Kunimatsu A, et al. - Experts intended to increase the educational value by discussing the epidemiology and pathophysiology of posttraumatic stress disorder (PTSD, a psychiatric condition that develops after a person experiences one or more traumatic events, characterized by intrusive recollection, avoidance of trauma-related events, hyperarousal, and negative cognitions and mood), followed by discussion on MRI findings that describe the structural and functional abnormalities correlated with PTSD. MRI findings suggested that brain regions related to PTSD pathophysiology include the medial and dorsolateral prefrontal cortex, orbitofrontal cortex, insula, lentiform nucleus, amygdala, hippocampus and parahippocampus, anterior and posterior cingulate cortex, precuneus, cuneus, fusiform and lingual gyri, and the white matter tracts connecting these brain regions. Of these, across structural and functional MRI, alterations in the anterior cingulate, amygdala, hippocampus, and insula are highly reproducible, supporting the hypothesis that abnormalities in fear learning and reactions to threat play a significant part in the development of PTSD. Moreover, most of these structures have been known to belong to one or more intrinsic brain networks regulating autobiographical memory retrieval and self-thought, salience detection and autonomic responses, or attention and emotional control. Modified functional brain networks have been exhibited in PTSD. Hence, in PTSD, MRI is expected to highlight disequilibrium among functional brain networks, malfunction within an individual network, and impaired brain structures intimately interacting with the networks.