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Map of an Insect’s Brain

smithsonianmag.com

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Re: Map of an Insect’s Brain

#71

Post by groestl »

lossolo wrote: post #63
epgui wrote: post #56

Earlier quoted context omitted.

I'm a biochemist, and I somewhat disagree with this take. Yes, it's true that modelling just a single cell's interactions with its environments is beyond our capacity. But here we're talking about simulating how a brain reacts to signals at a higher level of abstraction: we're studying an "emergent" phenomenon. We don't need to model molecular interactions, and we absolutely can model this using artificial neural net…

I specifically used "relevant interactions" to rule out "modelling just a single cell's interactions with its environments" but who knows how deep you need to go to have an accurate model. > we're studying an "emergent" phenomenon It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer. But still at abstract layer we just do not have a model of a wo…

> It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer.

Sounds more like they're saying: a knee is a knee, it doesn't have any magical properties. Build something that bends, and it will behave like a knee. I don't know how true that is, obviously.

Re: Map of an Insect’s Brain

#73

Post by actionfromafar »

groestl wrote: post #71
lossolo wrote: post #63

Earlier quoted context omitted.

I specifically used "relevant interactions" to rule out "modelling just a single cell's interactions with its environments" but who knows how deep you need to go to have an accurate model. > we're studying an "emergent" phenomenon It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer. But still at abstract layer we just do not have a model of a wo…

> It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer. Sounds more like they're saying: a knee is a knee, it doesn't have any magical properties. Build something that bends, and it will behave like a knee. I don't know how true that is, obviously.

It's not totally true even for knees. Artificial replacement knees aren't as good as original knees.

Re: Map of an Insect’s Brain

#74

Post by cyberax »

Groxx wrote: post #46
yyyk wrote: post #8

Earlier quoted context omitted.

>Is it simulated to the level where you could give it some visual stimulus and observe the actions it is trying to take? No way. First, this mapping doesn't tell us how the synapses are regulated - if we could 'run' this the weights would stay fixed forever and that's not how a brain works. Second, there must be some neurons dedicated to chemical management, and they'd go haywire unless you found a way to deal with t…

For some more context / concrete links: there are ongoing efforts to simulate the C. elegans worm, e.g. https://openworm.org/ , which has ~300 neurons. The actual precision of this model is: nobody knows, because nobody knows precisely what neurons do / what they react to. We know some of it but definitely not all. But, simulating what we do know, you get quite worm-like behavior, despite whatever flaws exist. To get…

OpenWorm is a bad model. To give a computer analogy, you're simulating highly optimized low-level code for Apple ][. That uses all the little hardware-specific tricks and timings to work.

A fruit fly brain is a better model to simulate in this regard. It's much more "generic", so there's a hope that we can recapture high-level behavior from it more easily.

Re: Map of an Insect’s Brain

#75

Post by toss1 »

epgui wrote: post #59
coldtea wrote: post #47

Earlier quoted context omitted.

I think you underestimating the problem. There's no way to even capture and record "observed behavior" at the required level atm...

I'm a biochemist and I think you're under-estimating how sophisticated fruit fly behaviour studies are.

Seems two different things are being discussed, sort of top-down, vs bottom-up modelling.

I'm sure we're not far from making a high-level LLM-ish model of behavior based on those extensive studies.

But the topic of discussion is not that, but making a model sufficiently accurate that you "turn the crank" and it yields similar behavior without any priors of what that behavior should be.

To do that, at a minimum, we'd need for each neuron, the profile of responses to each of the neurotransmitters at each synapse, the excitatory/inhibitory effects of each signal, the patterns of how each neuron reacts to those inputs (i.e., receiving a signal from upstream neuron 489327 does not mean that it'll just pass it downstream, but that it'll decide depending on rate of firing, other current excitatory/inhibitory inputs, etc., if and at what rate it'll send the signal downstream), the rate of learning in each of those neurons... and a bunch of other variables, fully modeled.

Then, compute all of those running through the system, and have it take an input like a photo and output the same behavior, from the bottom up, without hints from the behavioral studies.

What am I missing here?

Re: Map of an Insect’s Brain

#76

Post by nicoburns »

actionfromafar wrote: post #73
groestl wrote: post #71

Earlier quoted context omitted.

> It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer. Sounds more like they're saying: a knee is a knee, it doesn't have any magical properties. Build something that bends, and it will behave like a knee. I don't know how true that is, obviously.

It's not totally true even for knees. Artificial replacement knees aren't as good as original knees.

I guess the point is that we might be able to simulate an artificial knee equivalent for neurons. It won’t be as good as a real knee, but it might still be useful.

Re: Map of an Insect’s Brain

#77

Post by epgui »

toss1 wrote: post #75
epgui wrote: post #59

Earlier quoted context omitted.

I'm a biochemist and I think you're under-estimating how sophisticated fruit fly behaviour studies are.

Seems two different things are being discussed, sort of top-down, vs bottom-up modelling. I'm sure we're not far from making a high-level LLM-ish model of behavior based on those extensive studies. But the topic of discussion is not that, but making a model sufficiently accurate that you "turn the crank" and it yields similar behavior without any priors of what that behavior should be. To do that, at a minimum, we'd…

Edit: I got confused and didn’t write this comment in the right place.

—-

I somewhat agree with how you described it as top-down vs bottom-up. I think it’s not exactly how I was framing it, but it’s close enough, and it’s a useful way to think of it.

Even in the rest of your comment you’re taking a bit more of a bottom-up approach relative to what I’m saying: you’d be surprised how much we know about how the brain’s gross organization leads to complex phenomena (pick up the latest edition of Blumenfeld’s clinical neuroanatomy if you want the very-high-level summary).

You can, in principle, achieve a “broadly correct” outcome by doing tissue-level modelling of NNs. It’s surprising how much of the brain is macro components, as opposed to micro, cell-level processing. (Of course I’m handwaving a lot here. I’m afraid anything short of a concrete demonstration is bound to be unsatisfying.)

Re: Map of an Insect’s Brain

#78

Post by anonymouskimmer »

epgui wrote: post #59
coldtea wrote: post #47

Earlier quoted context omitted.

I think you underestimating the problem. There's no way to even capture and record "observed behavior" at the required level atm...

I'm a biochemist and I think you're under-estimating how sophisticated fruit fly behaviour studies are.

What do you actually work on? I'm a synthetic biologist and know a hell of a lot about manipulating pieces of DNA. I know a bit about other branches of lab and academic biology. And I can remember some of the chemistry classes I've taken, usually a bit after the fact.

Are you saying this because you've spent time reading and/or researching fruit fly behavior studies? Or for some other reason?

Re: Map of an Insect’s Brain

#79

Post by anonymouskimmer »

toss1 wrote: post #75
epgui wrote: post #59

Earlier quoted context omitted.

I'm a biochemist and I think you're under-estimating how sophisticated fruit fly behaviour studies are.

Seems two different things are being discussed, sort of top-down, vs bottom-up modelling. I'm sure we're not far from making a high-level LLM-ish model of behavior based on those extensive studies. But the topic of discussion is not that, but making a model sufficiently accurate that you "turn the crank" and it yields similar behavior without any priors of what that behavior should be. To do that, at a minimum, we'd…

> But the topic of discussion is not that, but making a model sufficiently accurate that you "turn the crank" and it yields similar behavior without any priors of what that behavior should be.

Change the expression levels of some genes, alter an amino acid here or there, change the input parameters (e.g. make a phenotype that lacks the ability to feel pain), and you can end up with a neuron network that responds subtly, or grossly, differently than another. Put memory into the picture and responses can be learned. Fruit fly behavior permanently changes in response to serious injury, similar to the manner in which humans experience chronic pain. Sure, now this is something that can be modeled, but before the experiment it wouldn't have been modeled.

https://www.sciencedaily.com/releases/2019/07/190712120244.h...

> After the injury healed, they found the fly's other legs had become hypersensitive. "After the animal is hurt once badly, they are hypersensitive and try to protect themselves for the rest of their lives," said Associate Professor Neely. "That's kind of cool and intuitive."

> "The fly is receiving 'pain' messages from its body that then go through sensory neurons to the ventral nerve cord, the fly's version of our spinal cord. In this nerve cord are inhibitory neurons that act like a 'gate' to allow or block pain perception based on the context," Associate Professor Neely said. "After the injury, the injured nerve dumps all its cargo in the nerve cord and kills all the brakes, forever. Then the rest of the animal doesn't have brakes on its 'pain'. The 'pain' threshold changes and now they are hypervigilant."

Re: Map of an Insect’s Brain

#80

Post by epgui »

actionfromafar wrote: post #73
groestl wrote: post #71

Earlier quoted context omitted.

> It's like saying that mapping all cells in human organism to addresses in memory will give us emergent human inside computer. Sounds more like they're saying: a knee is a knee, it doesn't have any magical properties. Build something that bends, and it will behave like a knee. I don't know how true that is, obviously.

It's not totally true even for knees. Artificial replacement knees aren't as good as original knees.

I’d argue they’re better (in some ways), given that they’re “dead” material as opposed to functional tissue. Human knees don’t last nearly as long when the tissue is dead.
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