Comments on: Is the Purpose of Sleep to Let Our Brains “Defragment,” Like a Hard Drive?

By: Quora

Quora — Sat, 09 Jun 2012 18:45:42 +0000

What differentiates “short-sleepers” from “normal sleepers”?…

From what I understand, neuroscientists still don’t know why some can operate with fewer hours of sleep than what is considered to be normal. Don’t forget, there are some of us that actually require more than 8 hours — the “long-sleepers”, if you w…

By: Sigmund

Sigmund — Wed, 23 May 2012 16:01:12 +0000

Oh God yes. I remember thinking this exact scenario when I was a Systems Administrator and I had to shut the network down in order for it to “re-set.” The memory boards had all been maxed out with data and the CPU had to organize everything in order for work to proceed. I often thought that, with all those synapses firing in our heads, at some point, the biochemicals involved have to somehow regain their electrons in order the brain to keep functioning. That’s why we can go without food or water longer than we can go without sleep.

By: James T. Dwyer

James T. Dwyer — Sun, 20 May 2012 23:34:41 +0000

Defragmentation of disk space is a pretty crude analogy, when more general computer operating system memory management strategies and database management systems have a much richer background to draw from.

A common strategy used to achieve optimal recording of new information is directly analogous to short term and long term memory partitioning. For example, new information might initially be captured by serially recording event data in a short term memory ‘buffer’. This would allow optimal ‘peripheral (sensory) device’ recording performance, with little concern for read access performance or storage space usage.

Retrieval could later be optimized to provide quick access to select data through the use of multiple indexes. The indexes might allow direct retrieval of all memories of a specific person, for example. Creating those indices would require sophisticated analyses of the simple short term memories. This could be accomplished along with migration from short term memory to long term memory during memory database ‘down time’, thus freeing up the high capture rate short term memory for reuse. Moreover, long term memories could be stored using shared links to redundant data, significantly saving total storage space required. This process would require the recall of stored memory elements, or snippets, to potentially generalize their content and update necessary cross-links.

Internet search engines are also employ sophisticated retrieval optimization methods using offline indexing, etc.

This is just a few of the many processes often employed in memory and database management systems. If similar processes are used to manage our own internal memories, they could help explain why sleep is necessary for maintaining memory performance, why dreaming can involve seemingly meaningless recall of memory ‘snippets’ and why memory details can change over time, for starters…

By: Sunny D

Sunny D — Sat, 19 May 2012 03:18:05 +0000

I feel that in exploring this topic we should begin to compare and contrast those individuals who sleep a lot and those who only need a few hours of sleep a night. Plus, why do depressed people sleep more? How does a sleep “cycle” allow you to sleep less?

Answering these questions may lead us to understanding sleep better.

By: Kenneth J. Epstein

Kenneth J. Epstein — Fri, 18 May 2012 14:17:57 +0000

The oldest theory of sleep is that it can be explained in terms of metabolism versus catabolism. Waking activity breaks down the body faster than it can be built up. Sleep is necessary to correct this imbalance. It allows animals to function beyond a sustainable capacity during hours when they can gain the most by doing so. Sleep repairs the damage done by this hyperactivity, and is most practical during hours when there is the least to gain from being hyperactive. Defragmentation may indeed be part of the metabolic process, while fragmentation is part of the catabolic process.

Sleep obviously has a great evolutionary advantage. Animals who can outdo themselves while awake are more fit to survive than those who do not need sleep but are limited to what they can do without it. A constant balance of metabolism and catabolism does not allow the spurts of energy that are often needed, just as a balanced budget amendment would place the country at a disadvantage when cash is needed quickly and borrowing is the only way to get it. Borrowing energy or money during the day and paying it back at night is much better than having no credit or borrowing power at all. Bodily economics is very similar to financial economics. You can live beyond your means temporarily, but not permanently.

By: William Turner

William Turner — Fri, 18 May 2012 11:30:08 +0000

As Tom says, synaptic pruning would seem to impose limits on knowledge. That does not seem to be the answer. There are some of us who believe that consciousness (knowledge and memory) resides outside the human brain. Until someone finds the “hard drive” physically in the brain, I have to stick with the idea that we communicate with a form of Cloud out there somewhere. In that chain of thinking, sleep may simply be a re-organization of the electromagnetic reception mechanisms in the brain – sort of a tune-up of the complex satellite radio. In that regard, the TMS and EEG experiment was very interesting because it showed that external electromagnetic waves do stimulate the brain.

By: Maxine

Maxine — Thu, 17 May 2012 20:37:48 +0000

Regarding REM sleep, this is when we dream, and we can become “awake” in the dream, conscious that we are dreaming. Check out “Lucid Dreaming”. This is related to astral travel and out-of-body experiences. I have had lucid dreams and been aware of traveling back into my body. If this sounds too woo-woo to neuroscience geeks, consider that our knowledge is constantly widening at an exponential rate (e.g. quantum physics), and that there’s a whole lot beyond what we think we know.

By: Tom

Tom — Thu, 17 May 2012 14:18:49 +0000

Does the process of synaptic scaling impose limits on our knowledge? This ‘down-sizing’ of synaptic strength that only preserves relative connection strengths presumably means that weaker connections (i.e. older or less used information) lose more strength when more new information has been learnt that day… Does it?

By: Neuroskeptic

Neuroskeptic — Tue, 15 May 2012 14:44:31 +0000

Paul: Oh, that’s very interesting. Thanks for the link. REM sleep is if anything even more mysterious than slow-wave sleep. Not all animals have it, and in humans REM deprivation is less disruptive than SWS loss. There are some drugs actually (MAOis) which abolish REM sleep while leaving SWS intact, and people seem to cope with that OK. So it seems likely that REM isn’t “necessary”, at least in the short term & medium term. But that raises the question of why we have it at all!

By: Jim Johnson

Jim Johnson — Mon, 14 May 2012 20:34:26 +0000

Interesting article, and the theory makes sense to me, I don’t personally think the answer to what sleep is, is going to be so simple. Maybe “pruning synapses” , plus ALSO “keeping us inactive, to save energy”, plus also physical recuperation (plus also etc., etc., etc.) If sleep is a system that’s been around since early in the development of complex nervous systems, the surprise would be if it weren’t performing multiple functions by now.

The ultimate question, and the one they’re pursuing I guess, isn’t “what is the function of sleep?” but “what function of sleep is so important that no known nervous systems go completely without it?”

And, of course this all reminds me of:
“People say, ‘I’m going to sleep now,’ as if it were nothing. But it’s really a bizarre activity. ‘For the next several hours, while the sun is gone, I’m going to become unconscious, temporarily losing command over everything I know and understand. When the sun returns, I will resume my life.’

If you didn’t know what sleep was, and you had only seen it in a science fiction movie, you would think it was weird and tell all your friends about the movie you’d seen.

They had these people, you know? And they would walk around all day and be OK? And then, once a day, usually after dark, they would lie down on these special platforms and become unconscious. They would stop functioning almost completely, except deep in their minds they would have adventures and experiences that were completely impossible in real life. As they lay there, completely vulnerable to their enemies, their only movements were to occasionally shift from one position to another; or, if one of the ‘mind adventures’ got too real, they would sit up and scream and be glad they weren’t unconscious anymore. Then they would drink a lot of coffee.’

So, next time you see someone sleeping, make believe you’re in a science fiction movie. And whisper, ‘The creature is regenerating itself.”
― George Carlin, Brain Droppings