Archive for the 'singularity' tag

Oy, singularitarians. Chris Hallquist has a post up about the brain uploading problem — every time I see this kind of discussion, I cringe at the simple-minded naivete that’s always on display. Here’s all we have to do to upload a brain, for instance: The version of the uploading idea: take a preserved dead brain, slice it into very thin slices, scan the slices, and build a computer simulation of the entire brain. If this process manages to give you a sufficiently accurate simulation It won’t. It can’t. I read the paper he recommended: it’s by a couple of philosophers. All we have to do is slice a brain up thin and “scan” it with sufficient resolution, and then we can just build a model of the brain. I’ve worked with tiny little zebrafish brains, things a few hundred microns long on one axis, and I’ve done lots of EM work on them. You can’t fix them into a state resembling life very accurately: even with chemical perfusion with strong aldehyedes of small tissue specimens that takes hundreds of milliseconds, you get degenerative changes. There’s a technique where you slam the specimen into a block cooled to liquid helium temperatures — even there you get variation in preservation, it still takes 0.1ms to cryofix the tissue, and what they’re interested in preserving is cell states in a single cell layer, not whole multi-layered tissues. With the most elaborate and careful procedures, they report excellent fixation within 5 microns of the surface, and disruption of the tissue by ice crystal formation within 20 microns. So even with the best techniques available now, we could possibly preserve the thinnest, outermost, single cell layer of your brain…but all the fine axons and dendrites that penetrate deeper? Forget those. We don’t have a method to lock down the state of a 1.5kg brain. What you’re going to be recording is the dying brain, with cells...
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