BrainMeta'   Connectomics'  

Welcome Guest ( Log In | Register )

Reply to this topicStart new topic
> Visual processing
post Sep 26, 2006, 08:58 PM
Post #1


Group: Basic Member
Posts: 1
Joined: Sep 26, 2006
Member No.: 5732

My question is about how the brain processes visual information and what kind of different parts or functions in the brain there are.

A couple of times I've abruptly waken up during sleep, possibly REM state or definitely some quite deep sleep (and not just one minute after falling asleep). Why I woke up I can't really say, but possibly due to sort of escaping from nightmare (or possibly just a sort of feeling of an electrical discharge but let's not get into that now).

As I wake up in this very special state, basically asleep but eyes open and observant enough to intelligently realize what is going on, my vision is extremely strange. For example, once I was looking at a pile of some cables and I could extremely clearly see that my cat was there, moving. But the cat was too long at the same spot (one minute?) and eventually I realized that it was rather hallucination and there was no cat. Another time I was looking at my blanket with some light coming from the window in the background. I could absolutely clearly see that the blanket was moving in different ways even at the same time I knew again it was a hallucination.

Let's forget about the cat for now. About the moving blanket incident. (Oh yes and I guess I have to mention that none of this has anything to do with drugs or such, I never tried them.) It very much seems that the blanket was moving either because some particular part of my brain was turned off due to the semi-sleeping state or it was turned on. The visual effect was NOT a product of imaginary dreaming. In a dream, you basically imagine everything. But in this case I was clearly looking at the blanket, extremely conscious that I was not sleeping and no matter how much I tried not to "imagine" or to get "sober", the blanket was still moving and wobbling in a certain way.

My question is, what is that part in my brain that was turned off or on and more importantly, what is the purpose of that part or function?

If I should give it a shot and quickly guess what it might be I might say that maybe there is a function in the brain that constantly alters each object in vision by changing their shape in multiple ways in order to compare the objects to memory prints. In other words, each candidate for an object (or it's shape) is subconsciously constantly altered until it matches with a memory print whereupon the object is recognized (or if it's not matched it either doesn't come across to consciousness or is interpreted basically as an unrecognizeable object). Note that this is just (remote?) speculation.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
post Sep 26, 2006, 09:07 PM
Post #2


Group: Full Member
Posts: 286
Joined: Jan 20, 2004
Member No.: 957

if I fixate on a ceiling, I can perceive it moving like the surface of a lake, but as soon as I move my eyes the effect is destroyed. Is this what you're talking about?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Paul King
post Oct 25, 2006, 03:18 AM
Post #3


Group: Basic Member
Posts: 49
Joined: Aug 14, 2005
From: San Francisco, CA
Member No.: 4500

The state one is in upon just waking up (or in the midst of falling asleep) is called the hypnogogic state. It is often likened to the highly suggestible trance state that is attained through hypnotic induction and other processes.

The view in neuroscience regarding sleeping and dreaming is that the sleep portion of the sleep/wake cycle (and particularly REM sleep) is a period in which the brain is switched into a different mode of operation. In this altered mode, the electrical oscillations in the brain as recorded by an EEG are different. The dominant theory is that the altered operational state of the brain during sleep is a memory house-cleaning state. In this state, memories collected in one part of the brain during the day are being reorganized and moved to other parts of the brain to be stored more efficiently and more permanently in a process called memory consolidation.

When the brain is in the sleep mode, it is believed that the information flows within the brain are different. In particular, during the waking state, sensory information is processed in a more "bottom-up" fashion. That is, visual information about light patterns enters the eyes and goes through various stages of processing in different parts of the brain, starting from "lower" areas and proceeding to "higher" areas. The so-called higher areas relate to object identification, cognitive reasoning, and planning. However during sleep, the flow of information from the sensory areas is mostly turned off, as is motor output (except when someone is sleep walking). During this period, it is believed that the brain is reorganizing information internally, probably starting from higher level information about situations and events. Thus information processing is likely to be flowing in a more "top-down" fashion while in the sleeping state.

Upon waking up, one is still in the hypnogogic in-between state. If this view of sleep is correct, one might imagine that the brain has not yet fully switched into organized bottom-up (sensory to cognitive) processing. Thus one would be likely to be more suggestible, to have a thought process that is "looser", and to find that one's imagination easily projects onto the external world. This would be especially true in a dark room when there is not much visual information available. In a dark room, it is easier to "fill in" the missing visual information with a speculation about the environment that has no sensory input information to contradict it. Because this process is all automatic and low-level in the brain, the net result is that what little information is visible is "organized" and "interpreted" in a way that might, under other circumstances, be filtered out before entering conscious awareness.

This process would not be much different from looking at clouds in the sky and "seeing" shapes in them. Or looking at a Rorschach Ink Blot and "seeing" fanciful forms in the sillohuettes.

One view that is circulating in theories of awareness and consciousness is that the vast majority of what we see is generated by the brain and is not actually "there". As an example, a flourescent lightbulb flashes on and off 60 times a second, and yet a room lit by flourescent light looks fully lit. Similarly, a TV screen is 90% black (take a photo with a fast camera) and is made up of tiny red, green, and blue lights, yet appears to us as solid full color. Taking this to its logical extreme, the argument would be that everything that we see is generated by the brain. What is actually out there are protons, electrons, and photons flying around. However the brain's process of image forming is so thorough and so stable that we never notice the seams of reality. The hypnogogic state in the morning would be a period when the brain's reality-forming function is less stable (it is still starting up for the day), and so we are more able to see the side-effects and seams resulting from its inaccuracies.

Incidently, it is not uncommon in the brain that the "top-down" pathways have more nerve fibers in them (and hence carry more information) than the "bottom-up" pathways. For example, consider the nerve fibers between the LGN (the first low-level relay for visual information processing) and the visual cortex (the next stage of processing which happens in the cerebral cortex). There are 10 times as many nerve fibers going top-down (away from higher brain centers) as those going bottom-up (from the eye to the higher centers).
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
post Nov 02, 2006, 08:43 AM
Post #4


Group: Basic Member
Posts: 1351
Joined: Sep 19, 2006
From: UK
Member No.: 5681

Hi jimhoyle, I thought I'd explain my experiences and give you another angle. Both experiences you have detailed are altered perceptions of reality, even an altered state brought about by sleep.

What you describe with your cat sounds like a combination of an optical illusion and a change of perception. I have had a similar effect several times, once on a dark night I couldnt work out what I was seeing, until I realised my eyes had reversed the outline of a tree and the horizon.

Another example happened to myself, my girlfriend and my brother. We were all stood outside a small shop, knocking on the door over and over because the light was on inside. We were there 15 minutes before the illusion broke and we realised the "light" was actually a light coloured vertical blind. That tricked all three of us.

The other description you have of movement where no movement should be is a common one. I first began to notice this kind of perception change when I was ill with flu, it seems it occurs naturally often when you have a temperature. Similar occurences are:

Things moving but not physically getting anywhere
Things growing but not getting any bigger
Things shrinking but no getting any smaller
Things just looking strangely large/small in comparison with the environment

All of these occurences happened to myself naturally, or as natural as fevers get. I have also experimented with various hallucinogens and am sure in my own heart that the movement you perceived in everyday inanimate things is the same as the movement seen in everything when tripping. The chemical induced state is obviously stronger so its easier to see.

Now some of my beliefs:
Chemical hallucinogens show the workings of the mind by altering parameters and perceptions. The similarity between this and naturally occuring altered states and perception shifts is not something to ignore, the fact the brain involves you in dreaming may be down to a chemical called DMT that is naturally occuring in the body of us and many many plants. This is the most potent hallucinogen on the planet and its within our bodies. I believe the brain produces this chemical in REM sleep, trances and mystical experiencse. The movement you saw was probably a residual perception change from the body not stopping production of it when it should have (ie when you awoke).

I believe the movement that is seen in various altered states is the raw uncensored reality. But thats my beliefs and definately not scientific.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
post Feb 17, 2007, 01:50 PM
Post #5


Group: Basic Member
Posts: 10
Joined: Feb 12, 2007
Member No.: 7740

To further discussion and/or knowledge on the mind bogglingly technical quantum neural network dynamics of "seeing things" (I mean, just look at all those integrals and watch how fast sigma notation flies by as each power point frame comes into focus, only then to dart away with its tongue sticking out):

[Lecture on Visual Processing; remove the dashes between "www" and "org" to follow the link- us low numbered posters get electric shocks when we post hyperlinks]

Believe you me, you will NOT regret watching the entire lecture. This is a man's life's work chasing after the Oz behind the curtain of visual processing, with an emphasis on patterns seen while having headaches and while undergoing hallucinogenic psychosis.

Still, do take this with a grain of salt. It's a brilliant way to spend an hour anyway, if you're into this kind of thing.

I especially like the point in his lecture where he begins to discuss what the map on the Visual Cortex must be like when considering how much space is reserved for the fovea compared to everywhere else in the visual field. I suppose it would be sort of like looking at an extremely convex funhouse mirror of yourself, with the center of the image being given the most biased detail.

But where the real fun comes in is how the visual cortex scales your end-image of the real world from this initial biased funhouse map, and what sort of visual artifacts and phenominon and patterns occur when noise (such as that experienced in the hypnogogic state, during headaches, and during hallucinogen psychosis) disrupts the well oiled machine.

Clicky clicky-->
On edit: Oho, nice system. If I edit my post post-posting, it forgets to zap me for doing web links? Was that set up as a psychological experiment to judge the problem solving IQ of the newbies? Is some moderator out there taking notes and publishing a study on this sort of thing?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:


Lo-Fi Version Time is now: 16th October 2018 - 07:36 AM

Home     |     About     |    Research     |    Forum     |    Feedback  

Copyright BrainMeta. All rights reserved.
Terms of Use  |  Last Modified Tue Jan 17 2006 12:39 am

BrainMeta is supported by donors of The Neurological Foundation. Donate today to help support us.