Proximal threats promote enhanced acquisition and persistence of reactive fear-learning circuits

Oscillatory correlates of threat imminence during virtual navigation

The Predatory Imminence Continuum Theory proposes that defensive behaviors depend on the proximity of a threat. While the neural mechanisms underlying this proposal are well studied in animal models, it remains poorly understood in humans. To address this issue, we recorded EEG from 24 (15 female) young adults engaged in a first-person virtual reality Risk-Reward interaction task. On each trial, participants were placed in a virtual room and presented with either a threat or reward conditioned stimulus (CS) in the same room location (proximal) or different room location (distal). Behaviorally, all participants learned to avoid the threat-CS, with most using the optimal behavior to actively avoid the proximal threat-CS (88% accuracy) and passively avoid the distal threat-CS (69% accuracy). Similarly, participants learned to actively approach the distal reward-CS (82% accuracy) and to remain passive to the proximal reward-CS (72% accuracy). At an electrophysiological level, we observed a general increase in theta power (4-8 Hz) over the right posterior channel P8 across all conditions, with the proximal threat-CS evoking the largest theta response. By contrast, distal cues induced two bursts of gamma (30-60 Hz) power over midline-parietal channel Pz (200 msec post-cue) and right frontal channel Fp2 (300 msec post-cue). Interestingly, the first burst of gamma power was sensitive to the distal threat-CS and the second burst at channel Fp2 was sensitive to the distal reward-CS. Together, these findings demonstrate that oscillatory processes differentiate between the spatial proximity information during threat and reward encoding, likely optimizing the selection of the appropriate behavioral response.

Fear in action: Fear conditioning and alleviation through body movements

Fear memories enhance survival especially when the memories guide defensive movements to minimize harm. Accordingly, fear memories and body movements have tight relationships in animals: Fear memory acquisition results in adapting reactive defense movements, while training active defense movements reduces fear memory. However, evidence in humans is scarce because their movements are typically suppressed in experiments. Here, we tracked adult participants' body motions while they underwent ecologically valid fear conditioning in a 3D virtual space. First, with body motion tracking, we revealed that distinct spatiotemporal body movement patterns emerge through fear conditioning. Second, subsequent training to actively avoid threats with naturalistic defensive actions led to a long-term (24 h) reduction of physiological and embodied conditioned responses, while extinction or vicarious training only transiently reduced the responses. Together, our results highlight the role of body movements in human fear memory and its intervention.

Conscious expectancy rather than associative strength elicits brain activity during single-cue fear conditioning

The neurocognitive processes underlying Pavlovian conditioning in humans are still largely debated. The conventional view is that conditioned responses (CRs) emerge automatically as a function of the contingencies between a conditioned stimulus (CS) and an unconditioned stimulus (US). As such, the associative strength model asserts that the frequency or amplitude of CRs reflects the strength of the CS-US associations. Alternatively, the expectation model asserts that the presentation of the CS triggers conscious expectancy of the US, which is responsible for the production of CRs. The present study tested the hypothesis that there are dissociable brain networks related to the expectancy and associative strength theories using a single-cue fear conditioning paradigm with a pseudo-random intermittent reinforcement schedule during functional magnetic resonance imaging. Participants' (n = 21) trial-by-trial expectations of receiving shock displayed a significant linear effect consistent with the expectation model. We also found a positive linear relationship between the expectancy model and activity in frontoparietal brain areas including the dorsolateral prefrontal cortex (PFC) and dorsomedial PFC. While an exploratory analysis found a linear relationship consistent with the associated strength model in the insula and early visual cortex, our primary results are consistent with the view that conscious expectancy contributes to CRs.

Neighborhood Disadvantage and Neural Correlates of Threat and Reward Processing in Survivors of Recent Trauma

Importance

Differences in neighborhood socioeconomic characteristics are important considerations in understanding differences in risk vs resilience in mental health. Neighborhood disadvantage is associated with alterations in the function and structure of threat neurocircuitry.

Objective

To investigate associations of neighborhood disadvantage with white and gray matter and neural reactivity to positive and negative stimuli in the context of trauma exposure.

Design, Setting, and Participants

In this cross-sectional study, survivors of trauma who completed sociodemographic and posttraumatic symptom assessments and neuroimaging were recruited as part of the Advancing Understanding of Recovery After Trauma (AURORA) study between September 2017 and June 2021. Data analysis was performed from October 25, 2022, to February 15, 2023.

Exposure

Neighborhood disadvantage was measured with the Area Deprivation Index (ADI) for each participant home address.

Main Outcomes and Measures

Participants completed separate threat and reward tasks during functional magnetic resonance imaging. Diffusion-weighted and high-resolution structural images were also collected. Linear models assessed the association of ADI with reactivity, microstructure, and macrostructure of a priori regions of interest after adjusting for income, lifetime trauma, sex at birth, and age. A moderated-mediation model tested whether ADI was associated with neural activity via microstructural changes and if this was modulated by PTSD symptoms.

Results

A total of 280 participants (183 females [65.4%]; mean [SD] age, 35.39 [13.29] years) completed the threat task and 244 participants (156 females [63.9%]; mean [SD] age, 35.10 [13.26] years) completed the reward task. Higher ADI (per 1-unit increase) was associated with greater insula (t274 = 3.20; β = 0.20; corrected P = .008) and anterior cingulate cortex (ACC; t274 = 2.56; β = 0.16; corrected P = .04) threat-related activity after considering covariates, but ADI was not associated with reward reactivity. Greater disadvantage was also associated with altered microstructure of the cingulum bundle (t274 = 3.48; β = 0.21; corrected P = .001) and gray matter morphology of the ACC (cortical thickness: t273 = -2.29; β = -0.13; corrected P = .02; surface area: t273 = 2.53; β = 0.13; corrected P = .02). The moderated-mediation model revealed that ADI was associated with ACC threat reactivity via cingulum microstructural changes (index of moderated mediation = -0.02). However, this mediation was only present in individuals with greater PTSD symptom severity (at the mean: β = -0.17; standard error = 0.06, t= -2.28; P = .007; at 1 SD above the mean: β = -0.28; standard error = 0.08; t = -3.35; P < .001).

Conclusions and Relevance

In this study, neighborhood disadvantage was associated with neurobiology that supports threat processing, revealing associations of neighborhood disadvantage with neural susceptibility for PTSD and suggesting how altered structure-function associations may complicate symptoms. Future work should investigate specific components of neighborhood disadvantage that may be associated with these outcomes.

Should perception of emotions be classified according to threat detection rather than emotional valence? An updated meta-analysis for a whole-brain atlas of emotional faces processing

BACKGROUND

Human navigation of social interactions relies on the processing of emotion on faces. This meta-analysis aimed to produce an updated brain atlas of emotional face processing from whole-brain studies based on a single emotional face-viewing paradigm (PROSPERO CRD42022251548).

METHODS

We conducted a systematic literature search of Embase, MEDLINE and PsycINFO from May 2008 to October 2021. We used seed-based d mapping with permutation of subject images to conduct a quantitative meta-analysis of functional neuroimaging contrasts between emotional (e.g., angry, happy) and neutral faces. We conducted agglomerative hierarchical clustering of meta-analytic map contrasts of emotional faces relative to neutral faces. We investigated lateralization of emotional face processing.

RESULTS

From 5549 studies identified, 55 data sets (1489 healthy participants) met our inclusion criteria. Relative to neutral faces, we found extensive activation clusters by fearful faces in the right inferior temporal gyrus, right fusiform area, left putamen and amygdala, right parahippocampalgyrus and cerebellum; we found smaller activation clusters by angry faces in the right cerebellum and right middle temporal gyrus (MTG) and by disgusted faces in the left MTG. Happy and sad faces did not reach statistical significance. Clustering analyses showed similar activation patterns of fearful and angry faces; activation patterns of happy and sad faces showed the least correlation with other emotional faces. Emotional face processing was predominantly left-lateralized in the amygdala and anterior insula, and right-lateralized in the ventromedial prefrontal cortex.

LIMITATIONS

Reliance on discretized effect sizes based on peak coordinate location instead of statistical brain maps, and the varying level of statistical threshold reporting from original studies, could lead to underdetection of smaller clusters of activation.

CONCLUSION

Processing of emotional faces appeared to be oriented toward identifying threats on faces, from highest (i.e., angry or fearful faces) to lowest level (i.e., happy or sad faces), with a more complex lateralization pattern than previously theorized. Emotional faces may be processed in latent grouping but organized by threat content rather than emotional valence.

Neural representations of anxiety in adolescents with anorexia nervosa: a multivariate approach

Anorexia nervosa (AN) is characterized by low body weight, fear of gaining weight, and distorted body image. Anxiety may play a role in the formation and course of the illness, especially related to situations involving food, eating, weight, and body image. To understand distributed patterns and consistency of neural responses related to anxiety, we enrolled 25 female adolescents with AN and 22 non-clinical female adolescents with mild anxiety who underwent two fMRI sessions in which they saw personalized anxiety-provoking word stimuli and neutral words. Consistency in brain response patterns across trials was determined using a multivariate representational similarity analysis (RSA) approach within anxiety circuits and in a whole-brain voxel-wise searchlight analysis. In the AN group there was higher representational similarity for anxiety-provoking compared with neutral stimuli predominantly in prefrontal regions including the frontal pole, medial prefrontal cortex, dorsolateral prefrontal cortex, and medial orbitofrontal cortex, although no significant group differences. Severity of anxiety correlated with consistency of brain responses within anxiety circuits and in cortical and subcortical regions including the frontal pole, middle frontal gyrus, orbitofrontal cortex, thalamus, lateral occipital cortex, middle temporal gyrus, and cerebellum. Higher consistency of activation in those with more severe anxiety symptoms suggests the possibility of a greater degree of conditioned brain responses evoked by personally-relevant emotional stimuli. Anxiety elicited by disorder-related stimuli may activate stereotyped, previously-learned neural responses within- and outside of classical anxiety circuits. Results have implications for understanding consistent and automatic responding to environmental stimuli that may play a role in maintenance of AN.

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.

Development and validation of the Dimensional Inventory of Stress and Trauma Across the Lifespan (DISTAL): A novel assessment tool to facilitate the dimensional study of psychobiological sequelae of exposure to adversity

Decades of research underscore the profound impact of adversity on brain and behavioral development. Recent theoretical models have highlighted the importance of considering specific features of adversity that may have dissociable effects at distinct developmental timepoints. However, existing measures do not query these dimensions in sufficient detail to support the proliferation of this approach. The Dimensional Inventory of Stress and Trauma Across the Lifespan (DISTAL) was developed with the aim to thoroughly and retrospectively assess the timing, severity (of exposure and reaction), type, persons involved, controllability, predictability, threat, deprivation, proximity, betrayal, and discrimination inherent in an individual's exposure to adversity. Here, we introduce this instrument, present descriptive statistics drawn from a sample of N = 187 adults who completed the DISTAL, and provide initial information about its psychometric properties. This novel measure facilitates the expansion of research focused on assessing the relative impact of exposure to key dimensions of adversity on the brain and behavior across development.

Depression and approach-avoidance decisions to emotional displays: The role of anhedonia

Depression is linked to dysfunctional appetitive and aversive motivational systems and effort-based decision-making, yet whether such deficits extend to social decisions remains unclear. Participants (23 non-depressed, 48 depressed - 24 with a past history of suicide attempt) completed a social decision-making task consisting in freely choosing whether to approach or avoid individuals displaying happy or angry expressions. Occasionally, participants had to make a further effort (change button press) to obtain the desired outcome. All participants preferentially avoided anger on their first choice. Yet, depressed patients less often chose to approach happy individuals, as a function of anhedonia severity. Depressed patients were also less inclined than controls to change their response when the anticipated outcome of their first choice was undesirable (approach angry and avoid happy). Again, such effect correlated with anhedonia severity. Our results support that both altered valuation and willingness to exert effort impact approach-avoidance decisions in social contexts in depression. On this basis, we propose a new integrating framework for reconciling different hypotheses on the effect of depression and anhedonia on motivational responses to emotional stimuli.

Comparison of behavioral and brain indices of fear renewal during a standard vs. novel immersive reality Pavlovian fear extinction paradigm in healthy adults

Pavlovian conditioning paradigms model the learned fear associations inherent in posttraumatic stress disorder, including the renewal of inappropriate fear responses following extinction learning. However, very few studies in humans investigate the underlying neural mechanisms involved in fear renewal despite its clinical importance. To address this issue, our lab designed a novel, immersive-reality Pavlovian fear acquisition, extinction, recall, and renewal paradigm. We utilized an ecological threat - a snake striking towards the participant - as the unconditioned stimulus (US). Context and background were dynamic and included both visual and auditory cues that are relevant to everyday life. Using functional magnetic resonance imaging and behavioral measures (US expectancy ratings), we examined the validity of this Novel paradigm in healthy adults (n = 49) and compared it to a Standard, well-validated 2D paradigm (n = 28). The Novel paradigm, compared to the Standard, was associated with greater hippocampal activation throughout the task. Participants who underwent the Standard paradigm, compared to the Novel, also displayed insula activation; however, this was not specific to stimulus or time. During fear renewal, the Novel paradigm was associated with dorsal anterior cingulate cortex activation to CS+ (> CS-). Overall, we found that our Novel, immersive-reality paradigm, which features an ecologically relevant US, elicited greater corticolimbic activation. These results suggest that immersive Pavlovian fear conditioning paradigms paired with innately fearful stimuli may improve translatability of preclinical paradigms to clinical interventions for fear-based disorders.

The cerebellum and fear extinction: evidence from rodent and human studies

The role of the cerebellum in emotional control has gained increasing interest, with studies showing it is involved in fear learning and memory in both humans and rodents. This review will focus on the contributions of the cerebellum to the extinction of learned fear responses. Extinction of fearful memories is critical for adaptive behaviour, and is clinically relevant to anxiety disorders such as post-traumatic stress disorder, in which deficits in extinction processes are thought to occur. We present evidence that supports cerebellar involvement in fear extinction, from rodent studies that investigate molecular mechanisms and functional connectivity with other brain regions of the known fear extinction network, to fMRI studies in humans. This evidence is considered in relation to the theoretical framework that the cerebellum is involved in the formation and updating of internal models of the inner and outer world by detecting errors between predicted and actual outcomes. In the case of fear conditioning, these internal models are thought to predict the occurrence of an aversive unconditioned stimulus (US), and when the aversive US is unexpectedly omitted during extinction learning the cerebellum uses prediction errors to update the internal model. Differences between human and rodent studies are highlighted to help inform future work.

VR for Cognition and Memory

This chapter will provide a review of research into human cognition through the lens of VR-based paradigms for studying memory. Emphasis is placed on why VR increases the ecological validity of memory research and the implications of such enhancements.

Neuroimaging of Fear Extinction

Extinguishing fear and defensive responses to environmental threats when they are no longer warranted is a critical learning ability that can promote healthy self-regulation and, ultimately, reduce susceptibility to or maintenance of affective-, trauma-, stressor-,and anxiety-related disorders. Neuroimaging tools provide an important means to uncover the neural mechanisms of effective extinction learning that, in turn, can abate the return of fear. Here I review the promises and pitfalls of functional neuroimaging as a method to investigate fear extinction circuitry in the healthy human brain. I discuss the extent to which neuroimaging has validated the core circuits implicated in rodent models and has expanded the scope of the brain regions implicated in extinction processes. Finally, I present new advances made possible by multivariate data analysis tools that yield more refined insights into the brain-behavior relationships involved.

Pattern analysis of neuroimaging data reveals novel insights on threat learning and extinction in humans

Several decades of rodent neurobiology research have identified a network of brain regions that support Pavlovian threat conditioning and extinction, focused predominately on the amygdala, hippocampus, and medial prefrontal cortex (mPFC). Surprisingly, functional magnetic resonance imaging (fMRI) studies have shown inconsistent evidence for these regions while humans undergo threat conditioning and extinction. In this review, we suggest that translational neuroimaging efforts have been hindered by reliance on traditional univariate analysis of fMRI. Whereas univariate analyses average activity across voxels in a given region, multivariate pattern analyses (MVPA) leverage the information present in spatial patterns of activity. MVPA therefore provides a more sensitive analysis tool to translate rodent neurobiology to human neuroimaging. We review human fMRI studies using MVPA that successfully bridge rodent models of amygdala, hippocampus, and mPFC function during Pavlovian learning. We also highlight clinical applications of these information-sensitive multivariate analyses. In sum, we advocate that the field should consider adopting a variety of multivariate approaches to help bridge cutting-edge research on the neuroscience of threat and anxiety.

Individual variation in the neurophysiological representation of negative emotions in virtual reality is shaped by sociability

Negative emotions play a dominant role in daily human life, and mentalizing and empathy are also basic sociability in social life. However, little is known regards the neurophysiological pattern of negative experiences in immersive environments and how people with different sociabilities respond to the negative emotional stimuli at behavioral and neural levels. The present study investigated the neurophysiological representation of negative affective experiences and whether such variations are associated with one's sociability. To address this question, we examined four types of negative emotions that frequently occurred in real life: angry, anxious, fearful, and helpless. We combined naturalistic neuroimaging under virtual reality, multimodal neurophysiological recording, and behavioral measures. Inter-subject representational similarity analysis was conducted to capture the individual differences in the neurophysiological representations of negative emotional experiences. The behavioral and neurophysiological indices revealed that although the emotion ratings were uniquely different, a similar electroencephalography response pattern across these negative emotions was found over the parieto-occipital electrodes. Furthermore, the neurophysiological representations indeed reflected interpersonal variations regarding mentalizing and empathic abilities. Our findings yielded a common pattern of neurophysiological responses toward different negative affective experiences in VR. Moreover, the current results indicate the potential of taking a sociability perspective for understanding the interpersonal variations in the neurophysiological representation of emotion.

Cerebellar contribution to threat probability in a SCA6 mouse model

Fear and anxiety have proven to be essential during the evolutionary process. However, the mechanisms involved in recognizing and categorizing threat probability (i.e. low to high) to elicit the appropriate defensive behavior are yet to be determined. In this study, we investigated the cerebellar contribution in evoking appropriate defensive escape behavior using a purely cerebellar, neurodegenerative mouse model for spinocerebellar ataxia type 6 which is caused by an expanded CAG repeat in exon 47 of the P/Q type calcium channel α1A subunit. These mice overexpress the carboxy terminus (CT) of the P/Q type calcium channel containing an expanded 27 CAG repeat specifically in cerebellar Purkinje cells (CT-longQ27PC). We found that our CT-longQ27PC mice exhibit anxiolytic behavior in the open field, elevated plus maze and light/dark place preference tests, which could be recovered with more threatening conditions such as brighter lighting, meowing sounds and an ultrasound repellent. Their innate fear to find safety in the Barnes maze and visual cliff tests was also diminished with subsequent trials, which could be partially recovered with an ultrasound repellent in the Barnes maze. However, under higher threat conditions such as in the light/dark place preference with ultrasound repellent and in the looming tests, CT-longQ27PC mice responded with higher defensive escape behaviors as controls. Moreover, CT-longQ27PC mice displayed increased levels of CT-labeled aggregates compared with controls. Together these data suggest that cerebellar degeneration by overexpression of CT-longQ27PC is sufficient to impair defensive escape responses in those mice.

A neuroimaging study of interpersonal distance in identical and fraternal twins

Keeping appropriate interpersonal distance is an evolutionary conserved behavior that can be adapted based on learning. Detailed knowledge on how interpersonal space is represented in the brain and whether such representation is genetically influenced is lacking. We measured brain function using functional magnetic resonance imaging in 294 twins (71 monozygotic, 76 dizygotic pairs) performing a distance task where neural responses to human figures were compared to cylindrical blocks. Proximal viewing distance of human figures was compared to cylinders facilitated responses in the occipital face area (OFA) and the superficial part of the amygdala, which is consistent with these areas playing a role in monitoring interpersonal distance. Using the classic twin method, we observed a genetic influence on interpersonal distance related activation in the OFA, but not in the amygdala. Results suggest that genetic factors may influence interpersonal distance monitoring via the OFA whereas the amygdala may play a role in experience‐dependent adjustments of interpersonal distance.

Cerebellar Circuits for Classical Fear Conditioning

Accumulating evidence indicates that the cerebellum is critically involved in modulating non-motor behaviors, including cognition and emotional processing. Both imaging and lesion studies strongly suggest that the cerebellum is a component of the fear memory network. Given the well-established role of the cerebellum in adaptive prediction of movement and cognition, the cerebellum is likely to be engaged in the prediction of learned threats. The cerebellum is activated by fear learning, and fear learning induces changes at multiple synaptic sites in the cerebellum. Furthermore, recent technological advances have enabled the investigation of causal relationships between intra- and extra-cerebellar circuits and fear-related behaviors such as freezing. Here, we review the literature on the mechanisms underlying the modulation of cerebellar circuits in a mammalian brain by fear conditioning at the cellular and synaptic levels to elucidate the contributions of distinct cerebellar structures to fear learning and memory. This knowledge may facilitate a deeper understanding and development of more effective treatment strategies for fear-related affective disorders including post-traumatic stress or anxiety related disorders.

Ventrolateral periaqueductal gray matter integrative system of defense and antinociception

Defensive responses are neurophysiological processes crucial for survival during threatening situations. Defensive immobility is a common adaptive response, in rodents, elaborated by ventrolateral periaqueductal gray matter (vlPAG) when threat is unavoidable. It is associated with somatosensory and autonomic reactions such as alteration in the sensation of pain and rate of respiration. In this study, defensive immobility was assessed by chemical stimulation of vlPAG with different doses of NMDA (0.1, 0.3, and 0.6 nmol). After elicitation of defensive immobility, antinociceptive and respiratory response tests were also performed. Results revealed that defensive immobility was followed by a decrease in the nociceptive perception. Furthermore, the lowest dose of NMDA induced antinociceptive response without eliciting defensive immobility. During defensive immobility, respiratory responses were also disturbed. Interestingly, respiratory rate was increased and interspersed with prolonged expiratory phase of breathing. These findings suggest that vlPAG integrates three different defensive behavioral responses, contributing to the most effective defensive strategies during threatening situations.

Distinct medial-tempora lobe mechanisms of encoding and amygdala-mediated memory reinstatement for disgust and fear

Current models of episodic memory posit that retrieval involves the reenactment of encoding processes. Recent evidence has shown that this reinstatement process - indexed by subsequent encoding-retrieval similarity of brain activity patterns - is related to the activity in the hippocampus during encoding. However, we tend to re-experience emotional events in memory more richly than dull events. The role of amygdala - a critical hub of emotion processing - in reinstatement of emotional events was poorly understood. To investigate it, we leveraged a previously overlooked divergence in the role of amygdala in memory modulation by distinct emotions - disgust and fear. Here we used a novel paradigm in which participants encoded complex events (word pairs) and their memory was tested after 3 weeks, both phases during fMRI scanning. Using representational similarity analysis and univariate analyses, we show that the strength of amygdala activation during encoding was correlated with memory reinstatement of individual event representations in emotion-specific regions. Critically, amygdala modulated reinstatement more for disgust than fear. This was in line with other differences observed at the level of memory performance and neural mechanisms of encoding. Specifically, amygdala and perirhinal cortex were more involved during encoding of disgust-related events, whereas hippocampus and parahippocampal gyrus during encoding of fear-related events. Together, these findings shed a new light on the role of the amygdala and medial temporal lobe regions in encoding and reinstatement of specific emotional memories.

The impact of security countermeasures on human behavior during active shooter incidents

Active shooter incidents represent an increasing threat to American society, especially in commercial and educational buildings. In recent years, a wide variety of security countermeasures have been recommended by public and governmental agencies. Many of these countermeasures are aimed to increase building security, yet their impact on human behavior when an active shooter incident occurs remains underexplored. To fill this research gap, we conducted virtual experiments to evaluate the impact of countermeasures on human behavior during active shooter incidents. A total of 162 office workers and middle/high school teachers were recruited to respond to an active shooter incident in virtual office and school buildings with or without the implementation of multiple countermeasures. The experiment results showed countermeasures significantly influenced participants’ response time and decisions (e.g., run, hide, fight). Participants’ responses and perceptions of the active shooter incident were also contingent on their daily roles, as well as building and social contexts. Teachers had more concerns for occupants’ safety than office workers. Moreover, teachers had more positive perceptions of occupants in the school, whereas office workers had more positive perceptions of occupants in the office.

In search of a naturalistic neuroimaging approach: Exploration of general feasibility through the case of VR-fMRI and application in the domain of episodic memory

Virtual Reality (VR) is an increasingly widespread tool for research as it allows the creation of experiments taking place in multimodal and daily-life-like environments, while keeping a strong experimental control. Adding neuroimaging to VR leads to a better understanding of the underlying brain networks activated during a naturalistic task, whether for research purposes or rehabilitation. The present paper focuses on the specific use of concurrent VR and fMRI and its technical challenges and feasibility, with a brief examination of the general existing solutions. Following the PRISMA guidelines, the review investigates the particular case of how VR-fMRI has explored episodic memory so far, with a comparison of object- and place-based episodic memory. This review confirms the involvement of cerebral regions well-known to be implicated in episodic memory and unravels other regions devoted to bodily and narrative aspects of the self, promoting new avenues of research in the domain of naturalistic episodic memory. Future studies should develop more immersive and interactive virtual neuroimaging features to increase ecological and embodied neurocognition aspects.

Contextual modulation of conditioned responses in humans: A review on virtual reality studies

Conditioned response (CRs) triggered by stimuli predicting aversive consequences have been confirmed across various species including humans, and were found to be exaggerated in anxious individuals and anxiety disorder patients. Importantly, contextual information may strongly modulate such conditioned responses (CR), however, there are several methodological boundaries in the translation of animal findings to humans, and from healthy individuals to patients. Virtual Reality (VR) is a useful technological tool for overcoming such boundaries. In this review, we summarize and evaluate human VR conditioning studies exploring the role of the context as conditioned stimulus or occasion setter for CRs. We observe that VR allows successful acquisition of conditioned anxiety and conditioned fear in response to virtual contexts and virtual cues, respectively. VR studies also revealed that spatial or temporal contextual information determine whether conditioned anxiety and conditioned fear become extinguished and/or return. Novel contexts resembling the threatening context foster conditioned fear but not conditioned anxiety, suggesting distinct context-related generalization processes. We conclude VR contexts are able to strongly modulate CRs and therefore allow a comprehensive investigation of the modulatory role of the context over CR in humans leading to conclusions relevant for non-VR and clinical studies.

Associative learning in peripersonal space: fear responses are acquired in hand-centered coordinates

Space coding affects perception of stimuli associated to negative valence: threatening stimuli presented within the peripersonal space (PPS) speed up behavioral responses compared with nonthreatening events. However, it remains unclear whether the association between stimuli and their negative valence is acquired in a body part-centered reference system, a main feature of the PPS coding. Here we test the hypothesis that associative learning takes place in hand-centered coordinates and can therefore remap according to hand displacement. In two experiments, we used a Pavlovian fear-learning paradigm to associate a visual stimulus [light circle, the conditioned stimulus (CS)] with an aversive stimulus (electrocutaneous shock) applied on the right hand only when the CS was displayed close (CS+) but when not far from it (CS-). Measuring the skin conductance response (SCR), we observed successful fear conditioning, with increased anticipatory fear responses associated with CS+. Crucially, experiment I showed a remapping of these responses following hand displacement, with a generalization to both types of CS. Experiment II corroborated and further extended our findings by ruling out the novelty of the experimental context as a driving factor of such modulations. Indeed, fear responses were present only for stimuli within the PPS but not for new stimuli displayed outside the PPS. By revealing a hand-centered (re)mapping of the conditioning effect, these findings indicate that associative learning can arise in hand-centered coordinates. They further suggest that the threatening valence of an object also depends on its basic spatial relationship with our body.NEW & NOTEWORTHY Associative fear learning takes place in hand-centered coordinates. Using a Pavlovian fear-learning paradigm, we show that the anticipatory skin conductance response indicating the association between the negative value and an initially neutral stimulus is acquired and then remapped in space when the stimulated body part moves to a different position. These results demonstrate the relationship between the representation of peripersonal space and the encoding of threatening stimuli. Hypotheses concerning the underlying neural network are discussed.

Fearful faces modulate spatial processing in peripersonal space: An ERP study

Peripersonal space (PPS) represents the region of space surrounding the body. A pivotal function of PPS is to coordinate defensive responses to threat. We have previously shown that a centrally-presented, looming fearful face, signalling a potential threat in one's surroundings, modulates spatial processing by promoting a redirection of sensory resources away from the face towards the periphery, where the threat may be expected - but only when the face is presented in near, rather than far space. Here, we use electrophysiological measures to investigate the neural mechanism underlying this effect. Participants made simple responses to tactile stimuli delivered on the cheeks, while watching task-irrelevant neutral or fearful avatar faces, looming towards them either in near or far space. Simultaneously with the tactile stimulation, a ball with a checkerboard pattern (probe) appeared to the left or right of the avatar face. Crucially, this probe could either be close to the avatar face, and thus more central in the participant's vision, or further away from the avatar face, and thus more peripheral in the participant's vision. Electroencephalography was continuously recorded. Behavioural results confirmed that in near space only, and for fearful relative to neutral faces, tactile processing was facilitated by the peripheral compared to the central probe. This behavioural effect was accompanied by a reduction of the N1 mean amplitude elicited by the peripheral probe for fearful relative to neutral faces. Moreover, the faster the participants responded to tactile stimuli with the peripheral probe, relative to the central, the smaller was their N1. Together these results, suggest that fearful faces intruding into PPS may increase expectation of a visual event occurring in the periphery. This fear-induced effect would enhance the defensive function of PPS when it is most needed, i.e., when the source of threat is nearby, but its location remains unknown.

Rewards that are near increase impulsive action

In modern society, the natural drive to behave impulsively in order to obtain rewards must often be curbed. A continued failure to do so is associated with a range of outcomes including drug abuse, pathological gambling, and obesity. Here, we used virtual reality technology to investigate whether spatial proximity to rewards has the power to exacerbate the drive to behave impulsively toward them. We embedded two behavioral tasks measuring distinct forms of impulsive behavior, impulsive action, and impulsive choice, within an environment rendered in virtual reality. Participants responded to three-dimensional cues representing food rewards located in either near or far space. Bayesian analyses revealed that participants were significantly less able to stop motor actions when rewarding cues were near compared with when they were far. Since factors normally associated with proximity were controlled for, these results suggest that proximity plays a distinctive role in driving impulsive actions for rewards.

Mapping the neural circuitry of predator fear in the nonhuman primate

In rodents, innate and learned fear of predators depends on the medial hypothalamic defensive system, a conserved brain network that lies downstream of the amygdala and promotes avoidance via projections to the periaqueductal gray. Whether this network is involved in primate fear remains unknown. To address this, we provoked flight responses to a predator (moving snake) in the marmoset monkey under laboratory conditions. We combined c-Fos immunolabeling and anterograde/retrograde tracing to map the functional connectivity of the ventromedial hypothalamus, a core node in the medial hypothalamic defensive system. Our findings demonstrate that the ventromedial hypothalamus is recruited by predator exposure in primates and that anatomical connectivity of the rodent and primate medial hypothalamic defensive system are highly conserved.

Proximal threats promote enhanced acquisition and persistence of reactive fear-learning circuits

Physical proximity to a traumatic event increases the severity of accompanying stress symptoms, an effect that is reminiscent of evolutionarily configured fear responses based on threat imminence. Despite being widely adopted as a model system for stress and anxiety disorders, fear-conditioning research has not yet characterized how threat proximity impacts the mechanisms of fear acquisition and extinction in the human brain. We used three-dimensional (3D) virtual reality technology to manipulate the egocentric distance of conspecific threats while healthy adult participants navigated virtual worlds during functional magnetic resonance imaging (fMRI). Consistent with theoretical predictions, proximal threats enhanced fear acquisition by shifting conditioned learning from cognitive to reactive fear circuits in the brain and reducing amygdala-cortical connectivity during both fear acquisition and extinction. With an analysis of representational pattern similarity between the acquisition and extinction phases, we further demonstrate that proximal threats impaired extinction efficacy via persistent multivariate representations of conditioned learning in the cerebellum, which predicted susceptibility to later fear reinstatement. These results show that conditioned threats encountered in close proximity are more resistant to extinction learning and suggest that the canonical neural circuitry typically associated with fear learning requires additional consideration of a more reactive neural fear system to fully account for this effect.