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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
http://weber.u.washington.edu/~wcalvin/bk7/bk7ch1.htm
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


--
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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