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Posttraumatic stress disorder and differences in eye gaze during a visual search task with cognitive load
Abstract
Military deployments often expose personnel to highly threatening and stressful circumstances that put them at greater risk for developing Posttraumatic Stress Disorder (PTSD). PTSD may alter internal processes that affect one’s ability to maintain situational awareness (SA). Military personnel conducting patrols must maintain SA to search for threats, with potentially life-threatening consequences if SA drops. Here an exploratory analyses was conducted to determine whether there were differences in performance and eye gaze behavior between those with and without PTSD during a free-viewing visual search task conducted in a virtual desktop environment. Cognitive workload was increased through an additional auditory Math Task. While performance did not differ significantly between the two Groups, key differences in gaze behavior were found. Results showed that those with PTSD viewed significantly more trail markers, had increased duration of individual fixations overall, and decreased fixation and saccade rates during the Math Task. These results appear consistent with previous findings suggesting those with PTSD may have difficulty disengaging from stimuli.
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Eye tracking has been an essential tool within the vision science community for many years. However, the majority of studies involving eye-tracking technology employ a relatively passive approach through the use of static imagery, prescribed motion, or video stimuli. This is in contrast to our everyday interaction with the natural world where we navigate our environment while actively seeking and using task-relevant visual information. For this reason, an increasing number of vision researchers are employing virtual environment platforms, which offer interactive, realistic visual environments while maintaining a substantial level of experimental control. Here, we recorded eye movement behavior while subjects freely navigated through a rich, open-world virtual environment. Within this environment, subjects completed a visual search task where they were asked to find and count occurrence of specific targets among numerous distractor items. We assigned each participant into one of four target conditions: Humvees, motorcycles, aircraft, or furniture. Our results show a statistically significant relationship between gaze behavior and target objects across Target Conditions with increased visual attention toward assigned targets. Specifically, we see an increase in the number of fixations and an increase in dwell time on target relative to distractor objects. In addition, we included a divided attention task to investigate how search changed with the addition of a secondary task. With increased cognitive load, subjects slowed their speed, decreased gaze on objects, and increased the number of objects scanned in the environment. Overall, our results confirm previous findings and support that complex virtual environments can be used for active visual search experimentation, maintaining a high level of precision in the quantification of gaze information and visual attention. This study contributes to our understanding of how individuals search for information in a naturalistic (open-world) virtual environment. Likewise, our paradigm provides an intriguing look into the heterogeneity of individual behaviors when completing an un-timed visual search task while actively navigating.
Post‐traumatic stress disorder (PTSD) is a debilitating condition that may develop after experiencing a traumatic event. Combat exposure increases an individual's chance of developing PTSD, making veterans especially susceptible to the disorder. PTSD is characterized by dysregulated emotional networks, memory deficits, and a hyperattentive response to perceived threatening stimuli. Recently, there have been a number of imaging studies that show structural and functional abnormalities associated with PTSD; however, there have been few studies utilizing electroencephalography (EEG). The goal of this study was to characterize **EEG brain dynamics in individuals with PTSD, in order to better understand the neurophysiological underpinnings of some of the salient features of PTSD, such as threat‐processing bias. Veterans of Operation Enduring Freedom/Iraqi Freedom completed an implicit visual threat semantic memory recognition task with stimuli that varied on both category (animals, items, nature, and people) and feature (threatening and nonthreatening) membership, including trauma‐related stimuli. Combat veterans with PTSD had slower reaction times for the threatening stimuli relative to the combat veterans without PTSD (VETC). There were trauma‐specific effects in frontal regions, with theta band EEG power reductions for the threatening combat scenes in the PTSD patients compared to the VETC group. Additionally, a moderate negative correlation was observed between trauma‐specific frontal theta power and hyperarousal symptoms as measured by clinically administered PTSD scale. These findings complement and extend current models of cortico‐limbic dysfunction in PTSD. The moderate negative correlation between frontal theta power and hyperarousal endorsements suggests the utility of these measures as therapeutic markers of symptomatology in PTSD patients.
The use of eye movements to explore scene processing has exploded over the last decade. Eye movements provide distinct advantages when examining scene processing because they are both fast and spatially measurable. By using eye movements, researchers have investigated many questions about scene processing. Our review will focus on research performed in the last decade examining: (1) attention and eye movements; (2) where you look; (3) influence of task; (4) memory and scene representations; and (5) dynamic scenes and eye movements. Although typically addressed as separate issues, we argue that these distinctions are now holding back research progress. Instead, it is time to examine the intersections of these seemingly separate influences and examine the intersectionality of how these influences interact to more completely understand what eye movements can tell us about scene processing.
Simultaneously presenting auditory and visual stimuli can hinder performance for one modality
while the other dominates. For approximately 40 years, research with adults has primarily
indicated visual dominance, while recent research with infants and young children has revealed
auditory dominance. The current study further investigates modality dominance with adults,
finding evidence for both auditory and visual dominance across three experiments. Using a
simple discrimination task, Experiment 1 revealed that cross-modal presentation attenuated
discrimination of auditory input, while at the same time, also slowed down visual processing.
Even when participants were instructed to only pay attention to the visual stimuli, both spoken
nonsense words and nonlinguistic sounds slowed down visual processing (Experiment 2).
Experiment 3 used a similar discrimination task while utilizing an eye tracker to examine how
auditory input affects visual fixations. Cross-modal presentation attenuated auditory
discrimination; however, it also slowed down visual response times. In addition, adults also
made longer fixations and were slower to make their first fixation when images were paired with
sounds. The latter finding is novel and consistent with a proposed mechanism of auditory
dominance: auditory stimuli automatically engage attention and attenuate or delay visual
processing.
Hypervigilance to threat is a core symptom of posttraumatic stress disorder (PTSD). The present study reports a relationship between reported hypervigilance and eye-tracking patterns in two novel tasks with non-threatening stimuli. Trauma-exposed British ex-servicemen with (N=12) and without (N=16) a diagnosis of PTSD freely viewed static photographs of street scenes whilst eye-movements were tracked. Despite rating scenes as more threatening, the PTSD group did not show hyperscanning behaviours compared to the non-PTSD group. However, participants reporting more severe hypervigilance made more saccades and fixations of shorter duration. In a second experiment participants wore a portable eye-tracking device whilst walking along unfamiliar London streets. In this task, hypervigilance severity was not related to either saccade frequency or duration. However, PTSD participants made less frequent saccades than non-PTSD participants. PTSD symptomatology also correlated negatively with saccade duration. The results from the present study suggest that reported hypervigilance has measurable eye movement correlates in the absence of actual threat. The observed discrepancy in findings between the two paradigms highlights the difficulty of generalising from laboratory to real-world.
Attentional biases to trauma-related stimuli have been widely demonstrated in individuals with posttraumatic stress disorder (PTSD). However, the majority of these studies used methods not suited to differentiating difficulty disengaging attention from threatening stimuli (interference) from facilitated detection of threat. In the current study, a visual search task (VST) with a lexical decision component was used to differentiate between attentional interference and facilitation. Forty-six sexual assault survivors with High PTSD or Low PTSD symptoms completed the VST with three types of stimuli (trauma-related, general threat-related, and semantically-related neutral words), to examine the specificity of attentional biases associated with PTSD symptoms. High PTSD participants showed increased interference to trauma-related words relative to Low PTSD participants. Furthermore, the increased attentional interference in High PTSD participants was specific to trauma-related stimuli. No evidence was found for facilitated detection of threatening stimuli in PTSD. These results provide additional support for attentional biases in PTSD relating to attentional interference with trauma-related cues rather than facilitated detection of threat. The implications for this pattern of results are discussed in relation to anxiety disorders that are characterized by rumination and/or intrusions (e.g., PTSD, GAD) rather than those more circumscribed to fight or flight response (e.g., phobias).
Although attentional biases have been demonstrated in individuals with posttraumatic stress disorder (PTSD), the cognitive methodologies used have not allowed for disambiguation of two types of attentional biases. It remains unclear if PTSD involves difficulty disengaging attention from threatening stimuli (interference) or facilitated detection. To differentiate between attentional interference and facilitation, 57 male Vietnam-era veterans (30 High PTSD and 27 Low PTSD) completed a visual search task with a lexical decision component. High PTSD veterans who engaged in the interference task first showed increased interference to threat-relevant words relative to Low PTSD veterans. However, no evidence was found for facilitated detection of threatening stimuli in PTSD.
Due to the limited capacity of working memory (WM), efficient suppression of no longer relevant memory contents (inhibition) and revising the current contents of the memory (updating) are crucial factors in memorizing. However, not every individual is able to do so; among them are post-traumatic stress disorder (PTSD) patients who seem to have trouble forgetting trauma-related materials, making their memory overloaded with irrelevant information. The present study assumes that the inability to forget in PTSD patients is due to the impaired updating function of WM and, therefore, suggests that these individuals have inferior WM function for both emotional and unemotional materials. A sample of 30 male veterans with PTSD and 30 healthy individuals (mean age = 46.62, SD = 5.23) participated in the study completing PTSD Checklist, Digit Span Task, and a computerized n-back task. Results revealed that although PTSD subjects showed a generally inferior WM compared with normal individuals; however, their WM performance for emotional and non-emotional stimuli was not significantly different. Supporting the main hypothesis of the study, the findings suggest that a dysfunctional updating function of WM underlies both forgetting and memorizing which affects memory for both emotional and non-emotional material similarly.
This comprehensive review surveys current literature on information processing biases in posttraumatic stress disorder (PTSD). The review is organized by information processing systems including attention, judgment and interpretation, and memory. Studies outlined suggest that information processing biases may be key factors involved in the development and maintenance of PTSD. However, inconsistencies exist in the literature within each domain, often depending on assessment paradigm employed or other methodological features. Studies on attention bias demonstrate both facilitated engagement toward and difficulty disengaging from threatening stimuli. Literature on judgment and interpretation biases indicates that those with PTSD are more likely to interpret ambiguous situations as threatening, in addition to over-estimating subjective risk. Memory studies reveal mixed findings; a number of studies found that those with PTSD exhibit a bias toward remembering trauma-relevant or negative stimuli compared to those without PTSD, while others do not replicate this effect. Existing evidence for information processing biases in each of these domains are integrated and future directions for empirical study outlined.
A number of prominent theories suggest that hypervigilance and attentional bias play a central role in anxiety disorders and PTSD. It is argued that hypervigilance may focus attention on potential threats and precipitate or maintain a forward feedback loop in which anxiety is increased. While there is considerable data to suggest that attentional bias exists, there is little evidence to suggest that it plays this proposed but critical role. This study investigated how manipulating hypervigilance would impact the forward feedback loop via self-reported anxiety, visual scanning, and pupil size. Seventy-one participants were assigned to either a hypervigilant, pleasant, or control condition while looking at a series of neutral pictures. Those in the hypervigilant condition had significantly more fixations than those in the other two groups. These fixations were more spread out and covered a greater percentage of the ambiguous scene. Pupil size was also significantly larger in the hypervigilant condition relative to the control condition. Thus the study provided support for the role of hypervigilance in increasing visual scanning and arousal even to neutral stimuli and even when there is no change in self-reported anxiety. Implications for the role this may play in perpetuating a forward feedback loop is discussed.
Holmqvist, K., Nyström, N., Andersson, R., Dewhurst, R., Jarodzka, H., & Van de Weijer, J. (Eds.) (2011). Eye tracking: a comprehensive guide to methods and measures, Oxford, UK: Oxford University Press.
Although several studies have documented an attentional bias toward threat in posttraumatic stress disorder (PTSD), the nature of this bias has not been clearly delineated. The present study utilized eye tracking technology to delineate the time course and components of attentional bias for threat cues in combat-related PTSD.
Veterans with PTSD (n = 21), combat-exposed veterans without PTSD (n = 16), and nonveteran controls (n = 21) viewed emotional expressions (fearful, disgusted, happy) paired with neutral expressions for 3 s presentations.
Veterans with PTSD maintained attention longer on the fearful and disgusted expressions relative to the happy expression. This negativity bias was sustained over the course of the 3 s trials, and robustly distinguished veterans with PTSD from both veterans without PTSD and nonveteran controls.
Dwelling on potential threat cues may reflect current PTSD symptoms, or it could reflect a cognitive vulnerability factor for PTSD.
The ability to process and integrate cross-modal input is important for many everyday tasks. The current paper reviews theoretical and empirical work examining cross-modal processing with a focus on recent findings examining infants' and children's processing of arbitrary auditory-visual pairings. The current paper puts forward a potential mechanism that may account for modality dominance effects found in a variety of cognitive tasks. The mechanism assumes that although early processing of auditory and visual input is parallel, attention is allocated in a serial manner with the modality that is faster to engage attention dominating later processing. Details of the mechanism, factors influencing processing of arbitrary auditory-visual pairings, and implications for higher-order tasks are discussed. Copyright © 2009 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website.
Copyright © 2009 John Wiley & Sons, Inc.
Reports of sex differences in wayfinding have typically used paradigms sensitive to the female advantage (navigation by landmarks) or sensitive to the male advantage (navigation by cardinal directions, Euclidian coordinates, environmental geometry, and absolute distances). The current virtual navigation paradigm allowed both men and women an equal advantage. We studied sex differences by systematically varying the number of landmarks. Eye tracking was used to quantify sex differences in landmark utilisation as participants solved an eight-arm radial maze task within different virtual environments. To solve the task, participants were required to remember the locations of target objects within environments containing 0, 2, 4, 6, or 8 landmarks. We found that, as the number of landmarks available in the environment increases, the proportion of time men and women spend looking at landmarks and the number of landmarks they use to find their way increases. Eye tracking confirmed that women rely more on landmarks to navigate, although landmark fixations were also associated with an increase in task completion time. Sex differences in navigational behaviour occurred only in environments devoid of landmarks and disappeared in environments containing multiple landmarks. Moreover, women showed sustained landmark-oriented gaze, while men's decreased over time. Finally, we found that men and women use spatial and response strategies to the same extent. Together, these results shed new light on the discrepancy in landmark utilisation between men and women and help explain the differences in navigational behaviour previously reported.
Fixational eye movements are subdivided into tremor, drift, and microsaccades. All three types of miniature eye movements generate small random displacements of the retinal image when viewing a stationary scene. Here we investigate the modulation of microsaccades by shifts of covert attention in a classical spatial cueing paradigm. First, we replicate the suppression of microsaccades with a minimum rate about 150 ms after cue onset. Second, as a new finding we observe microsaccadic enhancement with a maximum rate about 350 ms after presentation of the cue. Third, we find a modulation of the orientation towards the cue direction. These multiple influences of visual attention on microsaccades accentuate their role for visual information processing. Furthermore, our results suggest that microsaccades can be used to map the orientation of visual attention in psychophysical experiments.
Evidence for auditory dominance in a passive oddball task
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- V M Sloutsky
Robinson, C. W., Ahmar, N., & Sloutsky, V. M. (2010).
Evidence for auditory dominance in a passive oddball task.
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PTSD Issues for current military service members
- M Wadsworth
Wadsworth, M. (2022). PTSD Issues for current military
service members. NOLO. https://www.nolo.com/legalencyclopedia/ptsd-issues-current-military-servicemembers.html