Defensive freezing and its relation to approach-avoidance decision-making under threat

Pupil dilation reflects effortful action invigoration in overcoming aversive Pavlovian biases

"Pavlovian" or "motivational" biases describe the phenomenon that the valence of prospective outcomes modulates action invigoration: Reward prospect invigorates action, whereas punishment prospect suppresses it. The adaptive role of these biases in decision-making is still unclear. One idea is that they constitute a fast-and-frugal decision strategy in situations characterized by high arousal, e.g., in presence of a predator, which demand a quick response. In this pre-registered study (N = 35), we tested whether such a situation-induced via subliminally presented angry versus neutral faces-leads to increased reliance on Pavlovian biases. We measured trial-by-trial arousal by tracking pupil diameter while participants performed an orthogonalized Motivational Go/NoGo Task. Pavlovian biases were present in responses, reaction times, and even gaze, with lower gaze dispersion under aversive cues reflecting "freezing of gaze." The subliminally presented faces did not affect responses, reaction times, or pupil diameter, suggesting that the arousal manipulation was ineffective. However, pupil dilations reflected facets of bias suppression, specifically the physical (but not cognitive) effort needed to overcome aversive inhibition: Particularly strong and sustained dilations occurred when participants managed to perform Go responses to aversive cues. Conversely, no such dilations occurred when they managed to inhibit responses to Win cues. These results suggest that pupil diameter does not reflect response conflict per se nor the inhibition of prepotent responses, but specifically effortful action invigoration as needed to overcome aversive inhibition. We discuss our results in the context of the "value of work" theory of striatal dopamine.

The neurocomputational link between defensive cardiac states and approach-avoidance arbitration under threat

Avoidance, a hallmark of anxiety-related psychopathology, often comes at a cost; avoiding threat may forgo the possibility of a reward. Theories predict that optimal approach-avoidance arbitration depends on threat-induced psychophysiological states, like freezing-related bradycardia. Here we used model-based fMRI analyses to investigate whether and how bradycardia states are linked to the neurocomputational underpinnings of approach-avoidance arbitration under varying reward and threat magnitudes. We show that bradycardia states are associated with increased threat-induced avoidance and more pronounced reward-threat value comparison (i.e., a stronger tendency to approach vs. avoid when expected reward outweighs threat). An amygdala-striatal-prefrontal circuit supports approach-avoidance arbitration under threat, with specific involvement of the amygdala and dorsal anterior cingulate (dACC) in integrating reward-threat value and bradycardia states. These findings highlight the role of human freezing states in value-based decision making, relevant for optimal threat coping. They point to a specific role for amygdala/dACC in state-value integration under threat.

Dorsal hippocampus represents locations to avoid as well as locations to approach during approach-avoidance conflict

Worrying about perceived threats is a hallmark of multiple psychological disorders including anxiety. This concern about future events is particularly important when an individual is faced with an approach-avoidance conflict. Potential goals to approach are known to be represented in the dorsal hippocampus during theta sweeps. Similarly, important non-local information is represented during hippocampal high synchrony events (HSEs), which are correlated with sharp-wave ripples (SWRs). It is likely that potential future threats may be similarly represented. We examined how threats and rewards were represented within the hippocampus during approach-avoidance conflicts in rats faced with a predator-like robot guarding a food reward. We found representations of the pseudo-predator during HSEs when hesitating in the nest, and during theta prior to retreating as the rats approached the pseudo-predator. After the first attack, we observed new place fields appearing at the location of the robot (not the location the rat was when attacked). The anxiolytic diazepam reduced anxiety-like behavior and altered hippocampal local field potentials, including reducing SWRs, suggesting that one potential mechanism of diazepam's actions may be through altered representations of imagined threat. These results suggest that hippocampal representation of potential threats could be an important mechanism that underlies worry and a potential target for anxiolytics.

The anterior cingulate cortex and its interface with the dorsal periaqueductal grey regulating nitric oxide-mediated panic-like behaviour and defensive antinociception

The anterior cingulate cortex (ACC) Cg1 (24b) area modulates glutamate-mediated unconditioned fear and antinociception organised by hypothalamus. However, it remains unknown whether 24b area also modulates these latter defensive responses through connections with the dorsal periaqueductal grey matter (dPAG), a midbrain structure implicated in the genesis of innate fear-induced defence. The aim of this work is to examine the correlation between the behavioural effects of intra-ACC microinjections of vehicle, NMDA (1 nmol) or lidocaine (2%) with Fos protein expression and nitrergic activity in the dPAG of male C57BL/6 mice that were threatened by snakes. In addition, the 24b area-dPAG pathways were also characterised by neural tract tracing procedures. Finally, the effect of dPAG pretreatment with the neuronal nitric oxide synthase inhibitor N(omega)-propyl-l-arginine (NPLA; 0.2, 0.4 or 0.8 nmol) 10 min before 24b area treatment with NMDA on behavioural and nociceptive responses of threatened mice was studied. The activation of 24b area N-methyl-d-aspartic acid receptors facilitated escape and freezing rather than risk assessment, and enhanced Fos expression and nitrite levels in dPAG, while lidocaine decreased escape and risk assessment as well as Fos and nitrergic activity in dPAG. In addition, dPAG pretreatment with NPLA suppressed intra-24b NMDA-facilitated panicogenic effects while increased nociception. Infusions of an antegrade neurotracer into 24b area showed axonal fibres surrounding both dorsomedial and dorsolateral PAG perikarya. Neurons were identified in 24b area after deposits of a retrograde neurotracer into dPAG. Our findings suggest that the ACC/24b area modulates innate defensive responses through the recruitment of dPAG nitrergic neurons.

The empirical status of predictive coding and active inference

Research on predictive processing models has focused largely on two specific algorithmic theories: Predictive Coding for perception and Active Inference for decision-making. While these interconnected theories possess broad explanatory potential, they have only recently begun to receive direct empirical evaluation. Here, we review recent studies of Predictive Coding and Active Inference with a focus on evaluating the degree to which they are empirically supported. For Predictive Coding, we find that existing empirical evidence offers modest support. However, some positive results can also be explained by alternative feedforward (e.g., feature detection-based) models. For Active Inference, most empirical studies have focused on fitting these models to behavior as a means of identifying and explaining individual or group differences. While Active Inference models tend to explain behavioral data reasonably well, there has not been a focus on testing empirical validity of active inference theory per se, which would require formal comparison to other models (e.g., non-Bayesian or model-free reinforcement learning models). This review suggests that, while promising, a number of specific research directions are still necessary to evaluate the empirical adequacy and explanatory power of these algorithms.

Perceptual control or action-selection? Comment on: a perceptual control theory of emotional action

The Perceptual Control Theory of Emotional Action provides a compelling view of the synergy between action and perception in the context of emotion. In this invited response, we outline three suggestions to further clarify and concretesise the theory in the hope that it can provide a solid basis for the theoretical, empirical, and clinical fields of emotion and emotion regulation. First, we emphasise the importance of concretesising these ideas in a way that is biologically plausible and testable in terms of its neuronal implementation, which has not been addressed in the main manuscript. Secondly, we highlight the challenges for this account to effectively describe core symptoms in emotional disorders, an essential step if the theory aims to foster the development of better-tuned neurocognitively grounded interventions. Finally, we take a leap on what action-oriented accounts of emotion can mean for the field of emotion regulation.

Motor inhibition impacts the motor interference effect of dangerous objects based on a prime-target grasping consistency judgment task

Whether motor inhibition impacts the motor interference effect of dangerous objects is controversial. Previous studies have manipulated task type and found that dangerous objects elicited increased motor inhibition compared to safe objects in the reachability judgment task but not in the categorization task. However, it was still unclear why motor inhibition was reduced for dangerous objects in the categorization task. We speculated that the activation strength of object affordance might modulate the occurrence of motor inhibition. To test this hypothesis, the present study designed a prime-target grasping consistency judgment task and manipulated target grips (power grip vs. precision grip), target dangerousness (dangerous vs. safe), and Go/NoGo (Go vs. NoGo). The results showed that under the condition of high activation strength of the target affordance (i.e., power grip targets), processing dangerous targets evoked increased motor inhibition (reflected by a more negative frontal N2 component) compared to safe targets and produced a motor interference effect in reaction time (RT). In contrast, under the condition of low target affordance activation strength (i.e., precision grip targets), processing dangerous targets facilitated RT compared to safe targets, with no difference found between the dangerous and safe conditions in the frontal N2 component. Furthermore, compared to safe objects, dangerous objects attracted more attention and recruited more cognitive resources to select appropriate responses to them. This study extended the findings of previous studies on the motor interference effect by highlighting the importance of activation strength for eliciting motor inhibition based on the prime-target consistency judgment task.

The influence of aggressive exercise on responses to self-perceived and others' pain

Previous studies have reported relationships between exercise and pain. However, little is known about how aggressive exercise modulates individuals' responses to their own and others' pain. This present study addresses this question by conducting 2 studies employing event-related potential (ERP). Study 1 included 38 participants whose self-perceived pain was assessed after intervention with aggressive or nonaggressive exercises. Study 2 recruited 36 participants whose responses to others' pain were assessed after intervention with aggressive or nonaggressive exercise. Study 1's results showed that P2 amplitudes were smaller, reaction times were longer, and participants' judgments were less accurate in response to self-perceived pain stimuli, especially to high-pain stimuli, after intervention with aggressive exercise compared to nonaggressive exercise. Results of study 2 showed that both P3 and LPP amplitudes to others' pain were larger after intervention with aggressive exercise than with nonaggressive exercise. These results suggest that aggressive exercise decreases individuals' self-perceived pain and increases their empathic responses to others' pain.

Emotion regulation from an action-control perspective

Despite increasing interest in emotional processes in cognitive science, theories on emotion regulation have remained rather isolated, predominantly focused on cognitive regulation strategies such as reappraisal. However, recent neurocognitive evidence suggests that early emotion regulation may involve sensorimotor control in addition to other emotion-regulation processes. We propose an action-oriented view of emotion regulation, in which feedforward predictions develop from action-selection mechanisms. Those can account for acute emotional-action control as well as more abstract instances of emotion regulation such as cognitive reappraisal. We argue the latter occurs in absence of overt motor output, yet in the presence of full-blown autonomic, visceral, and subjective changes. This provides an integrated framework with testable neuro-computational predictions and concrete starting points for intervention to improve emotion control in affective disorders.

The Nature and Neurobiology of Fear and Anxiety: State of the Science and Opportunities for Accelerating Discovery

Fear and anxiety play a central role in mammalian life, and there is considerable interest in clarifying their nature, identifying their biological underpinnings, and determining their consequences for health and disease. Here we provide a roundtable discussion on the nature and biological bases of fear- and anxiety-related states, traits, and disorders. The discussants include scientists familiar with a wide variety of populations and a broad spectrum of techniques. The goal of the roundtable was to take stock of the state of the science and provide a roadmap to the next generation of fear and anxiety research. Much of the discussion centered on the key challenges facing the field, the most fruitful avenues for future research, and emerging opportunities for accelerating discovery, with implications for scientists, funders, and other stakeholders. Understanding fear and anxiety is a matter of practical importance. Anxiety disorders are a leading burden on public health and existing treatments are far from curative, underscoring the urgency of developing a deeper understanding of the factors governing threat-related emotions.

Exploring hazard anticipation and stress while driving in light of defensive behavior theory

In driving, poor hazard anticipation would provide drivers less time to prepare an appropriate response, increasing the urgency of the situation and generating more stress. Assuming this, the current study seeks to determine whether a predictable road hazard triggers hazard anticipation in drivers that can mitigate the ensuing stress response, and whether the stress response is influenced by driving experience. In a simulated road environment, a cue was used to trigger hazard anticipation, and a road hazard to induce a stress response. Heart rate, pupil diameter, driving speed, subjective stress, arousal, and negative emotions, were retrieved from 36 drivers who all faced the cue followed by the hazard (i.e. a predictable hazard), the cue only, and the hazard only. In the light of work on defensive behaviors, the findings indicate that a predictable hazard triggers hazard anticipation detectable via (1) freezing behavior-characterized by cardiac deceleration-(2) anticipatory pupil dilation and (3) anticipatory speed deceleration. The results also point to a beneficial role for hazard anticipation in reducing driver stress, as evidenced by reductions in peak heart rate levels, as well as in reported levels of stress and negative emotions. Finally, the findings showed an influence of driving experience on reported levels of stress. Overall, this study shows how previous work on defensive behaviors can be used to gain insight into the processes and driving behaviors involved in hazard anticipation and stress.

Validation of the neuroconnective endophenotype questionnaire (NEQ): a new clinical tool for medicine and psychiatry resulting from the contribution of Ehlers-Danlos syndrome

Introduction

The link between anxiety disorders and joint hypermobility syndrome (now under hypermobility spectrum disorders, which include hypermobile Ehlers-Danlos syndrome) has been widely replicated over the past 30 years and has grown beyond the initial nosological limits. To integrate clinical and research progress in this field, a new neuroconnective endophenotype (NE) and its corresponding instrument, the Neuroconnective Endophenotype Questionnaire (NEQ), have been developed. This new clinical construct, created with the active participation of patients, includes both somatic and psychological dimensions and symptoms and resilience items.

Methods

The NE includes five dimensions: (1) sensorial sensitivity, (2) body signs and symptoms, (3) somatic conditions, (4) polar behavioral strategies, and (5) psychological and psychopathological dimensions. The NEQ information is collected through four self-administered questionnaires (sensorial sensitivity, body signs and symptoms, polar behavioral strategies, and psychological characteristics) and a structured diagnostic part that should be completed by a trained observer. This hetero-administered part incorporates (a) psychiatric diagnoses (using structured criteria, e.g., MINI), (b) somatic disorders diagnosis, using structured criteria, and (c) assessment of joint hypermobility criteria.

Results

In a sample of 36 anxiety cases with 36 matched controls, the NEQ obtained high scores for test-retest, inter-rater reliability, and internal consistency. As for predictive validity, cases and controls significantly differed in all five dimensions and hypermobility measurements.

Discussion

We can conclude that the NEQ has achieved acceptable reliability and validity values and, therefore, is ready to be used and tested in different samples. This original and consistent construct including somatic and mental items may improve clinical specificity, the search for more comprehensive therapies, and their genetic and neuroimaging bases.

Quantifying aberrant approach-avoidance conflict in psychopathology: A review of computational approaches

Making effective decisions during approach-avoidance conflict is critical in daily life. Aberrant decision-making during approach-avoidance conflict is evident in a range of psychological disorders, including anxiety, depression, trauma-related disorders, substance use disorders, and alcohol use disorders. To help clarify etiological pathways and reveal novel intervention targets, clinical research into decision-making is increasingly adopting a computational psychopathology approach. This approach uses mathematical models that can identify specific decision-making related processes that are altered in mental health disorders. In our review, we highlight foundational approach-avoidance conflict research, followed by more in-depth discussion of computational approaches that have been used to model behavior in these tasks. Specifically, we describe the computational models that have been applied to approach-avoidance conflict (e.g., drift-diffusion, active inference, and reinforcement learning models), and provide resources to guide clinical researchers who may be interested in applying computational modeling. Finally, we identify notable gaps in the current literature and potential future directions for computational approaches aimed at identifying mechanisms of approach-avoidance conflict in psychopathology.

Spontaneous instrumental avoidance learning in social contexts

Adaptation to our social environment requires learning how to avoid potentially harmful situations, such as encounters with aggressive individuals. Threatening facial expressions can evoke automatic stimulus-driven reactions, but whether their aversive motivational value suffices to drive instrumental active avoidance remains unclear. When asked to freely choose between different action alternatives, participants spontaneously-without instruction or monetary reward-developed a preference for choices that maximized the probability of avoiding angry individuals (sitting away from them in a waiting room). Most participants showed clear behavioral signs of instrumental learning, even in the absence of an explicit avoidance strategy. Inter-individual variability in learning depended on participants' subjective evaluations and sensitivity to threat approach feedback. Counterfactual learning best accounted for avoidance behaviors, especially in participants who developed an explicit avoidance strategy. Our results demonstrate that implicit defensive behaviors in social contexts are likely the product of several learning processes, including instrumental learning.

The gene environment aetiology of freezing and its relationship with internalizing symptoms during adolescence

Background

The freezing response is a universal response to threat, linked to attentive immobility and action preparation. It is relevant for acute stress coping in animals and humans, and subtle deviations in toddler freezing duration (absence of, or excessively long reactions) have been linked to higher risk for internalizing symptoms in adolescence. Yet, while individual freezing tendencies are relatively stable throughout life, little is known about their gene-environment aetiology.

Methods

We investigated the heritability of toddler freezing in the Quebec Newborn Twin Study (QNTS; n=508 twins) by fitting behavioural genetic models to video-coded freezing responses during a robot confrontation. Furthermore, we examined the predictive associations between toddler freezing and internalizing symptoms (anxiety and depressive symptoms), as they unfold during adolescence (ages 12–19 years) using linear mixed-effects models.

Findings

Freezing was found to be moderately heritable (45% of the variance accounted for by genetic factors). The remaining variance was explained by unique environmental factors, including measurement error. No significant contribution of shared environmental factors was noted. Additionally, shorter freezing was associated with more internalizing symptoms in adolescence at trend level, a pattern that was significant for depressive but not anxiety symptoms.

Interpretation

Freezing is an adaptive coping mechanism in early childhood, which is partly driven by genetic factors. Crucially, the absence or shorter duration of these behaviours may signal vulnerability to depressive problems later in life.

Funding

Canadian Institutes of Health Research and Research Fund of Quebec–Health and Society and Culture. Consolidator grant from the European Research Council (ERC_CoG-2017_772337).

Freezing revisited: coordinated autonomic and central optimization of threat coping

Animals have sophisticated mechanisms for coping with danger. Freezing is a unique state that, upon threat detection, allows evidence to be gathered, response possibilities to be previsioned and preparations to be made for worst-case fight or flight. We propose that - rather than reflecting a passive fear state - the particular somatic and cognitive characteristics of freezing help to conceal overt responses, while optimizing sensory processing and action preparation. Critical for these functions are the neurotransmitters noradrenaline and acetylcholine, which modulate neural information processing and also control the sympathetic and parasympathetic branches of the autonomic nervous system. However, the interactions between autonomic systems and the brain during freezing, and the way in which they jointly coordinate responses, remain incompletely explored. We review the joint actions of these systems and offer a novel computational framework to describe their temporally harmonized integration. This reconceptualization of freezing has implications for its role in decision-making under threat and for psychopathology.

Acute threat enhances perceptual sensitivity without affecting the decision criterion

Threatening situations ask for rapid and accurate perceptual decisions to optimize coping. Theoretical models have stated that psychophysiological states, such as bradycardia during threat-anticipatory freezing, may facilitate perception. However, it’s unclear if this occurs via enhanced bottom-up sensory processing or by relying more on prior expectations. To test this, 52 (26 female) participants completed a visual target-detection paradigm under threat-of-shock (15% reinforcement rate) with a manipulation of prior expectations. Participants judged the presence of a backward-masked grating (target presence rate 50%) after systematically manipulating their decision criterion with a rare (20%) or frequent (80%) target presence rate procedure. Threat-of-shock induced stronger heart rate deceleration compared to safe, indicative of threat-anticipatory freezing. Importantly, threat-of-shock enhanced perceptual sensitivity but we did not find evidence of an altered influence of the effect of prior expectations on current decisions. Correct target detection (hits) was furthermore accompanied by an increase in the magnitude of this heart rate deceleration compared to a missed target. While this was independent of threat-of-shock manipulation, only under threat-of-shock this increase was accompanied by more hits and increased sensitivity. Together, these findings suggest that under acute threat participants may rely more on bottom-up sensory processing versus prior expectations in perceptual decision-making. Critically, bradycardia may underlie such enhanced perceptual sensitivity.

Human defensive freezing: Associations with hair cortisol and trait anxiety

The anticipation of threat facilitates innate defensive behaviours including freezing reactions. Freezing in humans is characterised by reductions in body sway and heart rate. Limited evidence suggests that individual differences in freezing reactions are associated with predictors of anxiety-related psychopathology including trait anxiety and hypothalamic-pituitary-adrenal (HPA) axis activity. However, previous human studies focused on acutely circulating cortisol levels, leaving the link between freezing and more stable, individual trait markers of HPA axis activity unclear. We investigated whether individual differences in anticipatory freezing reactions are predicted by accumulated hair cortisol concentrations (HCC) and trait anxiety, in a well-powered mixed sample of police recruits at the start of the police training, and age, sex and education matched controls (total N = 419, mean age = 24, N_women = 106, N_{police recruits} = 337). Freezing-related reactions were assessed with posturographic and heart rate measurements during an active shooting task under threat of shock. The anticipation of threat of shock elicited the expected reductions in body sway and heart rate, indicative of human freezing. Individual differences in threat-related reductions in body sway, but not heart rate, were related to lower HCC and higher trait anxiety. The observed links between postural freezing and predictors of anxiety-related psychopathology suggest the potential value of defensive freezing as a somatic marker for individual differences in stress-vulnerability and resilience. DATA AVAILABILITY: The datasets analysed during the current study are available from the corresponding authors upon reasonable request.