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> A theory about sleep..., Why we sleep
dutch84
post Nov 30, 2007, 01:39 AM
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Is it possible that the process of sleeping is just a period of time where the blood flows from our body to our brain...sort of like it's just a time period when oxygenated blood has a chance to flow to our brain because while we are moving around all day long blood is being pumped throughout the body and sleep is a chance for it to go to the brain.

If this is the case, then dreams would just be a byproduct of the oxygenation of nerve cells in the brain (producing the dream images we experience).

What do you guys think?

Any studies done on this?
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trojan_libido
post Nov 30, 2007, 02:04 AM
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I think blood is always flowing to your brain, you dont have to sleep to allow blood in. Can you explain how dreams would form from the oxygen a little more clearly?
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Palaver87
post Nov 30, 2007, 02:51 AM
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you still move a lot during your sleep. i forget which phase(s). i think you could sit still on a chair and rest if it was just about oxygenated blood.
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dutch84
post Nov 30, 2007, 03:31 AM
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QUOTE(trojan_libido @ Nov 30, 2007, 02:04 AM) *

I think blood is always flowing to your brain, you dont have to sleep to allow blood in. Can you explain how dreams would form from the oxygen a little more clearly?


Scientists use PET scans to study blood flow to the brain with the idea that blood supplied to the brain feeds the nerve cells which produce the nerve impulses which produce movement and activity throughout the body. So, the movement of the blood (which serves the purpose of supplying Oxygen) dictates the activity of the nerves. Dreams would be the result of activity that does not normally appear during a wakeful state. So, I guess my reasoning is that more blood goes to the neurons in the brain while we sleep causing neural activity that creates dreams via spontaneous imagery or something.
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dutch84
post Nov 30, 2007, 03:35 AM
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Has it ever been studied in hibernating bears?

Has anyone ever studied the specific physiology of a bear before and after it's 7 months of hibernation?

There has to be some significance to the fact that a bear can sleep for 7 whole months...no eating, no drinking, no pooping or pissing..............

What physiological changes occur during that time?

I think a lot could be discovered about the effects of sleep if this were studied.
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trojan_libido
post Dec 03, 2007, 01:02 AM
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QUOTE(dutch84)
So, the movement of the blood (which serves the purpose of supplying Oxygen) dictates the activity of the nerves.
Isn't the blood pumped to the places its needed most? This makes me assume that the activity of the nerves gets the blood pumping there.
QUOTE(dutch84)
Dreams would be the result of activity that does not normally appear during a wakeful state
We are storytelling creatures who are based in the visual realm. At its most basic this means we communicate in metaphors and fantasy. Its not that we don't have these fantasies happening during our waking life, its just we're too preoccupied to follow the thoughts through to conclusion, plus without our eyes shut and our brain in sleep mode, there is no vivid imagery.

I find it extraordinary that when we rest and sleep that these fantasies run riot while our bodies paralyse us. We're still no closer to understanding what dreams really are. But I think your ideas don't seem to take into account things like lucid-dreaming.
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Palaver87
post Dec 13, 2007, 05:48 AM
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There are probably multiple reasons why we sleep. I think the amount of REM sleep is correlated with memory consolidation. Perhaps new memories from the hippocampus are incorporated with other long-term memories in corresponding cortical areas. I was thinking that many of the things we dream about might be more related to episodic rather than semantic memories, and the hippocampus is known to be most important for forming new episodic memories. I wonder if people with hippocampal lesions dream, or if there dreams are different. They should do studies on that...
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dutch84
post Dec 15, 2007, 09:51 PM
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[/quote]We are storytelling creatures who are based in the visual realm.
[/quote]

We're not all storytelling creatures. Sure, us "Intellectuals" are, but what about athletes and people whose activities are mostly physical?

I think they dream too.
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Last Click
post Jan 07, 2008, 07:23 PM
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"Is it possible that the process of sleeping is just a period of time where the blood flows from our body to our brain...sort of like it's just a time period when oxygenated blood has a chance to flow to our brain because while we are moving around all day long blood is being pumped throughout the body and sleep is a chance for it to go to the brain."

If this were the case, then there would even be no need to sleep at all. Lay in a horizontal position for several hours without sleeping and then stand up completely refreshed. Or, how about getting the same amount (or more) of blood rushing to the brain by hanging upside down like a bat for a short period of time, obviating the need for the nightly nap?

It is an intriguing idea however and it is not something i ever thought of.
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Palaver87
post Jan 07, 2008, 11:42 PM
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or, lie a lot. any of you guys familiar with teh first lie detector? lay a man on a board made like a seesaw. if the board tips over to the head side it means he is lying because more blood is moving to the brain!
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trojan_libido
post Jan 08, 2008, 12:53 AM
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QUOTE
We're not all storytelling creatures. Sure, us "Intellectuals" are, but what about athletes and people whose activities are mostly physical?

I think they dream too.
Without being rude, I think this is a little short sighted. I don't mean in an intellectual way at all, but as a method of knowledge propagation, whether its songs or stories. But the simplest way to understand it is in our exaggerations of the facts to make the stories more attention grabbing:

Fisherman stories - <------------------------- it was this big -------------------->
War stories - There was 30,000 men, all ten feet high with acid for blood and swords bigger than houses. Our group of 300 killed them all.
Global Media - sensationalism sells...
etc. etc. ad nauseum.

The dreams we have are simply emotional stories that we are telling ourselves. Some dreams actually have a lasting change on our personalities and personal goals. I bet some athletes have been inspired by dreams of winning Gold for their country in the Olympics.
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Cassox
post Jan 08, 2008, 01:49 PM
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QUOTE(dutch84 @ Nov 30, 2007, 01:39 AM) *

Is it possible that the process of sleeping is just a period of time where the blood flows from our body to our brain...sort of like it's just a time period when oxygenated blood has a chance to flow to our brain because while we are moving around all day long blood is being pumped throughout the body and sleep is a chance for it to go to the brain.

If this is the case, then dreams would just be a byproduct of the oxygenation of nerve cells in the brain (producing the dream images we experience).

What do you guys think?

Any studies done on this?


02 exchange with hemoglobin is based on osmotic pressure. Even venous blood has a large amount of 02 left in it. The oxygen moves from the blood to the cerbrospinal fluid based on how much 02 is left in the cerbrospinal fluid. This is a very consistent process that does'nt changed based on blood flow, pressure etc.
It CAN be changed by a shift in environmental 02 levels and external pressures, but this isn't anything that occurs due to sleep. Even hyperventilation and hypoventilation don't actually effect how much oxygen an individual neuron takes up (for the most part). So no, sleep is not to increase Oxygen.
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Last Click
post Jan 08, 2008, 06:11 PM
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Trojan, they were actually 12 feet high and spit acid (reallllly bad acid reflux). And there were only 150 of us.

Last night i tried sleeping standing up (very scientific experiment). It didnt work too well so therefore i believe that this here blood theory is indeed correct. smile.gif
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trojan_libido
post Jan 09, 2008, 12:12 AM
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Haha, a man called horse!
I hope that last sentence is a joke though LastClick, because you have to attempt to prove the theory wrong and fail, rather than try to prove it right and succeed smile.gif
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dutch84
post Jan 09, 2008, 04:41 PM
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People do walk, drive and even eat in their sleep...

So I've heard.

So...

I dunno if this proves me wrong, but I'm sticking with my blood story.
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trojan_libido
post Jan 14, 2008, 01:09 AM
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I dont think anyone is in the position yet to state one way or another what the function of sleep is. The latest research in depression shows that too much dreaming gives less time to the apparent regenerative phase of sleep. Upping the amount of seratonin can block dreaming.
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sk1
post Jan 14, 2008, 11:21 AM
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Sleep is necessary for the body. The ultimate state of relaxation for a vessel that is in constant ebb and flow. A much needed chance to
re-energize

It seems to me that dreams are the mind's ability to play with the past, present and future.

an elaborate dream may occur because of flower you pass everyday in the corner of your living room, a TV show, song movie, friend etc. It could be caused by the sounds or vibrations you are feeling during sleep, or it simply can be a glimpse of what is to come.

Every time i have taken the time to make a dream journal, I have been able to pinpoint the cause of the dream. Except on the rare occasion that the dream foretells an event, then i have to wait.
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gehirn
post Jan 30, 2008, 07:36 PM
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You are assuming that oxygen triggers glutamic innervation, but it is (assumed to be) the other way around, that excited neurons require more oxygen to supply their needs for activity.

It's an interesting thought, but one reason I would suggest that it is the activity which causes the rise in blood oxygen levels rather than the reverse is that oxygen levels as indicated on PETs or fMRIs do succeed neuronal activation, so the rise in blood flow (and hence oxygen, hemoglobin, etc.) actually occurs following initial activation. So the activation precedes the obvious rise in blood flow.

Also, if oxygen causes excitation, then how would we control our movements, thoughts, etc., if they are solely activated by oxygen without inhibitory control?

And it's also possible to sleep sitting up.

Do we dream more or more feverishly were we to sleep hanging upside down?
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TaylorS
post Jan 31, 2008, 06:17 PM
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IMO we sleep for 3 reasons:

saving energy. differences in sleep length between species generally depends on how alert they need to be to avoid ending up being something's lunch as well as how much time individuals of a species need to eat.

Body growth and maintainence. Sleep is when most growth and general body upkeep occurs.

Memory consolidation. During REM sleep the hippocampi are busy making connections between old and new memories. I'll guess vivid dreams (dreaming occurs all all stages of sleep, but the most vivid dreams mostly occur during REM sleep) are a side effect of memory consolidation to some extent.
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gehirn
post Feb 02, 2008, 07:22 PM
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QUOTE(TaylorS @ Jan 31, 2008, 08:17 PM) *

IMO we sleep for 3 reasons:

saving energy. differences in sleep length between species generally depends on how alert they need to be to avoid ending up being something's lunch as well as how much time individuals of a species need to eat.

Body growth and maintainence. Sleep is when most growth and general body upkeep occurs.

Memory consolidation. During REM sleep the hippocampi are busy making connections between old and new memories. I'll guess vivid dreams (dreaming occurs all all stages of sleep, but the most vivid dreams mostly occur during REM sleep) are a side effect of memory consolidation to some extent.


I'd definitely agree with those. Also, REM sleep frequently varies by species: those with larger cortices tend to have longer bouts of REM. --Perhaps related to the amount of memory consolidation needed to take place, especially if length of sleep doesn't necessarily increase simply due to larger brains (I believe the fruit fly has about an 8-hour sleep period).

PS- Nice to see you here, Taylor. biggrin.gif
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TaylorS
post Feb 03, 2008, 05:35 PM
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QUOTE(gehirn @ Feb 02, 2008, 09:22 PM) *

PS- Nice to see you here, Taylor. biggrin.gif


Thanks!
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Dinesh
post Jun 30, 2008, 08:39 AM
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QUOTE(dutch84 @ Nov 30, 2007, 03:09 PM) *

Is it possible that the process of sleeping is just a period of time where the blood flows from our body to our brain...sort of like it's just a time period when oxygenated blood has a chance to flow to our brain because while we are moving around all day long blood is being pumped throughout the body and sleep is a chance for it to go to the brain.

If this is the case, then dreams would just be a byproduct of the oxygenation of nerve cells in the brain (producing the dream images we experience).

What do you guys think?

Any studies done on this?



Brain is a part of body ..do not segregate it ..it may confuse you .. ..hava nice sleep with lots of dream ..
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DreamStudies
post Dec 01, 2008, 10:57 PM
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QUOTE

Is it possible that the process of sleeping is just a period of time where the blood flows from our body to our brain...sort of like it's just a time period when oxygenated blood has a chance to flow to our brain because while we are moving around all day long blood is being pumped throughout the body and sleep is a chance for it to go to the brain.

If this is the case, then dreams would just be a byproduct of the oxygenation of nerve cells in the brain (producing the dream images we experience).

What do you guys think?

Any studies done on this?


Yes, studies have definitely been done on this. FMRI brain scans. They detect increases in blood flow, and thus an increase of oxygen, to different parts of the brain. Most dreaming occurs during REM sleep, which is sleep stage characterized by rapid movements of the eye, thus it has proven most useful to study the brain during this sleep stage. These studies have shown that the areas that are responsible for attention, logic, and short term memory are largely inactive which helps to explain why dreams are so bizarre. Neurologists have also found that the areas of the brain that control instinct and emotion are highly active during REM, more active than when awake. This may be why nightmares and other uncomfortable dreams can be so intensely emotional feeling, even after waking.
So dreams are more a byproduct of the parts of the brain that are active during sleep, and thus requiring more oxygen to function, than an actual byproduct of oxygen flow. However, this still does not help to explain why we dream, only what causes dreams to be as crazy as they are.
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fnord
post Dec 12, 2008, 12:50 AM
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I remember reading about a sleep study using mice where they gave them tiny electric shocks when they would fall asleep, to keep them awake. After a time period all the mice died from bacterial infections(overgrowth?). They never really elaborated or I glossed over one, in any event there's definitely some physiological maintenance/rest going on during sleep.
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GodConsciousness
post Dec 13, 2008, 07:51 AM
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QUOTE(Palaver87 @ Dec 13, 2007, 08:48 AM) *

There are probably multiple reasons why we sleep. I think the amount of REM sleep is correlated with memory consolidation. Perhaps new memories from the hippocampus are incorporated with other long-term memories in corresponding cortical areas. I was thinking that many of the things we dream about might be more related to episodic rather than semantic memories, and the hippocampus is known to be most important for forming new episodic memories. I wonder if people with hippocampal lesions dream, or if there dreams are different. They should do studies on that...


It does seem that REM sleep in particular is a period of memory consolidation involving the hippocampus and other brain regions. In my research on Alzheimer's Disease and memory enhancement, I am seeing a close relationship between drugs that heighten the dream experience (ie. lucid dreaming) and one's that effect memory centers. The release and absorption of the neurotransmitter acetylcholine appears especially relevant.
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rockmartinn24
post Aug 19, 2010, 06:26 AM
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Sleep is natural process. Early scientists and philosophers saw sleep as a passive condition where the brain is isolated from the other parts of the body. It is depend on our body brain system.

There are three important factors that determine when we fall a sleep:
1. Circadian Rhythm
2. Environmental Arousal
3. Sleep Deprivation
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Hey Hey
post Aug 19, 2010, 03:37 PM
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QUOTE(rockmartinn24 @ Aug 19, 2010, 03:26 PM) *

Sleep is natural process. Early scientists and philosophers saw sleep as a passive condition where the brain is isolated from the other parts of the body. It is depend on our body brain system.

There are three important factors that determine when we fall a sleep:
1. Circadian Rhythm
2. Environmental Arousal
3. Sleep Deprivation
And these explain 'why we sleep' (the topic question) how?
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Paul King
post Aug 20, 2010, 06:53 PM
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It is not known why we sleep, although there are lots of theories.

Brain activity is almost just as high during sleep as during wakefulness, so the idea that the brain is resting or conserving energy is not founded.

Sleep does not relate to blood oxygenation. Blood oxygen levels increase when brain activity increases to support the increased activity. This is what is measured by fMRI and the BOLD (Blood Oxygen Level Dependent) response.

Interesting sleep facts:
+ Rats deprived of sleep eventually die (as previously mentioned).
+ Humans deprived of sleep eventually experience delusional states.
+ Even insects have an inactive period analogous to sleep.
+ Cetaceans (whales and dolphins) sleep with half of their brain at a time so they can keep swimming and breathing.
+ Some people need very little sleep -- 1 - 3 hours of light resting per night

Some sleep theories:
1. Quiescence evolved to give the body time to restore itself and conserve energy
2. Sleep is used by the brain to reorganize and consolidate memories
3. Sleep is a period during which neurons repair and recalibrate themselves. Their functioning is impaired, and so the animal's behavior is stopped to keep the animal out of trouble.
4. Neurons need a restoration cycle. It is better for the organism if all neurons go into their restoration cycle at the same time (during sleep) so that all can be fully online at the same time as well (wakefulness)

An intriguing theory of sleep as a decentralized property of neural populations appeared in Nature Reviews Neuroscience (Kreuger et al, 2008):
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2586424/

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Rick
post Aug 23, 2010, 12:16 PM
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Well, except for the polar regions, we experience periods of night, which in primitive times, meant deprivation of one of our primary sensory input, vision. This goes for all animals. It will be interesting to see if some polar animals might have evolved 24 hour waking in polar summers. If so, I haven't heard of it. Some animals do hibernate through the winter. So maybe sleep evolved to keep us inactive during periods in which we would be of little use, to keep us from stumbling around in the dark, so to speak.

It's certainly less boring to deep sleep or dream than to lie awake at night doing nothing.
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astroidea
post Nov 26, 2010, 04:52 PM
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Just to further Paul King's post on the neuronal remodeling theory of sleep, currently a popular theory about how sleep restores neurons.
http://tononi.psychiatry.wisc.edu/pubs/BRB-62-143-03.pdf

It actually finds that sleep isn't restoring energy, but rather cutting down on energy requirements.

The basis of the theory is this:
1. As we are awake throughout the day, we are experiencing, learning, interacting. This results in the strengthening of synapses(synaptic potentiation). All of this requires energy. This is why the longer we stay awake, the more tired we get. Our brain is requiring more energy to keep all those synaptic connections up.

2. The synaptic potentiation results in slow wave activity. This is because all of the neurons are firing much more unison when the synapses are potentiated, as opposed to if they weren't potentiated, they'd just be firing randomly, and thus the neuronal activity would resemble more of random noise. Think of a choir singing together as opposed to a bunch of people chattering in a room. This random noise would also be in a much higher frequency. This also explains why slow alpha and beta waves are associated with the states of rest, while quicker delta and faster waves are associated with wakefulness and attention.

3. Experiments show that slow wave activity that's associated with sleeping trims the synaptic strength back to baseline level. This is probably what occurs during memory consolidation, as it is found that memory consolidation via the hippocampus is only involved with episodic memory(or the memories of your experiences).
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