Talk:Visual system

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Contents 1 The task of the visual system... 2 From the new york times - what you see depends on what you expect to see 3 139.xxx 4 Links to the Somatosensory system components 5 Strange sentence

[edit] The task of the visual system...

The article currently states: The task of the visual system is to interpret what would otherwise be a two-dimensional image of the world as a moving, colored three-dimensional world. There also would not be a two-dimensional world without the visual system. Isn't the task of the visual system to interpret what would otherwise be sensed only by touch, smell, taste, and hearing? AED 03:43, 7 October 2005 (UTC)

I agree that this definition is imprecise. I just changed it. Fell free to change further, obviously, and be bold! :) Gaelle 06:12, 24 October 2005 (UTC)

[edit] From the new york times - what you see depends on what you expect to see

"Photons bouncing off a flower first reach the eye, where they are turned into a pattern that is sent to the primary visual cortex. There, the rough shape of the flower is recognized. The pattern is next sent to a higher - in terms of function - region, where color is recognized, and then to a higher region, where the flower's identity is encoded along with other knowledge about the particular bloom. The same processing stream, from lower to higher regions, exists for sounds, touch and other sensory information. Researchers call this direction of flow feedforward. As raw sensory data is carried to a part of the brain that creates a comprehensible, conscious impression, the data is moving from bottom to top. Bundles of nerve cells dedicated to each sense carry sensory information. The surprise is the amount of traffic the other way, from top to bottom, called feedback. There are 10 times as many nerve fibers carrying information down as there are carrying it up. These extensive feedback circuits mean that consciousness, what people see, hear, feel and believe, is based on what neuroscientists call "top down processing." What you see is not always what you get, because what you see depends on a framework built by experience that stands ready to interpret the raw information" [1] 4.250.168.126 16:02, 22 November 2005 (UTC)

[edit] 139.xxx

I reverted the changes by 139.xxx on the strength of the related changes to the Eye article which was detected by others and partially reverted; I completely backed out 139's changes on this article and on Eye. --Ancheta Wis 02:52, 29 November 2005 (UTC)

[edit] Links to the Somatosensory system components

I can't find Edinger-Westphal nucleus in the index of Martin Tovée's book; perhaps this link should be part of a section which links to Somatosensory system, as part of the proprioception chain. But proprioception is not in Tovée's book either. Would it be acceptable for us to work out a way to include discusssion of the Edinger-Westphal nucleus in the proprioception article? We could craft the text here, if you like. --Ancheta Wis 01:47, 7 December 2005 (UTC)

The subsection regarding the eye mentions the lens which the EWN affects during accommodation. I guess it is only indirectly related to the processing of light, so I'm OK if you prefer to remove it. AED 05:40, 7 December 2005 (UTC)

While trying to link to somatosensory material, I was struck by a possible parasympathetic connection of the Postcentral gyrus and Edinger-Westphal nucleus. Is there anything about this? --Ancheta Wis 09:14, 7 December 2005 (UTC)

I'm afraid I can't help you. Cheers! AED 21:53, 7 December 2005 (UTC)

[edit] Strange sentence

From the article: In humans, the optic nerve is connected directly to the brain rather than through exclusive connection through the medulla

This doesn't really make sense to me. The medulla is part of the brain, so how can the optic nerve connect "directly to the brain rather than through ... the medulla"? Also, the olfactory nerve connects directly to cortex without going through the thalamus, and the optic nerve projects to they hypothalamus (for circadian and pupilary light response regulation) and the tectum. This seems misleading to me.

--Selket ^Talk 00:02, 16 March 2007 (UTC)

Clarified that the optical pathway described in the article bypasses the brain stem -- Ancheta Wis (talk

No offense meant, but that really doesn't fix the problem I was trying to raise. I may not have articulated my concern as well as I would have liked. Adding that the medulla is in the brain stem is helpful but doesn't address my concern. The brain stem is part of the brain. Therefore anything that does go through the medulla is still connected directly to the brain. --Selket ^Talk 00:49, 16 March 2007 (UTC)

Base of the brain. Brain stem is the part chopped off, next to the cerebellum

That is the point of the article. The neocortex is closer to the visual system than the brain stem. It is not stated anywhere that I can cite, but there appears to be a closer connection between the somatosensory system and the brain stem, not visual system. Have you looked at some of the other articles about the brain? Our brains are not unitary, but are composed of many other subsystems. I suppose that is the reason that we can live without significant amounts of cortex, but without the brain stem, we die. That's why neurosurgeons took out parts of Bob Woodruff's skull, to keep the swelling of the cortex (brain) from squashing the brain stem, which saved his life. The picture has been known for 400 years. The brain stem is what you see below the optic chiasm which is different from the cortex. But our eyes follow the red pathway to V1, the last part of the cortex which we can follow directly from our eyes. This is in the article. I agree that we should not discount other pathways, but this article has only items which I could cite from the references listed. If you have other information which you can cite, let's have it. Some of the very interesting information about mirror neurons etc appear to rely on these other nerve pathways which need citations for the encyclopedia. --Ancheta Wis 03:03, 16 March 2007 (UTC)

(edit conflict) Again, I mean no offense, but Bob Woodruff aside, we can't live without our brainstem because it controls breathing. We can live without visual cortex, but we're blind; we can live without motor cortex, but we're paralyzed; we can live without a temporal lobes, but we are unable to form memories (see: HM (patient)). Function is distributed and specialized, that is why some regions are required to sustain life and others aren't. But, you make my point for me. The medulla is part of the brain, so it is impossible to go directly to the brain not bypassing the medulla, because as soon as you get to the medulla, you are in the brain. Some of the somatosensory system's inputs go through the medulla other's don't. Tactile input from the face, for example, goes through the trigeminal nerve (Nolte explains it better) enters at the pons and then projects caudally to the medulla before projecting anteriorly to VPL and VPO in the thalamus.

I've fixed up the section somewhat and added references. If you have a citation for "there appears to be a closer connection between the somatosensory system and the brain stem, not visual system," put it back. I think it is unlikely that you will find one though. --Selket ^Talk 03:43, 16 March 2007 (UTC)

I like your citations. They send the article in another direction, which is not part of vision, but which appears to be part of our subsystem for attention. This begs for another article. Is there an article for the reticular activating system, for example. --Ancheta Wis 03:45, 16 March 2007 (UTC)

reduce indent There are articles for visual perception and the visual system. There is considerable overlap. This article seems to focus more on anatomy, while the other emphasizes psychology. You are right that the projections to the SCN, the VLPO, and the Edinger-Westphal nucleus are not part of the visual system per se. They use the visual system to regulate other functions. However, I think the superior colliculus is part of the visual system in that to do basically any visual task require eye movements. It is part of the system the same way the muscles that control rat whiskers are part of the whisker system. --Selket ^Talk 03:54, 16 March 2007 (UTC)

I thought of an experiment which should disambiguate the visual pathway processing (eye to V1) of the article from the attention processing which you are bringing up.

1. Find trained people, such as airplane pilots, who can act in specified ways based on what is in their visual field. Verify that their reactions to some feature will consistently trigger that visual pathway.
2. Increase the rate of stimulus of the visual pathway so that they cannot react consciously, but only automatically.
3. Identify the specific areas of the brain which are reacting.
4. Now find trained pilots who have damage to those areas
5. If your hypothesis is true, then the visual part of the brains of the damaged pilots will still fire under the stimulus, which would indicate that the visual pathway does not only depend on the eye-to-V1 path, but also on the posited brain stem connections. --Ancheta Wis 04:07, 16 March 2007 (UTC)

It is an interesting experiment. I don't think it has been tried exactly, but similar things have - I'll try to find a reference for you. I do think there is a problem in that it seems to confuse necessity with sufficiency. I agree that without V1, you can't see, but without the superior colliculus, vision is severely impaired as well. (See: here) Just because V1 is necessary for vision doesn't mean the the optic tectum is not. --Selket ^Talk 04:28, 16 March 2007 (UTC)