X-Message-Number: 10262 Date: Mon, 17 Aug 1998 10:21:03 -0700 From: "Joseph J. Strout" <> Subject: emulation by "computers" In Cryonet Message #10250, Thomas Donaldson <> writes: >There is a strong connection with cryonics, if you listen a bit. You >see, there is one segment of opinion among cryonicists that we might >eventually be emulated by a computer. Computers work by means of >manipulating symbols (if we exclude neural nets, which some may not >even see as computers). If ALL thinking consists of such manipulation, >then the claim of such cryonicists is proven. If it does not, then >the possibility that we cannot be emulated by any computer at least >becomes relevant and perhaps even important. As more or less the de facto "voice" of mind uploading within cryonics, I feel obliged to respond. Thomas is laboring under a misconception here. The idea of mind uploading is that the brain can be emulated by some *artificial device*. Such a device will almost certainly resemble what we call a computer today no more than my PowerMac resembles a mechanical hand-cranked calculator of the 1930s. A brain emulator will, in all likelyhood, consist of custom hardware, perhaps analog rather than digital. (In the limit, it may consist of proteins and lipids, but I think this rather unlikely.) Neurons (or at least, their spike initiation zone) can be emulated today in real time on conventional computers. But this neglects all the complex analog processing going on in the dendrites. To imitate that functionality, we generally use either compartmental models or Wiener kernels, but when we do this in a digital computer, it requires discretizing time and space. The result is a simulation that's slow, or inaccurate, or both. But already there is a field of "neuromorphic engineering" which is building analog VLSI hardware that mimics some of the functionality of neurons (often by implementing a Wiener kernel model for each neuron). These devices are already proving useful in machine vision etc., and they do nothing that resembles "manipulating symbols" any more than our own retinas or brains do. So it's a little misleading to speak of uploading as if it requires emulation of the brain in digital, symbol-processing hardware. >Why computers? Because at least to some they seem to provide a way to >resurrect us even in the worst cases. This is the idea, but please strike "computers" and insert "artificial devices." (And consider adding that such technology does not seem to require nanotechnology, provides a means for making backups in case of disaster, and would enable us to adapt ourselves to a much wider extreme of environments than is plausible for biological materials.) Best regards, -- Joe ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://www.strout.net | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=10262