Re: Ordinary Old Brains Go "Awry"

From: Robert J. Bradbury (
Date: Mon May 08 2000 - 20:35:09 MDT

On Mon, 8 May 2000, Robin Hanson wrote:

> >Full text:
> >
> This is disturbing; it suggests that ordinary brains get worse as
> they get older. It's not that they stay fine and the body they
> run gets worse.

Its worse than that Robin. The recent work by Pakkenberg & Gundersen
shows a neocortical neuron loss of 10% over the period from 20 to 90 yrs.
That puts you at ~50% loss around 400 years. How much lower would you
want to go???

The older ref of Anderson and Hubbard, shows that it may be increasing
to 1%/yr from 70 to 95. The methods used are different, and I'd trust
the more recent work more. But it sounds like you are losing neurons
at a rapid rate that is increasing with age.

So, its either regrow neurons or freeze early if you don't want
to be a shadow of your former self. Fortunately, recent work seems
to show growth factors can stimulate neuron outgrowth and the rewiring
experiments demonstrate a great deal of flexibility about taking on
new functions.

But it seems really undesirable to me to have to go back to college
every 100-200 years to relearn everything you once knew.

Side note some list members who like to express their positions
"passionately" -- you won't remember any of this in a couple of
hundred years unless you go look it up in the archives...
Gives new meaning to "byegones".


1. Pakkenberg B, Gundersen HJ
   J. Comp Neurol 1997 Jul 28;384(2):312-20
   Neocortical neuron number in humans: effect of sex and age.
2. Anderson JM, Hubbard BM, Coghill GR, Slidders W
   J Neurol Sci 1983 Feb;58(2):235-46
   The effect of advanced old age on the neurone content of the cerebral
   cortex. Observations with an automatic image analyser point counting method.

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