Fear conditioning
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Fear conditioning is the method by which organisms learn to fear new stimuli. It is a form of learning in which fear is associated with a particular neutral context (e.g., a room) or neutral stimulus (e.g., a tone). This can be done by pairing the neutral stimulus with an aversive stimulus (e.g., a shock, loud noise, or unpleasant odor). Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning, the neutral stimulus or context is the "conditioned stimulus" (CS), the aversive stimulus is the "unconditioned stimulus" (UCS), and the fear is the "conditioned response" (CR).
In humans, conditioned fear is often measured with verbal report and galvanic skin response. In other animals, conditioned fear is often measured with freezing (a period of watchful immobility) or fear potentiated startle (the augmetation of the startle reflex by a fearful stimulus). Changes in heart rate, breathing, and muscle responses via electromyography can also be used to measure conditioned fear.
Fear conditioning is thought to depend upon an area of the brain called the amygdala. Ablation or deactivating of the amygdala can prevent both the learning and expression of fear. Some types of fear conditioning (e.g. contextual and trace) also involve the hippocampus. Fear conditioning is used to study the formation of fear memory and to investigate the processes that may lead to pathological conditions such as phobias and post-traumatic stress disorder.
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