From: Rafal Smigrodzki (rms2g@virginia.edu)
Date: Thu Aug 08 2002 - 12:55:06 MDT
gts wrote:
Thanks for your comments. However this is a subject about which I happen to
be fairly well-informed. It is true that many parts of the brain are
involved in the reward circuitry, and true also that the circuitry varies
with the category of reward, but research shows the nucleus accumbens to be
the final node in the circuitry and the place from which the actual
experience of pleasure arises. The reward experience is best considered as a
cascade of neurological events that culminates in a pleasurable release of
dopamine in the nucleus accumbens.
### Can you point me to the research showing that the release of dopamine in
NAc (a physical event) has the experiential correlate of "pleasure"? I
thought we are still far from being able to explain conscious experiences in
mechanistic terms, aside from the simple correlations between activation of
brain regions and some experiences. I do not deny the importance of NAc for
the generation of reward (it might be indeed the structure sine-qua-non),
but as the research you quote shows, there *is* more to pleasure that
dopamine in NAc, especially in the case of such complex processes as
altruistic behaviors.
------
With respect to social reward, someone here posted a link to the following
article:(http://www.wired.com/news/print/0,1294,53945,00.html)
You'll find the following statement in the article:
"And every time the two cooperated, the volunteer in the scanner showed
activity in her brain's reward circuit: the nucleus accumbens, the caudate
nucleus, ventromedial frontal/orbitofrontal cortex and rostral anterior
cingulate cortex."
As you can see, the nucleus accumbens was found to be a part of the reward
circuitry associated with constructive social behavior (cooperation). This
is consistent with my statement above to which you objected.
### I am sorry if it sounded as an all-out objection - I meant rather a need
for a change in emphasis, to include the cortex, not exclude NAc. I do
believe some cortical areas are necessary to allow the perception of certain
types of pleasure, based on descriptions of cases with lesions of the ACC. I
could try to dig up the actual references if you wish.
------
To my knowledge the nucleus accumbens is the final node in the circuitry for
any category of reward. If you have reason to believe otherwise then I would
appreciate references.
### Would you mind explaining what you mean by "the final node"? Is it the
structure whose function has the direct experiential correlate of pleasure?
Or is it merely the final station integrating diverse inputs, whose output
stimulates large areas of the brain, which carry out the actual information
processing tasks subjectively perceived as pleasure? I am not sure if we
have enough understanding of these processes to differentiate between the
two but I am curious to hear your opinion.
Rafal
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