Do We Dream? Understanding Vision in Waking & Dream States

[bland]

I was thinking recently that when we dream and it appears to us in the dream that we are looking at objects, I was wondering if this dream vision originates from the same source as normal vision. That is in the waking world when we talk about 'seeing', we mean that photons from the Sun other other sources have reflected off objects and entered our eyes and ended up causing an electrical impulse to travel to a different part of the brain which then appears to us that we 'see' the object.

So would this 'seeing' while awake, be similar electrical signals going to the same part of the brain as what causes us to appear to see things when we dream? Hope that was clear enough. Or is it a completely different brain mechanism.

 

[UsableThought]

So would this 'seeing' while awake, be similar electrical signals going to the same part of the brain as what causes us to appear to see things when we dream? Hope that was clear enough. Or is it a completely different brain mechanism.

Since I seem to be the first person to post a response, let me say there are three ways those commenting can respond to your question:

1) If they know the topic quite well, they can give you a brief accurate answer. However one difficulty they will have is to judge what level of depth to provide in their answer, since you have not indicated how much you know about vision yourself, and have also left your profile blank of any information about yourself that might be helpful. They can guess from the nature of your question that you probably know very little; but how little?

2) If they don't have an exact answer, but are intrigued by this topic (for example if they're like me and have previously read a good deal about dreaming and about vision), they might do a quick Google and find an explanation that seems appropriate, and post it here. But they still will have the difficulty of not knowing how much you do or don't know yourself. Plus they may not actually want to do your work for you, since you too could Google.

3) They can follow the spirit of the forum & forum guidelines & suggest that you do some preliminary research yourself, before posting such a wide-open question. This is how I am going to respond, in fact, because I think you'll get more out of posting that way.

One big reason that I'd rather respond this way is that I have read enough about both vision and dreaming, and the neurophysiology of both, to be able to say that your initial assumptions about how vision works are inadequate. So anyone who tried to answer you directly would have to give you some very basic background information even before they get to the part about dreaming; but because you haven't indicated what your background is in biology or in any science at all, they won't know how to shape what they say so you can best understand it. So without realizing it, you're putting a big load on anyone who would like to help you.

Anyway here are my suggestions:

First, take a minute to check out this recent Insights article by forum member ZapperZ on why posting with no context isn't the best way to go in PF: https://www.physicsforums.com/insights/little-excuse-ask-question-cold/

Second, expand your question with some background info: How much do you know about neurobiology, dreaming, etc.? What's your science background in general? Also, why does this question intrigue you & what to you hope to gain from asking? E.g. is it just a one-off, isolated question, or are you very interested in either vision or dreaming, possibly even doing a project of some sort? This will help those who know the topic well & might be inclined to at least give you a "quick and dirty" summary answer.

Third - and this is optional, but recommended - consider doing at least some minimal research. At the very least this may help you better understand a "quick and dirty" answer if you get one. "Minimum" to me in this day and age means Googling for something like "human vision dreaming" and then patiently sorting through the hits until you get to those which look scholarly. Or perhaps searching in Wikipedia, or in known science sites such as Smithsonian magazine or Nature, etc. Or you can search for books on vision and/or dreaming, whether in your local public or school library or in a bookstore.

I do have one book recommendation for you, if this is a topic that you're really interested in learning about - it's an inexpensive paperback (also Kindle ebook) in the "Very Short Introduction" series from Oxford University Press. They have a book on vision and also a book on dreaming; the book on dreaming is the one you would want, because it covers how the brain makes vision & other senses available to us while we dream: Dreaming: A Very Short Introduction, by J. Allan Hobson, Oxford U. Press, $8.94 on Amazon US.

P.S. Also, if you're interested in learning more about research (e.g. if this wasn't something you were taught a great deal about in school), a book I often recommended when I was teaching is The Craft of Research: https://www.amazon.com/dp/022623973X/?tag=pfamazon01-20

 

[UsableThought]

P.S. I forgot to add - as someone who enjoys reading about both vision & dreams (usually separately), I do like your question a lot, as both these processes are fascinating. So I encourage you to stick with it & maybe flesh the context out a bit more as suggested.

Here is one way to think about the question that you might find intriguing: "Do blind people see in their dreams?" (This is literally a question that gets discussed in the "Very Short Introduction" book I recommended above.) There is more than one answer, and which answer is correct for a given situation depends on a fundamental aspect of vision.

 

[Dale]

@bland are you asking simply if the visual cortex gets activated during REM sleep? Or is your question something different?

 

[Blop]

A simple answer is no. We don't SEE light reflecting from our eyes when we dream, because there is no image. It's essentially just a stream of memories.

 

[UsableThought]

We don't SEE light reflecting from our eyes when we dream, because there is no image. It's essentially just a stream of memories.

This is inaccurate; and though I'm sure well-meant, not helpful to the OP. Again, given that this is a science forum, it would behoove folks who aren't familiar with the physiology of vision to actually do some reading on the subject before commenting.

I also suggest folks wait for the OP to get involved again. He is the one who asked the original question; he's been invited at least twice now to clarify; let's give him some time to do so.

 

[sysprog]

Some areas of the brain the activities of which are closely correlated with processing of normal visual information are also highly active during REM sleep and less active during non-REM sleep.

 

[rootone]

Sometimes I recall dream scenes later, when I am awake.
These seem just as visually real as a memory of a real life event.
(Even though, being a dream, the actual circumstances can be bizarre, for example I am able to fly)

 

[Evo]

The OP hasn't been back to the forum since they started this thread, so I wouldn't wait for them.

 

[BillTre]

I don't remember dreams that much, but I do have fairly strong visual imagery when I think about certain things.
Sometimes I can see vague graphs, layouts, or diagrams, somewhat like an overlay on the ordinary visual reality.
If I want to think about these things more intensely I look away from people (faces can be very distracting), at a homogeneous area (like a wall) or close my eyes.
Sometimes I can get very vivid images of things (kind of like cartoons) with closed eyes.

These may be like waking dreams, I don't know, but they do seem to compete with eye driven imagery.
Nor do I have any idea where all this might be occurring in the brain.

 

[Dale]

Some areas of the brain the activities of which are closely correlated with processing of normal visual information are also highly active during REM sleep and less active during non-REM sleep.

Yes, but not the primary visual cortex.

 

[UsableThought]

As a general FYI - back in my comment #3, I posed the question, "Do blind people see in their dreams?" I also asserted that "There is more than one answer, and which answer is correct for a given situation depends on a fundamental aspect of vision."

The answer turns out to be, "It depends on when you went blind." In a very general way, persons who are born blind (and never develop vision thereafter) don't see in their dreams, while persons who are born sighted, and lose sight only some years after infancy, typically do see in their dreams. The "fundamental aspect of vision" that I mentioned is merely that although we humans are born with what amounts to an "Ikea hardware kit" for vision, i.e. the necessary physical apparatus, "some assembly is required" - i.e., it actually takes quite some time after birth for this apparatus to develop; in particular, as I remember it, vision networks in the brain require a massive amount of real-time "learning" to make all the necessary connections and become functional. That isn't a very technical way of putting it, but it's what I remember from a huge amount of reading I did some years back on color vision.

So for someone blind from birth (or prior to to birth), these vision networks and so forth will never have had the chance to develop as they do in sighted people; thus won't be available to facilitate visual activity during dreaming, any more than when awake. I did a quick Google and one article I came across (this is the second cite below) says specifically that:

. . . people who are blinded after the age of 5–7 seem to have visual imagination and dream with visual imagery throughout life, while blinding at an earlier age leads to absence of visualization in both waking and dreaming.​

As to how this relates to the OP's original question about how we "see" in dreams - as I say my reading was years ago, so I can't any longer say exactly which parts of the brain do what; but the above clearly implies that "seeing" is a complex behavior that goes far beyond "light entering the eyes"; we have not merely rods and cones and so forth, but the necessary neural machinery to do huge amounts of what we could call "data processing", in which raw signals are transformed into many different kinds of meaning - e.g., color is processed separately from form and motion, as explained in this encyclopedia entry on color vision. As we might expect, a great deal, though not all, of this neural machinery is available to us when we "see" images without using our eyes, i.e. when daydreaming, imagining, or dreaming.

I don't have my reading materials from back then with me - they are in a box somewhere - but I did find a couple of reasonably recent review articles on this question of whether the blind can see in dreams - cites below. The first is on the development of human vision in detail, while the second is more to do with how science looks at the dreaming brain; it briefly mentions the development of vision. Both papers have free PDF downloads.

Oliver Braddick, Janette Atkinson, Development of human visual function, Vision Research, Volume 51, Issue 13, 1 July 2011, Pages 1588-1609, ISSN 0042-6989, https://doi.org/10.1016/j.visres.2011.02.018

Nir, Y., & Tononi, G. (2010). Dreaming and the brain: from phenomenology to neurophysiology. Trends in Cognitive Sciences, 14(2), 88. http://doi.org/10.1016/j.tics.2009.12.001​

There is also a Smithsonian article I found that touches on this, in discussing a survey of which of the five senses blind persons report in dreams (e.g. touch, smell, vision, etc.): http://phenomena.nationalgeographic.com/2014/02/26/how-the-blind-dream/

 

[bland]

...Snip...

First, take a minute to check out this recent Insights article by forum member ZapperZ on why posting with no context isn't the best way to go in PF: https://www.physicsforums.com/insights/little-excuse-ask-question-cold/

I do have one book recommendation for you, if this is a topic that you're really interested in learning about - it's an inexpensive paperback (also Kindle ebook) in the "Very Short Introduction" series from Oxford University Press. They have a book on vision and also a book on dreaming; the book on dreaming is the one you would want, because it covers how the brain makes vision & other senses available to us while we dream: Dreaming: A Very Short Introduction, by J. Allan Hobson, Oxford U. Press, $8.94 on Amazon US.

First I should apologise if I appeared rude by not returning sooner. I knew I'd be back and I wanted to be able to answer properly, however life sort of got in the way, not to mention being diagnosed with cancer, but I had an operation a few weeks ago and I think that's the end of it, I'll know for sure in a few months.

I read ZapperZ which was helpful and I have 'Dreaming' on the way from the UK to Australia, only cost $14AUD including delivery! So I'll be looking forward to that. I've also filled in my profile.

btw, The Craft Of Research book you suggest looks like it's going to be very serendipitously useful for the body of work I'm currently writing and I'm excited and happy you pointed me to it, thanks.

P.S. I forgot to add - as someone who enjoys reading about both vision & dreams (usually separately), I do like your question a lot, as both these processes are fascinating. So I encourage you to stick with it & maybe flesh the context out a bit more as suggested.

Here is one way to think about the question that you might find intriguing: "Do blind people see in their dreams?" (This is literally a question that gets discussed in the "Very Short Introduction" book I recommended above.) There is more than one answer, and which answer is correct for a given situation depends on a fundamental aspect of vision.

Yes I've often thought about that question what blind from birth people see, and I'll be looking forward to the arrival of the book. Actually my question was pretty much as it read. I understand 'seeing' is a very complex set of brain activities, but in my original question I was really only looking for a basic 'wiring' answer, but the more I think about the question the more I disappear down a rabbit hole. Basically though my question, if I flesh it out a bit more was...

From what I understand, electrical signals from the auditory neurones and electrical signals from the optic nerve are physically the same thing but they go to different parts of the brain, one becomes sound and one becomes images. When a simple image that is in your dream is perceived, does this perception of the image happen in the same part of the brain as when the same image is perceived in the waking state. I'm just talking about the perception of the image, not any emotional responses or understanding of the purpose of the object which I imagine would have other parts of the brain involved. OR do images that appear in your mind in dreams come about by totally different parts of the brain. I've re written this paragraph three times now and I can see my question is becoming problematic.

@bland are you asking simply if the visual cortex gets activated during REM sleep? Or is your question something different?

Pretty much, yes that is what I'm asking.

As a general FYI - back in my comment #3, I posed the question, "Do blind people see in their dreams?" I also asserted that "There is more than one answer, and which answer is correct for a given situation depends on a fundamental aspect of vision."

...but the above clearly implies that "seeing" is a complex behavior that goes far beyond "light entering the eyes"; we have not merely rods and cones and so forth, but the necessary neural machinery to do huge amounts of what we could call "data processing", in which raw signals are transformed into many different kinds of meaning - e.g., color is processed separately from form and motion, as explained in this encyclopedia entry on color vision. As we might expect, a great deal, though not all, of this neural machinery is available to us when we "see" images without using our eyes, i.e. when daydreaming, imagining, or dreaming.

Yes that is an excellent point and in trying to reformulate my question I'm trying to separate out the emotional processing from the simple formation of the image. For example I get from lectures on the brain by Prof Jeannette Norden and Books like the Man Who Mistook his Wife for a Hat, that separate to seeing something there's the processing required to actually recognise the object. It may very well be possible that my question cannot be answered. Or perhaps can be answered using a different analogy. For example a person who can see faces but he doesn't recognise who the face is. With that in mind my question would not be concerned with whether or not he recognised the face, simply that even if his brain was wonky and he did not recognise the face of his wife would the part of his brain that at least saw the face be the same part of his brain that 'saw' a face, any face, in a dream?

 

[UsableThought]

Sorry to hear about the cancer - definitely a major life event - hope the operation went well.

In terms of eye versus ear, obviously these organs are very different and so the raw data from each will be different; beyond that I know only that there are a vast number of processes that support the transmission of various types of messages in the nervous system; someone better up on biology could tell you more.

Also, as I think I mentioned, my reading on vision was too long ago for me to remember what parts of the brain do what; my current reading related to the brain has to do with pain vs. nociception, and one thing that is new to me is that in that field (pain research), models have evolved such that rather than particular functions being assigned to specific brain regions only, the more modern view is that a great deal of redundant or parallel processing goes on. But whether this is in any way the case for vision also, I have no idea.

Glad you are expecting the book & I hope you enjoy the reading and the learning!

 

[bland]

snip

The organs are different but the nerve impulse that travels down the neurone will be the same thing just organised differently, yes? I guess if optic nerve impulse went to the sound processing parts of the brain, it would just end up as noise, I'm guessing. Sort of like the way, all the stuff on your computer whether pictures or sounds that are sent to the processor are the same basic components, that is a particular orientation of an electronic state. On or off. I've since found the audiobook version of Dreaming and I've just loaded it up on my iPod and will be listening to it tonight, ironically it will likely go into my dreams like most stuff I listen to at night. It get's quite odd at times, but also interesting the way these lectures or books manifest in a dream.

Cancer was in the prostate, completely contained inside the capsule and they removed whole gland and left the nerves intact with the Da Vinci robotic playstation gadget, and all seems fine with the world again. It's like nothing ever happened. I'm not really bothered about it now, as it sort of makes sense with regards to the work I'm currently writing. Just another episode in the ongoing play that is my strange life.

 

[Dale]

life sort of got in the way, not to mention being diagnosed with cancer

That is very scary! I hope things go well with the treatments

Pretty much, yes that is what I'm asking.

That one at least has a clear answer. The primary visual cortex is not activated during REM sleep.

 

[Graeme M]

I think this is a very interesting question. I take the OP's question to mean quite simply is conscious awareness of dreams derived from the same neural mechanisms as conscious awareness of sensory input. I have often wondered about this myself and in the absence of any detailed knowledge I was curious to see what answers would be forthcoming.

My assumption about this is that yes, whatever makes us conscious of normal sensory input makes us conscious of dreams. However that is a different thing from whether or not all of the visual processing centres are stimulated equally in dreaming and vision.

As an earlier commenter said, many parts of the visual system are stimulated by dreams, but surely this would be in the same way that memory processes activate contributing processing centres? In other words, wouldn't the physical mechanism for "seeing" dreams deeply implicate the hippocampus and related memory processes?

 

[Graeme M]

Ahhh. A little Google action seems to point to that very thing, so I'm glad my guess is well founded. Dream processes appear to more than likely arise from memory processes and therefore rely upon hippocampal activity. Which makes sense as both dreaming and imagination cannot be using actual sensory input to generate conscious experience (though I'd assume some level of input still occurs during sleep?).

I hadn't realized that dreaming is still relatively unexplained given that it seems a fairly straight-forward event, but unravelling the complexity of brain function is a daunting task. I also assume that anyone well read in the field knows about the relationship between memory and dreaming, which I didn't until just now!

In terms of the original question then, the answer is something like no, the processes for actual seeing and dreaming are different, utilising some shared regions of the brain but not all. Seeing involves processing of sensory input through a defined sequence of visual centres with plenty of feedback and input from other regions to arrive at a presented representation in consciousness, whereas dreaming activates some of these areas to retrieve stored representations which are then represented to consciousness. The actual mechanism by which representations of any origin become conscious is not yet known, but presumably is the same in any case. Does that seem like a fair summary?

This paper offers a sort of brief summary of recent thinking about memory/hippocampal involvement in dreaming:

http://pages.stolaf.edu/cis-slemke/files/2013/03/Biological-Functions-of-Dreaming.pdf

From the paper:
"One of the main structures involved in memory storage and also believed to contribute to the creation of dream images is the hippocampus. Research has brought forth evidence of this involvement, including one study showing that hippocampus function is higher during REM sleep, than during both Non-REM sleep or waking (Nielsen & Stenstrom, 2005). While this increased Hippocampal function does not represent a casual relationship between its function and the creation of dream images in REM sleep, there are several lines of evidence that support the idea that the hippocampus is involved in dream image production.
"

 

[UsableThought]

In other words, wouldn't the physical mechanism for "seeing" dreams deeply implicate the hippocampus and related memory processes?

Seeing involves processing of sensory input through a defined sequence of visual centres with plenty of feedback and input from other regions to arrive at a presented representation in consciousness, whereas dreaming activates some of these areas to retrieve stored representations which are then represented to consciousness.

You're correct that the hippocampus is involved in dreaming, along with the rest of the limbic system; however the simple notion of dividing seeing into active seeing, when there is input from the eyes, versus passive retrieval of stored images, when there is no input from the eyes, is insufficient for explaining vision and/or visual imagery in dreams. Remember that we can imagine (whether our eyes are open or closed) infinitely many things we have never seen; this supports what I dimly recall from my prior reading, which is that visual imagination does not rely solely on literal memories; rather, the system as a whole has the ability to create entirely new composite images that make use of the same qualities of images our brain learned to process when we were very young & our vision was still forming: e.g. motion, form, color, brightness, edges, etc. - I don't know all the right terms, but the categories are quite elaborate. (And interestingly, it is these categories of processing that give rise to optical illusions). This is not to say that we don't remember images themselves; we do; but recall is not the only process involved in vision in dreams. So when thinking of image qualities or categories, these are not "memories" but more like "capabilities" that enable meaningful perception.

But regardless, thanks for posting your thoughts; you got my own curiosity going again on what you rightly say is a very interesting topic. Since my books on vision are still misplaced, I made another try at digging up relevant information online. I found a simple "explainer" website about the brain, The Brain From Top To Bottom; it was developed by a Canadian neuroscientist, Bruno Dubuc, and sponsored by McGill University, in Quebec. In 2005 the site received an award from MERLOT for outstanding public education, so I think it has credibility. Anyway to quote from the page on brain function during sleeping:

Brain imaging studies have found, for example, that the primary visual cortex, the first part of the brain involved in consciously decoding visual signals when people are awake, shows very little activity when they are dreaming during REM sleep. This is no surprise—when people are dreaming, their eyes are closed, and no visual signals are reaching them.

But brain imaging studies have also shown that certain extrastriate visual areas of the cortex, which decode complex visual scenes, are significantly more active during REM sleep. Thus, during REM sleep, these areas are apparently involved in analyzing complex visual scenes. This is completely consistent with the often highly elaborate visual dream scenes that people report when researchers awaken them from REM sleep.

During REM sleep, intense activity is also observed in the limbic system, a set of structures heavily involved in emotions. Two of these structures are especially active: the hippocampal region and, in particular, the http://thebrain.mcgill.ca/flash/d/d_04/d_04_cr/d_04_cr_peu/d_04_cr_peu.htm. Once again, it is interesting to note that this intense limbic activity does not occur during the phases of non-REM sleep, when the dreams that people have are far less emotional.​

You can find more information on these "extrastriate visual areas" via the links in the excerpt above; and also in Wikipedia's article on the visual cortex. A crude way of putting it is that the primary visual cortex, also known as V1, begins the processing of the most essential aspects of vision, e.g. detecting motion and recognizing patterns; areas V2 through V5 deal with further aspects. All this accords with what I have read in the little book I recommended to the OP, Dreaming: A Very Short Introduction, by the researcher J. Alan Hobson, as well as other sources; Hobson calls these additional visual areas in the brain "associative" to distinguish them from primary.

So back to the question of memory as a basis for seeing in dreams: From the reading I've managed to do, one model being used these days has to do with "encodings" of images or image qualities which have been previously processed by the various secondary areas of the visual cortex mentioned above. These days, with fMRI machines running around loose looking for expensive projects to do, apparently research has turned to some pretty interesting ways of looking at such encodings. Specifically, I found at least two studies that use fMRI and computerized algorithms called "decoders" to explore visual encodings in dreams; very technical, but fortunately I also found a couple of blog posts where others who follow this kind of research explain the studies in language suited for laypersons.

In closing, here are links for one of these studies, "Neural Decoding of Visual Imagery During Sleep"; it was first published in Science, May 3, 2013:

• Abstract in Pubmed: https://www.ncbi.nlm.nih.gov/pubmed/23558170
• Abstract at Science, with full text behind a paywall: http://science.sciencemag.org/content/340/6132/639.long
• A long excerpt from the article, not behind a paywall: http://www.brainproducts.com/files/public/products/brochures_material/pr_articles/1302_UR_Tamaki.pdf
• A blog piece explaining the study in simple terms: http://postcogtopics.blogspot.com/2013/04/dream-in-code-neural-decoding-of-visual.html
• Another blog piece: http://the-brain-box.blogspot.com/2013/04/in-news-decoding-dreams-with-fmri.html

I'll leave it at that for now. I'll be interested to see what the OP comes up with in his own reading later on.

 

[Graeme M]

Thanks for these links, UsableThought, I'll read them as soon as I can. It's an intriguing area of study, as I say I've often wondered about dreaming/imagination but haven't really dug into it. I had previously found Dubuc's website and agree it's an excellent resource, I'll have to get back to it on this subject.

One small point - I don't mean to say that imagination or dreaming implies "passive retrieval of stored images". My suggestion in that sense was that the hippocampus activates stored representations to compose dream sequences (or imaginative sequences), but such representations are not necessarily static images as such - rather they might take the form of more abstract or fundamental elements of visual processing.

Some of the material I have read proposes that the hippocampus is involved in detailed scenario construction and the playing out of possible behavioural options, for example the case of London taxi drivers whose hippocampi increase in size to better store 3D representations of locational arrangements and thereby simulate (imagine) potential solutions to paths through these locations (http://www.pnas.org/content/97/8/4398.full).

Presumably in imagination, we utilise the hippocampus to generate potential scenarios that are composed of both static images as well as more elemental representations, including emotional salience to such scenarios.

But I wonder whether dreams work in that sort of directed fashion. My guess is that we are "seeing" image sequences (or whatever modality the dream content takes) that derive from a mix of stimulus (for example representations that arrive at the hippocampus during memory consolidation: http://learnmem.cshlp.org/content/11/6/671.short) and which are then inserted into meaningful sequences by the same engine that drives imagination. Just a guess, mind you, but I would be surprised if that guess is a long way from the reality (http://www.jneurosci.org/content/27/52/14365.short).

What I find most engaging about this possibility is that conscious awareness of imagination, dreams and external sensory stimulus (ie "reality") might presumably occur on the scaffold of a common process...

Anyway, thanks again for all these great links, I look forward to reading further.

 

[UsableThought]

But I wonder whether dreams work in that sort of directed fashion. My guess is that we are "seeing" image sequences (or whatever modality the dream content takes) that derive from a mix of stimulus (for example representations that arrive at the hippocampus during memory consolidation: http://learnmem.cshlp.org/content/11/6/671.short) and which are then inserted into meaningful sequences by the same engine that drives imagination.

I don't have any idea myself. However, serendipitously, I find that in his 2011 book on dreaming, which I have already mentioned, Hobson asks exactly your question about the hippocampus - and proceeds to answer firmly in the negative: the hippocampus is rarely involved in dream recall. Here are a couple of excerpts from that section; I have bolded references to the hippocampus:

Now . . . we are in a much stronger position to ask such questions as the following: 1. As declarative memory (memory that results from conscious awareness and associations) depends so strongly on an intact hippocampus, are our daytime experiences temporarily stored there for further processing? 2. Are bits of declarative memory, but not entire scenarios, transferred out of the hippocampus when the brain is reactivated in REM sleep?​

He then provides a first-person narrative of a particular scary dream he had, very emotional but all mixed up in terms of sequence of action; he uses this example to make the following argument:

With our experimental data and dream reports such as this, we are now in a position to create a new model of learning in sleep and dream memory that transcends all existing technical analysis. In the dream example given, the emotional salience (or importance) of peril, triggered by the helicopter observation, integrates two other perilous subjects: tractor operation in Vermont and my vulnerable friend, Roger. It is already clear that the brain does not store information like a tape recorder, a microfilm filing system, or even content-addressable memory – in other words, it doesn’t simply take experience and lay it down somewhere in its depths for future reference.

What the brain does, instead, is to keep a rather impressive record of experience for a relatively short time, probably in the hippocampus and directly related cortical structures, which is accessible for about one week by day but inaccessible by night. This model can explain how and why I never dream of daytime experiences that are easy to recall the next day. The brain uses sleep to make bit-by-bit adjustments in its long-term repertoire of learning and memory, in a way that guarantees both efficacy and efficiency.

. . . declarative memories, which are presumably stored in the hippocampus and then moved out to the cortex, are . . . seldom available to dream consciousness. Clearly, all cognitive functions that depend on memory, except possibly emotional salience, are weakened in REM sleep. Dream consciousness is therefore both a poor analyser and a poor organizer of its content. Hyperassociativity and emotional salience are the rules that govern dream consciousness, not linear logic and specific, accurate, historical detail.​

Re-reading the above, clearly there are important parts of his argument that I have left out in managing my quotes; so a fuller reading would be required to really weigh what he is saying. It seems a wide territory of neuroscience that we have entered through a narrow doorway (the question of vision in dreaming).

 

[UsableThought]

P.S. I just remembered I recently bought a neuroscience primer to have handy: Neuroscience At A Glance, 3rd ed., 2008, by Barker and Barasi. They say this about those parts of the visual cortex that follow after the primary cortex, V1:

The extrastriate areas are those cortical areas outside V1 that are primarily involved in visual processing. The number of such areas varies from species to species, with the greatest number being found in humans. These areas are found within Brodmann's areas 18 and 19 and the inferotemporal cortex and are involved in more complex visual processing than V1. with one aspect of the visual scene tending to be dominant in terms of the analysis undertaken by that cortical area (e.g. colour or motion detection). In general, damage to these areas tends to produce complex visual deficits, such as the ability to recognize objects visually (visual agnosia) or selective attributes of the image such as colour (central achromatopsia) or motion.​

Here is a snippet from an accompanying diagram, listing briefly the sorts of processing done by V2 through V5 as well as an additional area that recognizes faces:

The full diagram is available here: https://photos.google.com/album/AF1.../AF1QipP3ODyo7tVP22IJlTKgVYCjw_vbncuqYITQk4eU

 

[.Scott]

That one at least has a clear answer. The primary visual cortex is not activated during REM sleep.

I think you need to amend that statement. Literature and TV are filled with examples where peoples dreams are affected by the noises or other conditions in the sleep environment, a reflection of what many find common place: the feeling of the bed sheets or lack there of; arguments in the next room; TV, etc.

Sleeping past sunrise with eyes not fully closed or not fully protected from the sunshine will have a huge affect on the dreams. I have experienced this affect now and then from my early teen years.

So, at least in my case, the visual cortex does not need to be active, but it can be. And if it is, it will make its mark on the dream.

 

[UsableThought]

I think you need to amend that statement <snip>
Sleeping past sunrise with eyes not fully closed or not fully protected from the sunshine will have a huge [effect] on the dreams. I have experienced this [effect] now and then from my early teen years.

@scott, the Biology & Medical forum, just like the other forums, is science-based; and so our questions, comments, and discussions should make every effort to reference scientific research findings (e.g. studies, textbooks, etc.).

It is understandable that since we all have bodies, and all experience phenomena such as dreaming, we might expect to be able to make claims in a thread like this based solely on our opinions & speculations; but that's not in the spirit of PF. In your comment above, you cite popular media ("Literature and TV") - these aren't acceptable references. You mention phenomena that aren't visual ("noises, feeling of bed sheets," etc.) - these are irrelevant to a thread about vision. You then make a claim that "sleeping past sunrise . . . will have a huge [effect] on the dreams" that will somehow involve the primary visual cortex; but you don't describe what you think this effect would be, and more importantly, you don't support your claim with any reference to actual research.

I would suggest re-phrasing your claim as a question, e.g. something like this: "What about when sleeping past sunrise? Doesn't the sun on your closed eyelids stimulate the primary visual cortex, and wouldn't this somehow be represented in any dreaming we are doing at that time?" If anyone had an answer based on actual knowledge of the literature, they could then supply this answer; or if not, it would remain an open question.

It may take a little getting used to, but it's no different than if you post on the Quantum Physics or Cosmology forums. It's all considered science.

 

[Dale]

I think you need to amend that statement.

I am not sure why. Your examples were about activation by external sources, not R.E.M. sleep. I never said that the primary visual cortex was inhibited during R.E.M. sleep, just not activated.

 

[.Scott]

I am not sure why. Your examples were about activation by external sources, not R.E.M. sleep. I never said that the primary visual cortex was inhibited during R.E.M. sleep, just not activated.

Your statement was "The primary visual cortex is not activated during REM sleep.". I think you meant "... by REM sleep". It does not sound to me as though you are disputing that the primary visual cortex may be activated during REM sleep.

But actually, now that I have been prodded into a bit of research, consider this article:
http://science.sciencemag.org/content/279/5347/91
The abstract describes an "attenuation of activity in the primary visual cortex" during REM sleep.
It also describes the "selective activation of extrastriate visual cortices" and suggests an REM model that isolates most of the visual system from the parts that "mediate interactions with the external world".

 

[Dale]

Very interesting.

You are right, I meant "by" rather than "during". But I didn't realize that the effect was actually inhibitory.

 

[.Scott]

@scott, the Biology & Medical forum, just like the other forums, is science-based; and so our questions, comments, and discussions should make every effort to reference scientific research findings (e.g. studies, textbooks, etc.).

It is understandable that since we all have bodies, and all experience phenomena such as dreaming, we might expect to be able to make claims in a thread like this based solely on our opinions & speculations; but that's not in the spirit of PF. In your comment above, you cite popular media ("Literature and TV") - these aren't acceptable references. You mention phenomena that aren't visual ("noises, feeling of bed sheets," etc.) - these are irrelevant to a thread about vision. You then make a claim that "sleeping past sunrise . . . will have a huge [effect] on the dreams" that will somehow involve the primary visual cortex; but you don't describe what you think this effect would be, and more importantly, you don't support your claim with any reference to actual research.

I would suggest re-phrasing your claim as a question, e.g. something like this: "What about when sleeping past sunrise? Doesn't the sun on your closed eyelids stimulate the primary visual cortex, and wouldn't this somehow be represented in any dreaming we are doing at that time?" If anyone had an answer based on actual knowledge of the literature, they could then supply this answer; or if not, it would remain an open question.

It may take a little getting used to, but it's no different than if you post on the Quantum Physics or Cosmology forums. It's all considered science.

I cited cultural references to make the point that it is commonly observed. I mentioned the senses of sound and touch because they are the most commonly used in literature. To me they suggest a systematic susceptibility of dream content to be affected by the senses.
Here is a study for sound:
http://journals.sagepub.com/doi/abs/10.2466/pms.1987.64.3.739
Abstract:

Dreams can be influenced by external stimuli. In this study attempts were made to influence or direct the theme of a dream or sleep mentation using a series of thematically related words. 10 subjects were presented one of four series of 6 tape-recorded theme words, repeated 10 times, during REM or Stage 2 sleep followed by awakening to collect the dream or mentation report. Of the 40 awakenings, 30 produced a report, 10 of which were judged by two “blind” judges to be on the same or a very similar theme to the words. It was concluded that the theme of a dream can be influenced by the theme of the words.

In my last post, I cited a study (http://science.sciencemag.org/content/279/5347/91) that found that activity in the the primary visual cortex is attenuated - further suggesting to me that external visual stimuli would affect dreaming - apparently in some counterproductive way.

I have not had luck finding studies that show affects from normal visual sensory processing, the kind that would be mediate through the primary visual cortex. Instead I find this type of thing:
http://onlinelibrary.wiley.com/doi/10.1046/j.1440-1819.2001.00819.x/full

The subjects were also exposed to visual stimulation by a circular checkerboard while awake, for comparison with sleep activation levels.

In other words, most studies are looking for something that contrasts with normal visual activity.

Given this situation, wouldn't an N=1 study suffice to show that something is at least possible?

Still, I will ask: Has anyone encountered a study that shows that outside visual influences can affect the content of a dream?

It shouldn't be a difficult study to conduct. Appropriately "illuminated" subjects would simply have to be awoken during REM sleep and asked to describe the visual content of their dream in terms of color, brightness, etc.