Immobility reactions under threat: A contribution to human defensive cascade and PTSD

Posture analysis in predicting fall-related injuries during French Navy Special Forces selection course using machine learning: a proof-of-concept study

INTRODUCTION

Injuries induced by falls represent the main cause of failure in the French Navy Special Forces selection course. In the present study, we made the assumption that probing the posture might contribute to predicting the risk of fall-related injury at the individual level.

METHODS

Before the start of the selection course, the postural signals of 99 male soldiers were recorded using static posturography while they were instructed to maintain balance with their eyes closed. The event to be predicted was a fall-related injury during the selection course that resulted in the definitive termination of participation. Following a machine learning methodology, we designed an artificial neural network model to predict the risk of fall-related injury from the descriptors of postural signal.

RESULTS

The neural network model successfully predicted with 69.9% accuracy (95% CI 69.3-70.5) the occurrence of a fall-related injury event during the selection course from the selected descriptors of the posture. The area under the curve value was 0.731 (95% CI 0.725-0.738), the sensitivity was 56.8% (95% CI 55.2-58.4) and the specificity was 77.7% (95% CI 76.8-0.78.6).

CONCLUSION

If confirmed with a larger sample, these findings suggest that probing the posture using static posturography and machine learning-based analysis might contribute to inform risk assessment of fall-related injury during military training, and could ultimately lead to the development of novel programmes for personalised injury prevention in military population.

Studying the influence of single social interactions on approach and avoidance behavior: A multimodal investigation in immersive virtual reality

When studying spontaneous or learned emotional responses to social stimuli, research has traditionally relied on simplified stimuli repeatedly presented on a computer screen in standardized laboratory environments. While these studies have provided important insights into social perception and cognition, their restricted ecological validity may impede the extrapolation of findings to everyday social contexts. Here, we developed a novel immersive virtual reality scenario that permits the examination of social approach and avoidance behavior under naturalistic circumstances while at the same time maintaining full experimental control. Using a combination of a social conditioning procedure with a social approach-avoidance test, we conducted two experiments (both with N = 48 female participants) to investigate how individuals differing in trait social anxiety adapt their behavior after a single encounter with an either friendly or unfriendly virtual agent. In addition to overt approach and avoidance behavior, we acquired subjective ratings, eye-tracking data, and autonomic responses. Overall, we observed significant effects of the social conditioning procedure on autonomic responses and participants' exploration behavior. After initially increased attention, participants exhibited avoidance of social threats as indicated by a higher interpersonal distance and decreased visual attention towards the negatively conditioned virtual agent in the test phase. We found no association between hypervigilance and trait social anxiety but observed higher fear ratings and enhanced avoidance of social threats in participants with elevated anxiety levels. Altogether, this study demonstrates the potential of immersive virtual environments for examining social learning processes under conditions resembling real-life social encounters.

Fear conditioning: Insights into learning, memory and extinction and its relevance to clinical disorders

Fear, whether innate or learned, is an essential emotion required for survival. The learning, and subsequent memory, of fearful events enhances our ability to recognise and respond to threats, aiding adaptation to new, ever-changing environments. Considerable research has leveraged associative learning protocols such as contextual or auditory forms of fear conditioning in rodents, to understand fear learning, memory consolidation and extinction phases of memory. Such assays have led to detailed characterisation of the underlying neurocircuitry and neurobiology supporting fear learning processes. Given fear processing is conserved across rodents and humans, fear conditioning experiments provide translational insights into fundamental memory processes and fear-related pathologies. This review examines associative learning protocols used to measure fear learning, memory and extinction, before providing an overview on the underlying complex neurocircuitry including the amygdala, hippocampus and medial prefrontal cortex. This is followed by an in-depth commentary on the neurobiology, particularly synaptic plasticity mechanisms, which regulate fear learning, memory and extinction. Next, we consider how fear conditioning assays in rodents can inform our understanding of disrupted fear memory in human disorders such as post-traumatic stress disorder (PTSD), anxiety and psychiatric disorders including schizophrenia. Lastly, we critically evaluate fear conditioning protocols, highlighting some of the experimental and theoretical limitations and the considerations required when conducting such assays, alongside recent methodological advancements in the field. Overall, rodent-based fear conditioning assays remain central to making progress in uncovering fundamental memory phenomena and understanding the aetiological mechanisms that underpin fear associated disorders, alongside the development of effective therapeutic strategies.

Neuropsychobiology of fear-induced bradycardia in humans: progress and pitfalls

In the last century, the paradigm of fear conditioning has greatly evolved in a variety of scientific fields. The techniques, protocols, and analysis methods now most used have undergone a progressive development, theoretical and technological, improving the quality of scientific productions. Fear-induced bradycardia is among these techniques and represents the temporary deceleration of heart beats in response to negative outcomes. However, it has often been used as a secondary measure to assess defensive responding to threat, along other more popular techniques. In this review, we aim at paving the road for its employment as an additional tool in fear conditioning experiments in humans. After an overview of the studies carried out throughout the last century, we describe more recent evidence up to the most contemporary research insights. Lastly, we provide some guidelines concerning the best practices to adopt in human fear conditioning studies which aim to investigate fear-induced bradycardia.

Electrocortical Responses in Anticipation of Avoidable and Inevitable Threats: A Multisite Study

When faced with danger, human beings respond with a repertoire of defensive behaviors, including freezing and active avoidance. Previous research has revealed a pattern of physiological responses, characterized by heart rate bradycardia, reduced visual exploration, and heightened sympathetic arousal in reaction to avoidable threats, suggesting a state of attentive immobility in humans. However, the electrocortical underpinnings of these behaviors remain largely unexplored. To investigate the visuocortical components of attentive immobility, we recorded parieto-occipital alpha activity, along with eye movements and autonomic responses, while participants awaited either an avoidable, inevitable, or no threat. To test the robustness and generalizability of our findings, we collected data from a total of 101 participants (76 females, 25 males) at two laboratories. Across sites, we observed an enhanced suppression of parieto-occipital alpha activity during avoidable threats, in contrast to inevitable or no threat trials, particularly toward the end of the trial that prompted avoidance responses. This response pattern coincided with heart rate bradycardia, centralization of gaze, and increased sympathetic arousal. Furthermore, our findings expand on previous research by revealing that the amount of alpha suppression, along with centralization of gaze, and heart rate changes predict the speed of motor responses. Collectively, these findings indicate that when individuals encounter avoidable threats, they enter a state of attentive immobility, which enhances perceptual processing and facilitates action preparation. This state appears to reflect freezing-like behavior in humans.

Threat directionality modulates defensive reactions in humans: cardiac and electrodermal responses

Features of threatening cues and the associated context influence the perceived imminence of threat and the defensive responses evoked. To provide additional knowledge about how the directionality of a threat (i.e. directed-towards or away from the viewer) might impact defensive responses in humans, participants were shown pictures of a man carrying a gun (threat) or nonlethal object (neutral) directed-away from or towards the participant. Cardiac and electrodermal responses were collected. Compared to neutral images, threatening images depicting a gun directed-towards the participant induced sustained bradycardia and an increased electrodermal response, interpreted as immobility under attack. This defensive immobility reaction is evoked by high perceived threat and inescapable situations and indicates intense action preparation. Pictures of guns directed-away from the participant induced shorter bradycardia and no significant modulation of the electrodermal response compared to neutral pictures, which might be consistent with the perception of a less threatening situation. The results show that the directionality of threat stimuli is a key factor that prompts different patterns of defensive responses.

Alterations in Vagal Tone Are Associated with Changes in the Gut Microbiota of Adults with Anxiety and Depression Symptoms: Analysis of Fecal Metabolite Profiles

Accumulating evidence suggests that interactions between the brain and gut microbiota significantly impact brain function and mental health. In the present study, we aimed to investigate whether young, healthy adults without psychiatric diagnoses exhibit differences in metabolic stool and microbiota profiles based on depression/anxiety scores and heart rate variability (HRV) parameters. Untargeted nuclear magnetic resonance-based metabolomics was used to identify fecal metabolic profiles. Results were subjected to multivariate analysis through principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), and the metabolites were identified through VIP score. Metabolites separating asymptomatic and symptomatic groups were acetate, valine, and glutamate, followed by sugar regions, glutamine, acetone, valerate, and acetoacetate. The main metabolites identified in high vagal tone (HVT) and low vagal tone (LVT) groups were acetate, valerate, and glutamate, followed by propionate and butyrate. In addition to the metabolites identified by the PLS-DA test, significant differences in aspartate, sarcosine, malate, and methionine were observed between the groups. Levels of acetoacetate were higher in both symptomatic and LVT groups. Valerate levels were significantly increased in the symptomatic group, while isovalerate, propionate, glutamate, and acetone levels were significantly increased in the LVT group. Furthermore, distinct abundance between groups was only confirmed for the Firmicutes phylum. Differences between participants with high and low vagal tone suggest that certain metabolites are involved in communication between the vagus nerve and the brain.

Posttraumatic stress disorder following childhood sexual and physical abuse: a study protocol for an 11-week randomised controlled trial comparing imaginal exposure and imagery rescripting

Background: There is a vast amount of evidence supporting the effectiveness of trauma-focused cognitive-behavioral therapy in treating posttraumatic stress disorder (PTSD). However, it remains unclear which specific treatment is most effective for patients with PTSD following childhood sexual and physical abuse (CSPA). Although Imaginal Exposure (IE) has proven highly effective in treating PTSD and is widely acknowledged as a standard method, Imagery Rescripting (IR) may be more suitable for CSPA-related PTSD. IR not only addresses fear but also targets other emotions and cognitions associated with childhood maladaptive schemas. Preliminary findings suggest lower drop-out rates for IR compared to IE, but no Randomized Controlled Trial (RCT) currently assesses the effectiveness of IR for CSPA-related PTSD.Objective: This article presents a study protocol designed to investigate the optimal treatment (IE or IR) for individuals with CSPA-related PTSD and explore predictors of treatment success.Method: In our study protocol, we suggest the inclusion of 173 patients (N = 64 in IR, N = 64 in IE, and N = 45 in the waitlist condition). The therapy procedures for both IE and IR will consist of 16 sessions lasting 90 min each, with treatment durations of 11 weeks. Measurements take place at baseline, at start of treatment, 11 weeks after the start of treatment (after 16 sessions) and at follow-up at 26 weeks after the last session. A mixed regression will be used to compare the three active conditions before and after measurement.Results: This article serves as a study protocol. The results are not yet available but they will be presented in a subsequent article.Conclusion: This study protocol outlines a RCT which will be the first to provide information on the effectiveness of IR versus IE versus a control group in CSPA-related PTSD.Trial registration: Netherlands Trial Register NTR 4817. Registered 26 September 2014.

Tonic immobility triggered by COVID-19-related trauma is associated with long-term PTSD symptoms

During the COVID-19 pandemic healthcare workers were repeatedly exposed to traumatic experiences. Facing life-threatening events and repeated exposure to traumatic duty-related situations may cause posttraumatic stress disorder (PTSD). While tonic immobility has been considered a key vulnerability factor for PTSD, little is known about this relationship in the long term. In this study, we aimed to determine whether peritraumatic tonic immobility triggered by COVID-19-related trauma predicts PTSD symptom severity six to twelve months later. We conducted an online longitudinal survey using the PTSD Checklist for the DSM-5 (PCL-5) and the Tonic Immobility Scale to assess PTSD symptoms and the tonic immobility response, respectively. Multivariate regression models revealed a significant association between tonic immobility and PTSD symptoms. Each one-unit increase in the tonic immobility score was associated with a 1.5 % increase in the average PTSD symptom score six to twelve months after the traumatic event that triggered the tonic immobility. Furthermore, participants who showed significant or extreme levels of tonic immobility were 3.5 times or 7.3 times more likely to have a probable PTSD diagnosis, respectively. Hence, peritraumatic tonic immobility seems to have a lasting deleterious effect on mental health. Psychological treatment for health care professionals is urgent, and psychoeducation about the involuntary, biological nature of tonic immobility is essential to reduce suffering.

Can I see it in the eyes? An investigation of freezing-like motion patterns in response to avoidable threat

Freezing is one of the most extensively studied defensive behaviors in rodents. Both reduced body and gaze movements during anticipation of threat also occur in humans and have been discussed as translational indicators of freezing but their relationship remains unclear. We thus set out to elucidate body and eye movements and concomitant autonomic dynamics in anticipation of avoidable threat. Specifically, 50 participants viewed naturalistic pictures that were preceded by a colored fixation cross, signaling them whether to expect an inevitable (shock), no (safety), or a potential shock (flight) that could be avoided by a quick button press. Body sway, eye movements, the heart rate and skin conductance were recorded. We replicated previously described reductions in body sway, gaze dispersion, and the heart rate, and a skin conductance increase in flight trials. Stronger reductions in gaze but not in body sway predicted faster motor reactions on a trial-wise basis, highlighting their functional role in action preparation. We failed to find a trait-like relationship between body and gaze movements across participants, but their temporal profiles were positively related within individuals, suggesting that both metrics partly reflect the same construct. However, future research is desirable to assess these response patterns in naturalistic environments. A more ethological examination of different movement dynamics upon threat would not only warrant better comparability between rodent and human research but also help determine whether and how eye-tracking could be implemented as a proxy for fear-related movements in restricted brain imaging environments.

I did not scream. i could not; i was terrified. i just followed them. . .i blocked my mind. then they all raped me: A narrative inquiry on the onset of tonic immobility among women rape victims in Nigeria

Tonic immobility (TI) is a common uncontrollable autonomic mammalian response to an extremely fearful situation. It is one of the most immediate devastating consequences of rape and remains poorly understood. While controversies over its definition persist among researchers, this also reflects on the care for and support to victims. The study aimed to explore and describe the onset of TI and the meaning attached to the experience among women raped victims in Nigeria. The study design was the qualitative narrative inquiry approach. Criterion and purposive sampling were conducted across four post-rape care facilities in Lagos, Nigeria, to recruit 13 participants. In-depth face-to-face interviews were conducted using a semi-structured interview guide to generate data that were thematically analysed. The findings of the study revealed five themes relating to the onset of TI as follows: the first two focused on the experience of TI: (1) the onset of TI prior to rape due to perceived imminent danger, (2) the onset of TI as a self-protection mechanism from further harm) while the last three relate to the meaning-making of the experience of TI (3) self-loathing as a meaning attached to TI, (4) suicidal ideations as a meaning attached to TI, and (5) divine intervention as a meaning attached to TI. Conclusion: The findings underscore the experiences and meanings that participants attach to TI following rape. There is a strong likelihood that tonic-immobility is not an uncommon experience amongst rape victims, but that in the absence of research, specialized care on the condition, and its associated consequences will haunt many women, affecting their psychological well-being and their entire quality of life. Describing the phenomenon as it is experienced by the participants is critical because understanding the condition is the first step toward effective appropriate management.

Effects of peritraumatic reactions on post-traumatic stress among Kahramanmaras earthquake survivors

PURPOSE

Peritraumatic reactions play a crucial role in the development of mental health problems, including depression and post-traumatic stress disorder. Therefore, this study sought to examine the influence of the peritraumatic reactions, including peritraumatic dissociation, peritraumatic distress, mental defeat, and tonic immobility, on post-traumatic stress disorder and major depressive disorder in earthquake survivors.

MATERIALS AND METHODS

A total of 261 adult participants aged between 18 and 65 (Mage=29.20, SD = 28.06, 162 were female, and 99 were male) who were exposed to the Kahramanmaras earthquake in February 2023 were recruited in the study. Data were collected between April 10 and 18 2023, two months after the earthquake. Participants completed questionnaires, including The International Trauma Questionnaire, The International Depression Questionnaire, The Mental Defeat Questionnaire, The Tonic Immobility Scale, and The Peritraumatic Dissociative Experiences Questionnaire.

RESULTS

Two-step multiple linear regression analyses indicated all peritraumatic reactions predicted both post-traumatic stress disorder and depression. Dominance analysis results showed that the contribution of peritraumatic dissociation in predicting PTSD and depression was higher among other peritraumatic reactions.

CONCLUSION

The findings of the study revealed a robust association between peritraumatic reactions and both depression and PTSD, shedding light on the underlying processes in the development of trauma-related disorders. Early assessment of peritraumatic reactions may be useful in identifying individuals at risk of developing PTSD and depression.

Temperament Behaviours in Individually Tested Sheep Are Not Related to Behaviours Expressed in the Presence of Conspecifics

Individual behavioural testing in sheep is common; however, outcomes may be misleading as they are a highly gregarious species that is usually managed in groups. We investigated whether behaviour expressed by 3-4-month-old Merino lambs (n = 220) in social isolation was related to their behaviour towards the same stimuli when three other conspecifics were present, and if measures of temperament (vocalisations and locomotory behaviours) were repeatable across both social situations. Expression of all behaviours were reduced when conspecifics were present, and vocalisations were rarely performed in social groups, suggesting that this behaviour is a response to social isolation. Similarities across the two social situations, in ranked order of how individual lambs expressed each behaviour, indicate that vigilance and attentional orienting towards a human were repeatable (p < 0.001), as was vigilance in a startle test (p < 0.05). However, no clear relationship between behaviours expressed across the two social situations was found. The results of this study suggest that testing sheep individually should be conducted with caution where the outcome is applied to animals managed in groups. Vigilance shows promise as a measure of an underlying trait that is stable across social contexts.

Fear lies in the eyes of the beholder-Robust evidence for reduced gaze dispersion upon avoidable threat

A rapid detection and processing of relevant information in our environment is crucial for survival. The human eyes are drawn to social or threatening stimuli as they may carry essential information on how to behave appropriately in a given context. Recent studies further showed a centralization of gaze that reminded of freezing behaviors in rodents. Probably constituting a component of an adaptive defense mode, centralized eye movements predicted the speed of motor actions. Here we conducted two experiments to examine if and how these presumably survival-relevant gaze patterns interact. Subjects viewed images including social, that is, faces (Experiment 1, N = 50) or threatening stimuli, that is, snakes or spiders (Experiment 2, N = 50) while awaiting an inevitable (shock), no (safety), or an avoidable shock (flight) they could escape from by a fast button press. The social and threatening cues within the scenes differed in their distance from the image center and we acquired eye-tracking and autonomic physiological data. Although we observed an initial orienting toward social and threatening stimulus aspects, this exploration pattern vanished towards the end of flight trials when a pronounced centralization of gaze emerged. Replicating previous findings, the amount of this center bias predicted the speed of motor reactions, and we observed a concurrent activation of the sympathetic and parasympathetic nervous system. Taken together, the exploration of potentially relevant cues seems to be part of a reflexive-orienting response regardless of contextual valence. However, centralization of gaze may be a threat-specific action-preparatory response that occurs across a wide range of stimulus contexts.

Position: A study protocol for the prevention of fall injuries in french special forces selection courses using a body-centered intervention

INTRODUCTION

The Military Physical and Sports Training program was developed by the French Army in order to train, optimize, and maintain individual readiness. Although the health benefits of sport practice do not need to be demonstrated, such activities can cause acute musculoskeletal injuries that need to be addressed. The prevalence of lower limb injury is rather high in the French military population and, in particular, ranges from 15 to 45% during Special Forces selection courses. Thus, this project aims to investigate the efficiency of a body-centered program designed to enhance body awareness. The program seeks to train the mind to actively pay attention to body information, while the latter is viewed as a protective factor against fall injuries. We assume: (i) that postural control can be improved by enhancing the level of body awareness; and (ii) that greater postural awareness could be beneficial in reducing the risk of fall injuries. The body-centered prevention program is based on the Optimization of the Resources of the Armed Forces (ORAF) intervention, which focuses on mental preparation and recovery, and has been deployed in the French Army for many years.

METHOD AND ANALYSES

The study focuses on five French Special Forces selection courses (400 soldiers/ participants). It is divided into two stages (year 1, year 2). The first year is dedicated to data collection from the control group (200 participants), while in the second year the ORAF intervention will be deployed. In both year, participants will be subjected to the same enrollment schedule (Fig 3). The main objective is to evaluate the effectiveness of the ORAF intervention in reducing the rate of fall injuries during military selection, based on a multidisciplinary method that captures demographic, biological, biometric, clinical, and para-clinical measures.

TRIAL REGISTRATION

Registration number: IDRCB number 2021-A02108-33, Clinical Trial: NCT05451394.

Low defensive cardiac reactivity as a physiological correlate of psychopathic fearlessness: Gender differences

Affective/interpersonal features of psychopathy have been consistently associated with diverse psychophysiological indicators of low threat sensitivity, suggesting an underlying deficit in the reactivity of the brain's defensive motivational system. This study examined the Cardiac Defense Response (CDR) -a complex pattern of heart rate changes in response to an aversive, intense, and unexpected stimulus- and its second accelerative component (A2), as a new physiological indicator of the fearlessness trait component of psychopathy. The differential contribution of dispositional fearlessness, externalizing proneness, and coldheartedness to the CDR pattern elicited during a defense psychophysiological test was examined in a mixed-gender sample of 156 undergraduates (62% women) assessed by the Psychopathic Personality Inventory-Revised (PPI-R). Higher PPI-R Fearless Dominance scores were related to lower heart rate changes throughout the CDR in women, but not in men. Further analyses on scales conforming the fearless dominance factor revealed that the hypothesized reduced A2 was specifically related to higher PPI-R Fearlessness scores only in women. Our findings provide initial evidence for the utility of the A2 to better understand the physiological aspects of fearlessness tendencies and its potential distinct manifestations across genders.

The relationship between tonic immobility and the development, severity, and course of posttraumatic stress disorder: Systematic and meta-analytic literature review

BACKGROUND

Tonic immobility (TI) is a reflexive, involuntary response that causes motor inhibition, vocal suppression, and analgesia. TI is elicited by extreme fear and perception of entrapment in a life-threatening situation. Research suggests that TI is a frequent peritraumatic response and may be related to subsequent posttraumatic stress disorder (PTSD). However, findings are mixed and, as of yet, no systematic or meta-analytic review examining associations between TI and PTSD has been published.

OBJECTIVE

We systematically and meta-analytically reviewed the literature and investigated whether TI is associated with the development, severity, and course of PTSD. Additionally, we evaluated whether different types of traumatic events are differentially associated with TI, and whether TI severity differs according to sex.

METHODS

A systematic literature search was conducted using Embase, PubMed, PsycINFO, and Scopus. Meta-analyses were performed on the included articles.

RESULTS

We identified 27 eligible articles. We found a significant association between TI and PTSD symptom severity (r = 0.39, 95% CI: 0.34-0.44; p < .0001). TI was more severe among females (Cohen's d=0.37, 95% CI: 0.25-0.48; p < .0001) and was more often elicited in situations involving interpersonal violence. We found limited longitudinal data to perform a meta-analysis of the association between TI and the development and/or course of PTSD. However, the literature available seems to support the role of TI in both the development and course of PTSD.

CONCLUSIONS

Peritraumatic TI is associated with PTSD symptom severity, occurs more often during interpersonal violence, and is more severe among females. More longitudinal research is needed to investigate the role of TI in psychopathology development and course.

Tonic immobility (freezing) during sexual and physical assaults produces stronger memory effects than other characteristics of the assaults

Tonic immobility (TI) is a phylogenetically conserved, passive, obligatory defense mechanism commonly engaged during sexual and physical assaults. During TI, people become immobile while remaining conscious and later reexperience intrusive memories of both their assault and of its accompanying immobility. Here we show that this well-studied biological process has powerful effects on memory and other processes. Participants had experienced either a serious sexual (n = 234) or physical (n = 137) assault. For both the assault and its accompanying immobility, the standard measure of the peritraumatic severity of TI correlated between .40 and .65 with post-assault effects on memory, including memory of the assault and memory of the immobility, the two memory-based self-concept measures of self-blame and event centrality, and post-assault anxiety and depression. The correlations with TI were much higher than other peritraumatic characteristics commonly used to predict and describe posttraumatic effects in assaults and other traumas. The results suggest that TI should be considered for a broader, more biologically based and ecologically valid understanding of the effects of trauma on memory and memory-based reactions.

Physical and social trauma: Towards an integrative transdiagnostic perspective on psychological trauma that involves threats to status and belonging

Current theories of psychological trauma assume that posttraumatic symptoms originate from stress reactions caused by extremely adverse life experiences. Since the diagnosis of PTSD is restricted to events that involve threats to the physical or sexual integrity of a person, such as accidents and physical and sexual violence, these theories are not well suited to explain the psychopathological consequences of severe violations of one's social integrity, such as emotional abuse and bullying. However, it is evident that social threats contribute to a broad range of mental disorders and increase symptom severity in patients with posttraumatic stress disorder. The aim of the Physical and Social Trauma (PAST) framework is to extend current memory theories of psychological trauma to incorporate threats to a person's social integrity. Within this perspective, the harmful effects of events that involve social threats result from violations of core social motives such as the need for status and belonging that bring about intense affective reactions, including despair and defeat. Within associative threat structures, these emotions are tied to the stimulus characteristics of the experiences and can be re-activated in social situations. The resulting psychopathology transcends PTSD criteria and other current classifications and suggests a transdiagnostic perspective of psychological trauma. Implications for treatment and further directions for research are discussed.

Peri-Traumatic Dissociation and Tonic Immobility as Severity Predictors of Posttraumatic Stress Disorder After Rape

Some individuals show abnormal reactions to extreme fear and life-threatening situations, including tonic immobility (TI) and peri-traumatic dissociation (PTD). We aimed to investigate the association of TI and PTD with posttraumatic stress disorder (PTSD) in women who experienced sexual violence and the risk factors for PTD occurrence. We compared PTSD severity in 86 young adult women with PTSD after a sexual violence exposure grouped according to the presence of PTD and TI. In addition, we investigated whether PTD is associated with depression and anxiety symptoms and assessed potential risk factors for PTD reaction. We found a significant positive correlation between PTSD severity and PTD occurrence (R² = .132; p = .001). PTD was also positively correlated with all clusters of PTSD symptoms except the Clinician-Administered PTSD Scale avoidance cluster (p = .058). PTD was strongly correlated with anxiety (R² = .619; p < .001) and depressive symptoms (R² = .547; p < .001). Multiple logistic regression showed that history of physical abuse (odds ratio [OR]: 1.386; p = .011) and sexual abuse (OR: 1.947; p = .004) during childhood were associated with PTD occurrence. Other risk factors for PTD were having less years of study (OR: 0.216; p = .016) and lower income (OR: 7.403; p = .028). TI measures were available for a subsample of 29 women. We found no association between TI and PTSD severity. PTD, but not TI, is significantly associated with more severe PTSD, depressive, and anxiety symptoms. Less-educated women with a history of childhood abuse and a lower income are at risk of PTD occurrence during a sexual violence episode.

Serotonin distinctly controls behavioral states in restrained and freely moving Drosophila

When trapped in a physical restraint, animals must select an escape strategy to increase their chances of survival. After falling into an inescapable trap, they react with stereotypical behaviors that differ from those displayed in escapable situations. Such behaviors involve either a wriggling response to unlock the trap or feigning death to fend off a predator attack. The neural mechanisms that regulate animal behaviors have been well characterized for escapable situations but not for inescapable traps. We report that restrained vinegar flies exhibit alternating flailing and immobility to free themselves from the trap. We used optogenetics and intersectional genetic approaches to show that, while broader serotonin activation promotes immobility, serotonergic cells in the ventral nerve cord (VNC) regulate immobility states majorly via 5-HT7 receptors. Restrained and freely moving locomotor states are controlled by distinct mechanisms. Taken together, our study has identified serotonergic switches of the VNC that promote environment-specific adaptive behaviors.

K. ZHENG ET AL.Gold-nanoparticle-based multistage drug delivery system for antitumor therapy

Nanoparticles can promote the accumulation of drugs in tumors. However, they find limited clinical applications because they cannot easily penetrate the stroma of cancer tissues, and it is difficult to control drug release. We developed a multiresponse multistage drug-delivery nanogel with improved tumor permeability and responsiveness to the tumor microenvironment for the controlled delivery of anticancer agents. For this purpose, ∼100 nm multistage drug delivery nanogels with pH, redox, near-infrared stimulation, and enzyme responsiveness were grown in situ using 20 nm gold nanoparticles (AuNPs) via an emulsion-aiding crosslinking technique with cysteine crosslinker. An alginate cysteine AuNP (ACA) nanocarrier can efficiently load the cationic drug doxorubicin (DOX) to produce a multistage drug delivery nanocarrier (DOX@ACA). DOX@ACA can maintain the slow release of DOX and reduce its toxicity. In cancer tissues, the high pH and reductase microenvironment combined with the in vitro delivery of alginate and near-infrared light drove drug release. The developed nanoparticles effectively inhibited cancer cells, and in vivo evaluations showed that they effectively enhanced antitumor activity while having negligible in vivo toxicity to major organs.

A cerebellar-prepontine circuit for tonic immobility triggered by an inescapable threat

Sudden changes in the environment are frequently perceived as threats and provoke defensive behavioral states. One such state is tonic immobility, a conserved defensive strategy characterized by powerful suppression of movement and motor reflexes. Tonic immobility has been associated with multiple brainstem regions, but the underlying circuit is unknown. Here, we demonstrate that a strong vibratory stimulus evokes tonic immobility in larval zebrafish defined by suppressed locomotion and sensorimotor responses. Using a circuit-breaking screen and targeted neuron ablations, we show that cerebellar granule cells and a cluster of glutamatergic ventral prepontine neurons (vPPNs) that express key stress-associated neuropeptides are critical components of the circuit that suppresses movement. The complete sensorimotor circuit transmits information from sensory ganglia through the cerebellum to vPPNs to regulate reticulospinal premotor neurons. These results show that cerebellar regulation of a neuropeptide-rich prepontine structure governs a conserved and ancestral defensive behavior that is triggered by an inescapable threat.

Tonic immobility is associated with posttraumatic stress symptoms in healthcare professionals exposed to COVID-19-related trauma

The Coronavirus Disease 2019 (COVID-19) pandemic has exposed healthcare workers (HCW) to traumatic situations that might lead to the development of posttraumatic stress disorder (PTSD). An important vulnerability factor for PTSD is the peritraumatic tonic immobility (TI) reaction, an involuntary and reflexive defensive response evoked by an intense and inescapable threat. TI is largely understudied in humans and has not been investigated during trauma related to COVID-19. For HCW, the pandemic context might be experienced as an intense and potentially inescapable threat, i.e., an overwhelming situation. Here, we investigated if TI response occurred during traumatic events related to the pandemic and its association with posttraumatic stress symptoms (PTSS). An online survey of 1001 HCW investigated COVID-19-related traumatic experiences, TI and PTSS. TI was reported for all types of traumatic events, and multivariate regression models revealed that TI was significantly associated with PTSS severity. HCW who reported high TI scores exhibited an increase of 9.08 times the probability of having a probable diagnosis of PTSD. Thus, TI was evoked by pandemic-related traumatic situations and associated with PTSS severity and higher odds of a PTSD diagnosis. Tonic immobility occurrence should be screened, and psychoeducation about its reflexive biological nature should be introduced.

Self-Reported Body Awareness: Validation of the Postural Awareness Scale and the Multidimensional Assessment of Interoceptive Awareness (Version 2) in a Non-clinical Adult French-Speaking Sample

Body awareness refers to the individual ability to process signals originating from within the body, which provide a mapping of the body's internal landscape (interoception) and its relation with space and movement (proprioception). The present study aims to evaluate psychometric properties and validate in French two self-report measures of body awareness: the Postural Awareness Scale (PAS), and the last version of the Multidimensional Assessment of Interoceptive Awareness questionnaire (version 2, MAIA-2). We collected data in a non-clinical, adult sample (N = 308; 61% women, mean age 35 ± 12 years) using online survey, and a subset of the original sample (n = 122; 62% women, mean age 44 ± 11 years) also completed the retest control. Factor analyses and reliability analyses were conducted. Construct validity of the PAS and the MAIA-2 were examined by testing their association with each other, and with self-report measures of personality (Big Five Inventory), alexithymia (Toronto Alexithymia Scale) and dispositional trait mindfulness (Freiburg Mindfulness Inventory). Factor analyses of the PAS supported the same two-factor structure as previously published versions (in other languages). For the MAIA-2, factor analyses suggested that a six-factor structure, excluding Not-Worrying and Not-Distracting factors, could successfully account for a common general factor of self-reported interoception. We found satisfactory internal consistency, construct validity, and reliability over time for both the PAS and the MAIA-2. Altogether, our findings suggest that the French version of the PAS and the MAIA-2 are reliable self-report tools to assess both components of body awareness (proprioception and interoception dimension, respectively).

Centralized gaze as an adaptive component of defensive states in humans

Adequate defensive responding is crucial for mental health but scientifically not well understood. Specifically, it seems difficult to dissociate defense and approach states based on autonomic response patterns. We thus explored the robustness and threat-specificity of recently described oculomotor dynamics upon threat in anticipation of either threatening or rewarding stimuli in humans. While visually exploring naturalistic images, participants (50 per experiment) expected an inevitable, no, or avoidable shock (Experiment 1) or a guaranteed, no, or achievable reward (Experiment 2) that could be averted or gained by a quick behavioural response. We observed reduced heart rate (bradycardia), increased skin conductance, pupil dilation and globally centralized gaze when shocks were inevitable but, more pronouncedly, when they were avoidable. Reward trials were not associated with globally narrowed visual exploration, but autonomic responses resembled characteristics of the threat condition. While bradycardia and concomitant sympathetic activation reflect not only threat-related but also action-preparatory states independent of valence, global centralization of gaze seems a robust phenomenon during the anticipation of avoidable threat. Thus, instead of relying on single readouts, translational research in animals and humans should consider the multi-dimensionality of states in aversive and rewarding contexts, especially when investigating ambivalent, conflicting situations.

Trauma-related dissociation and the autonomic nervous system: a systematic literature review of psychophysiological correlates of dissociative experiencing in PTSD patients

Background: Neurophysiological models link dissociation (e.g. feeling detached during or after a traumatic event) to hypoarousal. It is currently assumed that the initial passive reaction to a threat may coincide with a blunted autonomic response, which constitutes the dissociative subtype of post-traumatic stress disorder (PTSD). Objective: Within this systematic review we summarize research which evaluates autonomic nervous system activation (e.g. heart rate, blood pressure) and dissociation in PTSD patients to discern the validity of current neurophysiological models of trauma-related hypoarousal. Method: Of 553 screened articles, 28 studies (N = 1300 subjects) investigating the physiological response to stress provocation or trauma-related interventions were included in the final analysis. Results: No clear trend exists across all measured physiological markers in trauma-related dissociation. Extracted results are inconsistent, in part due to high heterogeneity in experimental methodology. Conclusion: The current review is unable to provide robust evidence that peri- and post-traumatic dissociation are associated with hypoarousal, questioning the validity of distinct psychophysiological profiles in PTSD.

Tonic Immobility is Associated with PTSD Symptoms in Traumatized Adolescents

Purpose

Growing evidence suggests that peritraumatic tonic immobility, an involuntary defensive response that involves extreme physical immobility and the perceived inability to escape, is a significant predictor of post-traumatic stress disorder (PTSD) symptomatology. However, this issue has not been specifically addressed in adolescents. Here, we investigated whether tonic immobility response experienced during the worst childhood or adolescent trauma is associated with PTSD symptom severity in a non-clinical student sample.

Methods

The sample was composed of students in 9th grade who were attending public and private schools. Symptoms of post-traumatic stress and tonic immobility were assessed using questionnaires. We performed bivariate and multivariate negative binomial regressions to examine whether tonic immobility was associated with PTSD symptomatology after controlling for confounders (peritraumatic dissociation, peritraumatic panic reactions, gender, age and time since trauma).

Results

We found an association between tonic immobility and PTSD symptom severity, even after controlling for confounders. Therefore, tonic immobility is associated with PTSD symptoms in trauma-exposed adolescents.

Conclusion

These findings highlight tonic immobility as a possible risk factor that could be used to provide direction for more targeted trauma interventions for individuals, particularly those at risk for developing PTSD. Therefore, it contributes to preventing and reducing the psychiatric burden in adolescence and later in life.

"I just became like a log of wood … I was paralyzed all over my body": women's lived experiences of tonic immobility following rape

Tonic immobility is considered the last involuntary self-protecting act/mechanism experienced by victims of rape when they are under attack. It is associated with trauma related mental health risks post-rape. Despite this, tonic immobility has not received priority as an area of research on Nigerian female victims of rape. As a result, little has been known about this phenomenon by nurses and other professionals who are involved in the care and management of rape survivors in Nigeria. The limited knowledge about tonic immobility as a phenomenon might have resulted in mismanagement and secondary victimization of rape victims experiencing manifestations suggestive of tonic immobility during or after rape. This study was a qualitative narrative inquiry that explored, analysed, and interpreted the lived experiences suggestive of tonic immobility, and the meaning attached to such experiences by victims. A sample of fourteen Nigerian women who self-identified as rape victims was utilized. Individual semi-structured, in-depth interviews were conducted to generate data. Thematic data analysis revealed four overarching themes: namely (i) Tonic immobility as an Altered Physical State, (ii) Tonic Immobility as Mental Paralysis, (iii) Painful Loss of Self-defence, and (iv) Constant Self-blame. The findings provided an insight into the traumatic experience of raped women and the psychological implication of tonic immobility as extreme defence mechanism. This study will prove invaluable to nurses and other professionals/stakeholders involved in the care and management of rape victims; to help them develop and use appropriate strategies for management and prevention of secondary victimisation.

During vigilance to painful stimuli: slower response rate is related to high trait anxiety, whereas faster response rate is related to high state anxiety

A pathological increase in vigilance, or hypervigilance, may be related to pain intensity in some clinical pain syndromes and may result from attention bias to salient stimuli mediated by anxiety. During a continuous performance task where subjects discriminated painful target stimuli from painful nontargets, we measured detected targets (hits), nondetected targets (misses), nondetected nontargets (correct rejections), and detected nontargets (false alarms). Using signal detection theory, we calculated response bias, the tendency to endorse a stimulus as a target, and discriminability, the ability to discriminate a target from nontarget. Owing to the relatively slow rate of stimulus presentation, our primary hypothesis was that sustained performance would result in a more conservative response bias reflecting a lower response rate over time on task. We found a more conservative response bias with time on task and no change in discriminability. We predicted that greater state and trait anxiety would lead to a more liberal response bias. A multivariable model provided partial support for our prediction; high trait anxiety related to a more conservative response bias (lower response rate), whereas high state anxiety related to a more liberal bias. This inverse relationship of state and trait anxiety is consistent with reports of effects of state and trait anxiety on reaction times to threatening stimuli. In sum, we report that sustained attention to painful stimuli was associated with a decrease in the tendency of the subject to respond to any stimulus over time on task, whereas the ability to discriminate target from nontarget remains unchanged.NEW & NOTEWORTHY During a series of painful stimuli requiring subjects to respond to targets, we separated response willingness from ability to discriminate targets from nontargets. Response willingness declined during the task, with no change in subjects' ability to discriminate, consistent with previous vigilance studies. High trait anxious subjects were less willing to respond and showed slower reaction times to hits than low anxious subjects. This study reveals an important role of trait anxiety in pain vigilance.

Peripersonal Space and Bodily Self-Consciousness: Implications for Psychological Trauma-Related Disorders

Peripersonal space (PPS) is defined as the space surrounding the body where we can reach or be reached by external entities, including objects or other individuals. PPS is an essential component of bodily self-consciousness that allows us to perform actions in the world (e.g., grasping and manipulating objects) and protect our body while interacting with the surrounding environment. Multisensory processing plays a critical role in PPS representation, facilitating not only to situate ourselves in space but also assisting in the localization of external entities at a close distance from our bodies. Such abilities appear especially crucial when an external entity (a sound, an object, or a person) is approaching us, thereby allowing the assessment of the salience of a potential incoming threat. Accordingly, PPS represents a key aspect of social cognitive processes operational when we interact with other people (for example, in a dynamic dyad). The underpinnings of PPS have been investigated largely in human models and in animals and include the operation of dedicated multimodal neurons (neurons that respond specifically to co-occurring stimuli from different perceptive modalities, e.g., auditory and tactile stimuli) within brain regions involved in sensorimotor processing (ventral intraparietal sulcus, ventral premotor cortex), interoception (insula), and visual recognition (lateral occipital cortex). Although the defensive role of the PPS has been observed in psychopathology (e.g., in phobias) the relation between PPS and altered states of bodily consciousness remains largely unexplored. Specifically, PPS representation in trauma-related disorders, where altered states of consciousness can involve dissociation from the body and its surroundings, have not been investigated. Accordingly, we review here: (1) the behavioral and neurobiological literature surrounding trauma-related disorders and its relevance to PPS; and (2) outline future research directions aimed at examining altered states of bodily self-consciousness in trauma related-disorders.

Hidden wounds of violence: Abnormal motor oscillatory brain activity is related to posttraumatic stress symptoms

Victims of urban violence are at risk of developing Posttraumatic Stress Disorder (PTSD), one of the most debilitating consequences of violence. Considering that PTSD may be associated with inefficient selection of defensive responses, it is important to understand the relation between motor processing and PTSD. The present study aims to investigate the extent to which the severity of posttraumatic stress symptoms (PTSS) is related to motor preparation against visual threat cues in victims of urban violence. Participants performed a choice reaction time task while ignoring a picture that could be threating or neutral. The EEG indices extracted were the motor-related amplitude asymmetry (MRAA) in the alpha frequency range, and the lateralized readiness potential (LRP). We observed a linear relation between longer LRP latency and a slower reaction time, selectively during threat processing (compared to neutral) in low PTSS, but not in high PTSS participants. Alpha MRAA suppression and the PTSS were also linearly related: the smaller the alpha MRAA suppression in the threat condition relative to neutral, the greater the PTSS. These results provide evidence that threatening cues affect motor processing that is modulated by the severity of PTSS in victims of urban violence.

Maladaptive Alterations of Defensive Response Following Developmental Complex Stress in Rats

Objective

Despite the etiological significance of complex developmental trauma in adult personality disorders and treatment-resistant depression, neurobiological studies have been rare due to the lack of useful animal models. As a first step, we devised an animal model to investigate the effects of multiple trauma-like stress during different developmental periods.

Methods

Twenty-one male Sprague-Dawley rats were classified into 3 groups based on the stress protocol: fear conditioning control (FCC, n = 6), complex stress (ComS, n = 9), and control (n = 6). While the ComS experienced three types of stress (maternal separation, juvenile isolation, electric foot shock), the FCC only experienced an electric foot shock stress and the control never experienced any. We compared fear responses at postnatal day (PND) 29 and PND 56 through freezing time per episode (FTpE), total freezing time (TFT), total freezing episodes (TFE), and ultrasonic vocalization (USV).

Results

ComS showed the longest FTpE in the conditioned fear response test. ComS and FCC exhibited the longer TFT and these two groups only displayed USV. ComS show difference TFE between PND 29 and PND 56.

Conclusion

The results of this investigation show that complex stress may affect not quantity of fear response but characteristics of fear response. Longer FTpE may be associated with tonic immobility which could be considered as a failed self-protective reaction and might be analogous to a sign of inappropriate coping strategy and self-dysregulation in complex trauma patients.

Possible outcomes of cumulative trauma in mental-health: a case report

ABSTRACT To discuss the resilience factors that may have prevented a patient from developing post-traumatic stress disorder (PTSD) after exposure to a variety of severe potentially traumatic events. A thirty-eight-year-old civilian has been exposed to at least ten dramatic situations of violence in his work and personal life. He developed only a few mild post-traumatic symptoms after being exposed to a particularly gruesome incident during work. Even though the number and severity of potentially traumatic events may be alarming, this does not determine that the patient will inexorably develop PTSD, or other disorders. The study of protective factors is mandatory so that we can acknowledge and develop more effective ways to prevent and treat disorders.

Interactions between emotion and action in the brain

A growing literature supports the existence of interactions between emotion and action in the brain, and the central participation of the anterior midcingulate cortex (aMCC) in this regard. In the present functional magnetic resonance imaging study, we sought to investigate the role of self-relevance during such interactions by varying the context in which threating pictures were presented (with guns pointed towards or away from the observer). Participants performed a simple visual detection task following exposure to such stimuli. Except for voxelwise tests, we adopted a Bayesian analysis framework which evaluated evidence for the hypotheses of interest, given the data, in a continuous fashion. Behaviorally, our results demonstrated a valence by context interaction such that there was a tendency of speeding up responses to targets after viewing threat pictures directed towards the participant. In the brain, interaction patterns that paralleled those observed behaviorally were observed most notably in the middle temporal gyrus, supplementary motor area, precentral gyrus, and anterior insula. In these regions, activity was overall greater during threat conditions relative to neutral ones, and this effect was enhanced in the directed towards context. A valence by context interaction was observed in the aMCC too, where we also observed a correlation (across participants) of evoked responses and reaction time data. Taken together, our study revealed the context-sensitive engagement of motor-related areas during emotional perception, thus supporting the idea that emotion and action interact in important ways in the brain.

Making translation work: Harmonizing cross-species methodology in the behavioural neuroscience of Pavlovian fear conditioning

Translational neuroscience bridges insights from specific mechanisms in rodents to complex functions in humans and is key to advance our general understanding of central nervous function. A prime example of translational research is the study of cross-species mechanisms that underlie responding to learned threats, by employing Pavlovian fear conditioning protocols in rodents and humans. Hitherto, evidence for (and critique of) these cross-species comparisons in fear conditioning research was based on theoretical viewpoints. Here, we provide a perspective to substantiate these theoretical concepts with empirical considerations of cross-species methodology. This meta-research perspective is expected to foster cross-species comparability and reproducibility to ultimately facilitate successful transfer of results from basic science into clinical applications.

The effects of trauma on brain and body: A unifying role for the midbrain periaqueductal gray

Post-traumatic stress disorder (PTSD), a diagnosis that may follow the experience of trauma, has multiple symptomatic phenotypes. Generally, individuals with PTSD display symptoms of hyperarousal and of hyperemotionality in the presence of fearful stimuli. A subset of individuals with PTSD; however, elicit dissociative symptomatology (i.e., depersonalization, derealization) in the wake of a perceived threat. This pattern of response characterizes the dissociative subtype of the disorder, which is often associated with emotional numbing and hypoarousal. Both symptomatic phenotypes exhibit attentional threat biases, where threat stimuli are processed preferentially leading to a hypervigilant state that is thought to promote defensive behaviors during threat processing. Accordingly, PTSD and its dissociative subtype are thought to differ in their proclivity to elicit active (i.e., fight, flight) versus passive (i.e., tonic immobility, emotional shutdown) defensive responses, which are characterized by the increased and the decreased expression of the sympathetic nervous system, respectively. Moreover, active and passive defenses are accompanied by primarily endocannabinoid- and opioid-mediated analgesics, respectively. Through critical review of the literature, we apply the defense cascade model to better understand the pathological presentation of defensive responses in PTSD with a focus on the functioning of lower-level midbrain and extended brainstem systems.

Tonic Immobility in PTSD: Exacerbation of Emotional Cardiac Defense Response

Among defensive behaviors, tonic immobility (TI) is considered the last defensive resort when life is at extreme risk. Post-Traumatic Stress Disorder (PTSD) is the main psychiatric consequence resulting from exposure to traumatic events. Increasing evidence indicate an association between peritraumatic tonic immobilility and severity of PTSD. Cardiac defense response, a reactivity to perceived danger or threat, has been studied by recording heart rate changes that follows the presentation of an unpredictable intense auditory aversive stimulus. The aim of this study was to investigate potential distinctiveness in cardiac defense response among PTSD patients who presented – compared to those that did not – TI reaction in the laboratory setting. Patients (N = 17) completed the TI questionnaire for signs of immobility elicited by passive listening to their autobiographical trauma script. After a while, they were exposed to an intense white noise, while electrocardiogram was recorded. The heart rate during the 80 s after the noise, subtracted from baseline, was analyzed. Higher reports of TI to the trauma script were associated with stronger and sustained heart rate accelerations after the noise. The effects on cardiac defense response add to increasing evidence that some PTSD patients are prone to repeated re-experiences of TI, which may implicate in a potentially distinct pathophysiology and even a new PTSD subtype.

Modulation of tonic immobility by GABAA and GABAB receptors of the medial amygdala

Tonic immobility (TI) is a temporary state of profound motor inhibition associated with great danger as the attack of a predator. Previous studies carried out in our laboratory evidenced high Fos-IR in the posteroventral region of the medial nucleus of the amygdala (MEA) after induction of the TI response. Here, we investigated the effects of GABA_A and GABA_B of the MEA on TI duration. Intra-MEA injections of the GABA_A agonist muscimol and GABA_B agonist baclofen reduced TI response, while intra-MEA injections of the GABA_A antagonist bicuculline and GABA_B antagonist phaclofen increased the TI response. Moreover, the effects observed with muscimol and baclofen administrations into MEA were blocked by pretreatment with bicuculline and phaclofen (at ineffective doses per se). Finally, the activation of GABA_A and GABA_B receptors in the MEA did not alter the spontaneous motor activity in the open field test. These data support the role of the GABAergic system of the MEA in the modulation of innate fear.

Hands Up! Atypical Defensive Reactions in Heavy Players of Violent Video Games When Exposed to Gun-Attack Pictures

Threatening cues and surrounding contexts trigger specific defensive response patterns. Posturography, a technique for measuring postural strategies, has been used to evaluate motor defensive reactions in humans. When exposed to gun pointed pictures, humans were shown to exhibit an immobility reaction. Short and long-term exposure to violent video games was shown to be a causal risk factor for increased violent and aggressive behavior. Assaultive violence with a gun is a major trigger for motor defensive reactions, and post-traumatic stress disorder (PTSD) is the most characteristic psychiatric sequelae. Recent studies point to links between PTSD symptoms and emotional shortfalls in non-clinical trauma-exposed samples. The present study investigated defensive reactions to gun threat and PTSD symptoms in heavy players of violent video games compared to non-players. Male university students were screened according to use of violent video games and divided in three groups: non-players, moderate players, and heavy players. Stimuli were pictures depicting a man pointing a gun directed at the participant. In matched control pictures, non-lethal objects replaced the gun. Posturography was recorded and PTSD symptoms were assessed. When exposed to the threat pictures, non-players exhibited the expected reduction in amplitude of body sway (immobility), heavy players presented atypical augmented amplitude of body sway, and moderate players showed intermediate reactivity. Heavy players presented a significant distinct reaction compared to non-players. They also scored significantly higher in PTSD symptoms than non-players. Disadvantageous defensive reactions and higher vulnerability to PTSD symptoms, revealed in the present study, add to other shortcomings for heavy players.

Assessing Post-Traumatic Tonic Immobility Responses: The Scale for Tonic Immobility Occurring Post-Trauma

BACKGROUND

Peri-traumatic tonic immobility has been associated with the development and course of post-traumatic stress disorder. Despite serving as an adaptive late-stage defense response, tonic immobility that continues in response to post-traumatic reminders may lead to reduced functioning and a diminished sense of well-being. At present, no validated self-report measures assess post-traumatic tonic immobility responses specifically.

METHODS

The primary objective of the present study was to evaluate the Scale for Tonic immobility Occurring Post-trauma (STOP), the first self-report measure developed to assess for the presence and severity of tonic immobility responses that persist following trauma exposure as part of post-traumatic symptomatology. Trauma-exposed clinical and non-clinical participants (N = 462) with a history of tonic immobility completed a demographic questionnaire, the STOP, and measures of post-traumatic symptoms, dissociation, anxiety, and depression.

RESULTS

STOP assessed four latent constructs, which were interpreted following the human defense cascade model. Together, these factors capture the sensorimotor and perceptual alterations, and dissociative experiences, associated with post-traumatic tonic immobility as a trauma-related altered state. Residual symptoms and the experience of negative affect following this response (including guilt and shame) are also represented. STOP scores demonstrated excellent reliability, as well as good construct and convergent validity, with other measures of dissociation and post-traumatic stress disorder. Results from the present study suggest tonic immobility is most consistent with other dissociative post-traumatic symptomatology.

CONCLUSIONS

STOP demonstrates excellent preliminary psychometric properties and may be useful for researchers and clinicians wishing to assess chronic forms of tonic immobility across trauma-exposed, clinical and community samples.

Tonic immobility during re-experiencing the traumatic event in posttraumatic stress disorder

Tonic Immobility (TI) is an evolved defence response, characterized by physical immobility. Peritraumatic TI has been linked to posttraumatic stress disorder (PTSD). However, samples sizes in clinical studies have been small, and little is known about TI reactions post trauma, for instance during trauma reminders. The prevalence of peritraumatic TI and TI during re-experiencing the traumatic event was examined by self-report in 184 patients with chronic PTSD. Moderate peritraumatic TI was reported by 26.6% of the participants (n = 49) and extreme peritraumatic TI by 52.2% (n = 96). During re-experiencing the traumatic event, 35.3% (n = 65) reported moderate TI, and 37.0% (n = 68) extreme TI. Peritraumatic TI was related to PTSD symptom severity and TI during re-experiencing mediated this relationship. In line with previous findings, reports of peritraumatic TI were high among PTSD patients. In addition, we showed that it often re-occurred during re-experiencing the traumatic event. The prevalence of TI at different stages post trauma warrants future study.

A Review of the Neurobiological Basis of Trauma-Related Dissociation and Its Relation to Cannabinoid- and Opioid-Mediated Stress Response: a Transdiagnostic, Translational Approach

Dissociative experiences have been associated with increased disease severity, chronicity, and, in some cases, reduced treatment response across trauma-related and other psychiatric disorders. A better understanding of the neurobiological mechanisms through which dissociative experiences occur may assist in identifying novel pharmacological and non-pharmacological treatment approaches. Here, we review emerging work on the dissociative subtype of posttraumatic stress disorder (PTSD), and other trauma-related disorders providing evidence for two related overarching neurobiological models of dissociation, the defense cascade model of dissociation and Mobb's threat detection model. In particular, we review neuroimaging studies highlighting alterations in functional connectivity of key brain regions associated with these models, including connectivity between the prefrontal cortex, the amygdala and its complexes, the insula, and the periaqueductal gray. Work implicating the kappa-opioid and endocannabinoid systems in trauma-related dissociative experiences is also reviewed. Finally, we hypothesize mechanisms by which pharmacological modulation of these neurochemical systems may serve as promising transdiagnostic treatment modalities for individuals experiencing clinically significant levels of dissociation. Specifically, whereas kappa-opioid receptor antagonists may serve as a pharmacological vehicle for the selective targeting of dissociative symptoms and associated emotion overmodulation in the dissociative subtype of posttraumatic stress disorder and transdiagnostically, modulation of the endocannabinoid system may reduce symptoms associated with emotional undermodulation of the fight or flight components of the defense cascade model.

A review of thanatosis (death feigning) as an anti-predator behaviour

Abstract

Thanatosis—also known as death-feigning and, we argue more appropriately, tonic immobility (TI)—is an under-reported but fascinating anti-predator strategy adopted by diverse prey late on in the predation sequence, and frequently following physical contact by the predator. TI is thought to inhibit further attack by predators and reduce the perceived need of the predator to subdue prey further. The behaviour is probably present in more taxa than is currently described, but even within well-studied groups the precise taxonomic distribution is unclear for a number of practical and ethical reasons. Here we synthesise the key studies investigating the form, function, evolutionary and ecological costs and benefits of TI. This review also considers the potential evolutionary influence of certain predator types in the development of the strategy in prey, and the other non-defensive contexts in which TI has been suggested to occur. We believe that there is a need for TI to be better appreciated in the scientific literature and outline potentially profitable avenues for investigation. Future use of technology in the wild should yield useful developments for this field of study.

Significance statement

Anti-predatory defences are crucial to many aspects of behavioural ecology. Thanatosis (often called death-feigning) has long been an under-appreciated defence, despite being taxonomically and ecologically widespread. We begin by providing much-needed clarification on both terminology and definition. We demonstrate how apparently disparate observations in the recent literature can be synthesised through placing the behaviour within a cost-benefit framework in comparison to alternative behavioural choices, and how aspects of the ecology differentially affect costs and benefits. Extending this, we provide novel insights into why the evolution of thanatosis can be understood in terms of coevolution between predators and prey. We offer further novel hypotheses, and discuss how these can be tested, focussing on how emerging technologies can be of great use in developing our understanding of thanatosis in free-living animals.

Mental Simulation of Painful Situations Has an Impact on Posture and Psychophysiological Parameters

Embodiment is made possible by the ability to imagine ourselves in a particular situation (mental simulation). Postural changes have been demonstrated in response to painful situations, but the effect of an implicit instruction has not been studied. The present study was designed to record differential responses according to whether or not subjects were instructed to imagine themselves in a painful or non-painful situation. Painful stimuli and instructions to mentally simulate the displayed situation were hypothesized to induce postural changes that could be demonstrated by changes in the center of pressure (COP) trajectory compared to viewing the same stimuli with no instructions. We hypothesized that mental simulation of a painful situation would induce embodiment of the emotional situation as reflected by posterior displacement of the COP and physiological responses as compared to passive observation of the same visual scene. Thirty-one subjects participated in this study while standing quietly on a posturographic platform with presentation of visual stimuli depicting scenes defining three experimental conditions (painful, non-painful and neutral situations) for 12 s. Physiological measurements [heart rate (HR) and electrodermal activity] and postural responses (COP displacements) were recorded in response to the stimuli with or without instructions to imagine themselves in the situation. Time-course analyses (1 s sliding window) were conducted for several postural parameters, HR and electrodermal response. An interaction effect (instruction × stimuli × time) demonstrated that mental simulation induced posterior displacement of the mean position of the COP at different times during presentation of visual stimuli (4 s; 9-12 s). An effect of instruction was reported for HR (HR was higher in the mental simulation condition), while a stimulation effect was reported only for HR (lower for painful stimuli than for non-painful stimuli). The results of time-course analyses demonstrated embodiment of painful situations by postural control modulations and physiological changes depending on whether or not the participants were instructed to imagine themselves in the situation.