Is extinction of fear erasure or inhibition? Why both, of course

摘要

For many decades, classically conditioned fear has provided fertile ground for neuroscientists interested in learning and memory. The paradigms are conceptually straightforward, the protocols robust, and the relevance to the human (and animal) condition unquestionable. Fear, or something very like it, is probably as old as the animal kingdom. One of the great advantages of being an animal, and thus being able to move, is the privilege of avoiding unpleasant experiences. Aversive learning is therefore ancient, and well conserved. The study of conditioned fear in mammals has benefited from this long history, since a large part of the circuitry of fear is old and relatively uncomplicated. The short circuits from senses to amygdala and back out to behavior have allowed neuroscientists to define the anatomy of fear in great detail and to provide a wealth of data that fear conditioning in mammals involves the same strengthening of synapses, and uses many of the same molecular switches to do so, as does the facilitation of the gill withdrawal reflex in Aplysia.