Although I can't speak to the issue of whether neurons are lost with sleep
deprivation or increased alcohol intake, I did become familiar with the
literature on neuron loss in old age during the process of writing a
review of memory and aging.
It's commonly believed that neurons are lost with aging, but in reading
some of this literature it is striking to see so many confusing,
contradictory results (for instance, early studies were consistent in
reporting neuron loss in aging human hippocampus, now it's believed that
virtually no neuron loss occurs -- although it seems possible that neural
loss does occur but that it is offset by neurogenesis). There are a lot
of issues to consider when estimating neuron numbers in young and older
adults -- currently there is no way to count neurons in living brains so
one cannot count neurons in a individual at different points in one's life
(which would be ideal). Instead, one must compare brains from a group of
young adults with brains from another group of older adults -- it is
possible, therefore, that fewer neurons in older adults could reflect
cohort differences (the older adults, having been born in an era in which
nutritional knowledge was not as sophisticated as it is today, could
simply have started off with fewer neurons).
When I was a kid I heard the "fact" that you lose 100,000 neurons every
day of your life. This is, of course, a myth, and I think I found the
root to this myth. It's traceable to the 1958 book, "The mammalian
cerebral cortex," by B. D. Burns, p. 101. In reviewing some of the first
studies comparing young vs. older adult brains, the author commented
(incredulously, I think), "These figures imply that during every day of
our adult life more than one hundred thousand neurones die!" But there is
no solid evidence backing this up -- the statement was based on an
extrapolation of data from these older studies based on hand-counting
methods; these methods have been replaced by more precise, computerized
techniques.
Matt
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Matthew W. Prull
Before July 31, 1999: After July 31, 1999:
Postdoctoral Research Scholar Assistant Professor
Stanford University Whitman College
Department of Psychology Department of Psychology
Jordan Hall, Bldg. 420 345 Boyer Avenue
Stanford, CA 94305-2130 Walla Walla, WA 99362-2083
Email: [EMAIL PROTECTED]
Web: http://matia.stanford.edu/~prullm
Phone: (650) 725-0797
Fax: (650) 725-5699
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