Hi Gregg,
By coincidence, I am currently grappling with some of the issues raised
by neurogenesis and antidepressants. The short answer to your question
is that the neurogenesis (NG) angle isn't a good argument for giving
Prozac to developmentally delayed children.
There are two main reasons: one is that the cells which migrate to the
olfactory bulbs are generated in the subventricular zone - the ones
generated in the hippocampus stay in the hippocampus, and they are the
ones increased by Prozac. So Prozac wouldn't increase cells going to
the olfactory bulbs.
The other reason, which is more a hypothesis of mine, is that the extra
NG we see from antidepressants is the result of their activity being
integrated into behaviour - i.e. the antidepressants make large changes
to the monoamine systems "out there" in the brain, but before these
changes play a part in behaviour, they have to be integrated with the
rest of the brain's activity. Gerd Kempermann had the idea that NG is
related to the hippocampus getting used to a new setup - so I want to
extrapolate that idea to suggest that antidepressant-enhanced NG is a
mark of the brain adjusting to the large changes caused elsewhere by the
drug, and not the direct agent of those changes.
So I think neurogenesis in the hippocampus is more about behavioural
flexibility rather than having "more brain" or developing faster. The
cells die at the same rate new ones are generated - it's just that the
new ones can grow into new patterns more easily than the old ones could
be adapted.
Interestingly, you can enhance neurogenesis by exposing an individual to
an enriched environment (lots of interesting things to see, hear, touch,
taste and smell). As a parent who's obviously reading widely and
seeking knowledge, it sounds like you are already likely to be doing
that sort of thing anyway! I wouldn't be messing with kids' serotonin
systems as a rule, especially kids who are maturing more slowly than the
norm.
Hope that helps. As an aside, I was disappointed to see the focus of
that Sci Am issue was "improving the brain". Every shred of evidence we
have is that the brain organises itself optimally to use its resources
and its potential to the fullest - it seems like fallacy of the worst
kind to think that we could just "stimulate" or "tune" something and
augment its powers. If it were that simple, don't you think we'd
already be doing it?
Regards,
Matthew.
