Individuals with PTSD can experience both an under-modulatory state (i.e. attentional bias toward threat and re-experiencing symptoms) as well as an over-modulatory state (i.e. attentional bias away from threat and avoidance symptoms). This recent study published in Molecular Psychiatry tested and found evidence for reciprocal inhibition between the amygdala and ventromedial prefrontal cortex underpinning alternations between the under- and over-modulatory states.
More information available here