Anders Sandberg wrote:
> HAH! Not so fast!
> Neurons are complicated, and have a lot of individuality. First, they
> come in many different types, each having quite different properties;
> both shape and size, but also electrochemical properties, receptor
> types, ion channels and behavior that interact in a very nonlinear
> way. Then each neuron may have tricky internal states, both in the
> synapses (concentrations of calcium and at present little understood
> proteins and other chemicals that affect their strength) and inside
> the cell body. Add to this the individual variations in geometry and
> perhaps chemical properties, and you get a very confucing picture.
> This is what you need to simulate to make a somewhat realistic
> neuron. Note that we are not talking about actual molecular scale
> simulations, just things like calcium concentrations in dendrite <1 2
> 1 3> or the membrane potential at the soma. So to do an upload we will
> need to set up an instance of this kind of simulation for each
> neuron. It is not that impossible really, except that we lack the
> necessary data for a truly complete neuron model (membrane
> conductivity is reasonably well understood, synapse behavior a hot
> topic, plasticity controversial and the more subtle or complex
> interactions between activity, modulation, geometry and genetic
> switches are completely unknown), and that we have too little
> computing power yet (both the computers and simulators need to get
> better). But it is in principle doable, and I hope to be there when it
Well, I didn't say we could do it *now*. A MD-level sim of a few hundred cells would take, what, maybe 10^20 MIPS? I was just pointing out that even that is a far cry from a full-brain sim.
> Can we simplify neurons? Probably; this is just how nature made them,
> and I think it is possible to create more computationally efficient
> input-output mappings retaining the same properties. This is an
> interesting problem, both from a research, a theoretical and an
> uploading standpoint. What can we do away with without losing the
> important? How much detail is needed? Could you upload yourself into
> an integrate-and-fire model? Could this process be continued on higher
I would think so. At the very least, you should be able to model the computation each neuron performs and do away with all the chemical details of how it gets done. If you want to get ambitious, you could probably also replace a large percentage of the simulated brain with ordinary software. Computer vision, hearing, and other sensory abilities will probably be much better than those of humans by then, for example. Of course, setting up the interface would be a bit of a challenge..
> The technology for doing uploads will likely at first be developed
> just for getting the data for advanced neuron and brain simulations.
I wouldn't be surprised.
> What we need now is better data, better models and better computers.
Billy Brown, MCSE+I