Who Needs Emotions? The Brain Meets the Robot

organization of motivational–emotional systems 39
missive bow and retreating. Thus, the particular behaviors aimed at maximal
adaptation are fixed, yet their expression is modifiable and sensitive to ongoing
stimulus conditions and outcomes. Here, we see the reptilian roots of
motivational–emotional systems and their functions in the domains of positive
affect (foraging, mating, sunning) and negative affect (aggressive defense,
submission, pain).
The notion of drives deserves mention before we explore the brain systems
that mediate affect. The concept of instinct is derived from two main
notions: that of essentially fixed, innate behavioral programs and that of drive,
or satisfaction of bodily needs. However, the term drive, like emotion, has a
somewhat checkered past in the history of psychology and motivation, particularly
in traditional learning theory. Drive theory essentially postulated
that learning was based on satisfaction of needs (Hull, 1943); however,
modern interpretations of learning often discount drive as an explanatory
concept, based on many examples of learning and flexible behavior in the
absence of satisfaction of any obvious need state (e.g., Berridge, 2001; Bindra,
1978; Bolles, 1972; Dickinson & Balleine, 1994). It is certainly true that drive
as conceptualized in a physiological sense (a biological need) cannot account
for the diversity of motivated and learned behaviors. However, if we broaden
our definition to include motivated, adaptive behaviors that are beneficial
to the organism in its environment, it is still a useful concept. For example,
most people would not argue that many mammalian species have an innate
“drive” to move about and explore, to seek social stimulation, or to learn
about spatial surroundings—behaviors that are not obviously mediated by
any deficit state such as hunger or thirst but that clearly maximize fitness
and availability of resources.
BRAIN CIRCUITS AND THE REGULATION
OF MOTIVATED BEHAVIOR
The foregoing account suggests that there are specific brain networks that
subserve motivations and emotions. In recent decades, knowledge concerning
these networks has advanced at a rapid pace in terms of the detailed
understanding of their organization, connectivity, neurochemical and neurohumoral
integration, and molecular biology. The purpose of this section is
to provide a condensed overview of the key elements and basic organization
of these networks. A number of excellent in-depth reviews of anatomy related
to motivated behavior exist, to which the reader is referred for more
detailed information as well as theoretical implications of brain neuroarchitecture
(Risold, Thompson, & Swanson, 1997; Swanson, 2000; Petrovich,
Canteras, & Swanson, 2001; Saper, 2000, 2002).