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Question about emotions versus reactions

david_olmsted at my-dejanews.com david_olmsted at my-dejanews.com
Thu Feb 25 07:31:58 EST 1999

In article <lxww1773mh.fsf at lci.isr.ist.utl.pt>,
  yoda at isr.ist.utl.pt ("Rodrigo Ventura") wrote:
>         Hi. I'm a researcher in the field of AI (artif. intelligence),
> my work is about artificial emotions (or emotion-based agents, if you
> prefer the name), but I am extremely interested in neuroscience. In
> our AI discussion group we have been debating the following issue, but
> we are kind-of stuck... Here is my question to this forum:
>         Let's assume a functional division of the CNS in three layers
> [MacLean]: a "reptile" brain which is based in reactive behavior, a
> "mamalian" brain which involves emotions (limbic system), and the
> neocortex associated with reasoning, etc. The question is: how can the
> reactive layer (e.g., the spinal cord response to a burning stimulus)
> and emotions (e.g., fear) be functionally distinguished. I mean, how
> can one describe these two layers without resorting to morpholigic
> arguments (such as this involves the thalamus, or that involves just
> the spinal cord)?
>         Another question that is related with this is: when did the
> limbic system appeared, in the species evolutio, in the brain
> (reptile? mamalian? birds? ants? bees? spiders?)? And more
> imposrtanty, what was the _qualitatively_ step that evolution took
> when emotions appeared? What was the shortcomings of the non-emotional
> animals that lead to the appearence of emotions?

The components of the limbic system such as the amygdala and septum are
present in the earliest vertebrates. The brains of non-verebrates are too
different anatomically to make any comparison.

Emotions can be defined as those signals influencing motivation levels whose
baseline levels are defined in the hypothalamus. Those from the amygdala
primarily modulate avoidance motivations while those from the septum
primarily modulate approach motivations. The prefrontal cortex is then
layered above this level to define the significance of these signals. I am
reminded of my room mate in college who had a tooth cavity filled under
nitrous oxide (laughing gas) anesthetic. He said it "hurt like hell" but that
he didn't care.

For more information on brain modeling see my site at

David Omsted

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