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Humans use 10% of brain... true?

Jaimie Polson jaimiep at cortex.physiol.usyd.edu.au
Thu Aug 26 01:46:20 EST 1999

In <7q2iee$cvd$1 at bgtnsc01.worldnet.att.net> "Martin Knopman" <mknopman at worldnet.att.net> writes:

>>>and acquired linguistic devices?) is x.  And has anyone ever even come up
>>>with an estimate for the average (?) computational work done by some
>>>brain, in some average situation, after an average amount of sleep,
>>>some average thought, within an average emotional environment, ... I think
>>>that it's even hard to determine %100 utilization of many simple
>>>machines - different contexts yield different answers, not to mention the
>>>unknown productive contexts.
>>Um, the brain does a lot more than "compute", think thoughts etc.

>Um, I think that, um, we have different definitions of computation ... but
>how is it that you KNOW that the brain does a lot more than compute? What
>are these other qualities?  If you are going to address a question that
>speaks about a specific proportion of utilization of some system then you
>must have some form of measurement on which you are basing your assessment.

Well, lets see.  The brains produces neural output for muscle contractions for
movement, breathing, maintenance of blood pressure, heart rate.  There's
regulation of glandular sectretions, regulation of body temperature....  etc. 
This is all vastly different from "thinking some average thought".

And I am not making any assesment of the proportion of brain used by man. I
have no idea.  As I said before, this idea of 10% is likely based on
neuronal numbers.  "How much brain do we need to function normally?"

>>And most of
>>the brain's functions work pretty well, even if you haven't had an average
>>amount of sleep.

>Yes, my thinking is always clear after 30 hours without sleep.  I always
>think best when I'm in a pressure situation, or when I'm depressed, or when
>I'm scared,...  Come on.

As I said, most of the brain's function is not "thinking".  Clearly is
is harder to think when we are tired, but I don't think its harder to
maintain our blood pressure or regulate our body temperature.

>By the way, why did you say "...the brain's functions..." which has a very
>computational ring to it?!?  If the brain is performing, by your account,
>important [my inference] non-computational tasks, then they are not
>functions ... unless you have some deeper insight into the Church/Turing
>Thesis than anyone else.

>>I think the question is pretty simple.  You have 100 neurons
>>in your brain and you use 100 of them (for what ever function).
>>  QED 100%
>>usage.   You use 10 of them, then 10% usage.

>Again, we have a basic problem here with what you term "use".  If I spill my
>brain out onto the table and feed 100 neurons to my cat, then they are being
>"used" ... but that is not what you mean, is it.  You have very specific
>types of uses in mind, so maybe you should be a little more specific.  You
>do not even touch on the subject of efficiency.  Raw neuronal usage is a
>measure that is of no interest, at all.  Again, you felt the need to include
>"(for whatever function)" to which my above comment applies.

Raw neuronal usage (electrical activity, action potential, ionic conductances,
whatever) is what neurons do.  To measurement  this would answer the question.
Does the brain only use 10% of its capacity?  It suggests if we remove the
other 90%, that we would function normally.  How do you measure it?  No idea.

>You also seem to be making the assumption, here, that all neurons could be
>"used" (in whatever way you want) constantly (you gave no time frame for
>usage, so I assume it was 'at all times').  If not, then you have to
>determine the mean temporal utilization of a neuron, just to get a standard
>by which you determine full usage.  Look, by your definition no human has
>ever worked "100%", and you would be led to say that every human workforce
>operates at less than 50% of capacity. That is clearly silly.  Sleep is
>something that has to be taken into account when woking with humans, and we
>do not know what the maximum load is that a neuron can take and still
>function properly.

I was not making the assumption that all neurons are used constantly.  Just
that they are used (thinking neurons are used when you think, muscle neurons
are used when you contract muscles, neurons in a neuronal network oscillator
are used whenever.  Clearly neurons are quiescent at times, and active at
other times (the time scale varies, depending on the neuron)).  But are some
neurons always quiescent?  Probably impossible to answer.

I've chopped out the rest of your discussion for brevity.   Your argument
is about what is usage and capacity.  By your definition, 100% capactiy would
mean all neurons firing together all the time.  My definition is that
100% capacity is that all neurons have an function that they fulfil at
some time.  They do not need to be always active.  They may only be
active under certain special circumstances.  But they have a function (other
than just filling up the skull or as cat food).

Clearly in either definition the idea of 100% capactiy is not likely (at
the very least due to redundancies in the system).  

I think my definition is what people are normally referring to when they
talk about brain capacity (10% or whatever).

>> I suppose
>>this kind of statement comes from knowledge of various insults to the
>>brain - small stroks, brain surgey, injury etc that do not appear to effect
>>our functioning.

>I do not agree with that statement.  I don't know of anyone who claims that
>a small stroke has no effect on brain function.  It is one thing for someone
>to appear normal after a stroke, but quite another to claim that their brain
>function has not changed.  As I mentioned above about error correction and
>such, any robust complex system must have certain redundancies built into
>it, but that does not mean that those redundant functional structures could
>just be utilized at any time.

Okay, one more point.  I did not say this was true, I said it was an 
basis for this kind of question to be asked.  But then consider, if you
lose one brain neuron does it affect your normal function?  Or if you lose
10 neurons?  Or 100, 1000, etc.

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