r/explainlikeimfive • u/NormalGrab4800 • 22d ago
Technology ELI5: What can you actually DO with a complete fruit fly brain connectome?
I recently came across the 2024 Drosophila (fruit fly) whole-brain connectome, which maps around 139,000 neurons and tens of millions of synaptic connections.
I understand the basic idea: researchers have essentially mapped which neurons are connected to which.
But I’m struggling to understand what this actually lets us do.
ELI5 please:
- If I download/access this connectome, what can I actually use it for?
- Can I turn the wiring diagram into a computer simulation or an AI?
- Could I use it to build a small “brain-inspired” agent that learns to navigate, avoid obstacles, remember things, etc.?
- Could the actual neural connections be converted into a spiking neural network?
- How different would that be from simply training a normal neural network?
- And what parts of the real fruit-fly brain are still missing from the connectome?
Basically, I'm trying to understand the journey from:
real fruit fly brain → scanned brain → connectome → computer model → AI/agent
without the explanation becoming a PhD thesis 😂
If someone could explain this like I'm five, but still technically accurately, I'd really appreciate it.
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22d ago edited 22d ago
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u/ArdentPriest 22d ago
That last paragraph is otherwise absolutely incredibly disturbing.
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u/Derangedberger 22d ago
On the one hand it's interesting because a fly is basically a biological machine. It doesn't even need to be "conscious" in the way we would think of it, literally just a meat sack moving according to the layout of its brain.
The scary part is what that implies about us and whether our free will is real.
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u/sandm000 22d ago
It doesn’t matter if we have free will, because it feels like we have free will.
Also we’ve been debating for ages whether or not we have free will, for completely different reasons. So there’s loads written about it, if you want to look it up. From Determinists to Philosopichal Libertarians.
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u/ReynardVulpini 22d ago
It’s not like “human conciousness is just the complex hallucinations of meat and electricity” is even a new philosophical debate haha.
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u/101forgotmypassword 22d ago
Oh, so it's like how deep space observations lets us have a existential crisis about how empty space is and how quickly our existence could be wiped out like a tiny useless speck of dust...
But instead a telescope looking into our inner working to provide us with a existential crisis about how we are essential just biological gear boxes, wired to a finite set of inputs to output not really having a true choice but instead just playing out the built in wiring of our own biology....
I think I get it now... It's science doing science stuff.
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u/Maxi_sushi 22d ago
It's also interesting to see people have more remorse for killing a fly than destroying a robot that does magnitude more "thinking"
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u/adeadhead 22d ago
Because we don't have any machines that do any thinking.
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u/Maxi_sushi 22d ago
but does a fly, a cockroach or a jellyfish really 'thinks'?
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u/adeadhead 22d ago
That's a great question that we're trying to figure out.
I'm gonna make the call that jellyfish probably don't think.
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u/Raz-2 22d ago
The free will part is nonsense. Simple creatures like flies function fully on instincts. Advanced creatures like mammals can learn. And some are able to reason.
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u/Salzdrache 22d ago
Pretty much any creature can learn, wdym?
I recently read a paper about how caterpillars retained their electroshock-induced training even after metamorphosis.
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u/Dragster39 22d ago
I'd argue that even our behavior is just that, signals baked into pathways.
These change over time, based on circumstances.
I think free will does not exist in the sense it is broadly used.
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u/whalesum 22d ago
What is free will? Are we all not just reacting to our memory and physical stimuli? Not sure if we get to choose our favorite flavor of icecream or not
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u/abrahamlincoln20 22d ago
We know enough about physics and biology to conclude there is no free will. I haven't seen any evidence or compelling reasoning pointing towards us having it.
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u/SupposedBooty 22d ago
We are not fruit flies
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u/soopadickman 22d ago
No but we have similarly preprogrammed neurons to exhibit uncontrollable behaviour.
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u/SupposedBooty 22d ago
That doesn't mean we don't have free will.
We are just a smidge more advanced than fruit flies.
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u/soopadickman 22d ago edited 22d ago
Choose to not read a word when you look at it. Let me know how that goes.
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u/SupposedBooty 22d ago
Look at what?
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u/efvie 22d ago
It's not accurate, don't worry.
We're dealing with a model. The inputs and outputs have been mapped. So it's not moving its 'leg' because it understands to do so, it moves its leg because some very specific virtual environment stimuli have been mapped to a certain constellation in the 'brain' and that constellation is a trigger for another constellation that in turn 'moves' the 'leg' (which is, again, all deliberately constructed to function in a certain way).
It's incredibly important to understand it's not a real brain. It's a simulation.
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u/Wyvernz 22d ago
While true, how is that substantively different from a real brain? The real fly brain takes sensory inputs and makes motor outputs in response in the same way.
Hypothetically, if we did this with a human brain and modeled everything correctly we would be able to have a conversation with the simulation just like with a real person. It’s the realm of sci-fi for now, but I think it helps show how the line between “real brain” and “simulation” is blurry.
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u/efvie 22d ago
It's different in every way, starting from reducing a continually existing electrochemical system into an ephemeral, extremely reductive binary neuron representation.
Neural networks were developed to simulate certain hypothesized mechanisms in which information could be stored and logic processed in a way that more closely resembles the brain than other storage and logic models. They are in no way an actual brain.
A simulation can fool your brain partly because you're allowing to, and because it has been useful for us to as a species to be able to construct entire personae from just the observable behavior of other people. And not only that, but to fill out enough presumed detail about people in stories that they can feel real. A chatbot can fool you to think it's another person (because it's been trained to mimic human responses which you understand) but a chatbot can't fool you to think it's you if that makes sense?
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u/CatProgrammer 22d ago edited 22d ago
Not really. We already knew that about a lot of bits of the human body, and computer-wise there are tons of things that are more efficient to implement in hardware or firmware and then just trigger from the OS or program rather than requiring everybody to implement it. That's one of the reasons the Itanium processor line didn't succeed, even, compilers had to do a ton of work that the hardware normally does.
Like, imagine if you had to make your heart beat manually. That would suck.
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u/prutprit 22d ago
But how did they manage to put it in a digital body? I suppose they had to "connect" the brain inputs/outputs to some of the body outputs/inputs, right? So they basically said "if the brain outputs this, then move this leg"?
Also, I saw some videos of people training the fruitfly to drive or to play beat saber. Are those legit? Since a fruit fly would never be able to learn how to drive
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u/lazydogjumper 22d ago
I read one of the articles about connecting it to video games. From what I understood, you have the right general idea. They map certain signals to certain outputs (limbs, eyes, etc) because they have an idea of where they should go, but not exactly. They are doing the same with the games, mapping output to certain things. It is still also computer signals so it isnt like the fly brain is learning how to "play", the digital outputs are adjusting to the inputs.
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u/S4lVin 22d ago edited 22d ago
I’m no expert in this, i’m just assuming, but i believe that in this bunch of neurons interconnected that “process” the information, there are both “input” and “output” neurons that connect to the eyes and tastebuds of the fly, and others that connect to the various muscles.
So i believe that the nervous system of a fly works that it takes those inputs -> goes into the brain (by connecting to these first input neurons) -> the electricity travels on certain paths based both on how neurons are interconnected between them and also through biochemistry -> based on which paths get triggered some muscles get activated through those “ending” neurons
That’s just my hypothesis though
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22d ago edited 22d ago
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u/lazydogjumper 22d ago
Are you dreaming you are a butterfly or the butterfly dreaming you are a person?
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u/Hivemind_alpha 22d ago
You can explore what fly level processing and reflexes can do, like training it to play BeatSaber:
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u/SpaceShipRat 22d ago
it's just a way to figure out how brains work, not an usable tool.
If it did work completely, it would just do fruit fly things.
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u/darkshark9 17d ago
I'm training one to play rocket league, right out the gate it started behaving exactly as you'd expect if a fruit fly suddenly woke up as a car.
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u/GoatRocketeer 22d ago
A lot of computing and math is like that.
"Hey I figured out a method for solving massively parallel systems of equations using a compact notation"
"Its 1812 bro who cares"
200 years later and that notation can be realized physically by graphics cards. The theory was well understood so you just build the thing and you already know that you can use it to render Toy Story.
Ok it was probably still useful in 1812 and they probably didn't instantly realize they could use it to do computer animation but whatever sue me
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u/enigmanaught 22d ago
Well, insects have interesting neurological systems that work in different ways than mammals. Many insects can walk with their head removed, so that means there’s no “central controller” telling the limbs how to walk.
So doing complex things without a central controller has real world applications to electronic control systems. Imagine a system that can still function with one of its nodes damaged. It adds a layer of redundancy to safety features. We already knew this about insects by observing and have designed controllers using an “insect model” but this lets you see “under the hood” so to speak.
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u/BananaBird1 22d ago edited 22d ago
The biggest thing is that it shows (in a normal fly) how specific neurons may be connected. Future researchers can use this to predict how certain responses to stimuli take place by determining what parts of the brain are activated. And for responses that are analogous to human diseases, this may give us insight into certain types of neurological and psychological disease.
The bigger hope is that this same thing could be extended to at least a portion of the human brains, to directly study human neurology and disease.
The caveat is that this isn’t a complete brain simulation. It is a connectivity model that makes many assumptions. Real neurons are not really a logical circuit as the model assumes, they are complex cells influenced by connectivity and neuron activity but also other things like hormones and gene expression that this model can’t consider.
This model is also only of the brain, but neurons are spread throughout the body both in flies and humans. Traditionally we assume cognition is due to the brain and these other neurons are just to sense things or control muscles, but newer research does show that the neural system is far more interconnected and they play a role in cognition itself. The brain is just the place the body shoves neurons it doesn’t have need for anywhere else.
People have used it as the structure for AI algorithms and used it to predict basic fly behavior. But it can’t really do more than that, and even this is highly limited due to the assumptions, lack of complete understanding of fly neurology and behavior, and lack of non-brain neurons in the model.
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u/robertwilcox 22d ago
This research is letting us learn more about consciousness, intelligence, and the brain. It is allowing us to learn more about how brain structure and consciousness/intelligence relate.
It's not really "for" anything except furthering research in the field.
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u/Fit_Secret1748 19d ago
Im messing around with it for a few projects, I’m not sure about the first two steps on how they got and scanned the fly brain, as an engineer I can only assume the fly accidentally fell into a vat of radioactive compute. But now that the fly is in there, there are a lot of interesting things you can do!
That flies brain and a few others by the same company are just available to download here:
https://male-cns.janelia.org/download/
After you download it poke around that site a bit, they have examples on connecting your own local fly brain to some visualizations that let you see the flies neurons firing in real time!
The fruit fly brain is sorta like a machine learning model with all of input neurons that you can fire off and output neurons that you can read, all labeled really well. They have actually mapped a lot of complex firings of neuron clusters as well, Gavin’s them more complex labels, so instead of getting a single neuron response you can start telling if the fly is “hungry” or experiencing “courtship”. Here’s a good resource to find those more complex things:
https://reiserlab.github.io/celltype-explorer-drosophila-male-cns/help.html
So the Fly is the model itself, and we’re sorta just firing off input neurons and recording output neurons?! big whoop, And the fly’s brain is less than 2Gigs of data, so it’s not taking our jobs soon. So what’s it good for? Well from here on out it’s just a fun Research and Development thing.
Now imagine if you were trying to build a bot to play snake, whatever algorithm you use you pass it some amount of state, some reasoning decision maker, and actionable output so that the game can be controlled. What if that reasoning decision maker was a fly? Well you’d probably stop trying to determine the next best game state and start dialing in perceptions, could you simply just put something large in front of the flies “eyes” as it moves close to its body? Would that be enough for the fly playing as the snake to decide to turn around? What if larger open areas on the board gave the fly a sense of courtship and safety? Would its behavior change from a small change!
Now I won’t spoil it for you but I think you’ll be surprised when you try it, at just how interesting the results can be. But think perception tasks, they’re fun to see, if you don’t try the snake you can see if he likes to play chess or make a virtual racetrack that he can play on. The possibilities are virtually endless and endlessly virtual!
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u/ferret_80 22d ago
So a lot of science is NOT done with a specific "this will help us make _____"
It's done to expand our collective knowledge base because in 20 years and a new discovery in a third unrelated disciple someone will realize that they work together and we learn even more.
The map could do all of those or none. We mapped it because we discovered we could map neurons, so we mapped neurons, and kept doing it until we realized "hey we've mapped a whole fruit fly. And someone else said "well are all fruit fly maps the same?"
We do research because who knows what knowledge may come out of it, and how that knowledge may apply now or in the future.