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Brain projection

  1. Apr 23, 2010 #1
    I was just wondering where or if the brain projects mental pictures. I see them in front of my forehead. Is there where everyone sees them or is it different for everyone?
     
  2. jcsd
  3. Apr 24, 2010 #2

    apeiron

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  4. Apr 24, 2010 #3

    Pythagorean

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    You mean imagined or memorized or live images?
     
  5. Apr 27, 2010 #4
    The lens of your eye projects an image onto your retina, which is the back part of your eye. The 90 million rods and 4.5 million cones detect light and color that hits a particular area of your eye and transmits a signal through your bipolar cells & retinal ganglion cells, through your (LGN) thalamus and back into the occipital lobe.

    I don't know if any "images" are formed after your lens projects an image onto your retina though.
     
  6. Apr 27, 2010 #5
    I can't tell exactly what you mean. It almost sounds like you experience real-seeming visual experiences, images you actually see with your eyes, that are located in space somewhere in front of your forehead.

    In that's the case you'd be talking about a kind of imagination that is much more vivid than most people experience. Tesla imagined things this way, and there are (only) a couple PF members who've reported similar things.

    I hope you come back and clear up what it is, exactly, you're talking about.
     
  7. Apr 27, 2010 #6
    Sorry I was not more clear. I mean the images of thought. When your eyes are closed. Are those images actaully projected anywhere. Or does my brain just nmake me beleive they are projected in front of me?
     
  8. Apr 27, 2010 #7

    Evo

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    In this case, your brain is making you believe that they are being projected outside. Sounds cool.
     
  9. Apr 27, 2010 #8
    You might want to research visual cortex and visual field. I'm not an expert on this, but a few points that might interest you:

    The "cortical homunculus" is a quite literal projection of the body into the brain. So it wouldn't be too surprising if something very similar occurs for vision.

    The image on the retina is very unlike the visual field in your mind, for example because your eyes are constantly twitching rapidly all over the place (scanning the high-resolution part of the retina over the detailed parts of the panorama), whereas I presume your visual field stays centred in the direction your head is facing.

    I think various details like the part of the neural pathway at which some signals from one eye cross into the visual field for the other eye (noting the fields of view from each eye do overlap) have been studied.

    Edit: should have read apeiron's link first..
     
  10. Apr 27, 2010 #9
    OK, I think I know what you mean now.

    If I close my eyes and imagine something, it seems to take up position in front of me, and outside of me. There is a certain vague vestige of the sense of exterior location of real vision that seems to accompany merely imagining a visual scene.

    That doesn't explain, though, why your images seem to be in front of your forehead instead of generally spread out over the visual field. Mine seem to correspond to what I'm imagining. If I remember being at the ocean all the elements of the image seem as close or far as in the real scene, and just as spread out.

    I wonder if you close your eyes now and "remember" what your computer and desk looks like in front of you if your imagination of it holds the same place and distance from you it is in reality or if it gets displaced to be in front of your forehead?
     
  11. Apr 28, 2010 #10

    apeiron

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    There is a lot of individual differences in mental imagery. Around 10 percent of the population have very vivid "like actually looking at it" imagery. They also are the highly hypnotisable as a result.

    I don't really get any strong sense of looking out into the world. But then I also score low on hypnotic susceptibility.

    The key thing to say about mental imagery is that it is all about generating states of perceptual anticipation - this is what seeing a cow or sherman tank might look like, without then having a cow or tank to confirm the expectation state.

    So it is about using the perceptual hierarchy in reverse. And those with strong imagery probably can push neural activity all the way down to primary visual cortex in a strong way.

    The brain does deal with what and where information in separate flows of information. So the idea of a cow as a visual object would be generated by the temporal lobes while the experience of a cow in some particular location in visual space would be a dorsal cortex action. So you can see more scope for individual differences there. Some might more strongly place images in a concrete spatial context than others.

    Cesiumfrog makes a good point about the way our eyes actually dance about so the apparent stability of visual experience is highly constructed.

    Here is an old article I wrote on that question.....

     
  12. Apr 28, 2010 #11

    apeiron

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    Oh I forgot, I also wrote a quick one on mental imagery too, which is even more relevant, so may as well post it.....

     
  13. Apr 28, 2010 #12
    If i'm trying to remember something, a formula for instance, I "see" it on the boundaries of my peripheral vision when my eyes are open. When my eyes are closed I can see the image wherever I want, but it usually appears in the position where I first saw the real thing when my eyes were open.

    Sometimes I can envision entire scenes while walking around. I look like i'm totally zoned out when I do it and am slightly aware of what's going on around me, but extremely aware of what's going on in my waking dream of sorts... Those are usually brought on when I consider future events, like when trying to figure out the tax of what i'm going to buy at the store before I get there, this triggers a whole scene of me talking to a cashier it's pretty cool, but I don't drive because I zone out too much...

    I also get the verbal meaning of the word too (like mentioned in the post above), if it's a sentence the image pops into my head then the sound comes. I have a really hard time copying down the image or explaining it without having a sound attached. I'm always the first one in class to ask "How is that symbol read?"
     
  14. Apr 28, 2010 #13
    I like rhinoceroces and had instant success recalling one I'd seen in a zoo in Omaha as soon as you said "For example, imagine a rhinoceros." Then, however, I read the next sentence that instructs that we should first anticipate that we are about to see a rhino. That struck me as cumbersome and unnecessary to the process. I didn't have to put myself in any anticipatory frame of mind for the image to come up. The act I performed would better be described as 'grabbing' the image.

    My attempt at anticipating seeing a rhino lead to a rather quick image of a vivid South African desert with some scrub trees and bushes. The rhino was behind a tree, not visible, and I was waiting for it to walk into view. I don't think that's what you meant.

    The process is pretty fast and I couldn't slow it down to observe it.

    I think that's pretty strange about the professor who had no mental images. To be clear: he was claiming he had no interior monolog as well?
     
  15. Apr 28, 2010 #14
    How vivid are the scenes you envision? What do you mean by "envision"? To what extent do they seem percieved by the eyes, if at all? Do they have the vividness of a movie projected out into the space in front of you?
     
  16. Apr 28, 2010 #15
    Isn't our normal vision mostly imaginary anyhow? My eyes are not scanning all of the room and printing an image in my mind (from vision) like an old dot matrix printer when I see. More like I see the some of the edges of objects, their general shape and movement and then my brain identifies what these objects are and fills them in. Magic parlor tricks and optical illusions can prove where there are gaps in this system.

    I have very poor vision without glasses but sometimes I can read printed words at a distance by seeing the shapes of words (but not letters in them) and some parts of the outer edges of these words and their logical placement within the sentence structure. I can read at a distance far better than my vision would suggest because my mind fills in more than I can see. I prefer to wear my glasses though. I have -10 vision without contacts but those mornings where I am late to put my glasses on, I still can get by fairly well. I think this is because even when I "see" it is mostly in my mind.
     
  17. Apr 28, 2010 #16

    apeiron

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    The process is fast - that has been measured. It takes around a third to half a second for a mental image to become intensely developed. And probably only a fifth of a second if the mental response is over-learnt and habitual rather than novel.

    So it sounds like your first response to reading the sentence was a stereotypical flash, the second was a more effortful and novel attempt to generate an image.

    Interesting that the rhino was hidden - you were indeed anticipating a more general rhinoceros scenario as a ruse that would encourage some unbidden novel imagery to "walk in".

    These are the kinds of tricks of thought we learn to employ to make things happen in our head.

    With practice at introspection (because self-awareness is a learnt skill not a neurological function!) you can learn to catch the early dawning stages of image formation. But most people only want to get to the results so don't ever learn to do this.

    It took me a few years to get to the stage I could catch the fine detail of my own unfolding thought processes with any clarity.

    No, he knew he was talking to himself. But I think the story was that he indeed had poorly developed introspective skills and had never really paid much attention to his thoughts as an objective process (rather than merely just getting on with thinking).
     
  18. Apr 28, 2010 #17
    thanks for the articles. Very interesting and well written. I just realised that my mental images are not only infront of my forehead. They are everywhere my eyes look. I just tend to look up when I close my eyes hence the image being there.
    Interesting that you mentioned drugs aswell. I did mushrroms a few times when I was younger and the things I saw when I closed my eyes were so strange that I could not beleive they were coming from my own brain. But I assume that is my brain miss firing so I percieve very random images of lots of things combined to form new strange things.
     
  19. Apr 28, 2010 #18
    Makes sense.


    I wonder if you saw any Kluver "Form Constants":

    http://en.wikipedia.org/wiki/Form_constant

    http://images.google.com/images?hl=en&q=kluver form constants&um=1&ie=UTF-8&source=og&sa=N&tab=wi

    These are elementary patterns that seemed to be inherent in our visual systems: they repeat across individuals and cultures. Apparently they often appear in hallucinogenic drug use.
     
  20. Apr 29, 2010 #19
    I heard that using transcranial magnetic stimulation (TMS) on the occipital cortex can cause the participant to perceive flashes of light. If this is true, what does this suggest about the formation of mental images in the brain?
     
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