Vol 4 n° 3 - Anxiety I
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Anxiety is a psychological, physiological, and behavioral state induced in animals and humans by a threat to well- being or survival, either actual or potential. It is character- ized by increased arousal, expectancy, autonomic and neu- roendocrine activation, and specific behavior patterns. The function of these changes is to facilitate coping with an adverse or unexpected situation. Pathological anxiety inter- feres with the ability to cope successfully with life chal- lenges. Vulnerability to psychopathology appears to be a consequence of predisposing factors (or traits), which result from numerous gene–environment interactions during development (particularly during the perinatal period) and experience (life events). In this review, the biology of fear and anxiety will be examined from systemic (brain–behav- ior relationships, neuronal circuitry, and functional neu- roanatomy) and cellular/molecular (neurotransmitters, hor- mones, and other biochemical factors) points of view, with particular reference to animal models. These models have been instrumental in establishing the biological correlates of fear and anxiety, although the recent development of noninvasive investigation methods in humans, such as the various neuroimaging techniques, certainly opens new avenues of research in this field. Our current knowledge of  the  biological  bases  of  fear  and  anxiety  is  already impressive, and further progress toward models or theo- ries integrating contributions from the medical, biological, and psychological sciences can be expected. Dialogues Clin Neurosci. 2002;4:231-249. n a book published in 1878 (Physiologie des passions), Charles Letourneau, who was contemporary with the French neuroanatomist Paul Broca, defined emotions as “passions of a short duration” and described a number of physiological signs and behavioral responses associated with strong emotions.1 Emotions are “inti- mately linked with organic life,” he said, and either result in an “abnormal excitation of the nervous network,” which induces changes in heart rate and secretions, or interrupt “the normal relationship between the periph- eral nervous system and the brain.” Cerebral activity is focused on the source of the emotion; voluntary muscles may become paralyzed and sensory perceptions may be altered, including the feeling of physical pain. This first phase of the emotional response is followed by a reac- tive phase, where muscles come back into action, but the attention still remains highly focused on the emotional situation. With the knowledge of brain physiology and anatomy that was available at the end of the 19th cen- tury, hypotheses on the mechanisms possibly involved in emotions were of course limited. However, Letourneau assumed  that  “the  strong  cerebral  excitation”  that accompanies emotions probably only concerned “cer- tain groups of conscious cells” in the brain and “must necessitate a considerable increase of blood flow in the cell  regions  involved.”1  He  also  mentioned  that  the intensity, the expression, and the pathological conse- quences of emotions were directly linked to “tempera- ments”  (which  he  defined  within  the  four  classic Hippocratic categories). S t a t e   o f   t h e   a r t 2 3 1 The biology of fear- and anxiety-related behaviors Thierry Steimer, PhD Keywords: anxiety; fear; emotions; animal models; neurobiology; behavior Author  affiliations:  Clinical  Psychopharmacology  Unit,  Geneva  University Hospital, Chêne-Bourg, Switzerland Address  for  correspondence:   Unité   de   Psychopharmacologie   Clinique, Domaine de Belle-Idée, 2, chemin du Petit-Bel-Air, CH-1225 Chêne-Bourg, Switzerland (e-mail: thierry.steimer@hcuge.ch) I