Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

An adult fruit fly brain has been mapped

economist.com

Post reply on HN
Print view View original

81–90 of 208 posts

Re: An adult fruit fly brain has been mapped

#81

Post by samatman »

criddell wrote: post #27
bhouston wrote: post #26

Earlier quoted context omitted.

It is useful. It is like getting a static map of the country's roads with no cars on it. You can not make it come alive with cars (activity), but you can infer where people need to drive but you don't know when and why they drive or what they are doing, but it is a major clue.

> It is like getting a static map of the country's roads with no cars on it. I was thinking it was more like giving somebody iPhone schematics and die shots of all the chips and then asking them to figure out how Portrait Mode works in the Camera app.

Sort of, but mostly not. The critical distinction is that, given better data (the instruction set, the source code or binary of the OS and camera app), the schematics and die shots aren't necessary or even useful.

It's unlikely that brains have an abstraction layer like that, so work like this is a necessary precondition to understanding the rest of how it works. That actual understanding may be elusive for quite some time to come, but without a connectome, forget it, no change.

Re: An adult fruit fly brain has been mapped

#82

Post by aithrowawaycomm »

nonameiguess wrote: post #78
aithrowawaycomm wrote: post #62

Earlier quoted context omitted.

Knowing what the individual neurons actually do. The connectome is like an electrical schematic but you don't even know which components are resistors, inductors, etc (let alone the resistances and inductances). The connectome for the C. elegans nematode was mapped in the 1980s and the OpenWorm project has successfully simulated all non-neuronal cells. But they are very far from simulating the brain abd it will take…

I'm frankly not sure it will ever be possible. Forget about observing the inside of a running neuron. In spite of how confidently people on the Internet will tell you their body fat percentage, in reality we can't even accurately measure that without killing you first.

I wouldn't say never, at least for C. elegans: there's been quite a bit of progress on imaging its brain, and it's plausible we'll have a fairly complete picture in a few decades: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7801769/

But the challenges are substantial, and these imaging techniques (mostly optical, not MRI/etc) depend on the simplicity of C. elegans: its brain is essentially a thin disk, with only 300 neurons in its entire nervous system, and it is surrounded by a transparent membrane. I am not sure how these techniques could possibly extend to something with a thick exoskeleton like Drosophila. And there are great difficulties keeping track of just the 300 neurons in a moving nematode with its own unique brain; it seems completely intractable with current tools to extend the complexity 50x, especially since fruit flies move far more rapidly and have far more individual variation.

Re: An adult fruit fly brain has been mapped

#84

Post by generuso »

bryan0 wrote: post #73
generuso wrote: post #43

Earlier quoted context omitted.

Unfortunately, not. We get the graph of the connections, but there are tons of essential parameters that are not captured. Such as the synaptic weights, the complex non-linear dynamics of the real neurons, their intricate modulation by various chemicals, etc. For example, after the connectome of the worm were finished, despite it being quite small, for many years it proved to be impossible to simulate the dynamics, b…

> after the connectome of the worm were finished, despite it being quite small, for many years it proved to be impossible to simulate the dynamics, because of so many unknown parameters. Apparently they have been able to simulate dynamics with the fruit fly connectome(?) [0]: > researchers used the connectome to create a computer model of the entire fruit-> fly brain, including all the connections between neurons. Th…

The researchers have taken a very simple idealized mathematical model of a neuron, assumed that all synaptic weights were the same, ignored modulation, ignored base level inhibitory inputs, and have shown that even in such a crude setting, for some important inputs (especially for a taste of sugar) the "logic" of how the inputs result in the activation of certain outputs still works, based on the connectome information alone.

This is certainly very cool. But as the authors themselves point out [1], much more work remains to be done to reproduce more subtle features of the dynamics of the system.

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

Re: An adult fruit fly brain has been mapped

#85

Post by Lonestar1440 »

A big reason for my imminent-AGI Skepticism is the fact that our understanding of the currently existing, Biological intelligence is so, so shallow.

We're here at "Systems level sketch of a fruit fly brain". It's incredible work! But as other comments detail, there is far more to the function of a fly brain than this "map". It's quite a long way from "Deep understanding of a Human Brain, to the point where we can begin engineering a replica".

Maybe we'll get lucky, and find that "Neural Network" techniques really are a pathway to Intelligence in a broad sense. But without some mechanistic understanding of Biological Intelligence, it seems no better than betting on the Numbers in roulette.

Re: An adult fruit fly brain has been mapped

#86

Post by twarge »

baanist wrote: post #16

Are all fruit fry brains the same? Does anyone know what has actually been mapped and why it would generalize from one fruit fly to the next?

Yes, they are apparently exactly the same, with exactly the same neurons and connections!

Happened to go for a walk with the corresponding author and made her repeat this fact for me.

Re: An adult fruit fly brain has been mapped

#87

Post by snorin »

samatman wrote: post #81
criddell wrote: post #27

Earlier quoted context omitted.

> It is like getting a static map of the country's roads with no cars on it. I was thinking it was more like giving somebody iPhone schematics and die shots of all the chips and then asking them to figure out how Portrait Mode works in the Camera app.

Sort of, but mostly not. The critical distinction is that, given better data (the instruction set, the source code or binary of the OS and camera app), the schematics and die shots aren't necessary or even useful. It's unlikely that brains have an abstraction layer like that, so work like this is a necessary precondition to understanding the rest of how it works. That actual understanding may be elusive for quite som…

Why exactly would it be unlikely?

Re: An adult fruit fly brain has been mapped

#88

Post by xandrius »

Animats wrote: post #36
rkp8000 wrote: post #29

Earlier quoted context omitted.

Connectome-adjacent neuroscientist here. Definitely not a dead end! But also definitely not the whole picture. One of the main open questions in neuroscience right now is how network structure, dynamics, and function are related in the brain. Connectomes provide tremendous insight into structure, but as mentioned this does not generically solve either the dynamics or function problem. For example, for many of these n…

How's Open Worm coming along? The connectome of C. Elegans has been known for years, and Open Worm tries to simulate it. [1] Not with enormous success. [1] https://openworm.org/assets/OpenWormPoster_Celegans_Glasgow_...

Like everything in science: we don't know until we know.

No need to treat research like a business.

Re: An adult fruit fly brain has been mapped

#89

Post by dekhn »

twarge wrote: post #86
baanist wrote: post #16

Are all fruit fry brains the same? Does anyone know what has actually been mapped and why it would generalize from one fruit fly to the next?

Yes, they are apparently exactly the same, with exactly the same neurons and connections! Happened to go for a walk with the corresponding author and made her repeat this fact for me.

I don't think that's correct- the nature article about the article says they don't, https://www.nature.com/articles/d41586-024-03190-y and drosophila are not eutelic (although I see that some insects do have "partial constancy"). Could you ask the author to clarify?

Looking in the paper more closely they say: """After matching, Schlegel et al.12 also compared our wiring diagram with the hemibrain where they overlap and showed that cell-type counts and strong connections were largely in agreement. This means that the combined effects of natural variability across individuals and ‘noise’ due to imperfect reconstruction tend to be modest, so our wiring diagram of a single brain should be useful for studying any wild-type Drosophila melanogaster individual. However, there are known differences between the brains of male and female flies46. In addition, principal neurons of the mushroom body, a brain structure required for olfactory learning and memory, show high variability12. Some mushroom body connectivity patterns have even been found to be near random47, although deviations from randomness have since been identified48. In short, Drosophila wiring diagrams are useful because of their stereotypy, yet also open the door to studies of connectome variation."""

i woudl expect the overall architecture to be the same, but not the cell identities or the connections. But as always, I'm happy to be shown wrong with facts.

Re: An adult fruit fly brain has been mapped

#90

Post by xandrius »

pepve wrote: post #70
keybored wrote: post #51

Earlier quoted context omitted.

Cartographers have mapped Scotland. [random scribe muses that] The whole world could be next.

Did a rough calculation, it would be more like Edinburgh. There's easily a century between the earliest accurate map of Edinburgh and the earliest accurate map of the world. And even at present, the accuracy of maps of Edinburgh is much greater than the accuracy of maps of the world. So yeah, the whole world could be next. But the person you're replying to has a point when they say significant improvements are needed…

We did map a handful of brains yet, the more we do the better we will get at it.

I don't understand all this rushing and skepticism when such amazing science is being done. It's not like some AI company marking claims to sell a product, it's some researchers trying to accomplish something. Yes, they should (and probably will) do it better but that's not the goal here.

If 3 million manual edits are still doable then it's ok. And when the manual step is not feasible, a jump in the tech will be required.

Post reply on HN