Who Needs Emotions? The Brain Meets the Robot

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voluntary control of actions is further enabled by superimposition of cortical
systems on the basic sensory-reflexive network. Moreover, there is extensive
reciprocal communication between the cerebral hemispheres and motor effector
networks. An additional major principle for organization of the behavioral
control columns is that they project massively back to the cerebral cortex/
voluntary control system directly or indirectly via the dorsal thalamus (Risold,
Thompson, & Swanson, 1997; Swanson, 2000). For example, nearly the entire
hypothalamus projects to the dorsal thalamus, which in turn projects to
widespread regions of the neocortex. Moreover, recently characterized
neuropeptide-coded systems have revealed that orexin/hypocretin- and melanin
concentrating hormone–containing cells within the lateral hypothalamus
project directly to widespread regions within the neocortex, amygdala, hippocampus,
and ventral striatum and may be very important for behavioral
state regulation and arousal (Espana, Baldo, Kelley, & Berridge, 2001;
Peyron et al., 1998). This feed-forward hypothalamic projection to the
cerebral hemispheres is an extremely important anatomical fact for grasping
the notions elaborated above, that intimate access of associative and
cognitive cortical areas to basic motivational networks enables the generation
of emotions or the manifestation of “motivational potential.” Thus, in the
primate brain, this substantial reciprocal interaction between phylogenetically
old behavioral control columns and the more recently developed cortex
subserving higher-order processes such as language and cognition has enabled
a two-way street for emotion. Not only can circuits controlling voluntary motor
actions, decision making, and executive control influence and modulate our
basic drives, but activity within the core motivational networks can impart
emotional coloring to conscious processes. A flat map anatomical diagram from
the work of Swanson (2000), showing some of the pathways described here,
is provided in Figure 3.5.
EVOLUTIONARY DEVELOPMENT OF
NEUROTRANSMITTER SYSTEMS
Neurochemical signaling pathways involved in emotional processing in the
mammalian brain have evolved over the billions of years since the origins
of life. Within the constraints of genetic evolution, nervous systems became
more complex and enabled progressively greater possibilities for the
animal in its relationship with its environment. Chemical signaling played
a critical role in this connectivity and adaptation. Neurotransmitter signaling
networks and their corresponding receptor molecules, particularly the biogenic
amines, small neuropeptides, and neuropeptide hormones, became
specialized for particular behaviors or motivational states (Niall, 1982;