Who Needs Emotions? The Brain Meets the Robot

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and brain neurotransmitters. Many of these compounds bind specifically to
brain receptors and are able to induce feelings of positive emotion or pleasure,
and relieve negative emotional states such as anxiety and depression.
In the present ecological environment, the overabundance and availability
of high quantities of pure drugs have resulted in maladaptive consequences
of uncontrolled use and addiction.
CONCLUSIONS
The present chapter has provided a framework for thinking about the evolution
of brain neurotransmitter systems that mediate motivational processes
and emotional expression. Emotions (or their equivalent state) are required
to activate adaptive behavior, from single-cell organisms to humans. Their
elaboration and expression, when elicited by appropriate stimuli, are instantiated
in complex but highly organized neural circuitry. A major feature of
this circuitry, at least in mammalian brains, is reciprocal and feed-forward
links between core motivational systems within the hypothalamus and
higher-order corticostriatal and limbic structures. This cross-talk between
cortical and subcortical networks enables intimate communication between
phylogenetically newer brain regions, subserving subjective awareness and
cognition, with ancestral motivational systems that exist to promote survival
behaviors. Neurochemical coding, imparting an extraordinary amount of
specificity and flexibility within these networks, appears to be conserved in
evolution; several examples with monoamines and peptides have been provided
above. Across the course of thousands of years, humans, through interactions
with plant alkyloids, have discovered how to facilitate or blunt
emotions with psychoactive drugs. Thus, while emotional systems generally
serve a highly functional and adaptive role in behavior, they can be altered
in maladaptive ways in the case of addiction. Future research will
undoubtedly generate more insight into the chemical, genetic, and organizational
nature of motivational–emotional systems.
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