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Medical Brain Capacity

  1. Jan 27, 2009 #1
    Is is possible to quantify how much "space" a human brain has? Kind of like in terms of hard-drive space?
    I am sure this depends on the person.
  2. jcsd
  3. Jan 27, 2009 #2


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  4. Jan 27, 2009 #3

    Andy Resnick

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    0.7 liter.
  5. Jan 27, 2009 #4
    There's no such thing as general purpose memory in the brain. So the answer would depend on the type of memory (episodic, semantic, procedural, etc) and on its salience.

    So the "memory capacity" would be highly dependent on the type of memory.

    As far as I know, the one area in which this kind of question has been extensively studied is with working memory. Though you may want to liken this more to RAM than to hard drive memory. People usually claim that the "magic number" is 7 plus or minus 3 items that can be simultaneously held in working memory... Though this is a somewhat misleading figure in the context of many tasks... Strategies like chunking and rehearsal can improve these values.
  6. Jan 30, 2009 #5
    Some people with photographic memory must have huge brain capacity because of the resolution of the images they have so as a stab in the dark it could be as much as hundreds of thousands of terrabytes.
  7. Jan 30, 2009 #6
    you cant measure a human brain's capacity using bytes. It doesnt work like that. Neuroscientists have been studying how the memory is stored in our brains for along time and the most current belief is that its something to do with the activity of the neurons and the way there activated so If you do a specific thing a lot those neurons are being used in a specific way in a relatively specific order so you begin to remember. Its something like that (correct if im wrong).
  8. Jan 30, 2009 #7
    It's actually more or less infinite. There is only a limit of how long we live to how much information we can potentially store, bits don't fall out if we get full up, if that were even remotely possible. So given the massive potential of those 100 trillion brain cells to make almost an infinite number of memories, as far as we know talking about brain capacity in terms of a computer is meaningless. Our brains are more sophisticated than binary, they use fuzzy logic, and a much more sophisticated version of that. Who knows perhaps a quantum computer might be able to keep up with us.

    Some people have a natural photographic memory, but practically anyone can train themselves to have one. A good example is Derren Brown who wasn't born with a photographic memory, or the world memory champion who started learning about memory because his was particularly bad. The brain is dynamic, it is far from hard wired and it is practically infinitely more flexible than 1 and 0.
  9. Jan 30, 2009 #8
    Everything in the brain is about memory. Its not just what you can consciously remember.
    When we are born (even before), our nervous system learns the succesfull neural impulses and memorices them for future use. We walk by memory, we remember to avoid danger, our brain remembers how to iterpret the optical nerve input, and how to breath, etc...
    So if we are to measure the amount of memory, we should count for all nerve-nerve possible interactions, in spatial, frequency, and maybe molecular domain.

    I don't think that memory is someting static tha we can account for every time. Consider forgetting and re-remembering, or consider creativity: the asocciation of memories. How do we count this "hidden" posibilities?
    What must be measured? Quantity, quality, or both?

    PD: sorry for my spelling.
  10. Jan 30, 2009 #9
    To be frank the brain is so mysterious atm that the answer to the OPs in anything more than a totally speculative manner is little more than a fairy tale based on what if they could be compared. They can't and there is no possibility of us ever running out of space, as the brains hardware is dynamic, unlike a PC's which has to be updated every 5 years or so. If you are talking about brute forcing information into the brain by some odd means all in one go, then it's anyones guess how many terabytes you could get in before you turned the person into a gibbering mental patient.
  11. Jan 31, 2009 #10
    I did not in my original post mean to offend anyone. I understand the workings of the mind and memory. I was just offering an educated guess. In reference to the above quote I myself suffered a mild stroke a few years ago and have relapses in my memory. I have had bad episodes which turn me into a "gibbering mental patient" but afterward i have drawn stuff that looks like it came out of a encyclopedia. So before I could have been brute forcing information into my brain which could be thousands apon thousands of terabytes if for example you looked at a brain as a computer.
  12. Jan 31, 2009 #11
    Oh no I'm not offended nor is anyone else, it's just a fact that you can't compare the two systems because of hardware differences. We need to make it clear that not only does the brain not store information in the same way, but it doesn't even store it as a series of 1's and 0's and. In fact one of the most intriguing questions is how it does so at all.
  13. Jan 31, 2009 #12
    Ok ok you got me.
    (holds up hands and surrenders)
    But as a last point it does make you curious about those movies when a person' brain is downloaded into a computer.
    I do understand that it is fiction and this is a place not to be discussing fiction just fact.
  14. Jan 31, 2009 #13
    Not at all, you just have to be careful to distinguish what is fiction and what is fact. If you had to have physical proof for everything then the beyond the standard model area of the forum wouldn't exist I suspect. It's fine to speculate, in SG1 for example Colonel O'niel has the knowledge of the ancients downloaded into his brain, from which he is able to construct a gate to another galaxy and save humanity with some fancy electronics. Problem is the information is so vast, it leaves no room for anything else, so he goes slowly ancient and slowly his mind begins to break down.
  15. Jan 31, 2009 #14
    Like a computer when it needs to defrag. LOL
    Last edited: Jan 31, 2009
  16. Feb 1, 2009 #15
    The brain does have an information capacity; you can measure it in bytes. Any physical system has some finite number of states which it can be in. This limits the amount of information that can be coded; for the same reason that there are only a finite number of books in Borges' Library of Babel*. This number is very large but certainly not infinite.

    * http://en.wikipedia.org/wiki/The_Library_of_Babel
  17. Feb 1, 2009 #16
    No one disputes that you could find it in theory, the problem is without knowing how the hardware works, how could you possibly guess?
  18. Feb 1, 2009 #17
    You do experiments! You can have people memorize lists, learn skills, recall experiences etc. You can measure their performance on all of these. The question "what is the information capacity of the brain" is not the question you mean to ask. What you want to know is: "how many things can be held in long term memory?" This is a question that is amenable to psychological experimentation.
  19. Feb 1, 2009 #18
    i searched for a while, but didn't find the answer to the data storage capacity of the brain. but if you look under information theory, there is a bit of research into channel capacity of input/output nerves of the brain. some things are kind of low, like a paper estimating the data output capacity of the hand at around 150 bits/sec.
  20. Feb 1, 2009 #19
    A psychology professor once explained memory to me as pathways that are made in the brain through experience. Imagine a giant field of grass. If you walk across it, you trample the grass beneath your feet. The more you follow the same path, the more pronounced the path is. Paths that are only followed once aren't pronounced, and over time, the grass can grow back and the path becomes hard to see. In our brains, the pathways are neural connections. I'm not sure how much of this metaphor translates into reality, and what it means in terms of storage capacity.
  21. Feb 1, 2009 #20
    Be very wary of those "results". In order to make those information theoretic calculations you need to assume that you know the neural representation that is being used. This is not something that is known (or agreed upon anyway).

    For example, let's say you didn't understand English and someone gave you a block of text without any spaces in it. Then say you wanted to calculate how much information is contained in the text. You would immediately notice that all the symbols were drawn from the same alphabet. So a reasonable guess as to the information capacity of the text could be 26^N where N is the number of characters and 26 is the number of letters in the alphabet.

    However, this would be much too high. In English, information is not conveyed by single letters. Rather, information is conveyed by words. If you really wanted to know how much information is in the text you would need to be counting words, not characters.

    Why stop at words though? Counting words is certainly a more reasonable approach to quantifying information in text than counting characters... Maybe, counting sentences would be even better? Or perhaps there is some higher order linguistic structures that could be invoked.

    This is analogous to the situation in neuroscience. The difference being that in neuroscience, we don't even know the alphabet being used. Any article that makes claims like "cells transmit X bits per second" is making assumptions about the nature of the neural code which may or may not be warranted.
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