The Influence of Combat Experience on Psychologically Healthy Soldiers' Attentiveness to Environmental Threats.

INTRODUCTION: In contrast to previous research that has primarily examined how psychological disorders (e.g., post-traumatic stress disorder [PTSD], anxiety) are affected by and affect individuals' threat perceptions, this study examines the relationship between combat experience and threat-monitoring in psychologically healthy Soldiers. Existing research has established how prolonged or intense experiences with war-related stressors can lead individuals to undergo an unconscious fear-conditioning process that affects the circuitry of the prefrontal cortex, hippocampus, amygdala, and anterior cingulate cortex regions of the brain. We predict that the intensity of one's combat experience positively influences Soldiers' attention to environmental threats. MATERIALS AND METHODS: Participants included U. S. Army Soldiers with a score of 50 or below on the PTSD Checklist-Military Version. Participants completed the Combat Exposure Scale and the State-Trait Anxiety Inventory. The experimental prediction task we employed assesses the expectation of an intrusively loud white noise sound that occurred on three variable patterns in a pseudorandomized order. Each tone pattern was used 20 times over a total of 60 trials. The experimental prediction task included two neutral tones (700 and 1,300 Hz) that were presented in a repeated pattern along with a 100-dB burst of white noise (0.5-second duration). In each trial, one of three possible tone combinations was presented. To assess their attentiveness to threats, participants were asked to continuously rate their expectancy of the burst of white noise using a visual analogue scale (VAS) ranging from 0 to 100. VAS ratings were collected at controlled points throughout the task. RESULTS: None of the participants reported scores on any of the diagnostic surveys that met standards for clinical significance. A repeated-measures analysis of variance was conducted to assess the overall effect of the three prediction conditions on participants' VAS ratings. There was a significant main effect for Combat Exposure Scale scores on VAS ratings [F(1, 27) = 5.19, p = 0.031], with high scorers demonstrating a generally higher expectancy of the white noise burst throughout the entire experimental sequence. Results suggest that within subclinical populations of Soldiers, the intensity of one's combat experience is positively associated with their attention to threats. CONCLUSION: These findings suggest that Soldiers who experience combat should be observed for signs of increased threat-attention bias, as this may indicate that their capacities for information processing, decision-making, and emotion regulation could be compromised. The positive relationship we observe between a level of combat experience and attentional biases toward threatening stimuli may also help to explain why these veterans engage in "externalizing" behaviors that are risky, aggressive, or violent as well as relational problems and antisocial behaviors that are reported in higher-than-average rates among these populations of Soldiers. Acknowledging that increased threat attention may be a preclinical indication of developing PTSD or other related psychological conditions (e.g., depression, anxiety) should motivate clinicians to more actively diagnose and treat this condition.

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

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.