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Medical What part of the brain is conscious?

  1. Aug 1, 2005 #1

    Q_Goest

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    The 15 July 2005 issue of Science has an interesting article regarding something called anosognosia.

    It seems very strange that one is unaware of their own paralysis while they are completely aware of the person they are being interviewed by asking them about it. The patient in this case would simply need to look down and realize that when consciously attempting to lift an arm, it would not move.

    Similar problems might include the belief that limbs are still attached when in fact they've been amputated. That seems to be a similar phenomena wherein the brain is consciously aware of a limb that simply doesn't exist. Another problem I've seen is people with memory loss not realizing they even have a memory problem or constantly forgetting they have this problem.

    If one were to model the brain as a mechanism of some sort with nerve inputs, it would seem that there is a borderline within the brain beyond which conscious awareness can not extend. In other words, if the input/output for the conscious portion of the brain simply goes silent and does not register anything, it would seem as if we can not be consciously aware of it or our consciousness is not impared by it except as that input/output may affect things such as memory.

    We often view consciousness as being seated in the brain, but I wonder if there is any evidence which points to some limited location within the brain. The article in Science mentions specific locations, but unfortunately I'm not a neuroscientist and have no idea if this entire concept of there being a specific region of the brain responsible for consciousness has been examined. Any comments would be appreciated.
     
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  3. Aug 1, 2005 #2

    hypnagogue

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    The technical term for those parts of the brain whose activity is correlated with consciousness is "neural correlates of consciousness" (NCC for short). It is certainly the case that not all systems in the brain are NCCs, since the brain does a lot of information processing that can be shown to be unconsciousness, that is, not available to conscious awareness. Much more work needs to be done before the NCCs of the various features of consciousness can be exhausitively mapped out in detail, although the thalamocortical circuit seems to be a centrally important system as regards correlation with consciousness. (The thalamus is located roughly in the middle of the brain, and is often described as a 'relay station' to the cortex; all sensory input channels except smell feed into the thalamus. From the thalamus, there are dense neural connections to the cortex, where sensory information is processed further.)

    Although it might seem intuitive and straightforward, the concept of what an NCC really is is somewhat subtle. A good discussion of what we should mean by an NCC can be found in David Chalmers' paper What is a Neural Correlate of Consciousness?. For some references on scientific research of NCCs, see this link; for references on research of the NCCs of visual consciousness, see this one.
     
    Last edited: Aug 1, 2005
  4. Aug 1, 2005 #3

    Q_Goest

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    Thanks for the info, I'll check those out shortly.
     
  5. Aug 2, 2005 #4
    Consciousness is so complex and so little understood that I beleive it is
    not productive to try to localize "it" in a specific part of the brain.
     
  6. Aug 2, 2005 #5
    How do you suppose we attempt to make it more understood if we do not try to locate it? Even failure is informative.
     
  7. Aug 2, 2005 #6

    Q_Goest

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    Yes, that's really my question, "is there a location, or more accurately, a given volume of the brain which is responsible for the phenomenon we call consciousness?"

    It seems in the case of people with anosognosia, severed limbs and other maladies, there is a disconnect. Similarly, I suspect there are portions of the brain itself, such as those portions which might store memories, that don't contribute directly to the conscious experience.

    I wonder what research has been done (especially on people that have undergone some brain damage) and what conclusions have been made. It seems the thalamus as mentioned by Hyp have been specifically mentioned in the literature.

    I seem to remember a famous case of a man shot through the head with a steel spike who was working on a railroad over 100 years ago that survived and who's consciousness was relativly unaffected, but his personality was significantly affected. This is another case of consciousness not being affected, but only things that govern behaviour being altered.

    So are there portions of the brain such as memory, or portions that govern behavior or other functions that DON'T contribute to the conscious experience?
     
  8. Aug 2, 2005 #7

    Q_Goest

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    On a separate note, there must also be portions of the brain which perhaps perform specific tasks related to the conscious experience. I seem also to remember hearing about a woman who could not distinguish how fast oncoming traffic was traveling. She could see a vehicle, but for some reason couldn't determine how fast it was coming. Other people have problems not consciously seeing something, but are able to react despite this.
     
  9. Aug 2, 2005 #8

    We should attempt to understand it as something that emerges from the
    complex interplay of many different parts of the organ, not as something
    that is spatially confined to one or another parts of it. K?
     
  10. Aug 3, 2005 #9

    Q_Goest

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    When you say "parts of the organ" I presume you mean "brain" which has some boundry around it, as opposed to "parts of the organ" meaning body which includes the brain as a sub-part. Is this to presume that only neurons (or does this include glia?) are capable of consciousness then? Because if we rule out every other part of the body, including nerve cells such as the spinal chord, we are left with a group of neurons with an interesting interface. Somewhere it changes from neurons to not neurons. What is that interface, and where is it?

    I tend to wonder though if this is a good assumption, that all the neurons in the brain are capable of consciousness, but no other cells are. Certainly not all the neurons in the brain are going to be used in the conscious experience at once, but many of them will. So there must be a switching on and off somehow. This switching on and off can also be affected by something as simple as xenon, used as an anesthetic for example. (Ref: Patent 5228434)
     
  11. Aug 3, 2005 #10

    Les Sleeth

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    Let's say you are trying to figure out what part of a radio produces language. You don't know where language comes from, but you have already assumed the radio itself generates language because that's the only place you hear it. The technology you have doesn't allow you to detect radio waves, so the idea that language might originate outside the radio, as a signal, seems non-parsimonious.

    What you do, because you are committed a priori to a radio explanation of language, is try to show exactly where in the radio that language emerges so you can say "THERE," that's the seat of language. In this analogy, it is obvious that just because language emerges from the radio's speaker doesn't mean the speaker created the language.

    Yet that is exactly what a great many thinkers assume about the brain even though we can't find any evidence that physicalness (i.e., the brain) is capable of generating consciousness. Affecting it, shaping it, organizing it, giving it a means for manifesting itself in this universe . . . yes. But creating consciousness . . . no.
     
  12. Aug 4, 2005 #11

    hypnagogue

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    Les is correct to point out that observing a correlation between brain activity and conscious experience is not, in itself, sufficient grounds to deduce the nature of the causal relationship between the two. Of course, that latter topic is itself the subject of much discussion and debate in the sciences and philosophy.

    However, I think we can and should proceed with this discussion without delving too much into the deeper metaphysical issues; those are further questions that are best left to other threads. Along these lines, saying that the brain is conscious, or that the brain produces or is causally responsible for conscious experience might seem relatively harmless, but in reality these phrasings are theoretically loaded. However, if we restrict our discussion to the neural correlates of consciousness, we can still have a fruitful discussion here that is faithful to the thrust of this thread's topic, while remaining neutral on the more complicated metaphysical issues.
     
  13. Aug 4, 2005 #12

    hypnagogue

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    There is something to be said for this view. For instance, it is believed that various neural correlates of visual consciousness lie along the visual processing stream, beginning in area V1 of visual cortex in the occipital lobe and traversing the ventral processing stream to areas of the temporal lobe. Roughly stated, this means that certain activations of certain neural systems in these brain regions are correlated with certain features of experiential, visual consciousness. This might create the appearance of something of a modular view, on which the neural systems in the visual processing stream alone are enough to provide sufficient conditions for the existence of visual consciousness.

    However, it is tacitly understood that for this correlation between neural systems in the visual processing stream and visual consciousness to hold, the relevant neural systems must be functioning in the wider context afforded by other neural systems. For instance, it is known that damage to the intralaminar nuclei in the thalamus leads to coma. If we assume for a moment that being in a coma implies the loss of unified, high level human consciousness, it follows that visual consciousness is lost as well. Thus, in order for neural systems in the visual processing stream to be correlated with visual consciousness, it seems that at least one background condition must be met: The intralaminar nuclei in the thalamus must be properly functioning. There are probably hosts of other such neural systems in the brain that must be functioning properly in order to provide the context in which certain neural systems are correlated with visual experience.

    Nonetheless, the activity of the visual processing stream is related to visual experience in more direct and finer-grained ways than the activity of the intralaminar nuclei, so we would be missing something if we didn't distinguish between the two. Ideally what we want is to be able to draw as fine-grained a correlation between neural activity and subjective experience as possible, while still paying heed to the more global, background conditions that come into play. In the paper I referenced earlier, Chalmers succinctly incorporates these considerations (and others) into his general definition of a neural correlate of consciousness (NCC):

    For a good extended discussion on this topic (modularity of NCCs vs. global considerations), see the section of Chalmers' paper titled "Direct correlation."
     
    Last edited: Aug 4, 2005
  14. Aug 4, 2005 #13
    The previous three posts are very good.

    We need a more comprehensive working definition of consciousness.
    Maybe this fellow's actual thought patterns changed. Or maybe they
    didn't but his temper (an emotional-glandular interaction) was altered.

    For humans anyway I would think that our emotional states should be
    included in the description of consciousness.

    And let's not forget that there is a subconscous layer that underpins this
    which is only faintly understood if at all.
     
    Last edited: Aug 4, 2005
  15. Aug 4, 2005 #14
    isn't hte entire brain consciousness? If i remember correctly, you can lesion off any part of the brain but youi will lose certain capabilities that that part of the brain processed. perhaps memory, perhaps learning, physical motion.
     
  16. Aug 4, 2005 #15

    LeonhardEuler

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    The fact that you loose abilities when a certain part of the brain is lost does not imply that this part of the brain is concious. It may be that this part simply performs calculations and gives relevant results to the part of the brain that is concious.
     
  17. Aug 4, 2005 #16
    the right part of the bran is concence thats what i know. see this girl got her left brain replaced cause of a desies and she still had a concence and went to rehab and the docs say so to
     
  18. Aug 4, 2005 #17
    leonard: then what is your definition of consciousness? awareness like that of an animal?
     
  19. Aug 4, 2005 #18

    LeonhardEuler

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    Being aware that you exist and having feelings.
     
  20. Aug 4, 2005 #19
    exactly your sences come from the left side of you brian :rofl: :bugeye:
     
  21. Aug 5, 2005 #20
    neo-cortex
     
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