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Impacts of Posttraumatic Stress Disorder on Eye-Movement during Visual Search in an Open Virtual Environment under High and Low Stress Conditions
Abstract
Exposure to stress and trauma is associated with military deployments, leading to a high prevalence of Posttraumatic Stress Disorder (PTSD). PTSD is associated with an attentional bias toward threatening stimuli and scanning behavior which is indicative of hypervigilance in the context of static scenes. Work exploring the impact of PTSD on visual attention during natural viewing of a threatening environment, is limited. Our recent work revealed that PTSD impacted eye-movement during a low-threat visual search task in an open virtual environment (VE) where cognitive load was increased, suggesting PTSD impacts visual attention. Here, we extended this work by developing stress-inducing VEs, where eye-movement was recorded from military personnel (active duty/veteran) with and without PTSD during a self-paced search task in four different open-world desktop VEs, that varied by stress (high/low) and theme (neutral/military). High-stress conditions included flashbangs and context-consistent sounds (e.g., loud gunfire or heavy construction). Low-stress conditions had no flashbangs and scenic sounds (e.g., birds). Preliminary results (N = 6 per group) found that the PTSD group had significantly increased individual fixation and blink durations, decreased fixation and saccade rates, and more horizontal saccades. Additionally, we observed an interaction where the Non-PTSD group showed larger differences in eye-movement behavior between the high and low-stress conditions, compared to the PTSD group. Thus far, our stress-inducing VEs appear to elicit noticeable differences in eye-movement between PTSD and Non-PTSD individuals. Preliminary findings suggest those with PTSD may be hypervigilant towards threatening objects regardless of the stress condition, supporting the theory of an attentional bias towards threats. This work will allow us to evaluate how stress impacts deployment of overt attention, which is critical for understanding how military personnel may function when completing duty relevant tasks.
... increasing cognitive load) and challenging SA via the environment itself could more accurately capture how military training impacts attentional resources. Such an environment could include threatening and nonthreatening neutral and military environments [82] and be more applicable to the type of multitasking and environment that military training is targeted toward. Regardless, even with the neutral nature of the current study stimuli and design, our findings suggest that the Active Duty group is a unique population and behaves differently than the Civilian group when searching for targets. ...
U.S. service members maintain constant situational awareness (SA) due to training and experience operating in dynamic and complex environments. Work examining how military experience impacts SA during visual search of a complex naturalistic environment, is limited. Here, we compare Active Duty service members and Civilians’ physiological behavior during a navigational visual search task in an open-world virtual environment (VE) while cognitive load was manipulated. We measured eye-tracking and electroencephalogram (EEG) outcomes from Active Duty (N = 21) and Civilians (N = 15) while they navigated a desktop VE at a self-regulated pace. Participants searched and counted targets (N = 15) presented among distractors, while cognitive load was manipulated with an auditory Math Task. Results showed Active Duty participants reported significantly greater/closer to the correct number of targets compared to Civilians. Overall, Active Duty participants scanned the VE with faster peak saccade velocities and greater average saccade magnitudes compared to Civilians. Convolutional Neural Network (CNN) response (EEG P-300) was significantly weighted more to initial fixations for the Active Duty group, showing reduced attentional resources on object refixations compared to Civilians. There were no group differences in fixation outcomes or overall CNN response when comparing targets versus distractor objects. When cognitive load was manipulated, only Civilians significantly decreased their average dwell time on each object and the Active Duty group had significantly fewer numbers of correct answers on the Math Task. Overall, the Active Duty group explored the VE with increased scanning speed and distance and reduced cognitive re-processing on objects, employing a different, perhaps expert, visual search strategy indicative of increased SA. The Active Duty group maintained SA in the main visual search task and did not appear to shift focus to the secondary Math Task. Future work could compare how a stress inducing environment impacts these groups’ physiological or cognitive markers and performance for these groups.
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