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The biology of fear- and anxiety-related behaviors
Try out PMC Labs and tell us what you think. Learn More. Language: English Spanish French. 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 characterized by increased arousal, expectancy, autonomic and neuroendocrine activation, and specific behavior patterns. The function of these changes is to facilitate coping with an adverse or unexpected situation.
Pathological anxiety interferes with the ability to cope successfully with life challenges. 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 theories integrating contributions from the medical, biological, and psychological sciences can be expected. La ansiedad es una condición psicológica, fisiológica y conductual que se induce en los animales y en el hombre por una amenaza al bienestar o a la sobrevivencia, sea presente o potencial. Se caracteriza por un aumento del alerta, expectación, activación autonómica y endocrina, y patrones conductuales específicos.
La función de estes cambios es facilitar la adaptación ante una situatión adversa o inesperada. La ansiedad patológica interfiere con la capacidad para adaptarse exitosamente a los desafíos de la vida.
La vulnerabilidad a la psicopatología parece ser una consecuencia de factores predisponentes o rasgos los cuales se deben a numerosas interacciones entre los genes y el ambiente durante el desarrollo especialmente durante el período perinatal y a lo largo del curso de la vida acontecimientos vitales. Estos modelos han constituido un medio para establecer los correlatos biológicos del miedo y la ansiedad; sin embargo, el reciente desarrollo de métodos de investigación no invasores en humanos, como las diversas técnicas md phd resume moscow neuroimágenes, ciertamente abre nuevas vías de investigación en este campo.
Nuestro conocimíento actual de las bases biológicas del miedo y la ansiedad ya es notable y se puede esperar que a futuro se progrese hacia modelos o teorías que integren contribuciones desde las ciencias médicas, biológicas y psicológicas.
L'anxiété est un état psychologique, physiologique et comportemental provoqué chez les animaux et les humains par une menace qui s'exerce sur le bien-être ou la survie, qu'elle soit réelle ou potentielle. Elle est caractérisée par une hypervigilance, une attente excessive, une activation des systèmes autonome et neuroendocrine et par des schémas comportementaux spécifiques.
Ces modifications doivent faciliter l'adaptation à une situation hostile ou inattendue. L'anxiété pathologique interfère avec la capacité de s'adapter avec succès aux aléas de la vie. La susceptibilité à la psychopathologie semble résulter de facteurs prédisposants ou de caractèreseux-mêmes issus de nombreuses interactions gène-environnement pendant la phase de développement particulièrement durant la période périnatale et de l'expérience événements de la vie.
Dans cet article, la biologie de la peur et de l'anxiété sera examinée d'un point de vue systémique relations cerveau-comportement, circuits neuronaux et neuroanatomie fonctionnelle et d'un point de vue cellulaire et moléculaire neurotransmetteurs, hormones et autres facteurs biochimiquesavec une référence particulière aux modèles animaux.
Ces modèles ont contribué à l'établissement de corrélations biologiques de la peur et de l'anxiété, bien que les avancées récentes des méthodes d'investigation non invasives chez les humains, telles les diverses techniques de neuro-imagerie, md phd resume moscow, ouvrent certainement de nouvelles voies de recherche dans ce domaine. Nos connaissances actuelles des bases biologiques de la peur et de md phd resume moscow sont déjà impressionnantes et nous pouvons espérer des progrès supplémentaires de la part de modèles ou de théories intégrant les données des sciences médicales, biologiques et psychologiques.
This first phase of the emotional response is followed by a reactive phase, md phd resume moscow, where muscles come back into action, but the attention still remains highly focused on the emotional situation, md phd resume moscow. With the knowledge of brain physiology and anatomy that was available at the end of the 19th century, hypotheses on the mechanisms possibly involved in emotions were of course limited.
It is amazing to see how Letourneau's views on emotions, more than a century ago, were in many ways premonitory. For a long time, emotions were considered to be unique to human beings, and were studied mainly from a philosophical perspective. This has progressively led to today's view of emotions being experienced or expressed at three different, but closely interrelated levels: the mental or psychological level, the neuro physiological level, and the behavioral level.
These three complementary aspects are present in even the most basic emotions, such as fear. However, a brief historical survey of the more biologically oriented ones may help to set some important conceptual issues. One of the main questions addressed by earlier scientific theories of emotions was whether physiological changes precede the emotional experience, or if they are only a consequence of it. Cannon and Bard criticized this theory and proposed that the neurophysiological aspects of emotions are subcortical and involve the thalamus.
Thus, a sudden noise or loss of physical support can induce an innate fear reaction, and restraint of bodily movements triggers rage. For him, connections between the cerebral hemispheres and the hypothalamus, and between the cerebral hemispheres and the dorsal thalamus mediate emotions. He held the view that emotion implies behavior expression and feeling experience, subjective aspects. Expression depends on the hypothalamus, and experience on the cortex. More recently, Schachter emphasized the importance of cognitive processes: bodily states are interpreted in a cognitive context and are modulated by experience.
He also showed that the visceral response appears to be a necessary, although not sufficient, condition for the occurrence of emotion. The main function of fear and anxiety is to act as a signal of danger, threat, md phd resume moscow, or motivational conflict, and to trigger appropriate adaptive responses, md phd resume moscow.
For some authors, fear and anxiety are undistinguishable, whereas others believe that they are distinct phenomena.
Ethologists define fear as a motivational state aroused by specific stimuli that give rise to defensive behavior or escape. Young animals may show an innate fear reaction to sudden noise or disturbances in the environment, but rapidly become habituated to them. When they are used to a familiar environment, then a fear of novelty may develop. Ethologists have also made the important observation that fear is often mixed up with other aspects of motivation, md phd resume moscow.
Thus, conflict between fear and approach behavior may results in displacement activities eg, self-grooming in rats. Such displacement activities may be the behavioral expression of an anxious state, but anxiety is a concept that is apparently not used by ethologists, perhaps because their definition of fear does in fact include all the more biological aspects of anxiety. Many authors, however, have argued that differences in their etiologies, response patterns, time courses, and intensities seem to justify a clear distinction between anxiety and fear.
Anxiety is a generalized response to an unknown threat or internal conflict, whereas fear is focused on known external danger. Also, it is reasonable to conclude that anxiety can be distinguished from fear in that the object of fear is 'real' or 'external' or 'known' or 'objective.
The uncertainty regarding these situations highlights a lack of control that contributes to feelings of anxiety and makes coping more difficult. At the heart of this structure is a sense of uncontrollability focused largely on possible future threats, danger, or other upcoming potentially negative events, md phd resume moscow, in contrast to fear, where the danger is present and imminent.
The fact that anxiety and fear are probably distinct emotional states docs not exclude some overlap in underlying brain and behavioral mechanisms. In fact, anxiety may just be a more elaborate form of fear, which provides the individual with an increased capacity to adapt and plan for the future. Fear or anxiety result in the expression of a range of adaptive or defensive behaviors, which are aimed at escaping from the source of danger or motivational conflict.
These behaviors depend on the context and the repertoire of the species. Active coping strategies are used when escape from threat is possible, and the autonomic changes associated md phd resume moscow these active strategies are mediated predominantly by sympathetic activation hypertension, tachycardia. This is the fight-or-flight response originally described by Cannon.
This type of passive response md phd resume moscow originally described by Engel and Schmale as a conservation-withdrawal strategy.
According to Panksepp, flight and other active coping behaviors are unconditional responses to proximate threat, whereas passive coping strategies, such as freezing, are conditioned responses to distal stimuli predictive of danger. These two strategies have distinct and successive roles, and are modulated by the cognitive apprehension of the environment and probability of success, md phd resume moscow, eg, whether or not there is a route of escape.
Md phd resume moscow, when an animal faces md phd resume moscow predator, freezing is preferentially activated when the source of known danger is still far away. Defensive behaviors have been studied in a large number of species, 23 and it has recently been shown that human defensive behaviors to threat scenarios arc not unlike those seen in nonhuman mammals.
It should be underlined, however, that the choice between an active or passive defense strategy does not entirely depend on contextual clues. Individual differences in coping styles do exist and may also influence this choice. These coping styles are characterized by consistent behavioral and neuroendocrine patterns, and may explain individual differences in vulnerability to stress-induced diseases. The capacity to cope successfully with life md phd resume moscow, whether innate or acquired, is probably a primary determinant of resistance to stress-induced md phd resume moscow. Although Pavlov's typology is outdated, it is now recognized that increased vulnerability to anxiety and its disorders is associated with particular traits or endophenotypes, ie, traits that may be intermediate in the chain of causality from genes to disease.
Barlow has defined three interacting sets of vulnerability factors for the development of human anxiety disorders in humans: i a generalized biological vulnerability, mainly of genetic origin; ii a generalized psychological vulnerability, md phd resume moscow, resulting in particular from early life experiences; and iii a specific psychological vulnerability, focused on particular events or circumstances.
Increased anxiety in animal models, as a trait, md phd resume moscow, can be attributed to at least two sets of factors: i a genetic predisposition, essentially linked to the expression of genes that are involved in the various neurochemical mechanisms underlying fear and anxiety; and ii the influence of environmental factors. These environmental factors can interact with the expression of the relevant genes during early development and determine the functional properties of the neural and biochemical systems involved in coping with stressful events.
They can also modulate the learning processes that occur at a later stage, when the individual is confronted with various life events, and determine the capacity to cope successfully with aversive or threatening situations in adulthood.
Some of the neurobiological mechanisms underlying anxiety may already be present in very simple organisms, such as the snail Aplysia, which can show forms of learning akin to anticipatory and chronic anxiety. In the first one, animals are confronted with situations that generate an anxious state state anxiety models.
This state of anxiety can be either conditioned eg, conditioned fear, avoidance, and punishment-induced conflict tests or unconditioned eg, aversive and ethological conflict tests. As already suspected by Letourneau and others, emotional.
experience and the associated behavioral responses are likely to activate specific circuits in the brain. The search for the neuroanatomical substrates of fear and anxiety has been a successful field of research over the last decades. The view that emotions and cognitions are separate functions md phd resume moscow the brain and must therefore have different underlying neuroanatomical substrates is probably responsible for this simplification.
And when a limbic area is activated in a cognitive task, it is often assumed that there must have been some emotional undertone to the task. Autonomic activation and increased arousal are among the earlier psychophysiological responses observed in a state of fear or anxiety. Since the immediate consequences of autonomic activation eg, tachycardia are perhaps the most readily perceived when experiencing a state of fear or anxiety, it has been proposed that the ascending noradrenergic system originating from the locus ceruleus LC is the core around which feelings of anxiety are organized.
The meaning, as well as the intensity of stimuli, seems to be an important factor in LC response. In cats, confrontation with a novel, but non-threatening stimulus, md phd resume moscow, such as a mouse, does not cause a specific increase in LC firing, whereas confrontation with a threatening stimulus eg, a dog causes a marked increase in LC firing. However, although 6-hydroxydopamine lesions of the LC in rats affect the HPA axis response to acute stress, they do not appear to substantially affect its response to chronic stress.
The LC is in turn innervated by areas such as the amygdala which processes fear-related stimuli and other areas receiving visceral stimuli relayed by the NTS. The LC is therefore in a key position to integrate both external sensory and internal md phd resume moscow stimuli and influence stress- and fear-related neuroanatomical structures, including cortical areas, md phd resume moscow. The inhibition of ongoing behaviors is the first behavioral manifestation of an anxious or fearful state.
In the s, Gray suggested that vulnerability to anxiety is associated with individual differences in the activity of a septohippocampal behavioral inhibition system BIS. Thus, according to Gray, anticipatory anxiety reflects a central state mediated by BIS activation, which is elicited by threats of punishment or failure, md phd resume moscow, md phd resume moscow by novelty or uncertainty.
The central role of behavioral inhibition in generating an anxious state has also been pointed out by Laborit, md phd resume moscow. Panksepp has argued that the activities of the ascending NA systems and the descending BIS are not causally related to the affective experience of fear and anxiety. These systems certainly participate in the genesis of fear and anxiety behaviors: the NA system is involved in the initial alarm reaction, whereas freezing promoted by septohippocampal inhibition may help regulate the intensity and duration of fear.
However, according to Panksepp, the amygdala-central gray axis plays an essential role in creating the emotional state associated with fear and anxiety.
In all mammalian species, there are three distinct sites in the brain where electrical stimulation will provoke a full fear response: the lateral and central zones of the amygdala, the anterior and medial hypothalamus, and specific areas of the PAG. A circuit coursing from the lateral and central nuclei of the amygdala, throughout the ventral-anterior and medial hypothalamic areas, down to the mesencephalic PAG, may constitute the executive system for fear, since freezing, as well as flight behavior and the autonomic indices of fear eg, increased heart rate and eliminative behavior can be evoked along the whole trajectory of this system.
In rats, stepwise increases in the electrical stimulation of the dorsolateral periaqueductal gray d1PAG produce alertness, then freezing and finally escape, replicating the sequence of natural defensive reactions when exposed to threat.
Recent data suggest that d1PAG stimulation produces freezing independently of any contextual fear conditioning, whereas stimulation of the ventral periaqueductal gray vPAG appears to be critical to the expression of conditioned fear. The elegant studies carried out by LeDoux, based on a simple fear conditioning paradigm in rats, have emphasized the primary role of the amygdala in controlling emotional behaviors.
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