As we see today the interconnection between the brain and computing is becoming thinner day by day, we could imagine a future that where we could install additional artificial neurons.

In a world where you could routinely buy these type of extensions, you would be accustomed to connect/disconnect a part of the brain.

The world building question is: How would it be like removing or adding such a neuronal mass? Would you loose some memory/ability, would it be more like an effort scale? Would you easily pinpoint core abilities that could be just switched on/off? would it be difficult to harness this additional neural network, and when you disconnect from it, what changes could you notice? Could you pinpoint an aspect of the memory of a fact/event that would be stored only in the extension? Would it be valuable to have different extensions? I guess you could not exchange them, and they would not be exchangeable because they would have been trained with your brain configuration, but what would you feel if you just tried once, or a little longer?

To restrain the complexity of the question, I'm considering these extensions as:

  • giving only more neuronal networks matter (no complex emotional or new organs connected with hormones release or any important chemicals needed by the body).
  • being lumps of artificial matter that you would wear (and by this mean connect) with various interfaces directly to your neurons.
  • The max section of communication could be considered up to the full 2d surface of coverage of your head the extension would provide (each organic neurons of this surface could have its state mirrored technologically with an artificial version on this surface in a 2-way sync)
  • The technology behind the artificial neuronal network wouldn't be conceptually far from the virtual ones we use today, except these would be physical and would be comparable in density and mass to brain's grey matter.
  • These would be bought blank, but wouldn't wear off or need replacement even on a life-time period. They would take probably weeks, month, years to harness and produce a noticeable effect.
  • They would be an everyday life object that we would have a lifetime to be accustomed to, especially since early childhood.
  • There are no technology allowing to control what happens with the neurons more than just interacting with the interface they give through our natural brain's neurons connected to artificial neurons on the surface of connection.
  • You won't have any technological means to help you storing a specific memory or ability inside an extension.
  • An individual would have access to different extensions (bought by the individual or provided by its job or by a state) for different occasions with bigger/smaller mass
  • there are no limit to the actual time individuals can wear such a peripheral and this would vary depending on the individual's habit.
  • You can consider the whole surface of the brain accessible to these extension (either because the whole brain is accessible directly after surgery considered as very common, systematic and accessible, or because of a technology allowing to 2 way connections with individual neurons through the bone.)
  • A typical extension would be the size of 200gr meat steak shaped lump that you would wear on the back of your head that you could wear on any occasions. But you could think of whole helmet going up to 5 kilograms of artificial neuronal matter (that you wouldn't wear in casual occasions, but typically for work).
  • A typical individual would easily possess between 1 to 5 of these 200gr meat steak shaped extensions and would wear one or two, 90% of the time.
  • For some cultural reasons (like natural life style or religious beliefs or obscure medical reasons), it wouldn't never be integrated as a non-removable part, and humans would value the fact to be able to remove these peripherals from time to time to enjoy life extension-less.
  • The location of extensions on your head could be of importance (visual processing is on the back of the brain, language in Broca's area).

3 Answers 3


I will only address a few points here, but I hope it will help:

First, a mass of neurons has functions by the virtue of its topology. If you buy "blanks" of neurons, I'm thinking you're imagining a group of neurons which will readily form synapses once they start being used by the brain. It will take time for that to happen. If the extension is non-neuronal (maybe digital, providing some specific functionality), then the area of the brain where you connected it will have to adjust itself. This area might or might not be able to discover the functions provided by the extension. Not sure you can help it consciously either.

When you wear a neuronal extension the first time, you'll have to "train" it to perform whatever function you want. Choosing the function you want it to perform is greatly dependent on where on the brain you're connecting it. Actually, that's probably the only thing that matters - you can't connect an extension to the back of your head and expect it to not be trained as a processor of visual information. Once you train an extension, you won't be able to use it anywhere else on the brain (unless you somehow reset it). Also expect the area of the brain to create quite an intimate relationship with its extension, and it might be difficult to attach another blank extension to the same are. Or worse, you might not be able to disconnect that extension without compromising the functionality of an entire area of your brain - the extension might become fully integrated, and not be an extension anymore!

Your brain will also change gradually with time, so if you're not wearing an extension for long enough, it might become incompatible, even if the extension itself has preserved its neuronal topology perfectly. Your brain is flexible all the time. And the extensions should also always be responsive of changes in the brain.

Your extensions will also be completely personal and 100% incompatible with anyone else's brain. This means that each person might value their extensions greatly, but anyone else couldn't care about them at all (unless through some advanced analysis in a lab).

Disconnecting an extension won't feel like anything. You would just stop feeling like you know whatever it was that the extension was providing, or you just stop thinking the thoughts that the extension was generating while connected to your brain. Basically, "extension connected" means some things happen, "extension disconnected" means certain things stop happening.

Though maybe your brain might eventually get used to disconnecting extensions and it will invent a feeling of "forgetting", specific for disconnecting an extension.

  • $\begingroup$ You are stressing important issues of this concept, this definitively helps. And you give a few insights on what it could be to connect or disconnect such device. To follow on your feeling of forgetting, I guess that you could notice with your organic brain that things happens and others don't upon removal... even if it will be probably difficult to pin-point precisely, and surely quite impossible to give an exhaustive list, but what these tasks could be like ? $\endgroup$
    – vaab
    Oct 3, 2015 at 15:54
  • 2
    $\begingroup$ @vaab Sure. (1) Better pattern recognition when extending your visual cortex, e.g. you just "notice" more subtle details that your eyes see, and faster (maybe better reaction time while driving). (2) Perfect pitch in music, which you didn't have. (3) Better spatial awareness, i.e. your mind is better at rebuilding the geometry of a city after exploring it, and you can trace paths faster through it. (4) Better empathy, even. Basically, every function of your mind that has an area dedicated to it on the cortex will somehow be improved. A brain function map would be a good source of inspiration. $\endgroup$
    – CamilB
    Oct 3, 2015 at 16:05
  • $\begingroup$ You can get quite creative with these extensions. Maybe you can bridge two areas of the brain which weren't supposed to be connected, and see what happens (someone in your story might conduct such an experiment). $\endgroup$
    – CamilB
    Oct 3, 2015 at 16:07
  • $\begingroup$ Google search of brain function maps. $\endgroup$
    – CamilB
    Oct 3, 2015 at 16:09

How would it be like removing or adding such a neuronal mass?

With your premises it won't be a dramatic change, since you aren't adding/removing the core parts of the brain. Adding shouldn't be bad at all, except for the additional effort that the brain should sustain to "map" the new extension. Since it's more or less an empty hard drive with computational power is up to you to decide which info it should keep and which "software" it should run to process these info.

On the other hand, when an extension is removed, the user should feel only some degraded cognitive functions. Imagine when you feel to know someone's name but you can't actually recall it? Same sensation, you know that you should remember it but you can't, no big deal, it's already part of our natural aging process. Another similar case is if you remove some mass that was trained to perform specific tasks, you correctly remember that you were able to do something but suddenly you can't. I don't think that by removing the extensions you could remove some basic skills, and as long as you don't it's not a big deal.

I don't really comprehend why people should occasionally remove the extensions sometimes but i guess that "religious" beliefs is enough to justify such a behave.

Actually, on a second tought, there's no need to rprovide specific justifications since "getting drunk" is usually considered a funny free time activity, and it basically consists in paying to have some "natural brain extension" bypassed for some time. :) In some hard cases you risk to have also some core functions bypassed, and this was proven to be source of really bad thing for you and for others. :(

Anyway, the main outcome would be to have unpleasant feeling because your processing metacognition kicks in, letting you know that something wrong happened. Probably with the habit to add and remove extensions this feeling could become less annoying.

These would be bought blank [...] They would take [...] time to produce a noticeable effect.

You won't have any technological means to help you storing a specific memory or ability inside an extension.

The best comparison that came to mind is to purchase a new laptop/mobile: you need some time to fill it with contents, and these contents can't be your abilities or your real memory. You usually have the device with you but for some reason sometimes you can't, and in these cases it could be really annoying (you need urgently to remember a phone number and to make a phone call, but you forgot your phone at home). Tanks to the extension (like a calculator) you got used to do complex calculation and you started to think yourself as a really fast person with math. When you have to remove the extension your math capabilities are not totally gone, but reduced a lot, and your metacognition starts telling you that you used to perform way better and this feeling sucks.

Knowing that it's only a matter of connecting and disconnecting extension you can rationalise ad keep this bad feeling under control or, as we usually do on holidays, you may want to remove some cognitive abilities to actually think less and just relax. So you won't forget the phone, you'll leave it at home on purpose just to avoid the stupid phone calls that you have to do every working day.

IMHO your extensions design seems to be perfectly usable and comfortable (so far).


From personal experience - it doesn't feel any different. Since the instrument you are measuring with is the one that has discontinuities, you have no internal basis for making a comparison.

However, you can indirectly observe that things that used to be easy are suddenly much more difficult or impossible. For example, a decade or so back I was one of those people you never play scrabble with. I'd regularly drop two three tiles and rake in 150 to 250 points. I can't do that today.


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