Robustness ?

[Paul King]

G. Bugmann writes:
> It is possibly based on the two following beliefs:
> 1) Millions of neurons in our brain die each day. 

> Does anyone know of any publications supporting belief 1 ?

Bill Skaggs writes:
> It's a myth.  I heard Robert Sapolsky discuss this in a talk
> once:  he said that the myth seems to have been inspired by
> some ancient studies of long-time alcoholics. ...


Moshe Abeles in _Corticonics_ (Cambridge Univ. Press 1991) writes
on page 208 that:
	"Comparisons of neuronal densities in the brains of people
	who died at different ages (from causes not associated with
	brain damage) indicate that about a third of the cortical
	cells die between the ages of twenty and eighty years [Gerald,
	Tomlinson, and Gibson, 1980].  Adults can no longer generate new
	neurons, and therefore those neurons that die are never replaced.
	    The neuronal fallout proceeds at a roughly steady rate
	throughout adulthood (although it is accelerated when the circulation
	of blood in the brain is impaired).   The rate of neuronal fallout
	is not homogeneous throughout all the cortical regions, but most
	of the cortical regions are affected by it.
	    Let us assume that every year about 0.5 percent of the cortical
	cells die at random...."

and goes on to discuss the implications for network robustness.

The reference is to:
    Gearald H., Tomlinson B. E., and Gibson P.H. (1980).  Cell counts
        in human cerebral cortex in normal adults throughout life using
        an image analysing computer.  J. Neurol. 46:113-36.

Paul King