Arets etc., We do know a lot about the brain now ... but the gaps are so big that it's still certainly possible we're missing something fundamental.... The roles of astrocytes and glia are still largely unknown; the hints Hameroff keeps pointing out about macroscopic quantum phenomena can't wholly be ignored (though I have no idea how important they are), along with his (somewhat independent) notion of a web of dendro-dendritic connections guiding the flow of attention..... And then there's our near utter lack of understanding of large-scale complex attractor patterns in the brain, in spite of great simulation work like that of Izhikevich & Edelman...
For a gov't contract, I recently looked into computational neuroscience models of one very particular brain function (accumulation of evidence), and the situation is that there are half dozen possible models, mostly based on perceptual decision making in monkeys, and nobody has any clear idea which model applicable to which parts of the brain, or how accurate each of the models is beyond some very simple situations.... Knowledge is progressing steadily -- and quickly on the historical scale -- but at the current rate it will be decades before the neuroscientists really understand what's going on. Though a massive breakthrough is always possible ;) Hawkins and others who pursue neuroscience based approaches to AGI, seem to me to be taking simplified models of individual aspects of brain function, and amplifying them into whole would-be AGI architectures. (In Hawkins case, what he has is probably best considered a simplified, qualitative model of parts of visual and auditory cortex.) For this sort of reason, I think that *if* one wants to pursue AGI R&D now, a neuroscience based approach is not the way to go... ben On Tue, Aug 28, 2012 at 5:34 PM, Arets Paeglis <[email protected]> wrote: > We do NOT know what mathematics are involved in the computations. > > Wow. Hodgkin, Huxley, Nagumo, Izhikevich and the others must, then, be > totally delusional. The more I know. > > [..] but we really don't know how they work and which of the observed >> features are actually important. > > Sure, there are still a lot of white spots in our understanding of how > brain works on its different levels. On the other hand, there exists a > massive corpus of academical neuroscience, both empirical and > computational, that *clearly *disagrees with the picture you apparently > are painting here - one where we are nearly clueless about what and how > goes on in our cerebral matter. > > /NJ/ > > > On Wed, Aug 29, 2012 at 12:11 AM, Steve Richfield < > [email protected]> wrote: > >> Arets, >> >> On Tue, Aug 28, 2012 at 10:00 AM, Arets Paeglis <[email protected]>wrote: >> >>> Are you seriously going to suggest that we still have no idea as to what >>> "neurons are doing"? >>> >> >> Yes. >> >> Most synapses are NOT the simplistic fractional transfer mechanisms used >> in NNs, We have NO idea how neurons learn as fast as they do. We have NO >> idea what guides their self-organization. We do NOT know what mathematics >> are involved in the computations. We have observed some interesting things, >> like some neurons becoming active under particular circumstances, but that >> is about all we now "know". >> >> The equivalent in astronomy: We still think the earth is at the center of >> the universe, that planets orbit in bizarre ways, and that celestial >> spheres make it all work as it does. >> >> Steve >> ================= >> >>> 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> >>> <https://www.listbox.com/member/archive/rss/303/10443978-6f4c28ac> | >>> Modify <https://www.listbox.com/member/?&;> Your Subscription >>> <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> > <https://www.listbox.com/member/archive/rss/303/212726-11ac2389> | > Modify<https://www.listbox.com/member/?&;>Your Subscription > <http://www.listbox.com> > -- Ben Goertzel, PhD http://goertzel.org "My humanity is a constant self-overcoming" -- Friedrich Nietzsche ------------------------------------------- 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
