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Background: The present study aimed to apply multivariate pattern recognition methods to predict posttraumatic stress symptoms from whole-brain activation patterns during two contexts where the aversiveness of unpleasant pictures was manipulated by the presence or absence of safety cues., Methods: Trauma-exposed participants were presented with neutral and mutilation pictures during functional magnetic resonance imaging (fMRI) collection. Before the presentation of pictures, a text informed the subjects that the pictures were fictitious ("safe context") or real-life scenes ("real context"). We trained machine learning regression models (Gaussian process regression (GPR)) to predict PTSD symptoms in real and safe contexts., Results: The GPR model could predict PTSD symptoms from brain responses to mutilation pictures in the real context but not in the safe context. The brain regions with the highest contribution to the model were the occipito-parietal regions, including the superior parietal gyrus, inferior parietal gyrus, and supramarginal gyrus. Additional analysis showed that GPR regression models accurately predicted clusters of PTSD symptoms, nominal intrusion, avoidance, and alterations in cognition. As expected, we obtained very similar results as those obtained in a model predicting PTSD total symptoms., Conclusion: This study is the first to show that machine learning applied to fMRI data collected in an aversive context can predict not only PTSD total symptoms but also clusters of PTSD symptoms in a more aversive context. Furthermore, this approach was able to identify potential biomarkers for PTSD, especially in occipitoparietal regions., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Violence exacts a burden on public health. Gun violence is a major trigger for motor defensive reactions in humans and post-traumatic stress disorder (PTSD) is its main psychiatric sequela. However, studies of the human defensive cascade, especially the motor reactions, are at an early stage. This review focuses on studies that employ stabilometry, a methodology that assesses whole body motor reactions, to address defensive behaviors to violence-related threats. Special attention is given to three reactions: "attentive immobility", "immobility under attack" and "tonic immobility", with emphasis on the latter - a peritraumatic reaction which has been strongly associated with the severity of PTSD. These reactions are characterized by reduced body sway and bradycardia, except tonic immobility that presents robust tachycardia. The advances made by investigations into the immobility reactions of the human defensive cascade contribute to helping to bridge the gap between human and non-human species. Furthermore, progresses in basic research to objectively monitor motor defensive reactions under threat can help to develop a dimensional, trans-diagnostic approach to PTSD., (Copyright © 2017 Elsevier Ltd. All rights reserved.)