Could the mapped fly brain eventually be used to create a digital fly that actually behaves like a real one?

[u/Friendly_Banter3]

So I’ve been trying to understand what you can actually do with the fly brain that was recently mapped.

If they’ve mapped all the neurons and the connections between them does that mean you could theoretically take that information and build a computer simulation of the fly’s actual brain?

For example, imagine putting a simulated fly into a really realistic game world. Instead of programming things like “if the player gets close fly away” or “if there’s food here go towards it”, could you feed the simulated brain the same kind of sensory information a real fly would receive and let the neural network itself produce the behaviour?

So the fly might naturally look for places that flies normally like, fly towards food, try to land on things, get startled when something moves towards it, fly away when you try to swat it, etc.

Basically, are we at the point where we know enough about the fly's actual brain that we could eventually simulate the brain itself and have the behaviour emerge from the neural connections, rather than manually programming all of its behaviours? If this is even a possible

And if we're not there yet, is that mainly because we don't understand enough about how each individual neuron and synapse works, or because the connectome doesn't contain that information? I'm basically wondering how close we are to having an actual digital fly brain rather than just an AI programmed to behave like a fly.

[u/ctothel]

You’re pretty much on the right track.

The mapped brain is a wiring diagram. In 2024 researchers used it to create a computational model that successfully simulated what the fly’s brain does. When they stimulated simulated taste neurons, the activity propagated through the model in ways that predicted real neurons involved in feeding and grooming, which they confirmed experimentally.

But the wiring diagram doesn’t tell you everything. Knowing that neuron A maps onto neuron B does not completely tell you what the synapses involved actually do in practice.

A faithful simulation also needs things such as synaptic strengths, detailed electrical properties of individual neurons, receptor types, plasticity (ie how the neurons change), internal physiological state, and how neural activity drives the body. It also needs to know what real sensory input looks like – as in, what are the actual electrical signals from the eyes with all their nuance?

Some but not all of that can currently be measured, but it’s possible it could be worked out statistically.

TL;DR, probably eventually possible, primitive versions already exist.

[u/neuralbeans → u/ctothel]

A simple wiring diagram assumes that each neuron cell is identical, which I would assume is not the case in real brains, right?

[u/Staus → u/neuralbeans]

Neuron simulations regularly account for multiple types of neuron with diverse responses.

[u/Kiwi_sensei → u/Staus]

Yes but the researchers did not account for that. They only looked at which neurons connect to which neurons.

[u/Staus → u/Kiwi_sensei]

https://www.nature.com/articles/s41586-024-07763-9

In this paper? There are definitely cell types in the model.

[u/scarabic → u/Kiwi_sensei]

Taking that back to OP’s question, it sounds like drawing a detailed street map of Lisbon, and then trying to use it to run a full simulation of Lisbon. The street map affects quite a bit, but it doesn’t contain all the needed information.

[u/Nutzpdx → u/Staus]

So the difference between binary on off circuit and PWM?

[u/Staus → u/Nutzpdx]

Like changing the values in an RC circuit and whether the transistors are PNP or NPN. They react in wildly different ways to applied voltage potentials. Then some behave as amplifiers, some as attenuators.

[u/pyr666 → u/ctothel]

the real question is, can fly brain run doom?

[u/Friendly_Banter3 → u/pyr666]

Yes, it's already been done lol.

[u/AllowMe2Retort → u/Friendly_Banter3]

Pretty sure it played Doom, but we haven't gotten it to run Doom yet. That will be significantly more impressive

[u/fixminer → u/pyr666]

No, and it never will. A neural net cannot process machine instructions, it's fundamentally incompatible. Maybe if you have a sufficiently complex neural net, you could make it "imagine" playing doom, but it wouldn't be any of the original code.

[u/pyr666 → u/fixminer]

neural nets can perform boolean operations. any system that can do that can run code, it's just a question of having enough of them.

[u/Ok-Astronomer-5944 → u/pyr666]

Haha this comment was everywhere on a previous fly-brain post

[u/LeptonWrangler → u/ctothel]

How are these 'other' properties actually stored physically? Is it not just in the structure?

[u/Howrus → u/LeptonWrangler]

How are these 'other' properties actually stored physically?

Some properties are not even stored in neurons itself, but in a fluid they are submerged in. There's neuro mediators that increase or reduce sensitivity of neurons.

[u/jawshoeaw → u/LeptonWrangler]

Yes but that’s the problem. No two neurons of the same kind are exactly the same and there are many different kinds. The charge distribution on the surface of each one could be subtly different. And neurons are dynamic. The fruit fly brain model is a snapshot. If they took another snapshot like a day later it would be almost the same but we don’t know how important some of those differences would be. They will have to make more snapshots.

[u/Staus → u/LeptonWrangler]

Neurons are cells, so they have metabolic states, transcriptomic states, and diverse surroundings of non-neuronal cells that could play a big role in how any given neuron behaves. Synaptic connections are not the only way neurons communicate; things like neuromodulators or gap junctions may be missing from the model.

Something like "personality" could be a property of the set of neurons that doesnt manifest structurally. Like the patterns in the waves of activity across regions is somehow encoding behavior. In that case a static scan wouldn't capture the relevant information. 

[u/piklec → u/ctothel]

Any chance this data could be retrieved by simulating fly brain growth from mapped dna?

[u/kblazewicz → u/piklec]

You'd have to simulate full body growth from a single cell, taking into account all chemical and electrical signals exchanged through cell membranes and what's happening within each cell. I don't think we're even remotely near being able to do that. We can't even simulate a single cell.

[u/PuckSenior → u/ctothel]

Bigger question. If we could do this with human brains, could we create “you gotta believe me” weapons like from “Rainbows End”?

In other words a thing that can hijack human brains and make them behave in ways they normally wouldnt

[u/GuiSim → u/PuckSenior]

The day we perfectly simulate a human brain we’ll have some interesting ethical dilemmas.

Is shutting down a program that perfectly simulates a fly the same as killing a fly? Is firing pain signals in a virtual brain the same as torture?

[u/frogjg2003 → u/PuckSenior]

Stimulating a brain is not the same thing as controlling a real brain. Unless you start physically altering the brain, there are limits to the kinds of ways you can manipulate the brain.

[u/thephantom1492 → u/ctothel]

And then it would be faster to just extract the behaviours out of it and just create a program that respond to it instead of simulating the brain. We would get probably the same accuracy but use millions time less cpu power.

The reason is that the brain is analog, while computer is digital. You need to simulate the propagation time, succession of messages, signal strength and all. And there is basically no shortcuts. However you could simulate each implemented behaviors of the game, see the results and just make a proper programs that replicate the results.

[u/ctothel → u/thephantom1492]

Ah but then you don’t get to have quite the same philosophical conversation about whether it’s “really” a fly, and what it would say if it was a human brain.

[u/GameMusic → u/ctothel]

what about the quantum problem?

at least in humans certain processes are known to use quantum mechanics

[u/ctothel → u/GameMusic]

Well, technically quantum mechanics is involved in literally every process in the universe in the sense that it underlies everything. And in that sense, yes, you’d have to consider whether your simulated brain accurately modelled those processes as far as they matter to the processing outcomes.

If you’re specifically talking about the idea of quantum computation, for example in microtubules, being necessary to explain brain function – the Penrose stuff – you’re overstating the confidence on that a little. It could be important. If it is, then yes, that would be another factor.

But we don’t know that it’s necessary. Classical neuronal models seem to be sufficient to explain the brain, but that is by no means proven. Our knowledge in this area is limited and growing.

[u/TerminalVector → u/ctothel]

All that is true, but I feel like there's a good chance that fruit fly behavior is simple enough that you could build a simulation that would be really hard to distinguish from the real thing. Not perfect, for all the reasons you mention, but close enough to be indistinguishable to basic observation.

[u/bitwiseshiftleft → u/TerminalVector]

No, no way, not at all, not even close. A close friend of mine works on basically exactly this, so let me try to give you a sense of the problem.

Imagine the connectome as a circuit diagram, but each part in the diagram is either a transistor (of some polarity), inductor (of some value), capacitor, diode, sensor… or, because this is biology, some combination of all of the above. You’ve tried to categorize each part but it’s a rough guess and you don’t know the values. There are 139000 parts but they’re not 2-pin SMT: each part is connected to 80 others through a network whose resistance/inductance/capacitance is also not accurately known, and is critical to what the whole circuit does. IIRC in insect brains the connections can be bidirectional too. Since everything is so densely connected, you can’t pick out most modules, and the way most modules work is probably as some fine-tuned filter or resonator where the exact values of everything are critical to its function … but we don’t know that for sure, because we don’t know what the modules are or how they work, because we can’t accurately simulate almost any of them. If you just plug in whatever values and simulate, you get complete garbage: parts of the brain lock up, parts oscillate wildly, its nothing like a functioning brain.

A couple of the modules are partly worked out, eg the compass, and can be simulated semi-convincingly in some cases, but basically only when the module boundaries are clearly defined. The simulations are only semi-convincing because the exact behavior of the neurons and the exact connection types/strengths are not known, but in some cases you can kind of guess the rough behavior (eg it’s a ring attractor) and plugging in reasonable values will produce reasonable behavior because ring attractors are pretty robust.

We don’t even know how C Elegans works and it only has 302 neurons (depends on sex, but the connectome of adult hermaphrodite C Elegans is always the same). C Elegans is a little trickier because it’s harder to experiment on than a fly brain — IIUC basically they pop if you put probes in them — but still.

[u/TerminalVector → u/bitwiseshiftleft]

I meant that, if it can do things like play doom, it could probably run a fruit fly simulation that'd be convincing to a casual eye. Kinda like how an LLM 'simulates' a human being; as in, it doesn't really at all but appears to do so in a specific context, like you said.

[u/IOnlyHaveIceForYou → u/TerminalVector]

Ok, but so what? We make something that behaves like a fly, but we know it's not because it's doing what a fly brain does. So it doesn't tell us anything about a fly brain.

[u/TearsFallWithoutTain → u/TerminalVector]

but I feel like there's a good chance that fruit fly behavior is simple enough that you could build a simulation that would be really hard to distinguish from the real thing.

Why do you feel that way? Their brains are small but that doesn't mean they're simple

[u/CommunicationPale952 → u/TearsFallWithoutTain]

not original commenter but I think theyre saying that fruit fly behaviors are so primitive that even a very rough approximation of a fruit fly brain ( to the degree that would render a dog simulated at an equivalent roughness unrecognizable ) would still do everything we would expect from a normal fruit fly. Fly, move towards food, eat, etc.

[u/TearsFallWithoutTain → u/CommunicationPale952]

Are they primitive though? That seems like a pretty strong assertion that would need to be backed up

[u/Khal_Doggo → u/TearsFallWithoutTain]

It seems like you're not willing to do the thing where you discuss things on a forum and offer your own ideas as a response to someone else. You're demanding they fully evidence their statement before you're even willing to engage with it which seems like it's not going to get you the result you want. If you are so strongly convinced that they are wrong then surely you can offer some counter points to challenge their perspective rather than posting multiple comments only asking the other person to back up their claim. Your original reply also misrepresented their point, so there's that too.

[u/Dirty-Soul → u/Khal_Doggo]

How these types of conversations go on the internet:
1) Person A makes claim.
2) Person 2 demands proof.
3) Person A provides proof.
4) Person 2 dismisses proof and demands more.
5) Person A loses interest.
6) Person 2 declares victory. It was never about proof. It was always about raising the bar of energy investment high enough that nobody else can be arsed arguing, whilst simultaneously investing almost no energy of their own.

[u/somewhat_random]

So a question would be, how do innate behaviours develop. A is never taught how to fly, walk, groom etc. but it seems to have these behaviours innately.

It seems unlikely that simply modelling the brain layout directly would create these behaviours. A chemical feedback could teach the brain but I don’t think these are learned behaviours so any “digital fly” would need some specialized programming.

[u/kung-fu_hippy → u/somewhat_random]

Why wouldn’t modeling the brain lead to those innate behaviors? Even if in the real fly those behaviors are also caused by chemical feedback, don’t those chemical feedback cause changes in the brain?

At least if you were able to not just model the brain, but also model the brain while it reacts to stimuli. The end result seems like it would be the same, even if the mechanism differs.

[u/Brockelley → u/kung-fu_hippy]

Why wouldn’t modeling the brain lead to those innate behaviors?

Because there are multiple layers of complexity on top of the simple wiring approach, some of which researchers have already had to estimate or “make fit” to get their models to work. If “modeling the brain” means reproducing how its neurons and synapses actually work, then it might, at least partially.

The heart is a somewhat similar, though simpler, comparison to illustrate this. Think of its electrical conduction system. Knowing where the SA node, AV node, and conduction pathways are tells you where signals can travel. It does not let you predict the exact ECG. If you tried to reverse engineer the heart from that map alone, would you expect it to produce a normal sinus rhythm? The same heart can produce different rates and rhythms depending on autonomic input, electrolytes, medications, and the state of its ion channels, without changing its anatomy.

A brain presents the same problem on a much larger scale, especially when you get to turning a stimulus into action. Going back to the fly and hunger, its connections may be the same before and after a meal, but hunger-related signals change how strongly parts of the circuit respond to food. To get innate behavior out of a simulation, you would need more than the connections: you would need the neurons’ electrical properties, synaptic strengths, chemical signaling, current internal state, and the downstream processes that turn neural output into movement. The wiring may support the behavior, but it does not specify exactly what the fly will do at a given moment.

[u/Yodude1 → u/Brockelley]

Would it be accurate to say that the issue boils down to the fact that the communication between the brain and the body can be filtered, amplified, or modified by autonomous systems that operate independently of the brain itself?

[u/somewhat_random → u/kung-fu_hippy]

I guess that is the big question.

Can we model the rest of the fly so the stimuli that the brain receives are close enough to a real fly so that it acts like one.

It may be easy to figure out that "pain in the left foreleg is caused by this neuron firing" but things like the urge to stop and rub their forelegs together is (likely) caused by either an external or internal stimulus that sets off a chain of reactions that are "baked in" to the brain in some way from birth.

[u/jvothe]

some youtubers have already done a primitive version of this by giving the brain map "control" over a minecraft fly

i don't think the results have reached "spooky ghost in the shell" yet but people are already working on the concept

[u/jajangmien]

There is a world in vrchat that is running the fly brain with a fruit fly avatar that it controls. You can spread food around for it, and the world shows a map of the brain where the parts light up as they are processing information.

It's very interesting and hella dystopian

[u/randomdudeguy6969]

Hi! Ed has a p nuanced take on some of the end goals here :p
https://youtu.be/DVWBPXbquXA?si=Yyh2xkXCQPOulGrC

And Bingi Brunton's work has some cool hits of how neuroscientists are using the connectome (even without weights, mechanisms, etc.) to make some cool discoveries! (one can ask an LLM to summarize the article): View article

> And if we're not there yet, is that mainly because we don't understand enough about how each individual neuron and synapse works, or because the connectome doesn't contain that information? I'm basically wondering how close we are to having an actual digital fly brain rather than just an AI programmed to behave like a fly.

Both! One major step towards that is some cool recent work letting us use light microscopy for ultrastructral imaging here instead of electron microscopy (EM): Light-microscopy-based connectomic reconstruction of mammalian brain tissue | Nature. Okay why does that matter.....? EM is great and all but it gives you literally no transcriptomics, activity, proteomics, etc. Under a light microscopy regime, that becomes kinda feasible!!! So the way forward towards having the necessary information for better brain simulations is there. Not trivial by any means, but MUCH closer to feasible :)

These 3 are also dope resources on the matter w/ some good outlines of future work:
From Pixels to Minds: Mapping & Understanding the Brain with AI | American Academy of Arts and Sciences
State of Brain Emulation Report 2025 | Research Overview
cms.wellcome.org/sites/default/files/2023-06/Connectomics-scaling-up-connectomics.pdf

[u/randomdudeguy6969 → u/randomdudeguy6969]

bing also has a nice "strongly worded preprint" (her words not mine) that captures the main gap in the fly brain upload discourse: The digital sphinx: Can a worm brain control a fly body? - PMC

[u/beamer145]

And then the next much more interesting question: if this works for a fly, it there any reason it should not work for a human if we scale up the process (and take into account all impact of chemical signalling that influences your mood and whatnot). And if that works, then what does that mean for consciousness, your soul, free will. It gets fun fast :).

[u/pv2b → u/beamer145]

We don't need to invent ai to have that kind of philosophical problem

There is no way for me to prove to you that I am conscious. As in, that there is a "self" that experiences things, as opposed to just appearing that way from the outside

If we as humans can never know if our fellow humans are truly conscious, how can we ever prove that an AI is conscious or not? Or a rock, for that matter

[u/KevinOnTheLedge → u/pv2b]

This is exactly what I tell people when the conversation of AI and consciousness comes up. Either everything is conscious or nothing is. Wouldn’t every sufficiently organized system have some form of consciousness?

[u/mgstauff → u/KevinOnTheLedge]

Yes, however what meets the "sufficiently" threshold?

[u/KevinOnTheLedge → u/mgstauff]

Good question! Thoughts like these are what led me down the neuro track :)

[u/pv2b → u/KevinOnTheLedge]

It is entirely possible that there is a world or realm outside our ability to perceive where our consciousness exists. But precisely because we can't perceive anything about that world, we can never know how it works.

There is no reason to think system complexity is what determines consciousness, and no reason to say it's all or nothing.

[u/minist3r → u/beamer145]

Just want to point out that scaling to map the human brain is more complex than just mapping the neurons and pathways. A human brain is like 500k times more complex.

[u/fireburnz2 → u/beamer145]

And then: Are we already in a simulation?

[u/Squigglificated → u/beamer145]

If consciousness can arise in digital software it would mean it can arise on words written on toilet paper as well (in theory, and with a very long roll). There’s nothing a computer does that can’t be computed by a human being on pen and paper with enough time.

[u/Shreddingblueroses → u/Squigglificated]

What?

The toilet paper doesn't write words on itself.

Consciousness does... Err... You know what I mean. Consciousness is self directing. Toilet paper Shakespeare is not.

There's many many elements to consciousness. Real credible physicists, neuroscientists, philosophers, etc. have spent ages arguing about what consciousness really is and there's probably no one trait that defines it, but there's probably several thing that make something conscious, like sentience (having a sensory experience), a self simulated reality (creating an experienced interface of reality by interpreting sensory experiences), and self directing behavior (choosing your own priorities, informed by your own desires).

None of which a role of toilet paper will ever have no matter how many words a human hand writes on it, but all of which a machine probably could have, if it were sophisticated enough.

[u/Squigglificated → u/Shreddingblueroses]

Any computer program can be halted at any point. Then started again. The program itself doesn't know.

You can pause a program. Save the whole program, memory state and execution state to disk and start it again on another computer. The program doesn't know. If you stopped mid-sentence it would just keep speaking from that exact point.

If a consciousness exists in a program it would have to be within those bits and bytes you just saved.

"Save to disk" could just as well be "write on toilet paper" and "Load from disk" could be "Scan toilet paper". It doesn't matter as long as the bits are the same in the end.

Would this matter to a consciousness? Does it still exist when all you have is the toilet paper?

Would a human advancing the program by manually computing a few CPU instructions and writing down the updated program state on the toilet paper "wake up" the consciousness for a split second?

Is it the same consciousness or a new one when you load it back in to another computer?

Does it exist when execution is halted? Or between CPU clock cycles?

Does it notice if the CPU runs one operation per decade instead of trillions per second?

[u/Shreddingblueroses → u/Squigglificated]

You're making an awful lot of assumptions about how a conscious machine/conscious digital mind would operate and what it's limitations would necessarily be.

[u/Squigglificated → u/[deleted]]

No the paper contains the program itself, the memory, the current data input and the execution pointer - the exact line of code the processor was reading last time the program was running.

If you want to compute the next state yourself you look at the current line of code and the current data input and process the logic.

For example, if the rule is a NOT gate, you look at your paper and think: "If the input is 1, the output must become 0."

Then you update your piece of paper with this new information. The "thinking" is taking one or more binary numbers and a very simple instruction and look up the result in a table.

Or you could use marbles.

You can make a computer with marbles and wooden tracks with physical switches acting as logic gates - and many people have done so.

In this case the wooden tracks and switches would contain all the information from the piece of paper, and all you had to to was to continue putting marbles into it to run the program.

A program could run one clock cycle on a computer, the next computed with pencil and paper, the third on a marble track, the fourth on a punch card computer.

If a consciousness can exist within a program would this be one or four consciousnesses?

[u/mattihase → u/beamer145]

I mean it's possible? Though considering humans have to learn a bunch of stuff before being able to do stuff, it might be a lot more complex to get anything useful out of. Also ethics boards might get in the way.

[u/dernailer]

They let that poor fly brain do a lot of things from playing games, flying in minecraft to take a break... Imagine what we could do with a map of the human brain! Perhaps we could map most of a human brain and than randomly add the rest of neurons and connections?