Who Needs Emotions? The Brain Meets the Robot

A
B
Conditioned stimulus
(tone)
Unconditioned stimulus
(footshock)
Natural threat
or
Conditioned stimulus
basic principles for emotional processing 87
Time
Defensive behavior
Autonomic arousal
Hypoalgesia
Reflex potentiation
Stress hormones
Figure 4.1. (A) Fear conditioning involves the presentation of a noxious
unconditioned stimulus (US), such as footshock, at the end of the occurrence
of a neutral conditioned stimulus (CS), such as a tone. (B) After conditioning,
the CS elicits a wide range of behavioral and physiological responses that
characteristically occur when an animal encounters a threatening or feararousing
stimulus. Thus, a rat that has been fear-conditioned to a tone will
express the same responses to a CS as to a natural threat (e.g., a cat). (Adapted
cally occur in the presence of danger) will be elicited by the tone alone. Examples
of species-typical defensive responses that are brought under the control
of the CS include behaviors such as freezing in rodents and autonomic
(e.g., heart rate, blood pressure) and endocrine (e.g., hormone release) responses,
as well as alterations in pain sensitivity (hypoanalgesia) and reflex
expression (fear-potentiated startle and eye blink responses). This form of
conditioning works throughout the phyla, having been observed in flies, worms,
snails, fish, pigeons, rabbits, rats, cats, dogs, monkeys, and humans.
Research from several laboratories combined in the 1980s to paint a
relatively simple and remarkably clear picture of the neuroanatomy of fear
conditioning (Davis, 1992; Kapp, Whalen, Supple, & Pascoe 1992; LeDoux,
1992; Fanselow & Gale, 2003). In such studies, the CS and US are typically
an audible tone and a foot shock, and the responses measured include freezing.
It was shown that fear conditioning is mediated by the transmission of
information about the CS and US to a small almond-shaped area (the