99. Ballerini, L., Bracci, E. & Nistri, A. Pharmacological block of the electrogenic sodium pump disrupts rhythmic bursting induced by strychnine and bicuculline in the neonatal rat spinal cord. J. Neurophysiol. 77, 17–23 (1997). 100. Darbon, P., Tscherter, A., Yvon, C. & Streit, J. The role of the electrogenic Na/K pump in disinhibition-induced bursting in cultured spinal networks. J. Neurophysiol. 90, 3119–3129 (2003). 101. Stauffer, D. & Aharony, A. Introduction to Percolation Theory 181 (Taylor & Francis, London, 1992). 102. Barabasi, A.-L. Linked: The New Science of Networks 280 (Perseus, Cambridge, Massachusetts, 2002). 103. Newman, M. E. The structure and function of complex networks. SIAM Review 45, 167–256 (2003). 104. Watts, D. J. Six Degrees: The Science of a Connected Age 368 (Norton, New York, 2003). 105. Callaway, E. M. A molecular and genetic arsenal for systems neuroscience. Trends. Neurosci. 28, 196–201 (2005). 106. Slimko, E. M. & Lester, H. A. Codon optimization of Caenorhabditis elegans GluCl ion channel genes for mammalian cells dramatically improves expression levels. J. Neurosci. Methods 124, 75–81 (2003). 107. Slimko, E. M., McKinney, S., Anderson, D. J., Davidson, N. & Lester, H. A. Selective electrical silencing of mammalian neurons in vitro by the use of invertebrate ligand-gated chloride channels. J. Neurosci. 22, 7373–7379 (2002). 108. McCrimmon, D. R., Alheid, G. F., Jiang, M., Calandriello, T. & Topgi, A. Converging functional and anatomical evidence for novel brainstem respiratory compartments in the rat. Adv. Exp. Med. Biol. 551, 101–105 (2004). Acknowledgments The authors thank G. F. Alheid and D. R. McCrimmon of Northwestern University, Illinois, USA, for the figures and for editing the text in BOX 2. We thank our colleagues in the Systems Neurobiology Laboratory at the University of California, Los Angeles, USA, for their incisive comments on earlier versions of this manuscript. This work was supported by grants from the National Institutes of Health, USA, the Jeffress Memorial Trust, Richmond, Virginia, USA, and the Parker B. Francis Fellowship in Pulmonary Research, Parker B. Francis Foundation, Kansas City, Missouri, USA. Competing interests statement The authors declare no competing financial interests. DATABASES The following terms in this article are linked online to: OMIM: http://www.ncbi.nlm.nih.gov/entrez/query. fcgi?db=OMIM Amyotrophic lateral sclerosis | Congenital central hypoventilation syndrome | Parkinson’s disease | Rett syndrome | Sudden infant death syndrome Access to this interactive links box is free online. OPINION Towards the neurobiology of emotional body language Beatrice de Gelder Abstract | People’s faces show fear in many different circumstances. However, when people are terrified, as well as showing emotion, they run for cover. When we see a bodily expression of emotion, we immediately know what specific action is associated with a particular emotion, leaving little need for interpretation of the signal, as is the case for facial expressions. Research on emotional body language is rapidly emerging as a new field in cognitive and affective neuroscience. This article reviews how whole-body signals are automatically perceived and understood, and their role in emotional communication and decision-making. What do body positions and movement reveal about emotions? From everyday exp- erience we know that an angry face is more menacing when accompanied by a fist, and a fearful face more worrisome when the person is in flight (that is, running away). When a frightening event occurs, there might not be time to look for the fearful contortions in an individual’s face, but a quick glance at the body may tell us all we need to know. This article reviews what has been discovered so far and provides a framework for the interpretation of and further investigation of emotional body language (EBL). Many valuable insights into human emo- tion and its neurobiological bases have been obtained from the study of facial expressions. By comparison, the neurobiological bases of EBL are relatively unexplored 1–5 . Human and non-human primates are especially sensi- tive to the gestural signals made by other primates, and use these signals as guides for their own behaviour. Fearful faces signal a threat, but do not provide information about either the source of the threat or the best way to deal with it. By contrast, fearful body positions signal a threat and at the same time specify the action undertaken by the indi- viduals fearing for their safety. Unravelling these behavioural aspects brings emotion researchers closer to the evolutionary link between emotion and behaviour and the phylogenetic continuity of emotion–action circuitry across species. It also sheds light on disorders that combine emotional and motor components, such as autism, schizophrenia and Huntington’s disease. Studying the neurobiology of EBL is particularly timely because the topic introduces a new and biologically realistic context to what has already been learned about human emotion from isolated facial expressions during the past two decades. EBL consists of an emotion expressed in the whole body, comprising coordinated move- ments and often a meaningful action, and so prompts research to go beyond facial expres- sions and to consider issues of perception of movement and action, which have so far been researched in isolation and not specifi- cally related to perception of EBL. After discussing why the role of the body is important in understanding emotion and communication, I describe research on per- ceptual similarities in the neuroanatomy and temporal dynamics between face and body perception, and conclude that recognition of facial expressions is strongly influenced by EBL. First, I ask why seeing emotional bodies automatically transmits the emotion and I relate this question to the combined presence of emotions, movement and actions. Next, I review dissociations between these different aspects in some clinical populations, including the role of deliberate processes and consciousness. Finally, I sug- gest an integrated framework for research on EBL perception and discuss key outstanding questions. History of emotional body language There is considerable history associated with the link between emotion and behav- iour 6 , and the relationship between emotion and whole-body action was at the centre of the pioneering work of Bulwer 7 , Bell 8 , Gratiolet 9 and Duchène de Boulogne 10 , culminating in Darwin’s evolutionary approach to emotions and their bodily expressions 11 . In a radical departure from the Cartesian view of emotions as private mental episodes, Darwin argued that emo- tions are adaptive in the sense that they prompt an action that is beneficial to the organism, given its environmental circum- stances. Darwin described the body expres- sions (for example, EBL, vocalizations and facial expressions) associated with emotions in animals and humans, with a particular emphasis on the link between emotion and action 6,12 , and highlighted the roots of facial expressions in adaptive actions 13 . So, a spe- cies’ ability to produce and perceive some basic categories of EBL is an integral part of its phylogenetic history. PERSPECTIVES 242 | MARCH 2006 | VOLUME 7 www.nature.com/reviews/neuro