[Neuroscience] Re: What role do chemicals play in motivation?

r norman via neur-sci%40net.bio.net (by r_s_norman from _comcast.net)
Sun Feb 11 15:58:07 EST 2007

On 11 Feb 2007 12:24:56 -0800, "chadmaester"
<chad.d.johnson from gmail.com> wrote:

>> >Where might I look to understand the 'in-between'? Any book/course
>> >suggestions?
>> I don't know but Google produces a few hundred thousand hits. There
>> must be something useful in that.
>> Steve
>Sorry to bug you further, but can you give me basic a hint as to what
>you all are labeling as 'in-between'? Are you referring to processes
>involving neurotransmitters and also fuzzy logic with NNs, or
>something(s) else?

The original  by "Benjamin" was "Neurochemicals are to memory as
"nuts and bolts" are to "machine". There's a lot in-between that has
to be understood if your Q is to actually be answered."

What that means is that chemicals play about the same role in
motivation as electrical potentials or cell metabolism.  They are all
part of the mechanism of the nervous system.  Motivation is a "higher
level" construct that is the result of activity in the nervous system.
That means it depends on everything about the nervous system;  the
cells and their physiology and how they interact.  It is _not_ a
simple matter of this chemical or that chemical (no matter what the
pop psychology books say!).  If you want to understand it, you really
have to study neurobiology in some depth.

In another post you say "What I am hoping to do is make a basic
computer model of Aplysia sensitization/desensitization. I was
wondering what the slug's motivation is for pulling away as it does
when touched. Would it be a matter of self-preservation?"

You do not ordinarily attribute "motivation" to the behavior of an
animal like Aplysia unless you are talking about behavior at the level
of ethology.  The gill withdrawal is a simple reflex.  You might as
well ask "what is the motivation of a person for kicking the lower leg
when the tendon just under the knee cap is tapped?"  That is the way
the nervous circuits are wired. No "thinking" or "planning" or
"motivation" need be invoked.  In the knee jerk case, it is part of
the muscle spindle regulatory system involved in motor control.  In
the gill withdrawal case it is a defensive mechanism akin to our
jerking our foot up when we step on a tack, the flexor reflex.

There are numerous texts of neurobiology that include details of the
Aplysia sensitization/desensitization system.   "Neuroscience" by
Purves et al. is a very good one that is available (in an older
edition, but still very useful) on-line at the NCBI Bookshelf: 
Search for "Aplysia" and you will get good information.

An older bibliography I used for teaching a number of years ago (I am
now retired) included (these are probably all older editions)

Principles of Neural Science (4th Ed)
Eric Kandel, James Schwartz, and Thomas Jessell
McGraw-Hill, 2000

Neuroscience (2nd Ed)
Dale Purves, and others
Sinauer Associates, 2000

Fundamental Neuroscience
M.J.Zigmond, F.E.Bloom, S.Landis, J.L.Roberts, and L.R.Squire, eds.
Academic Press, 1998

Essentials of Neural Science and Behavior
Eric Kandel, James Schwartz, and Thomas Jessell
McGraw-Hill, 1996

I know chapter 24 of "Foundations of Neurobiology", by Fred Delcomyn,
WH Freeman, 1998, included information on what you are looking for
because I used it as a text for an introductory course.  All of these
sources should be able to give you good citations to Eric Kandel's
work on Aplysia where you will find all the details.

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