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Despite the obvious importance of emotion to human existence, scientists concerned with human nature have not been able to reach a consensus about what emotion is and what place emotion should have in a theory of mind and behavior. Controversy abounds over the definition of emotion, the number of emotions that exist, whether some emotions are more basic than others, the commonality of certain emotional response patterns across cultures and across species, whether different emotions have different physiological signatures, the extent to which emotional responses contribute to emotional experiences, the role of nature and nurture in emotion, the influence of emotion on cognitive processes, the dependence of emotion on cognition, the importance of conscious versus unconscious processes in emotion, and on and on (see Ekman & Davidson 1994).
Although there has been no shortage of psychological research on these topics, the findings have not resolved many of the issues in a compelling manner. But psychological research is not the only source of information about the nature of emotion. Information about the representation of emotion in the brain may shed light on the nature of emotional processes. First, information about how emotion is represented in the brain can provide constraints that could help us choose between alternative hypotheses about the nature of some emotional process. Second, findings about the neural basis of emotion might also suggest new insights into the functional organization of emotion that were not apparent from psychological findings alone. The brain, in other words, can constrain and inform our ideas about the nature of emotion.
This review examines the neural basis of emotion and considers how research on brain mechanisms can potentially help us to understand emotion as a psychological process.
NEURAL BASIS OF EMOTION
Studies of the neural basis of emotion have a long history within neuroscience (see LeDoux 1987, 1991). This research culminated around mid-century in the limbic system theory of emotion (MacLean 1949, 1952), which claimed to have identified the limbic system as the mediator of emotion. However, in recent years both the limbic system concept (Brodal 1982, Swanson 1983, Kotter & Meyer 1992) and the limbic system theory of emotion (LeDoux 1991) have been questioned. Despite problems with the conceptualization of the brain system that mediates emotion in general,...