Monday, August 30, 2010

The evolution of topology in the visual field: 2

Part 2

Likewise the experience of movement and colour in the visual field also develop in stages. The primitive visual field may contain only pure motion, usually rotary. Colours appear first as space and film colours. These only later enter their objects. Objects are often seen first as parts (e.g. the handle only of a teacup) that join up together later.

All this complexity may readily be explained on the grounds that we are observing the successive stages of recovery of an image-constructing representative mechanism that has several different basic parts (one for motion, one for colour and one for shape). It is difficult, for me at least, to think of it as representing the gradual recovery of the direct awareness of external objects that naïve realism supposes. How can a film colour be regarded as ‘the way we see” the colour located on the surface of e.g. a rose?

So, this data suggests that, topologically, the basic visual field is a pure formless expanse of nothing. Formal geometrical shapes (lines, curves, triangles, etc) only develop later. So what else can we say about its topology? In my book “Analysis of Perception” I described how fact that the boundary of an ordinary after-image forms a Jordan curve (that separates the whole of introspectable visual space into one ‘inside’ and one ‘outside’) can be used to define a basic topological property of visual space. However, no entire visual field itself (including that of Poppelreuter’s stage 1) forms a Jordan curve, as there is no ‘outside’. So can we say that in imagination a patient could “draw” a visual image of a Jordan curve somewhere on the P. stage1 primitive visual field, as we can on a normal visual field? It is difficult to say. No experiments, as far as I know, have been done to determine what visual imagery is available to patients in Poppelreuter’s stage 1. However, as we know that visual imagery uses the same brain mechanisms as are used in vision, it seems unlikely that such patients posses the required imagery. So can a formless spatial expanse be said to possess any kind of topology? If so, what? More clinical investigations of Poppelreuter’s stage 1 patients might yield some interesting results. It is also possible that the development of vision in very early infancy may follow a similar course but this would be difficult to determine.

There is, however, another topological relation that may be relevant. We can ask if visual space, however primitive and so long as it is ontologically a basic ‘given’ (i.e. a real space), is topologically ‘inside’ or ‘outside’ physical space (as an entirety), or any part of physical space (e.g. brain space). To this question naïve realism, the Identity Theory, and material dualism give different, but definite, answers. So perhaps that gives us a clue as to the basic topology of visual space? Not which answer is true, but that such a question can be asked at all.

18 comments:

  1. Thank you, John, for this useful review and basic questions for us to ponder.

    Presumably there are many other studies of recovering visual function as a result of injuries sustained in subsequent wars? Perhaps even more revealing are the cases described in Marius Von Senden’s well-known monograph “Space and Sight: the Perception of Space and Shape in the Congenitally Blind Before and After Operation” (1932), since it is about those who have never seen before. There is a nice little glimpse of some examples from the cases in this article http://www.ralphmag.org/CO/blind.html

    As I recall, for these individuals (mostly youngsters) what they initially reported seeing was something like an amorphous reddish fog (though they probably do not use the word “fog”—I haven’t read the book in years, so I am relying on memory). So there would seem to be an initial impression of color in these cases, in contrast to the reports of the resighted blind to which John alludes.

    The question of the Jordan curve might well be applied to our universe, if conceived as a bounded volume: What then is outside it? (For now I am not addressing the question of other universes or multiverses.) So the problem of how visual space (VS) is bounded is comparable. The answer would seem to be that VS is bounded by “nothing,” at least nothing visual, yet one can clearly hear sounds that are localized beyond the lateral extent of VS, even to regions behind the head (the perceived head). Sounds in auditory space often seem to be “behind” or “emanate from” visual objects.

    Clearly the sighted congenitally blind and resighted blind do not perceive topological properties of VS per se at first, as they start to perceive definite contours and shapes (if fragmentary initially), and these are not topological properties, but geometric ones.

    I think that there is an alternative to representationalism, as proposed by Pribram, and that is that our perceptual reality is brought into existence much as a holographic image is, and it is not necessarily “representing” anything—at least anything that in any way resembles it. How could one construe the first of Eddington’s two writing tables as “representing” the second one that consists mostly of empty space?

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  2. To show the relationship between VS and sounds in auditory space, try holding up your hand and clicking your fingers together in front of your nose. Then without moving your head, continue clicking your fingers while moving your hand out of visual range above your head to the back of your head. It should be clear that while what is seen and what is heard occupy a common perceptual space, sounds extend beyond the bounds of VS.

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  3. Yes, the attainment of sight by the congenitally blind and following occipital lobe injuries differ in various ways due to the differences in their lesions.
    Bill's point about the relation of visual space and auditory space (as well as somato-sensory space) is important: I agree that they are different parts of a common phenomenal space. But what lies outside that? Jason Brown put it that "no one ever asks what lies outside of a dream". Stephen Harrison calls this no-mans-land the "pons innominatum". Hindu psychology distinguishes between illusionary 'Maya' (our sensations) and the deeper reality 'Brahman' that lies 'behind' them.
    When I talked earlier about "Plato's Cave", I was, of course, using this vivid model in a different way from Plato. The shadows on the wall of the cave represented for him Maya, and the objects, carried the prisoners that gave rise to the shadows, represented Brahman. Whereas, for my use of the model, the shadows equals phenomenal objects and the statues equals physical objects: both of these are part of Maya. Brahman "outside" or "beyond" could perhaps be represented by the countryside around the cave?

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  4. C.G. Jung felt that the best way to think of our consciousness was that it was surrounded on all sides by the unconscious--whatever that might ultimately be. But topologically, perceptual space is like a volume or topographic relief that has an inside by no outside, rather like a one-sided surface, and not unlike how astrophysics initially viewed the universe.

    Prospero says, "We are such stuff
    As dreams are made on; and our little life
    Is rounded with a sleep."

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  5. Just because people have come up with a variety of different models (computer, cinema, TV, etc.) as to how the brain works, does not mean that there may not be a particle of truth in one or more of them. There is evidence that the brain uses instantaneous information compression technology to mix 'virtual reality' with 'reality' in constructing the visual field. This cannot be done using cinematography but it is commonplace in television. However, this fact poses no problem for IT, which simply has to propose that NCC neurones receive input directly from the retina, as well as input from a part of higher visual cortex that is continually predicting what should be 'out there' based on the particular retinal input at that moment screened against the whole retained history of the system. But that does not solve the deeper problem which is, for vision, what is the relationship between NCCs and what is going on in the visual field in consciousness.

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  6. Good point Bill about perceptual/phenomenal space being a Moebius strip with an inside and no outside. Nevertheless a Moebius strip can exist only in a overall 3D space for the twist to occur? What you suggest reminds me of the model of consciousness that Henry Habbberley Price presented in his SPR paper "Survival and the idea of another world", in which he claimed that sensations occupied a different (ontological) space to physical space, and that they had causal relations, but no spatial relations, to events in physical space. An alternative theory is that of Charlie Dunbar Broad, who first suggested that P/P space and physical space are two different cross-sections of a common higher-dimensionial space. So, in his theory, P/P space does have an 'outside', but we cannot observe that from our location 'inside' it (Stephen Harrison's "pons innominatum" again).

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  7. Pace, John, but I seriously doubt that "there is evidence that the brain uses instantaneous information compression technology," for the simple reason that the brain is not a machine nor a form of technology. As Raymond Tallis is at pains to show in his "Why the Mind is not a Computer," the problem with reasoning from analogy is when one takes the analogy too far--or too literally.

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  8. The problem is that VS is not a continuous loop as a Moebius strip is. VS is clearly bounded--perhaps by itself, and thus, one of the peculiar properties of sensations, i.e., they bound themselves. As I stated a few comments ago, sounds seem to extend behind and above VS, yet sounds and sights do not seem to be exactly coextensive. We do not, for example, seem to experience VS as if it had a patch of sound in the middle of it, or in any portion of it. Sights and sounds are not side by side. Rather, it is more that visual objects seem to emit sounds, or have sounds behind them or "off stage" from the visual world altogether.

    The geometrical/topological implications of Erwin Schroedinger's famous final chapter "The Mystery of the Sensual Qualities" in his book "Mind and Matter" are that it makes more sense to believe that our ideas about physical space are derived from sensations, rather than the converse. How science has managed to alienate us from what is most real to us all--namely, the perceptual world--by attributing a greater reality status to a physical world beyond the senses is quite a feat! As Schroedinger writes: "Democritus introduces the intellect having an argument with the senses about what is 'real.' The former says: 'Ostensibly there is colour, ostensibly sweetness, ostenibly bitterness, actually only atoms and the void,' to which the senses retort: 'Poor intellect, do you hope to defeat us while from us you borrow your evidence? Your victory is your defeat."

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  9. Bill, the evidence that the brain uses ICT is that we now know in some detail (by experiment) that the visual field is always a mixture of reality (clustering around the center of attention) and virtual reality (outside this center). Furthermore Yu, Dayan and I worked out the cholinergic mechanism in the brain that actually does this. Thus, as Crick said rightly, "We do not see what is actually 'out there' but what the brain computes to be most probably 'out there'." To say that the brain is, or is not, a machine seems to me to depend on our definition of 'machine'. The brain is not a 'piece of technology" but uses processes that are also used in human technology. Would you say that the heart is a pump? —that it uses pump technology? Is the elbow a lever?
    John

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  10. This illustrates rather well what Raymond Tallis discusses in terms of "transferred epithets" in a section of his book punnily entitled "Myth-Information." He writes about how through "thinking by transferred epithet" one is able to "sneak across the mind-brain barrier using, as cover, terms that have roots in both mental and physical domains; machinising the mind; anthropomorphising and machinising the brain and bits of the brain; attributing to isolated brains--or neural ensembles or even single synapses--properties, qualities and faculties that whole persons in entire worlds would be proud to possess; succumbing to the fallacy of misplaced explicitness--all of these intellectual follies have spread have spread . . . from a philosophical epidemic to a near-pandemic." In his view this reflects a form of magical thinking, much as Howard Bursen showed in his book "Dismantling the Memory Machine" that all trace theories of memory share a common defect that would require that the brain works by magic.

    More specifically again with reference to the potential pitfalls of reasoning from analogy, one goes from likening the action of a bodily organ to that of a man-made device, to saying that the heart *is* such a device. But surely one would never do the reverse and liken a pump to a heart, let alone say that a pump is a heart, because the heart possesses many characteristics that a npump lacks (for one thing, it is alive). Appealing to "virtual reality" is just another technological analogy, because it presupposes--rather like Crick apparently did--that we somehow know what reality "out there" is, which only begs the question of how.

    For these reasons I suspect that the conclusion you offer, John, may be somewhat overstated and theory laden. If one removed the layers of theoretical interpretation from the findings you mention, it would be interesting to see what remains, and what it tells us--perhaps something very interesting that calls for a different model altogether to explain.

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  11. When one says that the heart is a pump one is saying something about its essential function, and not that all pumps are alike in all respects. Likewise when one says that the brain uses information compression technology one is not saying that the brain is like digital television in other respects. Tallis's dicta seem to me to put an unnecessary constraint on useful thinking in neuroscience. Let me give a personal example. When Yu and Dayan described the function of the cholinergic input to the cortex from N. Basalis (excitatory to retina input and inhibitory to the cortico-cortical input) they did so in terms of 'induction', which did not explain much. However, shortly after I had read their anatomical findings, I happen to be talking with a friend, who is a TV engineer and specialist in the design of information compression systems, about what he was doing in this field, and what he told me allowed me to make much more sense to me of Yu and Dayan's findings than their own explanation did.
    What counts in science is what works.

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  12. Tallis is not faulting the value of analogies per se, but problems with their use that are rampant not only in the field of cognitive neuroscience, but in cosmology as well. Quite simply put, ICT is only a valid analogy if the brain is processing information. As Tallis is at pains to show, that idea (or assumption) itself may rest on false premises, and even on mixing different senses of the term "information" indescriminately that results in fallacious arguments. I highly recommend his book for being the first (that I know of) to question head on much loose quasi-engineering jargon being applied to both the physical sciences and life sciences, and particularly to the understanding of the senses and brain. Walter Elsasser and Paul Weiss also had problems with the application of certain concepts borrowed from communications engineering technology (such as genetic coding). I was surprised that Lord Russell Brain adopted information processing as an explanation for perception late in his career, rejecting representationalism in the process.

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  13. It has long been known that the heavens appear finite, the so-called "vault of the heavens" appearing as a flattened, interior of a sphere. This is a perfect example of what Mach meant about the dual role of the selfsame sensations in science: The same perception is applied to describing the physical heavens above us, yet we talk about it being the shape of visual space when it refers to visual perception itself.

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  14. I can answer the question of the reason for the apostasy of Lord Brain. He came under the malign influence of Donald Mackay, who was a fanatical information theory protagonist and also a born-again Christian, who tortured logic to "prove" that a complete psychoneural identity theory was quite compatible with Christian doctrines. I knew them both quite well. Anyway he it was that did Brain in.
    I agree that "information" is a term wildly misused in the brain sciences. Consider the fact that patients with associative agnosia can see the world perfectly well but cannot obtain information from what they see. Therefore seeing does not = information gathering.
    Re "vault of sky argument". Following Broad, is it not better to distinguish between perception (of external objects) and sensing (of our own sensations). Otherwise we tend to fall into the TV fallacy (that the images on the TV screen are actually the objects in the TV studio?

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  15. Cases of associative agnosia recall what Sherlock Holmes says to Watson in "The Adventure of the Blue Carbuncle": "You can see everything. You fail, however, to reason from what you see." Under such conditions the visual field is singularly uninformative. As Tallis points out, the notion of "information processsing" in cog. sci. somehow has energy from stimuli magically converted into so-called "information" once it stimulates the nervous system--voilà! That's where all the the nonsense begins, once one accepts that unexplained magical transformation of energy into "information" in which no human agency is involving in doing the "informing": What a whole person does is magically attributed to the activity of even single neurons.

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  16. John, I am not sure how Broad's distinction to which you allude above helps us here. Can you perhaps elaborate a little more?

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  17. Re Broad's distinction: I interpret him as saying that, in discussing a functioning representative mechanism, one needs to distinguish between the process as a whole (perceiving) and the end result of the process, when you decide to introspectively study that (sensing)

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  18. I was unaware that Broad talked about representationalism as such, but as I have argued already, we need to distinguish two kinds of perceptual process: (1) that involving posited physical interactions (between physical objects, light, retina, and brain) and (2) the process of perception as it is experienced *within* the visual world, as when I shift my gaze to look at a painting on the wall, or to read a paper on my desk. Those are acts *within* the perceptual world, i.e., what we ordinarily call "seeing." So the act of perceiving itself is clearly in some sense experienced *within* the visual world which, in that case, involves no direct interface with physical interactions, but only perceptual ones. The physical interactions are therefore outside the perceptual ones in that sense, whereas a psychophysical account would involve putative interactions *between* the physical and the perceived worlds.

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