Comment by kelnos
5 years ago
> C elegans is a small nematode [...] We still can't simulate it.
This for some reason struck me as profoundly disappointing. I have a couple neuroscientist friends, so I tend to hear a lot about their work and about interesting things happening in the field, but of course I'm a rank layperson myself. I guess I expected/hoped that we'd be able to do more with simpler creatures.
If we can't simulate C elegans, are there less complex organism we can simulate accurately? What's the limit of complexity before it breaks down?
I don't think there's anything we can simulate "completely", in the sense that a fire-and-forget model would subsequently go onto have a typical life.
The stomatogastric ganglion might be the closest. It is a network of three dozen neurons in the crustacean stomach. Like the worm, the wiring diagram is completely known and the physiology is easier to measure. Despite being very simple, it can generate intricate patterns of activity in the stomach muscles that let the crab/lobster/etc eat. Scholarpedia has the diagram and some references (http://www.scholarpedia.org/article/Stomatogastric_ganglion) Eve Marder, who has done a lot of pioneering work on this circuit, wrote a book (Lessons From the Lobster) that I'm looking forward to reading.
Don't be disappointed! A lot of media coverage tends to present new results as "we're almost there." In most cases, I think that's nonsense, but it's also exciting to think how many things there are left to discover and how fascinatingly complex the world is.
c. elegans is pretty much the only one we fully mapped. (Possibly some fish larvae, too? Recall fuzzy)
But given that we can't even fully simulate animals with exactly zero neurons (Trichoplax), I'd say the current limit is "we can't". It's literally the world's simplest animal, and we're far from understanding how it works.
So, probably no brain uploads by 2031 ;)