happened before they took it, but rather they forget what happened after they took it. Similar effects can be achieved with other drugs too, like alcohol in sufficient quantities.

I don't see any fundamental reason why technologically advanced people with less moral/ethical scruples about human experimentation couldn't develop or stumble across a drug that allows the recent memories of the taker to be "wiped" or otherwise reduced.

Sidenote: If someone could invent a medication which caused short term retrograde amnesia, even if it's not full memory-loss, they could easily become a billionaire because it would be extremely valuable to the military. Every combat soldier would be given this in an epi-pen style injector, and they'd be taught to self-administer after undergoing a traumatic event in order to prevent PTSD and thus save the taxpayer and the VA uncountable billions in medical expenses (along with protecting themselves from a lifetime of potential mental health issues).


Practically, No.

A neuralyser as shown in Men in Black is a cigar-sized object that removes a selectable period of the most recent memories with a flash.

Firstly, memory doesn't work that way. While we don't know the mechanisms involved in the many different types of memory, it is unlikely that memories are laid down in such an orderly fashion, that earlier memories could be sorted and categorised easily by a machine.

Secondly, if a device could be made that could map a human brain and identify memories, it would necessarily require an unimaginable amount of processing power by 21st century standards. If the neuralyser was a real device, aside from its power supply, it would need to be packed solid with atomic-level quantum computing capabilities in order to process the structure and locate the memories in anything approaching the time shown in the MiB movies.

Thirdly, a neuralyser operating on a number of subjects at range makes the whole process just that much more difficult, and we also need to consider that it's one thing to map a human brain in an advanced machine like a MRI that the subject is placed within, and entirely another matter to achieve this with such a small handheld device.

Fourthly, having located the necessary memories, the issue of how to remove them remains. As we don't know how memories are stored, I couldn't begin to say how they might realistically be specifically destroyed. Since it has been shown that brain damage can result in memory loss, I would expect that targeted brain damage would be required to remove memories. Damaging such small parts of the brain would be difficult enough with a machine that the human head fits within, and many orders of magnitude more difficult to achieve at range.

So, I would say that a device like a neuralyser would be impossible in the 21st century at any scale, hand-held or the size of a building, and probably not possible in the 22nd century either, and if it was, it would be the size of a MRI machine, and certainly not effectively instant, but rather likely to take the better part of a day, and likely to require that the probably unwilling subject be sedated... if it could work at all on a sedated or uncooperative subject.

I'm sorry to say that in all liklihood, a neuralyser will remain nothing but a Hollywood magic plot device invented to explain how an otherwise impossible-to-keep secret can be kept.

  • $\begingroup$ "it is unlikely that memories are laid down in such an orderly fashion" - this isn't necessary. If you have a device which can read, edit, and write memories at will, then it is indeed impossible to just erase memory between two given times, but if you download it all, edit it so that you delete what you want in your downloaded data, and then upload it again, then you've solved it. $\endgroup$
    – vsz
    Commented Nov 17, 2023 at 10:16
  • $\begingroup$ @vsz Editing may turn out to be orders of magnitude more complex than merely deleting. Additionally, you'd have to parse all those memories and decide what you wanted to alter. That's definitely not trivial, or likely to be quick. $\endgroup$
    – Monty Wild
    Commented Nov 17, 2023 at 10:20
  • $\begingroup$ I think in spirit of world building a helpful answer can show possibilities in addition to limitation. While the exact device cannot be created, the question also asks for something similar. It seems to be good enough if one can prevent the most recent memories (last minutes ) from being persisted to long term memory. This could probably be done with certain drugs, the question is how reliable and how to administer them with a small device over a group of people. $\endgroup$
    – Falco
    Commented Nov 17, 2023 at 14:08
  • $\begingroup$ @vsz The idea of "downloading" and "uploading" memories is as far outside our current understanding and abilities as Star Trek transporters and replicators. It's a fun premise to use as a starting point for all sorts of plots, but not even remotely rooted in current science. $\endgroup$
    – IMSoP
    Commented Nov 18, 2023 at 18:58

We may not know much about how the brain works at the microscopic or macroscopic level. But we do know a few things.

The brain is composed of brain cells connected to many other brain cells. One brain cell fires, stimulating others. If this happens between several cells, a signal of some sort has been passed. At the same time the cells adapt subtly, so the next time the first cell fires it is more likely to do the same thing.

It is this sort of network that machine learning models aim to copy. For experimental reasons we generally separate the response (the passing of the signal) from the training (the adaption of the network). This lets us run experiments on our neural net models which are almost impossible to do with real neural nets.

Our vision system has two main pathways - the ventral stream is associated with identifying and recognising objects, and has access to our long-term memory, and the dorsal stream is more concerned with spatial relationships between objects, and with muscular actions and coordination, and has no obvious access to the long-term memory. But both streams have 'neuroplasticity' - they will react to the signal they pass, and can adapt to change and recover from damage. Memory is everywhere. This makes it hard to remove a memory completely.

In the very short term, we are continuously forgetting things. If a clock strikes, and someone asks what the time is, we can could remember what we heard, count the strikes, and say what time it was. A minute or so later, we may have forgotten that we had ever heard the clock strike.

If something has our attention, then the memory gets harder to erase. If you think "what did I just see/hear?" then there will be some conscious memory. This is not yet the long-term memory. If we do not use the information, it will probably be lost. This seems to be a bit of what anaesthetics do. But if it was a significant memory and you are not on drugs then you will remember it, even if you would rather not. Experience tells us that we can modify our memories. Police interrogation can change witness memories. Peer pressure can cause us to doubt ourselves. But this is more like rubbing out parts of a drawing drawn with an H pencil rather than a 3B, and putting something else over the top.

If we were a neural net model, we might be able to locate the particular set of weights at a node that (say) recognised our ex, and disable them. In a brain, this is much harder, because the experiments necessary to find the cell (or probably many cells) that do this would reinforce the memories you want to erase. This does not mean it is impossible, for therapy is supposed to do this sort of thing. It may be more efficient, if assisted by dream image reconstruction from MRI (a real thing), and drugs, and a better understanding of how to go about this sort of thing. But it is unlikely to be a 'Men in Black' flash erasure if the memory is older than a minute or so.


You would need a two step process:

  1. Imaging and cognitive stimuli.

Use fMRI to map blood flow to active areas of the brain. Use pictures and sounds to locate the areas of the brain associated with the memories you wish to remove. You then narrow down the areas where the memories are stored by correlating areas that light up when the images and/or sounds are presented.

https://www.jneurosci.org/content/36/22/6069 -- evidence visual stimuli

https://pubmed.ncbi.nlm.nih.gov/30937831/ -- evidence that auditory and visual memories may be stored the same way long term

Present olfactory stimuli in a second testing session. Olfactory stimuli are processed differently. The inputs from olfactory nerves are passed directly into the brain. Auditory and visual stimuli pass through the thalamus -- a sort of bottle-neck in the sensory integration system.

https://scholarblogs.emory.edu/artsbrain/2021/03/09/olfaction-and-memory/ -- olfactory and visual / auditory memories differ

The two different routes allow you to peform something close hypothesis test. The auditory and visual stimuli suggest an area. The olfactory stimuli verify the area.

  1. Lobotomy / Selective Cell Death

Selectively lesion the areas indicated by the scan stimuli pairings. The least invasive technique would be mutli-axial electromagnetic beams -- I believe microwave (actually xrays are used) No single beam should be enough to do damage the parts of the brain where the beams pass through separately. The combination of eight beams that intersect at the point where a memory is stored will accumulate enough energy to lesion the area and destroy the memory.

https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526 -- multiaxial beams: another named is used same concept

Repeat ad-nausia till you end up with a vegetable or someone who has lost the appropriate memories.

  • $\begingroup$ Apologies. I didn't see your science based tag. I need, perhaps, two nights to address this. I can probably cover most of the referrals here. $\endgroup$ Commented Nov 21, 2023 at 3:26
  • $\begingroup$ I know that this is a very touchy board. I mean no disrespect. $\endgroup$ Commented Nov 21, 2023 at 3:26
  • $\begingroup$ The scholarship is not the tightest, but i had no grant money and sacrificed only four undergraduates. $\endgroup$ Commented Nov 22, 2023 at 1:34

Some users have already pointed out that some drugs will do it. Dragongeek mentioned date rape drugs, those are the most classic examples.

I'll add something else: sleep deprivation. From Harvard Health Publishing:

What else could be causing memory problems at a young age? The most common cause of memory problems below age 65 is poor sleep.

If you give someone a drug, use a device, or simply apply brute force to keep them awake for, say, 36 hours straight, the person may remember a few things prior to the drugging or torturing, but the details will be hazy at most.

Actually, you may even have funny side effects. From the Sleep Foundation (emphasis mine):

Impaired Memory: Both NREM and REM sleep appear to be important for broader memory consolidation, which helps reinforce information in the brain so that it can be recalled when needed. NREM sleep has been linked with declarative memory, which includes things like basic facts or statistics, and REM sleep is believed to boost procedural memory such as remembering a sequence of steps. Poor sleep impairs memory consolidation by disrupting the normal process that draws on both NREM and REM sleep for building and retaining memories. Studies have even found that people who are sleep deprived are at risk of forming false memories.



Knowing as much as in the 1940s and 1950s, medical professionals repeatedly and very targeted destroyed parts of the brain of the patient to alter behavior or skills. With the knowledge we have today, a much more directed lobotomy could be aimed using activity measurements when requesting to retell the specific event.

The downside is clearly, that the process destroys more, at times much more, than just the aimed area.

  • $\begingroup$ Eh, it destroys your whole frontal lobe and thus personality + drive? It's basically murder with a warm, breathting body left behind? $\endgroup$
    – Pica
    Commented Nov 19, 2023 at 9:54
  • $\begingroup$ @Pica if you go for the frontal lobe. You can go for other areas too. Especially with modern technology you could aim for areas of memory or like.. .anything. $\endgroup$
    – Trish
    Commented Nov 19, 2023 at 10:55
  • $\begingroup$ Yes, and that regularly happened. But it was never controlled or targeted. More like a artifical stroke that just makes a defiant person a retard. $\endgroup$
    – Pica
    Commented Nov 19, 2023 at 14:09
  • $\begingroup$ @Trish the problem is you can't target it because it is spread over a large area. memory is not stored discreetly. you would have to remove the persons ability to have memory at all. $\endgroup$
    – John
    Commented Nov 20, 2023 at 1:39

Removing a memory is almsot certainly not possible, without technology so advanced it borders on magic.

Alternative: consider a drug that makes a person extremely susceptible to permanent suggestion. This is something that could possibly be done, because it does not rely on identifying any specific memories, and allows the patient's brain to do the work:

  • administer the Open Mind drug
  • the person becomes incapable of resisting your suggestions, and takes them as absolute truth.
  • tell them to intentionally ignore the memory or information you are trying to target ("Joe never existed, never ever think or talk about Joe. Thinking about Joe makes you a bad person, avoid doing it at all costs.")

release the patient. They are capable of remembering Joe, they are just incapable of thinking about Joe without instant severe anxiety, and they shut down in stupor if they try to talk about Joe. Joe is not forgotten, just perfectly tabooed.


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