Interesting, but PTSD does not always come from fear based conditioning. Often it arises from a one off traumatic event: being shot at, raped, assaulted, etc. Therefore, the preconditions for PTSD must already exist before the triggering event. So you cannot "unlearn" a fear based response that was never learned in the first place. You can only disconnect from it, split yourself off from what lies underneath it. What you are learning in exposure therapy is no different to mindfulness, the ability to distract yourself. And it is a never ending task, not a cure. But with this study the main concern was to find a chemical intervention. That should ring warning bells. We need to understand the psychology or we will never understand the role of the underlying mechanisms.