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Author Topic:   My problem with evolution
obsidian
Inactive Member


Message 62 of 120 (23460)
11-21-2002 2:14 AM
Reply to: Message 55 by robinrohan
11-20-2002 5:31 PM


Robinrohan,
You pretty much got the gist of what Quetzal said, but your analogy is flawed.... Yes, I would suggest that the image, such as that of the beautiful woman you are using in your example, is physical. But it is a different physical than what you seem to be proposing.

Take your analogy to the TV... In a TV an exact scaled replica in 2D is emitted from the screen based off of an input hundreds of miles away.... Yes, in that case there are certain set things you can measure physically (such as a scaled height). However in the brain, the visual inputs of different wavelengths(e.g.colors) excite different neurons in the eye. The signals are sent via the optic nerve and other pathways until it hits the occipital lobe (at the back of the brain) Here the information is divided up even farther.

For instance, you are looking at a red cube in bright light. Well, the photoreceptors in your eye, specifically the cones that respond to red wavelengths are activated and send their info to the brain. If you were looking at another color, a different set of cones would be activated and in low light conditions an entirely different set of receptors, rods, would be activated. The information sent from the optic nerve from the receptors is topographically (spatially in relation to the neuron input) maintained on its way to the visual cortex (I am trying to drop the really specific stuff here to give you an overwiew). Approaching the visual cortex, visual information is processed to 'recognize' edges and at the occipital lobe its broken down into stimuli from right and left eyes, color and non color, and orientation (what direction the stimulus was in).

So you see, even when you look at a beautiful women (physically), there is no mini beautiful women hiding in your brain somewhere... just a collection of electrical impulses that your brain interprets from past experience. So when you are imagining a beautiful women, your brain is firing a lot of the same signals, and some from the hippocampus (the center for memory) in order to produce that image. But the imagined is never as concrete as the original .

Also, to help cement the idea that it is physical, like your TV analogy, certain physical aspects of a visual image, whether real or imagined can be measured through EMG (recording electrical signals from firing nerves), from experiments with PET scans, and the results from lesions in the brain. Place an electrode into a region of the brain and you can record signals, which correspond to sensory/motor input/output. You can also stimulate parts of the brain as well by applying an electrical signal, which will in turn cause a patient to feel what is not really happenning... maybe that their arm is moving etc....

Hope this helps a little,
Obsidian


This message is a reply to:
 Message 55 by robinrohan, posted 11-20-2002 5:31 PM robinrohan has not yet responded

Replies to this message:
 Message 64 by Quetzal, posted 11-21-2002 3:56 AM obsidian has not yet responded

  
obsidian
Inactive Member


Message 69 of 120 (23496)
11-21-2002 10:46 AM
Reply to: Message 66 by robinrohan
11-21-2002 9:00 AM


Robinrohan,
I wanted to add an addendum to my post above, the information that is sent to the occipital lobe is also sent to other areas of the brain for post processing to glean even more info from the data.... Anyway, back to the topic....

In terms of "'seeing in your mind's eye' as it were is an image presented to your visual cortex." I think the words 'presented to the visual cortex' are key here. Whether real or imagining your visual cortex recieves info about an image (not necessarily the unified image itself)from certain set neural networks, plus some added ones (the eyes or the hippocampus). This information is organized in different sections and your brain interprets the signals that it received based on past experience.

I don't think there is a 'monitor' in the brain. The brain, to me, is just one big sensory receiver and motor output device with some memory thrown in there that has internal circuitry to process all the info. You recognize something if you are looking at it, like a woman, based on certain characteristics... when you imagine a woman, your brain uses memory (coupled with alterations according to preference, hair color, weight etc) and the same pathways to 'fool' (although you are not really duping your brain) the brain into 'seeing' what you are imagining.

I would like to bring up additional points. The brain is NOT like a TV, deficits in the brain can produce deficits in the visual system and can affect what you can imagination. For instance, a color blind person (from birth)..... how would you describe the colors to them? Give me a definition of red... or yellow? The parts of the brain that are used for color processing are not present in color blind individuals. An image that you and an color blind individual see are not what is getting coded/received into the color blind persons brain the same way. Now I don't know if color blind people dream in color, (it would be an interesting experiment) but how could you test it? They couldn't describe the colors in their own dream, because there is no past experience. (They might be able to dream in color because of random firings of nerves, but I don't know really) And completely blind people (from birth) there is no 'image' at all, they use an entirely different set of sensory info to 'look' around their world. There would be no 'image' at all in that case.

Essentially the brain is a tool used to gather information about the world. Memory helps us to navigate safely around the world.... For instance, a person who has never seen a snake before(that includes books/internet) is bit by a snake. Before, if I asked that person what does a snake look like, they wouldn't know. But afterward, memory gives you a basis for what a snake is supposed to look like and your experience allows your imagination to modify that image (bigger fangs, creepy color). And it is impressed on you that snake=bite=bad, so you can avoid it in the future. So when you are out walking in the woods and you see one, you won't go up and try to pet it. The brain is geared up for our survival, it receives sensory info in order to derive relevant info to keep us alive. Imagination is a form of memory recall, which is key to our survival.

Obsidian


This message is a reply to:
 Message 66 by robinrohan, posted 11-21-2002 9:00 AM robinrohan has responded

Replies to this message:
 Message 70 by robinrohan, posted 11-21-2002 12:03 PM obsidian has not yet responded
 Message 71 by Minnemooseus, posted 11-21-2002 12:41 PM obsidian has not yet responded

  
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