Pharyngula

And everyone gets a robot pony!

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 3kg brain. What you’re going to be recording is the dying brain, with cells spewing and collapsing and triggering apoptotic activity everywhere.

And that’s another thing: what the heck is going to be recorded? You need to measure the epigenetic state of every nucleus, the distribution of highly specific, low copy number molecules in every dendritic spine, the state of molecules in flux along transport pathways, and the precise concentration of all ions in every single compartment. Does anyone have a fixation method that preserves the chemical state of the tissue? All the ones I know of involve chemically modifying the cells and proteins and fluid environment. Does anyone have a scanning technique that records a complete chemical breakdown of every complex component present?

I think they’re grossly underestimating the magnitude of the problem. We can’t even record the complete state of a single cell; we can’t model a nematode with a grand total of 959 cells. We can’t even start on this problem, and here are philosophers and computer scientists blithely turning an immense and physically intractable problem into an assumption.

And then going on to make more ludicrous statements…

Axons carry spike signals at 75 meters per second or less (Kandel et al. 2000). That speed is a fixed consequence of our physiology. In contrast, software minds could be ported to faster hardware, and could therefore process information more rapidly

You’re just going to increase the speed of the computations — how are you going to do that without disrupting the interactions between all of the subunits? You’ve assumed you’ve got this gigantic database of every cell and synapse in the brain, and you’re going to just tweak the clock speed…how? You’ve got varying length constants in different axons, different kinds of processing, different kinds of synaptic outputs and receptor responses, and you’re just going to wave your hand and say, “Make them go faster!” Jebus. As if timing and hysteresis and fatigue and timing-based potentiation don’t play any role in brain function; as if sensory processing wasn’t dependent on timing. We’ve got cells that respond to phase differences in the activity of inputs, and oh, yeah, we just have a dial that we’ll turn up to 11 to make it go faster.

I’m not anti-AI; I think we are going to make great advances in the future, and we’re going to learn all kinds of interesting things. But reverse-engineering something that is the product of almost 4 billion years of evolution, that has been tweaked and finessed in complex and incomprehensible ways, and that is dependent on activity at a sub-cellular level, by hacking it apart and taking pictures of it? Total bollocks.

If singularitarians were 19th century engineers, they’d be the ones talking about our glorious future of transportation by proposing to hack up horses and replace their muscles with hydraulics. Yes, that’s the future: steam-powered robot horses. And if we shovel more coal into their bellies, they’ll go faster!

Comments

  1. #1 Tim Spear
    United Kingdom
    July 20, 2012

    Hi PZ
    While your points are interesting and fair enough the title of the Hallquist article does say “in the next century or two.” Don’t you think techniques might advance sufficiently in that sort of time frame? I mean the KEMS machine can already kind of scan brains at 0.3um resolution, admittedly just microscope images, but things might move on? http://www.wired.co.uk/news/archive/2012-05/02/brain-slicing-and-mapping

  2. #2 Greg Kochanski
    http://kochanski.org/gpk
    July 21, 2012

    I agree completely that nobody is going to scan and simulate a brain anytime in the forseeable future.

    But, _if_ you had a computer simulation of a brain, there is nothing intrinsically difficult in making the entire brain run faster. You wouldn’t change the physiology, as you seem to assume. You’d simulate the same physiology, but just change the relationship between the computer’s clock and the real world’s clock. It’s just like simulating the motions of the solar system more rapidly: rather than fiddling with gravity within the simulations, you just put it on a faster computer and turn up the clock.

  3. #3 Jonathan
    Oak Park, IL
    July 21, 2012

    Greg, how would you get real-time, accurate scans of the precise chemical state of the entire brain? That’s the whole point of what PZ’s saying–the minute you take it apart enough to observe it closely, it’s already starting to degrade. Even flash-freezing it would still cause such massive degradation that reconstructing your identity from what’s left is about as plausible as the folks on CSI producing court-admissible photos with an enhancing tool. We just don’t know enough about how the whole machine works to replicate it yet.
    Besides, consciousness isn’t just about processing power–IIRC, we already have prototype computers that are theoretically more powerful than a small rodent brain, but that doesn’t mean we can build realistic mouse androids (musoids?) any more than we can get an ant colony to run Fedora.

  4. #4 Anonymous
    July 22, 2012

    I enjoy your rebuttal of Kurzwail and the singularitarians, but I see one person missing from the kook category – Aubrey De Grey.

  5. #5 Mungojelly
    Burlington, VT, USA
    July 23, 2012

    Please don’t argue with strawmen; we need your help to deal with this unusual and dangerous situation. OK, so you know some specific facts about extraction of information from brains– that’s useful to us, if you will put that information to use in helping us to predict WHEN certain transitions will take place. It seems like from what you’re saying that you don’t think we’ll have full uploading until we have robots small enough to enter a live brain and take readings directly, yes? That much of a postponement in full uploading could have important consequences for how the Immortalists will act in the coming decades– those are the questions we need to think about. It’s not productive to debate whether the future is even going to occur at all, unless you have some thought-through notion of a particular steady-state rejectionist society for us to consider.

  6. #6 PhysicistDave
    homeschoolingphysicist.blogspot.com
    July 24, 2012

    Mungojelly wrote:
    >It’s not productive to debate whether the future is even going to occur at all, unless you have some thought-through notion of a particular steady-state rejectionist society for us to consider.

    MJ, do you have any real-world experience in research science or engineering?

    I’m a physicist: for nearly fifty years I have been reading about research in “controlled fusion.” People were more optimistic about the prospects for practical controlled fusion fifty years ago than they are today.

    “The future” has gotten more and more distant with each passing decade.

    The devil is in the details. And, the details that PZ has laid out are absolutely overwhelming to anyone with serious technical training.

    Sure, something may come up. Someday. And, maybe it will turn out that G. W. Bush was really a space alien.

    Personally, I’d bet on seeing pigs fly (genetically modified pigs, to be sure – let PZ tell you how hard that would be, given the embryological development of pigs vs. birds!) before we see the kind of brain scan that PZ is debunking.

    Dave Miller in Sacramento

  7. #7 Logan
    July 25, 2012

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