Emotion: Systems, Cells, Synaptic Plasticity

not to generate states of consciousness. For example, Center for Neural Science all animals defend themselves from danger. When the New York University system that takes care of defense is operative in a brain 6 Washington Place that also happens to have consciousness, then the sub-Room 1066 jective state of mind called fear arises. It seems very New York, New York 10003 likely that these behavioral control systems emerged long before self-awareness did. The history of neuroscience in the 20th century is punc-If this view is correct, it means that a fundamental job tuated by periods in which the neural basis of emotion of emotion researchers is to determine how the brain has been avidly studied and discussed. We are now in controls emotional responses based on the computa-such a period, one marked by technical and conceptual tion of the emotional significance of stimuli. And if emo-advances that allow a consideration of emotional pro-tional responses and conscious emotions are both prod-cesses in terms of neuroanatomical circuits, cellular ucts of these computations, then defining the brain functions, and molecules. This short article will survey mechanisms that control emotional responses also re-some of the recent advances. veals important aspects of the system that generates subjective emotional states in conscious brains. Breaking Through the Consciousness Barrier A fundamental problem in studying the mind as a func-Emotions, One at a Time, in the Brain tion of the brain is getting past the fact that we are often In the past, researchers interested in the physiology of consciously aware of the mental states that our own emotion have sought to find a universal brain system of brain produces. This has historically led to the assump-emotion (MacLean, 1952). This effort culminated around tion that the study of the mind necessarily involves the mid-century in the limbic system concept, which is still study of consciousness. Following the rise of cognitive widely discussed as an explanation of where our emo-science, however, mental functions have been conceptions come from. But in attempting to account for all tualized in terms of computational processes—uncon-emotions in one system, it actually accounts for no emo-scious turnings of mental gears—rather than as subjective states. From this perspective, the exact nature of tions (LeDoux, 1991). The alternative approach, which conscious states, and the relative inaccessibility of has proven to be more productive, is to track down these states to empirical study (especially as brain func-emotional …