concepts Fundamental feelings Emotion Emotion and feelings are closely stimulus — an object or situation, for exam- Antonio Damasio ple. The processing of the stimulus may be related but separable phenomena; he groundwork for the science of emo- conscious but it need not be, as the responses their elucidation, at long last, is now tion was laid down most auspiciously are engendered automatically. Emotional proceeding in earnest. Tover a century ago, but neuroscience has responses are a mode of reaction of brains that given the problem a resolute cold shoulder are prepared by evolution to respond to cer- until recently. By the time that Charles Dar- tain classes of objects and events with certain elucidating the neurobiology of feelings. win had remarked on the continuity of emo- repertoires of action. Eventually, the brain If emotions provide an immediate tional phenomena from non-human species associates other objects and events that occur response to certain challenges and opportu- to humans; William James had proposed an in individual experience with those that are nities faced by an organism, the feeling of insightful mechanism for its production; innately set to cause emotions, so that another those emotions provides it with a mental Sigmund Freud had noted the central role of set of emotionally competent stimuli arises. alert. Feelings amplify the impact of a given emotions in psychopathological states; and The main target of the emotional situation, enhance learning, and increase the Charles Sherrington had begun the physio- responses is the body — the internal milieu, probability that comparable situations can logical investigation of the neural circuits the viscera and the musculoskeletal system be anticipated. involved in emotion, one might have expected — but there are also targets within the brain The neural systems that are involved in neuroscience to be poised for an all-out attack itself, for example, monoaminergic nuclei in the production of emotions are being identi- on the problem. It is not usually appreciated the brainstem tegmentum. The result of the fied through studies of humans and other that the probable cause of the neglect of the body-targeting responses is the creation of animals. Various structures, such as the topic was the improper distinction between an emotional state — involving adjustments amygdala and the ventromedial prefrontal the concepts of emotion and feelings. in homeostatic balance — as well as the cortices, trigger emotions by functioning as Some traits of feelings — their subjective enactment of specific behaviours, such as interfaces between the processing of emo- nature, the fact that they are private, hidden freezing or fight-or-flight, and the produc- tionally competent stimuli and the execution from view, and often difficult to analyse — tion of particular facial expressions. The of emotions. But the real executors of emo- were projected onto emotions, so that they result of the brain-targeting responses is an tions are structures in the hypothalamus, in too were deemed subjective, private, hidden alteration in the mode of brain operation the basal forebrain (for example, the nucleus and elusive. Not surprisingly, neuroscien- during the emotional body adjustments, the accumbens) and in the brainstem (for tists were disinclined to give their best consequence of which is, for example, a example, the nuclei in the periaqueductal efforts to a problem that did not seem to change in the attention accorded to stimuli. grey). These are the structures that directly be amenable to proper hypothesizing and Emotions allow organisms to cope signal, chemically and neurally, to the body measurement. Somewhat alarmingly, this successfully with objects and situations that and brain targets at which alterations conflation of the two concepts persists, as are potentially dangerous or advantageous. constitute an emotional state. does the idea that the neurobiology of feel- They are just the most visible part of a huge No less importantly, recent functional ings is out of reach. A clarification is in order. edifice of undeliberated biological regula- imaging studies reveal that body-sensing An emotion, be it happiness or sadness, tion that includes the homeostatic reactions areas, such as the cortices in the insula, the embarrassment or pride, is a patterned that maintain metabolism; pain signalling; second somatosensory region (S2) and the collection of chemical and neural responses and drives such as hunger and thirst. Most cingulate region of the brain, show a statisti- that is produced by the brain when it detects emotional responses are directly observable cally significant pattern of activation or VICKY ASKEW the presence of an emotionally competent either with the naked eye or with scientific deactivation when normal individuals exp- probes such as psychophysiological and erience the emotions of sadness, happiness, neurophysiological measurements and fear and anger. Moreover, these patterns vary endocrine assays. Thus, emotions are not between different emotions. Those body- subjective, private, elusive or undefinable. related patterns are tangible neural correlates Their neurobiology can be investigated of feelings, meaning that we know where to objectively, not just in humans but in labora- look further to unravel the remaining neuro- tory species, from Drosophila and Aplysia to physiological mysteries behind one of the rodents and non-human primates. most critical aspects of human experience. ■ A working definition of feelings is a Antonio Damasio is in the Department of Neurology, different matter. Feelings are the mental University of Iowa College of Medicine, 200 Hawkins representation of the physiological changes Drive, Iowa City, Iowa 52242, USA. that characterize emotions. Unlike emo- tions, which are scientifically public, feelings FURTHER READING are indeed private, although no more subjec- Damasio, A. R. The Feeling of What Happens: Body and tive than any other aspect of the mind, for Emotion in the Making of Consciousness (Harcourt example my planning of this sentence, or the Brace, New York, 1999). mental solving of a mathematical problem. Davidson, R. J. & Irwin, W. Trends Cogn. Neurosci. 3, Feelings are as amenable to scientific analysis 11–22 (1999). as any other cognitive phenomenon, pro- Panksepp, J. Affective Neuroscience: The Foundations vided that appropriate methods are used. of Human and Animal Emotions (Oxford Univ. Press, Moreover, because feelings are the direct New York, 1998). consequences of emotions, the elucidation Vuillemier, P., Driver, J., Armony, J. & Dolan, R. J. of emotional neurobiology opens the way to Neuron 30, 829–841 (2000). NATURE | VOL 413 | 25 OCTOBER 2001 | www.nature.com © 2001 Macmillan Magazines Ltd 781.