Human Responses to Visually Evoked Threat

Transition ability to safe states reduces fear responses to height

Previous studies on fear extinction have primarily focused on repeated exposure to fear-inducing context without negative consequences. However, it is also possible that an individual can reduce fear responses by predicting that they can transition to a safe environment through their own actions, even if a fear-inducing context appears. Here, by conducting two virtual reality (VR) experiments (Exp 1 and Exp 2) involving height and flight scenarios, we examined whether participants' fear responses to height decrease after actively experiencing low-altitude VR flight, which allowed them to predict that they would be in a safe state by flying even if they fell from a height. Specifically, participants in the flight group (n = 44 and 46) flew over a city at altitudes below 5 m for 7 min, while participants in the control group (n = 41 and 28) watched a video of a flight group participant's experience. Before and after the active flight or passive viewing task, both groups walked on a plank while having their skin conductance response (SCR) and subjective fear score (SFS) measured. In both Exp 1 and Exp 2, the active flight group exhibited a greater reduction in both SCR and SFS compared to the control group. Additionally, a multivariate regression of SCR using the questionnaires collected in Exp 2 revealed that the action-dependent safety prediction has a positive contribution to the SCR reduction in the flight group. These results clarified that the ability to transition to safe states by self-actions can reduce physiological and subjective fear responses.

Assessment of PTSD in military personnel via machine learning based on physiological habituation in a virtual immersive environment

Posttraumatic stress disorder (PTSD) is a complex mental health condition triggered by exposure to traumatic events that leads to physical health problems and socioeconomic impairments. Although the complex symptomatology of PTSD makes diagnosis difficult, early identification and intervention are crucial to mitigate the long-term effects of PTSD and provide appropriate treatment. In this study, we explored the potential for physiological habituation to stressful events to predict PTSD status. We used passive physiological data collected from 21 active-duty United States military personnel and veterans in an immersive virtual environment with high-stress combat-related conditions involving trigger events such as explosions or flashbangs. In our work, we proposed a quantitative measure of habituation to stressful events that can be quantitatively estimated through physiological data such as heart rate, galvanic skin response and eye blinking. Using a Gaussian process classifier, we prove that habituation to stressful events is a predictor of PTSD status, measured via the PTSD Checklist Military version (PCL-M). Our algorithm achieved an accuracy of 80.95% across our cohort. These findings suggest that passively collected physiological data may provide a noninvasive and objective method to identify individuals with PTSD. These physiological markers could improve both the detection and treatment of PTSD.

No cardiac phase bias for threat-related distance perception under naturalistic conditions in immersive virtual reality

Previous studies have found that threatening stimuli are more readily perceived and more intensely experienced when presented during cardiac systole compared with diastole. Also, threatening stimuli are judged as physically closer than neutral ones. In a pre-registered study, we tested these effects and their interaction using a naturalistic (interactive and three-dimensional) experimental design in immersive virtual reality: we briefly displayed threatening and non-threatening animals (four each) at varying distances (1.5-5.5 m) to a group of young, healthy participants (n = 41) while recording their electrocardiograms (ECGs). Participants then pointed to the location where they had seen the animal (approx. 29 000 trials in total). Our pre-registered analyses indicated that perceived distances to both threatening and non-threatening animals did not differ significantly between cardiac phases-with Bayesian analysis supporting the null hypothesis. There was also no evidence for an association between subjective fear and perceived proximity to threatening animals. These results contrast with previous findings that used verbal or declarative distance measures in less naturalistic experimental conditions. Furthermore, our findings suggest that the cardiac phase-related variation in threat processing may not generalize across different paradigms and may be less relevant in naturalistic scenarios than under more abstract experimental conditions.

The Adaptiveness of Emotion Regulation Variability and Interoceptive Attention in Daily Life

OBJECTIVE

In daily life, we must dynamically and flexibly deploy strategies to regulate our emotions, which depends on awareness of emotions and internal bodily signals. Variability in emotion-regulation strategy use may predict fewer negative emotions, especially when people pay more attention to their bodily states-or have greater "interoceptive attention" (IA). Using experience sampling, this study aimed to test whether IA predicts variability in strategy use and whether this variability and IA together predict negative affect.

METHODS

University student participants ( n = 203; 165 females; Mage = 20.68, SD age = 1.84) completed trait questionnaires and reported state levels of IA, emotional awareness, negative affect, and emotion-regulation strategies, seven times daily for 1 week.

RESULTS

State IA significantly predicted between-strategy variability, which was mediated by emotional awareness (indirect effect = 0.002, 95% confidence interval = <0.001-0.003). Between-strategy variability was associated with lower negative affect, particularly when individuals had higher state IA (simple slope = -0.83, t = -5.87, p < .001) versus lower IA (simple slope = -0.31, t = -2.62, p = .009).

CONCLUSIONS

IA appears to facilitate adaptative emotion regulation and help alleviate negative affect. Findings underscore the key roles of IA and emotion-regulation flexibility in mental health.

The influence of threat on visuospatial perception, affordances, and protective behaviour: A systematic review and meta-analysis

Perception has been conceptualised as an active and adaptive process, based upon incoming sensory inputs, which are modified by top-down factors such as cognitions. Visuospatial perception is thought to be scaled based on threat, with highly threatening objects or contexts visually inflated to promote escape or avoidance behaviours. This meta-analytical systematic review quantified the effect and evidence quality of threat-evoked visuospatial scaling, as well as how visuospatial scaling relates to affordances (perceived action capabilities) and behavioural avoidance/escape outcomes. Databases and grey literature were systematically searched inclusive to 10/04/24. Studies were assessed with a customised Risk of Bias form and meta-analysis was performed using a random-effects model. 12,354 records were identified. Of these, 49 experiments (n = 3027) were included in the review. There was consistent evidence that threat the of height influenced contextual perception (g = 0.66, 95% CI: 0.45, 0.88) and affordances (g = -0.43, 95% CI: -0.84, -0.03). Threatening objects were viewed as larger (g = 0.76, 95% CI: 0.26, 1.26) and as closer (g = 0.30, 95% CI: 0.17, 0.42). Bodily threat (pain) yielded conflicting effects on visuospatial perception/affordances. We conclude that threat may influence visuospatial perception and affordances. However, since behavioural measures were poorly reported, their relationship with visuospatial perception/affordances remains elusive.

Immersive VR for investigating threat avoidance: The VRthreat toolkit for Unity

All animals have to respond to immediate threats in order to survive. In non-human animals, a diversity of sophisticated behaviours has been observed, but research in humans is hampered by ethical considerations. Here, we present a novel immersive VR toolkit for the Unity engine that allows assessing threat-related behaviour in single, semi-interactive, and semi-realistic threat encounters. The toolkit contains a suite of fully modelled naturalistic environments, interactive objects, animated threats, and scripted systems. These are arranged together by the researcher as a means of creating an experimental manipulation, to form a series of independent "episodes" in immersive VR. Several specifically designed tools aid the design of these episodes, including a system to allow for pre-sequencing the movement plans of animal threats. Episodes can be built with the assets included in the toolkit, but also easily extended with custom scripts, threats, and environments if required. During the experiments, the software stores behavioural, movement, and eye tracking data. With this software, we aim to facilitate the use of immersive VR in human threat avoidance research and thus to close a gap in the understanding of human behaviour under threat.

Human Anterior Insular Cortex Encodes Multiple Electrophysiological Representations of Anxiety-Related Behaviors

Anxiety is a common symptom across psychiatric disorders, but the neurophysiological underpinnings of these symptoms remain unclear. This knowledge gap has prevented the development of circuit-based treatments that can target the neural substrates underlying anxiety. Here, we conducted an electrophysiological mapping study to identify neurophysiological activity associated with self-reported state anxiety in 17 subjects implanted with intracranial electrodes for seizure localization. Participants had baseline anxiety traits ranging from minimal to severe. Subjects volunteered to participate in an anxiety induction task in which they were temporarily exposed to the threat of unpredictable shock during intracranial recordings. We found that anterior insular beta oscillatory activity was selectively elevated during epochs when unpredictable aversive stimuli were being delivered, and this enhancement in insular beta was correlated with increases in self-reported anxiety. Beta oscillatory activity within the frontoinsular region was also evoked selectively by cues-predictive of threat, but not safety cues. Anterior insular gamma responses were less selective than gamma, strongly evoked by aversive stimuli and had weaker responses to salient threat and safety cues. On longer timescales, this gamma signal also correlated with increased skin conductance, a measure of autonomic state. Lastly, we found that direct electrical stimulation of the anterior insular cortex in a subset of subjects elicited self-reported increases in anxiety that were accompanied by enhanced frontoinsular beta oscillations. Together, these findings suggest that electrophysiologic representations of anxiety- related states and behaviors exist within anterior insular cortex. The findings also suggest the potential of reducing anterior insular beta activity as a therapeutic target for refractory anxiety-spectrum disorders.

The influence of postural threat-induced anxiety on locomotor learning and updating

The ability to adapt our locomotion in a feedforward (i.e., "predictive") manner is crucial for safe and efficient walking behavior. Equally important is the ability to quickly deadapt and update behavior that is no longer appropriate for the given context. It has been suggested that anxiety induced via postural threat may play a fundamental role in disrupting such deadaptation. We tested this hypothesis, using the "broken escalator" phenomenon: Fifty-six healthy young adults walked onto a stationary walkway ("BEFORE" condition, 5 trials), then onto a moving walkway akin to an airport travelator ("MOVING" condition, 10 trials), and then again onto the stationary walkway ("AFTER" condition, 5 trials). Participants completed all trials while wearing a virtual reality headset, which was used to induce postural threat-related anxiety (raised clifflike drop at the end of the walkway) during different phases of the paradigm. We found that performing the locomotor adaptation phase in a state of increased threat disrupted subsequent deadaptation during AFTER trials: These participants displayed anticipatory muscular activity as if expecting the platform to move and exhibited inappropriate anticipatory forward trunk movement that persisted during multiple AFTER trials. In contrast, postural threat induced during AFTER trials did not affect behavioral or neurophysiological outcomes. These findings highlight that actions learned in the presence of postural threat-induced anxiety are strengthened, leading to difficulties in deadapting these behaviors when no longer appropriate. Given the associations between anxiety and persistent maladaptive gait behaviors (e.g., "overly cautious" gait, functional gait disorders), the findings have implications for the understanding of such conditions.NEW & NOTEWORTHY Safe and efficient locomotion frequently requires movements to be adapted in a feedforward (i.e., "predictive") manner. These adaptations are not always correct, and thus inappropriate behavior must be quickly updated. Here we showed that increased threat disrupts this process. We found that locomotor actions learned in the presence of postural threat-induced anxiety are strengthened, subsequently impairing one's ability to update (or "deadapt") these actions when they are no longer appropriate for the current context.

Attenuation of visual exploration following stress

When we explore our surroundings, we frequently move our gaze to collect visual information. Studies have extensively examined gaze behavior in response to different visual scenes. Here, we examined how differences in an individual's state may affect visual exploration, for example, following acute stress. In this study, participants were exposed to either a psychosocial stressor-performing a public speaking task in front of a two-person committee-or a control condition absent stress induction. Elicitation of stress responses was validated using cortisol levels and subjective reports. Stress also led to an extended increase in pupil diameter (a proxy of arousal responses), suggesting it may also affect eye movements. Gaze behavior measures were taken prior and following the stress or control tasks. Acute stress attenuated visual exploration, reflected by fewer saccades and a smaller scanned area. Stress did not have a significant effect on either the tendency to look at social features or at salient regions of the images. These findings diverge from theoretical predictions suggesting that acute stress may facilitate social affiliative behaviors (e.g., Tend-and-Befriend theory). Reduced saccades and a smaller scanned area may be a possible mechanism explaining previous reports showing stress-related effects on various cognitive processes (e.g., visual working memory) that rely on visual exploration.

Pathway-specific inputs to the superior colliculus support flexible responses to visual threat

Behavioral flexibility requires directing feedforward sensory information to appropriate targets. In the superior colliculus, divergent outputs orchestrate different responses to visual threats, but the circuit organization enabling the flexible routing of sensory information remains unknown. To determine this structure, we focused on inhibitory projection (Gad2) neurons. Trans-synaptic tracing and neuronal recordings revealed that Gad2 neurons projecting to the lateral geniculate nucleus (LGN) and the parabigeminal nucleus (PBG) form two separate populations, each receiving a different set of non-retinal inputs. Inhibiting the LGN- or PBG-projecting Gad2 neurons resulted in opposing effects on behavior; increasing freezing or escape probability to visual looming, respectively. Optogenetic activation of selected inputs to the LGN- and PBG-projecting Gad2 cells predictably regulated responses to visual threat. These data suggest that projection-specific sampling of brain-wide inputs provides a circuit design principle that enables visual inputs to be selectively routed to produce context-specific behavior.

Slow Breathing Reduces Biomarkers of Stress in Response to a Virtual Reality Active Shooter Training Drill

Tactical occupations regularly encounter life-threatening situations while on duty. Although these occupations are often trained to utilize slow breathing (SB) during intense stress, there is no evidence supporting the effects on markers of stress in response to a virtual reality active shooter training drill (VR-ASD). The purpose of the study was to determine the impact of acute SB on biomarkers of stress in response to a VR-ASD. Seventy-nine (n = 79) subjects performed either slow breathing method 1 (SB1), slow breathing method 2 (SB2), or normal breathing (control) for five minutes, both pre- and post-VR-ASD. Saliva samples were analyzed for stress markers, including α-amylase (sAA) and secretory immunoglobulin-A (SIgA). Both methods of SB resulted in significantly lower sAA concentrations at 5 (p < 0.001) and 30 min post-VR-ASD (SB1: p = 0.008; SB2: p < 0.001) compared to the control. In the control condition, the sAA concentrations were significantly elevated 5 min post-VR-ASD (p < 0.001) but did not change across time in SB1 or SB2 (p > 0.05). Thus, both SB1 and SB2 reduced the sAA response and resulted in lower concentrations post-VR-ASD. This study was pre-registered as a clinical trial ("Impact of Breathing Interventions on Stress Markers"; NCT05825846).

Resting state dynamics in people with varying degrees of anxiety and mindfulness: A nonlinear and nonstationary perspective

Anxiety and mindfulness are two inversely linked traits shown to be involved in various physiological domains. The current study used resting state electroencephalography (EEG) to explore differences between people with low mindfulness-high anxiety (LMHA) (n = 29) and high mindfulness-low anxiety (HMLA) (n = 27). The resting EEG was collected for a total of 6 min, with a randomized sequence of eyes closed and eyes opened conditions. Two advanced EEG analysis methods, Holo-Hilbert Spectral Analysis and Holo-Hilbert cross-frequency phase clustering (HHCFPC) were employed to estimate the power-based amplitude modulation of carrier frequencies, and cross-frequency coupling between low and high frequencies, respectively. The presence of higher oscillation power across the delta and theta frequencies in the LMHA group than the HMLA group might have been due to the similarity between the resting state and situations of uncertainty, which reportedly triggers motivational and emotional arousal. Although these two groups were formed based on their trait anxiety and trait mindfulness scores, it was anxiety that was found to be significant predictor of the EEG power, not mindfulness. It led us to conclude that it might be anxiety, not mindfulness, which might have contributed to higher electrophysiological arousal. Additionally, a higher δ-β and δ-γ CFC in LMHA suggested greater local-global neural integration, consequently a greater functional association between cortex and limbic system than in the HMLA group. The present cross-sectional study may guide future longitudinal studies on anxiety aiming with interventions such as mindfulness to characterize the individuals based on their resting state physiology.

Brief structured respiration practices enhance mood and reduce physiological arousal

Controlled breathwork practices have emerged as potential tools for stress management and well-being. Here, we report a remote, randomized, controlled study (NCT05304000) of three different daily 5-min breathwork exercises compared with an equivalent period of mindfulness meditation over 1 month. The breathing conditions are (1) cyclic sighing, which emphasizes prolonged exhalations; (2) box breathing, which is equal duration of inhalations, breath retentions, and exhalations; and (3) cyclic hyperventilation with retention, with longer inhalations and shorter exhalations. The primary endpoints are improvement in mood and anxiety as well as reduced physiological arousal (respiratory rate, heart rate, and heart rate variability). Using a mixed-effects model, we show that breathwork, especially the exhale-focused cyclic sighing, produces greater improvement in mood (p < 0.05) and reduction in respiratory rate (p < 0.05) compared with mindfulness meditation. Daily 5-min cyclic sighing has promise as an effective stress management exercise.

The Effect of Expertise during Simulated Flight Emergencies on the Autonomic Response and Operative Performance in Military Pilots

Heart rate variability (HRV) and performance response during emergency flight maneuvers were analyzed. Two expert pilots (ages 35 and 33) and two rookie pilots (ages 25) from the Portuguese Air Force participated in this case-control report study. Participants had to complete the following emergency protocols in a flight simulator: (1) take-off engine failure, (2) flight engine failure close to the base, (3) flight engine failure far away from the base, and (4) alternator failure. The HRV was collected during all these maneuvers, as well as the performance data (the time it took to go through the emergency protocol and the subjective information from the flight simulator operator). Results regarding autonomic modulation showed a higher sympathetic response during the emergency maneuvers when compared to baseline. In some cases, there was also a higher sympathetic response during the emergency maneuvers when compared with the take-off protocol. Regarding performance data, the expert pilots accomplished the missions in less time than the rookie pilots. Autonomic modulation measured from HRV through portable devices can easily relay important information. This information is relevant since characterizing these maneuvers can provide helpful information to design training strategies to improve those psychophysiological responses.

Promises and challenges of human computational ethology

The movements an organism makes provide insights into its internal states and motives. This principle is the foundation of the new field of computational ethology, which links rich automatic measurements of natural behaviors to motivational states and neural activity. Computational ethology has proven transformative for animal behavioral neuroscience. This success raises the question of whether rich automatic measurements of behavior can similarly drive progress in human neuroscience and psychology. New technologies for capturing and analyzing complex behaviors in real and virtual environments enable us to probe the human brain during naturalistic dynamic interactions with the environment that so far were beyond experimental investigation. Inspired by nonhuman computational ethology, we explore how these new tools can be used to test important questions in human neuroscience. We argue that application of this methodology will help human neuroscience and psychology extend limited behavioral measurements such as reaction time and accuracy, permit novel insights into how the human brain produces behavior, and ultimately reduce the growing measurement gap between human and animal neuroscience.