<qa>  What is the potential to advance the development of effective treatments for these patients?Fear potentiation of the acoustic startle response ASR can be demonstrated in both animals and humans Davis et al., 1993; Grillon et al., 1991. The neural correlates of fear potentiated startle are well studied Davis et al., 1993 and this paradigm has face validity with cardinal symptoms of posttraumatic stress disorder PTSD. Central to the clinical problem of PTSD is the inability of these patients to inhibit their fear to stimuli reminiscent of their traumatic experience, even during safe conditions. The elucidation of mechanisms of fear inhibition that may be abnormal in these patients has the potential to advance the development of effective treatments for these patients. 