What is it about?
Posttraumatic stress disorder (PTSD) is common and debilitating. Despite extensive efforts to develop and test new treatments for PTSD, available treatments have shown only limited efficacy. The cause of limited treatment efficacy may lie not only in the treatments themselves but also in the heterogeneity within the diagnosis of PTSD. PTSD is frequently comorbid with other disorders; it lacks clear biological margins as it shares its biological underpinnings with other disorders. To address these problems, a wealth of functional neuroimaging studies, informed by extensive cross-species research of fear processes, has attempted to characterize aberrant circuitries in PTSD with a two-fold goal: first, to expand knowledge about the pathophysiology of PTSD; and second, to identify treatment targets that would potentially drive the development of novel PTSD treatments, for which measurable, replicable targets hardly exist. Here, focusing on task-based functional magnetic resonance imaging (fMRI) and resting-state functional connectivity (rs-FC), I review the attempts to successfully translate knowledge about fear processing mechanisms from research in healthy humans to patients with PTSD. Having discussed emergent findings in fMRI and rs-FC, together with key challenges and inherent limitations, I elaborate on the heterogeneity of PTSD and the difficulties this poses for such research. The overview concludes with a description of the promising inroads that big data alliances may enable current and future research in the field.