On Sun, 17 Feb 2013, Annette Taylor went:
Question 2:
I think I know this one but want to verify: Why do stimulants help
with ADHD. And I think the correct answer here is that they stimulate
INHIBITORY circuits. Is that correct? I know that supposedly
stimulants act to increase other neurotransmitter activity but
doesn't the key lie in which neurotransmitters?
I think the answer is not yet known and is going to be complicated,
but part of it may lie in some now-classic primate work by Patricia
Goldman-Rakic...
<http://scholar.google.com/scholar?as_q=&as_epq=modulation+of+memory+fields&as_oq=&as_eq=&as_occt=any&as_sauthors=%22goldman+rakic%22&as_publication=&as_ylo=1995&as_yhi=1995&hl=en&as_sdt=0%2C21>
...in which she showed that one type of dopamine receptor in
prefrontal cortex has a narrow optimal window of activation within
which it encodes data most efficiently. In other words, stimulating
those dopamine receptors either too MUCH or too LITTLE could produce
similar symptoms of distractability/inattention. I sometimes use the
analogy of trying to read a book under a one-watt lightbulb (too
little dopamine activity in prefrontal cortex), a million-watt
lightbulb (too much), or a hundred-watt lightbulb (juuust right).
The implication, at first glance, would seem to be that ADHD is a
hypodopaminergic disorder (meaning, a disorder resulting from too
little dopamine activity). From what I can see, however, there's no
consensus about that. One complication might be that what happens
with dopamine in one brain region needn't be the same as what's
happening with dopamine in other brain regions. And dopamine has
different, complicated functions in every brain region it's released
into. A real understanding is going to be a long time coming.
--David Epstein
[email protected]
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