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An adult fruit fly brain has been mapped

economist.com

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Re: An adult fruit fly brain has been mapped

#41

Post by twojacobtwo »

IshKebab wrote: post #18
qafy wrote: post #15

"human brains could follow" feels like a few jumps ahead? a fruit fly has on the order of 100k neurons, a human brain has on the order of 100 billion neurons. that's 6 orders of magnitude larger. that's like saying "A map of San Francisco has been completed, the entire solar system could follow!"

Well assuming the same density it's "only" 100 times bigger in linear dimensions. Doesn't sound quite as crazy...

Isn't that just saying "if you take the cube root of the number, it's a smaller number"?

I don't mean to be facetious - I'm struggling to to see what other consideration this helps with.

Re: An adult fruit fly brain has been mapped

#43

Post by generuso »

fabiensanglard wrote: post #5

What does it mean "mapped". Does it mean we know what each nerve/axon does?

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, because of so many unknown parameters.

This was one of the criticisms that the opponents of connectomics have always brought up. "You spend a lot of money that could have been used for other research, but in the end you do not get a true insight into how the brain really works." For the researchers who thought that knowing all the connections was important, it was an uphill battle to overcome such attitudes.

But one has to start somewhere -- like a genome, the connectome is not the whole story, but it is a very important part of it, on which many other advances can be built up.

Re: An adult fruit fly brain has been mapped

#44

Post by inglor_cz »

qafy wrote: post #15

"human brains could follow" feels like a few jumps ahead? a fruit fly has on the order of 100k neurons, a human brain has on the order of 100 billion neurons. that's 6 orders of magnitude larger. that's like saying "A map of San Francisco has been completed, the entire solar system could follow!"

Given that for a map, it is the sqkm which matters, 6 orders of magnitude from the map of San Francisco is a jump from 121 sqkm to 121 000 000 sqkm ... which is not even all dry land on Earth, much less in the Solar System.

Surely a daunting task, but depending on the tools used to create the smaller map, possibly a realistic one. Maybe with a bit of a less precision.

Re: An adult fruit fly brain has been mapped

#45

Post by bhouston »

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.

Yup, it is similar to that as well. It is a part of the puzzle definitely, but not at all the whole picture.

Re: An adult fruit fly brain has been mapped

#46

Post by inglor_cz »

willcipriano wrote: post #37

50 years from now I am dying in a hospital bed, the nurse informs me that my consciousness will be uploaded to a computer with all the other brains, a digital heaven if you will. Get there and its full of flies.

Well, the big question is if a human is "just" a mega-fly when it comes to brain structure.

Re: An adult fruit fly brain has been mapped

#47

Post by _giorgio_ »

Is this correct?

It this like knowing only this:

which neuron is connected to which neuron

But you don't know:

the values of the weights (the value of the neuron, or the parameters)

the activation functions

what circuit do neurons implement (fully connected? CNN?)

Re: An adult fruit fly brain has been mapped

#48

Post by mjfl »

mjburgess wrote: post #3

It was my understanding that all this connectome-based research was largely a deadend, because it doesnt capture dynamics, nor a vast array of interactions. if you've ever seen neurones being grown (go search YT), you'll see it's a massive gelatinous structure which is highly plastic and highly dynamic. Even in the simplest brains (eg., of elgans), you get 10^x exponential growth in number of neurones and their conne…

Connectome is a necessary component to understanding dynamics.

Re: An adult fruit fly brain has been mapped

#49

Post by SubiculumCode »

rkp8000 wrote: post #29
mjburgess wrote: post #3

It was my understanding that all this connectome-based research was largely a deadend, because it doesnt capture dynamics, nor a vast array of interactions. if you've ever seen neurones being grown (go search YT), you'll see it's a massive gelatinous structure which is highly plastic and highly dynamic. Even in the simplest brains (eg., of elgans), you get 10^x exponential growth in number of neurones and their conne…

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…

Very Nice. --from a Connectome-Centric neuroimager :) One technique that I am pursuing right now is information decomposition of timeseries to separate the mutual information of two timeseries into redundant and synergistic informational atoms (synnergystic here means the degree to which knowing both timeseries gives you more information than the individual parts give (more than sum of parts). The big limitation of the method is the geometric explosion in complexity of the decomposition as the number of time series grow, with most analyses being limited to two or three times series at a time. However, the scale of the data on which it is applied is not requisite, meaning the approach can equally be used on the mutual information between two regions of interest in rsfMRI , or two spiking timeseries from individual neurons. https://en.wikipedia.org/wiki/Partial_information_decomposit...

Re: An adult fruit fly brain has been mapped

#50

Post by svara »

twojacobtwo wrote: post #41
IshKebab wrote: post #18

Earlier quoted context omitted.

Well assuming the same density it's "only" 100 times bigger in linear dimensions. Doesn't sound quite as crazy...

Isn't that just saying "if you take the cube root of the number, it's a smaller number"? I don't mean to be facetious - I'm struggling to to see what other consideration this helps with.

The physical process of cutting. We're physically sectioning 3 dimensional blocks of tissue.
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