On Mon, 8 May 2000, Robin Hanson wrote:
> >Full text:
> >http://helix.nature.com/nsu/000323/000323-4.html
>
> 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".
Robert
Refs:
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.
URL: http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9215725&dopt=Abstract
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.
URL: http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6834079&dopt=Abstract
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