Previously, or even today, brain imaging for psychiatric disorders in the clinical arena has been used to eliminate organic brain lesions such brain tumor, stroke, or congenital anomaly. The changes in the central nervous system (CNS) of psychiatric patients are too subtle to discern by our visual inspection at a single subject level. However, with the advancement not only in magnetic resonance imaging (MRI) technologies but also sophisticated post-processing techniques and powerful analytical tools, we can find there should be certain CNS differences between psychiatric patients and matched control. Posttraumatic stress disorder (PTSD) is characterized by debilitating conditions such as recurrent trauma-related memories, increased fear response, physiological reactivity to reminders of the trauma coupled with sleep disturbances, nightmares, avoidance, increased startle, and other symptoms that can persist for many years after the original traumatic event (1). PTSD may develop following exposure to severe trauma (e.g., abuse during childhood) and/or threat to life. Although considering its prevalence and the wide-ranging negative effects on behavior, mood, and, cognition, PTSD represents a significant public health concern for the wider population, as well as highly susceptible groups such as terrorism victims and combat veterans (2-4), we have never had any objective diagnostic tool so far. In this context, brain MRI may be able to play a pivotal role in the diagnosis and therapeutic effect of PTSD. Recent neuroimaging has provided important insights into the neurobiological basis for normal development, aging, and various disease processes including psychiatric disorders in the CNS. A number of unbiased techniques to analyze the entire brain are now emerging due to the improved spatial and temporal resolutions of structural and functional MRI scans as well as the development of sophisticated image-processing tools. For example, the voxel-based approach has advantages over manual region-of-interest (ROI) analysis when searching for abnormalities throughout the brain. Statistical parametric mapping (SPM, http://www.fil.ion.ucl.ac.uk/spm/) and FMRIB Software Library (FSL, https://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FSL) are most popular tools for voxel-based morphometry (5), diffusion (6), and functional MRI (7) analysis. Neuroimaging analyses in a voxel-wise manner have provided objective and reliable results in several studies, eliminating the effects of operator bias whilst it could also give some controversy as to registration or spatial normalization accuracy. More recently, MRI can provide us the network information between brain regions. In the graph theoretical analysis, the predefine areas in the cortex or subcortical gray matter represent nodes. All pairs of connectivity between two different nodes can be quantified and a comprehensive map of different neural connections of nodes in the brain is created and referred to as connectivity matrix. A connectivity between a pair of two nodes is called an edge. When this matrix is estimated from diffusion and functional MRI data, it is called structural and functional connectivity, respectively. Once connectivity matrix is obtained, graph theoretical analysis can provide measures of graph (i.e., clustering coefficient, characteristic path length, degree, betweenness centrality, etc) (8). Hippocampus, amygdala and prefrontal cortex including anterior cingulate cortex (ACC) are three key brain regions, confirmed by structural, diffusional, and functional MRI. These structures are related to the impairment both in salience network (SN) and default mode network (DMN) in patients with PTSD. In this talk, we will show the audience recent results for voxel-based analyses and brain connectivity measured by diffusion and functional MRI in the above mentioned areas in PTSD sufferers.

Acknowledgements

The author has no conflict of interest to disclose with respect to this presentation.