Exploring the Neurocircuitry Underpinning Predictability of Threat in Soldiers with PTSD Compared to Deployment Exposed Controls

Abstract

Background:Prior work examining emotional dysregulation observed in posttraumatic stress disorder (PTSD) has primarily been limited to fear-learning processes specific to anticipation, habituation, and extinction of threat. In contrast, the response to threat itself has not been systematically evaluated.Objective:To explore potential disruption in fear conditioning neurocircuitry in service members with PTSD, specifically in response to predictable versus unpredictable threats.Method:In the current study, active-duty U.S. Army soldiers with (PTSD group; n = 38) and without PTSD (deployment-exposed controls; DEC; n = 40), participated in a fear-conditioning study in which threat predictability was manipulated by presenting an aversive unconditioned stimulus (UCS) that was either preceded by a conditioned stimulus (i.e., predictable) or UCS alone (i.e., unpredictable). Threat expectation, skin conductance response (SCR), and functional magnetic resonance imaging (fMRI) signal to predictable and unpredictable threats (i.e., UCS) were assessed.Results:Both groups showed greater threat expectancy and diminished threat-elicited SCRs to predictable compared to unpredictable threat. Significant group differences were observed within the amygdala, hippocampus, insula, and superior and middle temporal gyri. Contrary to our predictions, the PTSD group showed a diminished threat-related response within each of these brain regions during predictable compared to unpredictable threat, whereas the DEC group showed increased activation.Conclusion:Although, the PTSD group showed greater threat-related diminution, hypersensitivity to unpredictable threat cannot be ruled out. Furthermore, pre-trauma, trait-like factors may have contributed to group differences in activation of the neurocircuitry underpinning fear conditioning.

The impact of pre-existing anxiety on affective and cognitive processing of a Virtual Reality analogue trauma

“…This is in line with previous studies showing increased difficulties returning to initial emotional states after negative emotions in participants with anxiety symptoms [ 18 ] and the result of higher anxiety symptoms in patients with PTSD [ 64 , 65 ]. Physiological stress responses did not differ between the groups, which is in contrast to our expectation and a previous fMRI study showing increased skin conductance responses to unpredictable threat in individuals who were exposed to stressful events and in patients with PTSD [ 66 ]. Our finding that there is no difference in physiological stress responses between HA and LA may be related to (i) a blunted hormonal and skin conductance response to acute stress found to be specific for HA individuals [ 67 , 68 ], (ii) efficient coping behaviour [ 69 ] or (iii) the fact that analogue traumatic situations are less intense than real traumatic situations [ 45 ].…”

Identifying disease foci from static and dynamic effective connectivity networks: Illustration in soldiers with trauma

“…Items are rated using a 5‐point Likert scale; 1 = “Not at all” through 5 = “Extremely.” A total symptom severity score (range: 20–100) is obtained by summing the scores for each of the 20 items, with a cut score of 38 for a precursory diagnosis of PTSD [Weathers et al, ]. PCL5 has been shown to be able to differentiate between soldiers with PTSD and healthy controls [Dretsch et al, ].…”

Psychophysiological approaches to understanding the impact of trauma exposure

“…Whereas Lis et al (2019) concluded a crucial role for compromised expectation with subsequent overgeneralization of threat and undergeneralization of safety signals from fear-potentiated startle and subjective measures, other articles used structural and functional brain imaging to identify predictors of PTSD susceptibility. Resting-state network connectivity and activity in response to fear or trauma-related stimuli in the hippocampus, amygdala, insula, and prefrontal cortex have been found to predict PTSD in trauma-exposed individuals (e.g., see overviews by Suarez-Jimenez et al, 2019;Dretsch et al, 2016). In the present volume, Sambuco et al (2019) suggest that post-traumatic stress, related affective psychopathology, and trauma exposure, when considered transdiagnostically, may confer a risk for emotional hyporeactivity: fMRI was monitored while patients with different anxiety and mood disorders viewed emotional and neutral scenes.…”