Richard, It might be more useful to discuss more recent papers by the same authors regarding the same topic, such as the more accurately-titled
*** Sparse but not "Grandmother-cell" coding in the medial temporal lobe. Quian Quiroga R, Kreiman G, Koch C and Fried I. Trends in Cognitive Sciences. 12: 87-91; 2008 *** at http://www2.le.ac.uk/departments/engineering/extranet/research-groups/neuroengineering-lab/ -- Ben G On Mon, Nov 24, 2008 at 1:32 PM, Richard Loosemore <[EMAIL PROTECTED]> wrote: > Ben Goertzel wrote: >> >> Hi, >> >> BTW, I just read this paper >> >> >>> For example, in Loosemore & Harley (in press) you can find an analysis of >>> a >>> paper by Quiroga, Reddy, Kreiman, Koch, and Fried (2005) in which the >>> latter >>> try to claim they have evidence in favor of grandmother neurons (or >>> sparse >>> collections of grandmother neurons) and against the idea of distributed >>> representations. >> >> which I found at >> >> http://www.vis.caltech.edu/~rodri/ >> >> and I strongly disagree that >> >>> We showed their conclusion to be incoherent. It was deeply implausible, >>> given the empirical data they reported. > > > The claim that Harley and I made - which you quote above - was the > *conclusion* sentence that summarized a detailed explanation of our > reasoning. > > That reasoning was in our original paper, and I also went to the trouble of > providing a longer version of it in one of my last posts on this thread. I > showed, in that argument, that their claims about sparse vs distributed > representations were incoherent, because they had not thought through the > implications contained in their own words - part of which you quote below. > > Merely quoting their words again, without resolving the inconsistencies that > we pointed out, proves nothing. > > We analyzed that paper because it was one of several that engendered a huge > amount of publicity. All of that publicity - which, as far as we can see, > the authors did not have any problem with - had to do with the claims about > grandmother cells, sparseness and distributed representations. Nobody - not > I, not Harley, and nobody else as far as I know - disputes that the > empirical data were interesting, but that is not the point: we attacked > their paper because of their conclusion about the theoretical issue of > sparse vs distributed representations, and the wider issue about grandmother > cells. In that context, it is not true that, as you put it below, the > authors "only [claimed] to have gathered some information on empirical > constraints on how neural knowledge representation may operate". They went > beyond just claiming that they had gathered some relevant data: they tried > to say what that data implied. > > > > Richard Loosemore > > > > > > > >> Their conclusion, to quote them, is that >> >> " >> How neurons encode different percepts is one of the most intriguing >> questions in neuroscience. Two extreme hypotheses are >> schemes based on the explicit representations by highly selective >> (cardinal, gnostic or grandmother) neurons and schemes that rely on >> an implicit representation over a very broad and distributed population >> of neurons1–4,6. In the latter case, recognition would require the >> simultaneous activation of a large number of cells and therefore we >> would expect each cell to respond to many pictures with similar basic >> features. This is in contrast to the sparse firing we observe, because >> most MTL cells do not respond to the great majority of images seen >> by the patient. Furthermore, cells signal a particular individual or >> object in an explicit manner27, in the sense that the presence of the >> individual can, in principle, be reliably decoded from a very small >> number of neurons.We do not mean to imply the existence of single >> neurons coding uniquely for discrete percepts for several reasons: >> first, some of these units responded to pictures of more than one >> individual or object; second, given the limited duration of our >> recording sessions, we can only explore a tiny portion of stimulus >> space; and third, the fact that we can discover in this short time some >> images—such as photographs of Jennifer Aniston—that drive the >> cells suggests that each cell might represent more than one class of >> images. Yet, this subset of MTL cells is selectively activated by >> different views of individuals, landmarks, animals or objects. This >> is quite distinct from a completely distributed population code and >> suggests a sparse, explicit and invariant encoding of visual percepts in >> MTL. >> " >> >> The only thing that bothers me about the paper is that the title >> >> " >> Invariant visual representation by single neurons in >> the human brain >> " >> >> does not actually reflect the conclusions drawn. A title like >> >> " >> Invariant visual representation by sparse neuronal population encodings >> the human brain >> " >> >> would have reflected their actual conclusions a lot better. But the >> paper's >> conclusion clearly says >> >> " >> We do not mean to imply the existence of single >> neurons coding uniquely for discrete percepts for several reasons: >> " >> >> I see some incoherence between the title and the paper's contents, >> which is a bit frustrating, but no incoherence in the paper's conclusion, >> nor between the data and the conclusion. >> >> According to what the paper says, the authors do not claim to have >> solve the neural knowledge representation problem, but only to have >> gathered some information on empirical constraints on how neural >> knowledge representation may operate. >> >> -- Ben G >> >> >> ------------------------------------------- >> agi >> Archives: https://www.listbox.com/member/archive/303/=now >> RSS Feed: https://www.listbox.com/member/archive/rss/303/ >> Modify Your Subscription: https://www.listbox.com/member/?&; >> Powered by Listbox: http://www.listbox.com >> >> > > > > ------------------------------------------- > agi > Archives: https://www.listbox.com/member/archive/303/=now > RSS Feed: https://www.listbox.com/member/archive/rss/303/ > Modify Your Subscription: > https://www.listbox.com/member/?&; > Powered by Listbox: http://www.listbox.com > -- Ben Goertzel, PhD CEO, Novamente LLC and Biomind LLC Director of Research, SIAI [EMAIL PROTECTED] "The empires of the future are the empires of the mind." -- Sir Winston Churchill ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=120640061-aded06 Powered by Listbox: http://www.listbox.com
