Songji Zhao, C. Fatema, Jingmin Zhao
May 19, 2016
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Journal
The Journal of Nuclear Medicine
Abstract
Nearly 100 y ago, Ivan Pavlov presented the most famous example of classic conditioning, which occurs when a conditioned stimulus is paired with an unconditioned stimulus. Usually, the conditioned stimulus is a neutral (e.g., the sound of a tuning fork) and the unconditioned stimulus is biologically potent (e.g., food) and produces an unconditioned response (e.g., salivation). In anxiety disorders, such as posttraumatic stress disorder (PTSD), a trauma can be considered an unconditioned stimulus; this type of conditioned fear fails to extinguish, and reminders of traumatic events can cause pathologic conditioned fear responses for decades after danger has passed (1). PTSD affects up to 40% of individuals with over-lifetime exposure to traumatic events (2,3). Over the past decade, there has been a surge of interest in the experimental extinction of fear for its own sake. Beyond the interest in the basic mechanisms of learning and memory, this renewed interest in fear extinction is due in large part to the clinical significance of this extinction for the treatment of a variety of psychiatric