# Brain Capacity?

Tue Mar 11 15:23:56 EST 1997

```Dag Stenberg (stenberg at cc.Helsinki.FI) wrote:
: Kevin Spencer <kspencer at s.psych.uiuc.edu> wrote:
: > ak057 at chebucto.ns.ca (Shane Markle) writes:
: > >I recently heard of a calculation of the general amount of information
: > >stored in a human brain, represented in bits, and need to know what that
: > >capacity is.  ...

: > Whatever this number turns out to be, I wouldn't put any faith in it.
: > The brain isn't a computer based on binary logic.  It certainly doesn't
: > store information as bits.

: I applaud Kevin's comment.

Well, even if the brain is analog, the information capacity can be
measured in bits so to speak. If we then say that the brain's storage
capacity is X megabytes, then we can rationalize this to be an equivalent
statement to "the brain has enough space to store the same amount of
information that a hard disk with a X Mb capcity can store".

The brain being analog would store information differently but the
capacity can be measured in any form nevertheless. Just a case of scaling
units. Of course the anlog to digital translation would imply a higher
scaling factor of say a magnitude of order higher.

a somewhat similar analogy would be ' the power lines supplying
electricity operate on A.C. and the average power in a sine wave (or
cosine) is zero... but we still get power measured as rms power which is
the amount of power that an equivalent dc voltage would supply.

Would this be an acceptible statement?

Brain has N neurons.
Each neuron has M synapses (on average).
ASSUMING that the brain is digital (which its not)
and ASSUMING that each synapse is digital (which its not/we dont know)

the least information capacity possible is M*N bits

Information capacity will obviously increase with nonlinearity of
synaptic integration (i.e. non digital and more than two states) and
decrease with homologous activity required to activate a threshold
voltage (dependent upon a large number of factors like where the synapses
are wrt spike initiation pt (1st node of ranvier)) or how many there are
or what the concentration of receptor activators are (in cases of
receptor mediated transfer) or what the intracellular and extracellular
concentration of charges (i.e. voltage differences) are etc. etc.

This part is impossible to quantify, but for a start cant we say that the
minimal capacity of the brain can be ballpark estimated (just to order of
magnitude) by the M*N relation ?

--
..and still partly at..
Ward 5-223 : Ph (312) 503 0202
Dept. of Physiology			Dept. of Biomedical Engineering
Northwestern University			University of Akron
--

"I have no data yet. It is a capital mistake to theorize before one has
data. Insensibly one begins to twist facts to suit theories, instead of
theories to suit facts."    - Sherlock Holmes

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