Are you seriously going to suggest that we still have no idea as to what "neurons are doing"?
/NJ/ On Tue, Aug 28, 2012 at 7:52 PM, Steve Richfield <[email protected]>wrote: > Alan, > > Your discussion fits right in with some of my postings. I have discussed > the equivalent unity gain frequency of neurons (for 741s it is ~1MHz), > negative feedback in the form of variable driven impedance, etc. It appears > that internally, neurons may "compute" about as fast as vacuum tubes, and > NOT at the much slower pulse rates seen at the outputs of spiking neurons. > > However, I fear that we are throwing pearls before swine. > > Also, I wonder if everyone else is missing an essential point. We are NOT > saying "neurons are SO much faster and smarter that we can never duplicate > such function on a human scale", but rather "if we make the effort to > understand what neurons are doing, then we will have some chance of > understanding the problems they are solving, after which we can then > engineer human scale systems without being encumbered by the neuronal > legacy." > > Steve > =================== > On Tue, Aug 28, 2012 at 9:34 AM, Alan Grimes <[email protected]>wrote: > >> om >> >> The elemental unit of an analog computer, akin to an NAND gate, is the >> operational amplifier. The canonical opamp is the LM741, which was >> introduced in 1968 and is still the standard opamp that everyone uses. >> The Japanese have an equivalent part which has pretty much identical >> specs. >> >> Better parts are now available but engineers usually start out with the >> LM741 and chose a different part only if it can't meet their performance >> goals. I'm kinda fond of the Jfet input opamps myself but they can be a >> bit more fragile. >> >> I did some computer simulations of my father's stereo (made in 1974). >> The power amplifiers are basically power opamps made with discreet parts. >> >> You think of an amplifier as conveying a signal from input to output. A >> classic tube amplifier does exactly that, sometimes with 6-12 db of >> negative feedback.The creepy thing about the simulation was that the >> signal appeared to disappear in the middle of the circuit, so I had >> trouble even figuring out which wire was even conveying it. >> >> Logically, the signal MUST pass from the collector of Q402 to the base >> of Q410. However the voltage swing at that point is many decimal places >> below the DC voltage at that point. >> >> But that's the thing. The amplifier doesn't amplify signal! The >> difference between the voltages at the input parts, (Q402, non >> inverting, Q404 inverting). is in the microvolts range. (Q406 is >> basically a 2mA CCS with a 20-30 second time delay), so the input signal >> to the amplifier is essentially null. >> >> But the circuit does work. It has a gain defined by R410 and R414. >> >> It is an error amplifier. The brain works in much the same way. Neurons >> don't say much to each other unless there is an error signal. The >> amplifier's output is your imagination and the input signal are your >> sense organs. >> >> Anyway, just a different perspective. =P >> >> -- >> E T F >> N H E >> D E D >> >> Powers are not rights. >> >> >> >> >> ------------------------------------------- >> AGI >> Archives: https://www.listbox.com/member/archive/303/=now >> RSS Feed: >> https://www.listbox.com/member/archive/rss/303/10443978-6f4c28ac >> >> Modify Your Subscription: https://www.listbox.com/member/?&; >> Powered by Listbox: http://www.listbox.com >> > > > > -- > Full employment can be had with the stoke of a pen. Simply institute a six > hour workday. That will easily create enough new jobs to bring back full > employment. > > > *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> > <https://www.listbox.com/member/archive/rss/303/20912103-eed2d0e1> | > Modify<https://www.listbox.com/member/?&;>Your Subscription > <http://www.listbox.com> > ------------------------------------------- AGI Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/21088071-c97d2393 Modify Your Subscription: https://www.listbox.com/member/?member_id=21088071&id_secret=21088071-2484a968 Powered by Listbox: http://www.listbox.com
