Quotes About Defense responses

In order for extinction to reduce the ability of a Pavlovian CS to elicit defense responses, the amygdala's control over these responses has to be changed. Key to this process is the ventromedial prefrontal cortex (PFCVM) and its ability to regulate the amygdala-housed circuits that store the CS-US memory, which when activated results in the expression of defense responses. The

So how does the new learning that occurs in extinction (learning of the CS–no US association) prevent the expression of the original memory (CS-US association) and the defense responses it controls? To