X-Message-Number: 7947 Date: Wed, 26 Mar 1997 08:58:06 -0800 (PST) From: Joseph Strout <> Subject: And another thing... [Sorry for the mostly useless subject line, which describes the topics not at all, but does perhaps characterize the level our discussion has reached!] To Bob Ettinger: You make good points about the possibility of a self circuit. I certainly agree that conscious is mysterious, and not yet fully understood. But it seems to me that increasing evidence indicates that, however it arises, it is distributed throughout more or less the entire brain -- or at least, the entire cortex. For example, cortical lesions can cause specific deficits in consciousness, e.g., an inability to be consciously aware of visual information in a certain part of the visual field; or on one side of any object (a complex concept, but true); or except when it is moving. For another example, experiments in monkeys have found neurons in MT (a motion-responsive visual cortical area) whose activity corresponds to the monkey's report of its conscious percept -- and moreover, by stimulating these neurons, the experimenter can actually influence the monkey's conscious percept, though the actual input to the eyes remains unchanged. You might argue that the cortex is merely feeding inputs to the self circuit, which is located elsewhere. But it seems more parsimonious to me to assume that cortex either is the seat of consciousness, or is a significant part of it. There are extensive connections in both directions between cortex and the thalamus; some theories have proposed that awareness results from these thalamocortical loops. Perhaps. Whatever the details, it seems clear to me that consciousness somehow arises from the interaction of spike trains among neurons arranged in the particular configuration of our brains. This still leaves the metaphysical question of how ANY physical process can result in consciousness. Clearly this can happen. I think Dennett may be on the right track when he proposes that consciousness is related to information. Perhaps simple information processing produces simple consciousness, and complex info-processing produces complex consciousness. We may seem qualitatively different from other things in the world only because our brains perform more complex information processing than any computer ever built on Earth. Bob writes: > 5. Pizer, Perry and thought experiments again: It is simply a fact that NONE > of the usual intuitive survival criteria, nor any combination, can be shown > to be EITHER necessary or sufficient--not continuity of matter, not identity > of matter, not continuity of pattern, not identity of pattern. It is not > possible, and in my opinion not psychologically necessary, to form a firm > opinion before we have the necessary knowledge of biology and physics. What knowledge of biology and physics will help answer questions regarding survival and personal identity? I suppose you will want to understand the basis of consciousness, but I suspect that biology and physics are not up to this task. They can tell us what properties it has (such as its relation to neurons, for example) but not why it arises; that will require some new kinds of theories. However, we can still test proposed theories of personal identity. We should demand that they are not falsified by common observations, e.g.: 1. A person is (mostly or entirely) the same person over time. 2. A person is not (mostly or at all) the same person as his spouse, neighbor, etc. 3. If you put the same person in the same situation, he will react in similar ways. 4. If person A and person B are (mostly or entirely) the same person, they will usually have similar knowledge, personality, and other mental traits. 5. A person is (mostly or entirely) the same person after sleep, hypothermic surgery, etc. 6. A theory of personal identity should be logically self-consistent. Most proposed theories of personal identity can be falsified by at least one of these observations. So we CAN make some progress towards a reasonable theory of identity. What I call "fuzzy memory theory" (a simple extension of classical memory theory) is the only theory I have found which satisfies the above. So, until something better is proposed, it is what I will believe. ...on another matter, Thomas wrote: > Finally we come to the chaos issue. Here I should have explained myself a > bit better. If we set up a (slightly faulty) copy of you, not only will it > simply not behave like you, but it will go very badly awry, breaking down > after a short time. I do not believe that you are going to break down in > the same way or in a short time. Why is it that we do not quickly go awry? In simulation terms, it appears that we are robust, whereas a poor simulation is fragile, and small changes in parameters cause it to break -- why? I believe that neurons (and almost all biological gadgets) are replete with feedback loops that keep everything functioning. It's still a chaotic system, but the feedback loops keep all variables within a useful range. The same can (and must) be done in emulation. There was a thread on the Neuron Emulation List about this last year; see, for example <http://www-ncmir.ucsd.edu/~jstrout/nel-arch/msg00122.html> > To Dr. Strout: Yes, you might consider that I was using the word "computer" > in a different way. Since I don't want to get involved in arguing about > right and wrong uses of words, I will say this: "computers" of the sort > we are differ a great deal from Crays, PCs, etc --- not matter how large > and elaborate such machines may become. I believe that is an essential > distinction. OK, we agree here, and differ merely in our terminology. It will only get more confusing as analog computers make a comeback, and quantum computers start to be built, etc... I use "computer" in this general sense, and reserve "conventional computers" to refer to Crays, PCs, etc. As you say, there is no problem as long as we try to make clear what we mean. (On a side note: I haven't earned the honorific "Doctor", so please use "Mr." if you must be formal. But "Joe" will do; we're all friends here!) Regards, -- Joe ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://www-acs.ucsd.edu/~jstrout/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=7947