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brain usage capacity

Didier A. Depireux didier at Glue.umd.edu
Sun Apr 11 15:44:16 EST 1999

antoine (antoine at ifu.net) wrote:
: I am looking for any info on justifying the fact that we use less than 1%
: How did the neuro-scientists came up with this number?

It is quite nicely explained in "Conversations with Neil's brain", by W.
Calvin. You can find the relevant chapter on
in its entirety.

The book is definitely worth reading in its entirety, but for this thread's 
purpose, I will quote part of the relevant material:

	Indeed, this is the origin of that dubious factoid: "You use only
	20 percent of your brain anyway." This is true, but only in a
	very limited sense.  Before the hand starts acting weak or
	 paralyzed, a slowly growing tumor has to kill about 80
	percent of the cells in the hand region of the motor strip. Yet
	that is a very crude test of function.	A pianist or mechanic
	would probably notice problems long before then. And a stroke
	that suddenly killed perhaps 30 percent of the neurons in the
	motor strip would also cause paralysis. but

So the argument of the 10% (that's the number I used to hear) is that
there's enough plasticity in cortex that if parts of your motor cortex die
_slowly_, the brain can adapt, and you are left with the impression that 90%
of your (motor, for instance) cortex was not needed. 


Didier A Depireux                              didier at isr.umd.edu
Neural Systems Lab                 http://www.isr.umd.edu/~didier
Institute for Systems Research          Phone: 301-405-6557 (off)
University of Maryland                                -6596 (lab)
College Park MD 20742 USA                     Fax: 1-301-314-9920

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