3 ms·

I would recommend taking the "0.16 times per second" number with a real grain of salt. That neuron is evaluating inputs from (oh, say) 1k-10k sources simultaneo

I would recommend taking the "0.16 times per second" number with a real grain of salt. That neuron is evaluating inputs from (oh, say) 1k-10k sources simultaneously, computing some analog function that we don't really understand, which involves membrane dynamics, past spiking history, the amount of post-synaptic intracellular calcium, etc. These little units are absolutely incredible, and we don't quite know yet what parts of this behavior are actually the "secret sauce" that makes it work. For me the most authoritative answer is what the Human Brain Project in europe is able to achieve: http://www.nature.com/news/fragment-of-rat-brain-simulated-in-supercomputer-1.18536 http://www.nature.com/news/fragment-of-rat-brain-simulated-i... 31k cells with 37M synapses. That's a start, but pretty far from a mouse brain (100M cells) or a human brain (80B? ). Also if Moore's law really is dead, this all gets much more depressing.

logicallee 10y ago
You don't go into my most important figure, which is 100 m/s speed limit: this means that we can simulate a brain in a server room of any reasonable size (10,000 computers are no problem), racing back and forth thousands of times without issue. That radically simplifies the task, and makes the 1k-10k sources much easier. You mention membrane dynamics, past spiking history, etc - but neural nets accomplish a lot without these things. A simplification surely works. You are not thinking about simulating a brain using a large cluster with a lot of back and forth. Why not? Don't you get how incredibly slow 100 m/s is? This is 7 orders of magnitude difference in speed. Silicon is seven orders of magnitude faster at signal propagation than the brain, which isn't electrical. To you this doesn't unlock vast possibilities for simulating the analog in real time? It just doesn't seem that permanently impossible, given the results you are already claiming are occurring. Also although I directly addressed you, I guess you don't have any answer as to why someone would choose a target date like "never" or "300 years" as opposed to some reasonable extrapolation of the results being achieved today.

logicallee 10y ago

You don't go into my most important figure, which is 100 m/s speed limit: this means that we can simulate a brain in a server room of any reasonable size (10,000 computers are no problem), racing back and forth thousands of times without issue. That radically simplifies the task, and makes the 1k-10k sources much easier. You mention membrane dynamics, past spiking history, etc - but neural nets accomplish a lot without these things. A simplification surely works. You are not thinking about simulating a brain using a large cluster with a lot of back and forth. Why not? Don't you get how incredibly slow 100 m/s is? This is 7 orders of magnitude difference in speed. Silicon is seven orders of magnitude faster at signal propagation than the brain, which isn't electrical. To you this doesn't unlock vast possibilities for simulating the analog in real time? It just doesn't seem that permanently impossible, given the results you are already claiming are occurring. Also although I directly addressed you, I guess you don't have any answer as to why someone would choose a target date like "never" or "300 years" as opposed to some reasonable extrapolation of the results being achieved today.