Viewpoints: Approaches to defining and investigating fear

There is disagreement on how best to define and investigate fear. Nature Neuroscience asked Dean Mobbs to lead experts from the fields of human and animal affective neuroscience to discuss their viewpoints on how to define fear and how to move forward with the study of fear.

Slow escape decisions are swayed by trait anxiety

Theoretical models distinguish between neural responses elicited by distal threats and those evoked by more immediate threats^1-3. Specifically, slower 'cognitive' fear responses towards distal threats involve a network of brain regions including the ventral hippocampus (vHPC) and medial prefrontal cortex (mPFC), while immediate 'reactive' fear responses rely on regions such as the periaqueductal grey^4,5. However, it is unclear how anxiety and its neural substrates relate to these distinct defensive survival circuits. We tested whether individual differences in trait anxiety would impact escape behaviour and neural responses to slow and fast attacking predators: conditions designed to evoke cognitive and reactive fear, respectively. Behaviourally, we found that trait anxiety was not related to escape decisions for fast threats, but individuals with higher trait anxiety escaped earlier during slow threats. Functional magnetic resonance imaging showed that when subjects faced slow threats, trait anxiety positively correlated with activity in the vHPC, mPFC, amygdala and insula. Furthermore, the strength of functional coupling between two components of the cognitive circuit-the vHPC and mPFC-was correlated with the degree of trait anxiety. This suggests that anxiety predominantly affects cognitive fear circuits that are involved in volitional strategic escape.

How the Brain Converts Negative Evaluation into Performance Facilitation

Surpassing negative evaluation is a recurrent theme of success stories. Yet, there is little evidence supporting the counterintuitive idea that negative evaluation might not only motivate people, but also enhance performance. To address this question, we designed a task that required participants to decide whether taking up a risky challenge after receiving positive or negative evaluations from independent judges. Participants believed that these evaluations were based on their prior performance on a related task. Results showed that negative evaluation caused a facilitation in performance. Concurrent functional magnetic resonance imaging revealed that the motivating effect of negative evaluation was represented in the insula and striatum, while the performance boost was associated with functional positive connectivity between the insula and a set of brain regions involved in goal-directed behavior and the orienting of attention. These findings provide new insight into the neural representation of negative evaluation-induced facilitation.

The pursuit of social acceptance: aberrant conformity in social anxiety disorder

The defining pathological features of social anxiety disorder primarily concern the social landscape, yet few empirical studies have examined the potentially aberrant behavioral and neural patterns in this population using socially interactive paradigms. We addressed this issue by investigating the behavioral and neural patterns associated with social conformity in patients with social anxiety disorder. We recorded event-related potentials when healthy subjects (n = 19), and patients with social anxiety disorder (n = 20) made attractiveness judgements of unfamiliar others, while at the same time, being exposed to congruent/incongruent peer ratings. Afterwards, participants were asked to rerate the same faces without the presence of peer ratings. When compared with healthy controls, social anxiety disorder patients exhibited more positive attitudes to unfamiliar others and conformed more with peers-higher feedback. These behavioral effects were in parallel with neural responses associated with social conflict in the N400 signal, showing higher conformity to peers-higher feedback compared with peers-lower or peers-agree feedback among social anxiety disorder patients. Our findings provide evidence on the behavioral and neural patterns of social anxiety disorder during social interactions, and support the hypothesis that individuals with social anxiety disorder are more motivated to pursue social acceptance and possibly avoid social rejection.

How Dynamic Brain Networks Tune Social Behavior in Real Time

During social interaction, the brain has the enormous task of interpreting signals that are fleeting, subtle, contextual, abstract, and often ambiguous. Despite the signal complexity, the human brain has evolved to be highly successful in the social landscape. Here, we propose that the human brain makes sense of noisy dynamic signals through accumulation, integration, and prediction, resulting in a coherent representation of the social world. We propose that successful social interaction is critically dependent on a core set of highly connected hubs that dynamically accumulate and integrate complex social information and, in doing so, facilitate social tuning during moment-to-moment social discourse. Successful interactions, therefore, require adaptive flexibility generated by neural circuits composed of highly integrated hubs that coordinate context-appropriate responses. Adaptive properties of the neural substrate, including predictive and adaptive coding, and neural reuse, along with perceptual, inferential, and motivational inputs, provide the ingredients for pliable, hierarchical predictive models that guide our social interactions.

Attentional set to safety recruits the ventral medial prefrontal cortex

Early detection of danger is highly adaptive, yet fast orientation towards safety is also key to survival. This study aimed to explore how human brain searches for safety by manipulating subjects' attentional set. Subjects were asked to judge random dots motion (RDM) direction and could be shocked for incorrect responses (RDM trials) while keeping alert in detecting shock probability cues (cue detection trials). Relative to safe condition, where attention was set to search cues associated with no shock, incorrect responses to 'dangerous+' cues would increase and correct responses to 'dangerous-' cues would decrease shock probability. In RDM trials, relative to the 'dangerous+', the safe and 'dangerous-' attentional set induced stronger activation in the ventral medial prefrontal cortex (vmPFC), a core region involved in flexible threat assessment and safety signalling. In cue detection trials, shorter response times and greater accuracy were observed for 'dangerous+' than 'dangerous-' and safe cues. At neural level 'dangerous+' cues induced stronger activity in the frontoparietal attention network than safe cues. Overall, our findings demonstrate that attentional set for searching safety recruits the vmPFC, while detection of threat-related cues elicits activity in the frontoparietal attention network, suggesting new roles for these regions in human defensive survival circuitry.

The ethological deconstruction of fear(s)

The natural world presents a myriad of dangers that can threaten an organism's survival. This diversity of threats is matched by a set of universal and species specific defensive behaviors which are often subsumed under the emotions of fear and anxiety. A major issue in the field of affective science, however, is that these emotions are often conflated and scientists fail to reflect the ecological conditions that gave rise to them. I attempt to clarify these semantic issues by describing the link between ethologically defined defensive strategies and fear. This in turn, provides a clearer differentiation between fears, the contexts that evoke them and how they are organized within defensive survival circuits.

How cognitive and reactive fear circuits optimize escape decisions in humans

Flight initiation distance (FID), the distance at which an organism flees from an approaching threat, is an ecological metric of cost-benefit functions of escape decisions. We adapted the FID paradigm to investigate how fast- or slow-attacking "virtual predators" constrain escape decisions. We show that rapid escape decisions rely on "reactive fear" circuits in the periaqueductal gray and midcingulate cortex (MCC), while protracted escape decisions, defined by larger buffer zones, were associated with "cognitive fear" circuits, which include posterior cingulate cortex, hippocampus, and the ventromedial prefrontal cortex, circuits implicated in more complex information processing, cognitive avoidance strategies, and behavioral flexibility. Using a Bayesian decision-making model, we further show that optimization of escape decisions under rapid flight were localized to the MCC, a region involved in adaptive motor control, while the hippocampus is implicated in optimizing decisions that update and control slower escape initiation. These results demonstrate an unexplored link between defensive survival circuits and their role in adaptive escape decisions.

The role of empathy in experiencing vicarious anxiety

With depictions of others facing threats common in the media, the experience of vicarious anxiety may be prevalent in the general population. However, the phenomenon of vicarious anxiety-the experience of anxiety in response to observing others expressing anxiety-and the interpersonal mechanisms underlying it have not been fully investigated in prior research. In 4 studies, we investigate the role of empathy in experiencing vicarious anxiety, using film clips depicting target victims facing threats. In Studies 1 and 2, trait emotional empathy was associated with greater self-reported anxiety when observing target victims, and with perceiving greater anxiety to be experienced by the targets. Study 3 extended these findings by demonstrating that trait empathic concern-the tendency to feel concern and compassion for others-was associated with experiencing vicarious anxiety, whereas trait personal distress-the tendency to experience distress in stressful situations-was not. Study 4 manipulated state empathy to establish a causal relationship between empathy and experience of vicarious anxiety. Participants who took an empathic perspective when observing target victims, as compared to those who took an objective perspective using reappraisal-based strategies, reported experiencing greater anxiety, risk-aversion, and sleep disruption the following night. These results highlight the impact of one's social environment on experiencing anxiety, particularly for those who are highly empathic. In addition, these findings have implications for extending basic models of anxiety to incorporate interpersonal processes, understanding the role of empathy in social learning, and potential applications for therapeutic contexts. (PsycINFO Database Record

Social pain and social gain in the adolescent brain: A common neural circuitry underlying both positive and negative social evaluation

Social interaction inherently involves the subjective evaluation of cues salient to social inclusion and exclusion. Testifying to the importance of such social cues, parts of the neural system dedicated to the detection of physical pain, the dorsal anterior cingulate cortex (dACC) and anterior insula (AI), have been shown to be equally sensitive to the detection of social pain experienced after social exclusion. However, recent work suggests that this dACC-AI matrix may index any socially pertinent information. We directly tested the hypothesis that the dACC-AI would respond to cues of both inclusion and exclusion, using a novel social feedback fMRI paradigm in a population-derived sample of adolescents. We show that the dACC and left AI are commonly activated by feedback cues of inclusion and exclusion. Our findings suggest that theoretical accounts of the dACC-AI network as a neural alarm system restricted within the social domain to the processing of signals of exclusion require significant revision.

Moral Chivalry: Gender and Harm Sensitivity Predict Costly Altruism

Moral perceptions of harm and fairness are instrumental in guiding how an individual navigates moral challenges. Classic research documents that the gender of a target can affect how people deploy these perceptions of harm and fairness. Across multiple studies, we explore the effect of an individual's moral orientations (their considerations of harm and justice) and a target's gender on altruistic behavior. Results reveal that a target's gender can bias one's readiness to engage in harmful actions and that a decider's considerations of harm-but not fairness concerns-modulate costly altruism. Together, these data illustrate that moral choices are conditional on the social nature of the moral dyad: Even under the same moral constraints, a target's gender and a decider's gender can shift an individual's choice to be more or less altruistic, suggesting that gender bias and harm considerations play a significant role in moral cognition.

Is fear perception special? Evidence at the level of decision-making and subjective confidence

Fearful faces are believed to be prioritized in visual perception. However, it is unclear whether the processing of low-level facial features alone can facilitate such prioritization or whether higher-level mechanisms also contribute. We examined potential biases for fearful face perception at the levels of perceptual decision-making and perceptual confidence. We controlled for lower-level visual processing capacity by titrating luminance contrasts of backward masks, and the emotional intensity of fearful, angry and happy faces. Under these conditions, participants showed liberal biases in perceiving a fearful face, in both detection and discrimination tasks. This effect was stronger among individuals with reduced density in dorsolateral prefrontal cortex, a region linked to perceptual decision-making. Moreover, participants reported higher confidence when they accurately perceived a fearful face, suggesting that fearful faces may have privileged access to consciousness. Together, the results suggest that mechanisms in the prefrontal cortex contribute to making fearful face perception special.

Neuroethological studies of fear, anxiety, and risky decision-making in rodents and humans

Prey are relentlessly faced with a series of survival problems to solve. One enduring problem is predation, where the prey's answers rely on the complex interaction between actions cultivated during its life course and defense reactions passed down by descendants. To understand the proximate neural responses to analogous threats, affective neuroscientists have favored well-controlled associative learning paradigms, yet researchers are now creating semi-realistic environments that examine the dynamic flow of decision-making and escape calculations that mimic the prey's real world choices. In the context of research from the field of ethology and behavioral ecology, we review some of the recent literature in rodent and human neuroscience and discuss how these studies have the potential to provide new insights into the behavioral expression, computations, and the neural circuits that underlie healthy and pathological fear and anxiety.

Inferences of Others' Competence Reduces Anticipation of Pain When under Threat

On a daily basis, we place our lives in the hands of strangers. From dentists to pilots, we make inferences about their competence to perform their jobs and consequently to keep us from harm. Here we explore whether the perceived competence of others can alter one's anticipation of pain. In two studies, participants (Receivers) believed their chances of experiencing an aversive stimulus were directly dependent on the performance of another person (Players). We predicted that perceiving the Players as highly competent would reduce Receivers' anxiety when anticipating the possibility of an electric shock. Results confirmed that high competence ratings consistently corresponded with lower reported anxiety, and complementary fMRI data showed that increased competence perception was further expressed as decreased activity in the bilateral posterior insula, a region localized to actual pain stimulation. These studies suggest that inferences of competence act as predictors of protection and reduce the expectation of negative outcomes.

The ecology of human fear: survival optimization and the nervous system

We propose a Survival Optimization System (SOS) to account for the strategies that humans and other animals use to defend against recurring and novel threats. The SOS attempts to merge ecological models that define a repertoire of contextually relevant threat induced survival behaviors with contemporary approaches to human affective science. We first propose that the goal of the nervous system is to reduce surprise and optimize actions by (i) predicting the sensory landscape by simulating possible encounters with threat and selecting the appropriate pre-encounter action and (ii) prevention strategies in which the organism manufactures safe environments. When a potential threat is encountered the (iii) threat orienting system is engaged to determine whether the organism ignores the stimulus or switches into a process of (iv) threat assessment, where the organism monitors the stimulus, weighs the threat value, predicts the actions of the threat, searches for safety, and guides behavioral actions crucial to directed escape. When under imminent attack, (v) defensive systems evoke fast reflexive indirect escape behaviors (i.e., fight or flight). This cascade of responses to threat of increasing magnitude are underwritten by an interconnected neural architecture that extends from cortical and hippocampal circuits, to attention, action and threat systems including the amygdala, striatum, and hard-wired defensive systems in the midbrain. The SOS also includes a modulatory feature consisting of cognitive appraisal systems that flexibly guide perception, risk and action. Moreover, personal and vicarious threat encounters fine-tune avoidance behaviors via model-based learning, with higher organisms bridging data to reduce face-to-face encounters with predators. Our model attempts to unify the divergent field of human affective science, proposing a highly integrated nervous system that has evolved to increase the organism's chances of survival.

Reflected glory and failure: the role of the medial prefrontal cortex and ventral striatum in self vs other relevance during advice-giving outcomes

Despite the risks, people enjoy giving advice. One explanation is that giving beneficial advice can result in reflected glory, ego boosts or reputation enhancement. However, giving poor advice can be socially harmful (being perceived as incompetent or untrustworthy). In both circumstances, we have a vested interest in the advice follower's success or failure, especially when it reflects specifically on us compared with when it is diffused between multiple advisors. We examined these dynamics using an Advisor-Advisee Game, where subjects acted as an Advisor to a confederate Advisee who selected one of the three options when trying to win money: accept the subject's advice, accept the advice of a second confederate Advisor or accept both Advisors' advice. Results showed that having one's advice accepted, compared with being rejected, resulted in activity in the ventral striatum--a core reward area. Furthermore, the ventral striatum was only active when the subject's advice led to the advisee winning, and not when the advisee won based on the confederate's advice. Finally, the medial prefrontal cortex (MPFC) was more active when the Advisee won or lost money based solely on the subject's advice compared with when the second Advisor's advice was accepted. One explanation for these findings is that the MPFC monitors self-relevant social information, while the ventral striatum is active when others accept advice and when their success leads to reflected glory.

Empathic concern drives costly altruism

Why do we self-sacrifice to help others in distress? Two competing theories have emerged, one suggesting that prosocial behavior is primarily motivated by feelings of empathic other-oriented concern, the other that we help mainly because we are egoistically focused on reducing our own discomfort. Here we explore the relationship between costly altruism and these two sub-processes of empathy, specifically drawing on the caregiving model to test the theory that trait empathic concern (e.g. general tendency to have sympathy for another) and trait personal distress (e.g. predisposition to experiencing aversive arousal states) may differentially drive altruistic behavior. We find that trait empathic concern – and not trait personal distress – motivates costly altruism, and this relationship is supported by activity in the ventral tegmental area, caudate and subgenual anterior cingulate, key regions for promoting social attachment and caregiving. Together, this data helps identify the behavioral and neural mechanisms motivating costly altruism, while demonstrating that individual differences in empathic concern-related brain responses can predict real prosocial choice.

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Trait empathic concern predicts altruistic action.

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State distress, but not trait distress, predicts altruistic action.

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A network comprised of VTA, caudate and sgACC support other-oriented prosocial decisions.

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Neural evidence supporting caregiving model: social reward and attachment guides altruism.

The neural signature of escalating frustration in humans

Mammalian studies show that frustration is experienced when goal-directed activity is blocked. Despite frustration's strongly negative role in health, aggression and social relationships, the neural mechanisms are not well understood. To address this we developed a task in which participants were blocked from obtaining a reward, an established method of producing frustration. Levels of experienced frustration were parametrically varied by manipulating the participants' motivation to obtain the reward prior to blocking. This was achieved by varying the participants' proximity to a reward and the amount of effort expended in attempting to acquire it. In experiment 1, we confirmed that proximity and expended effort independently enhanced participants' self-reported desire to obtain the reward, and their self-reported frustration and response vigor (key-press force) following blocking. In experiment 2, we used functional magnetic resonance imaging (fMRI) to show that both proximity and expended effort modulated brain responses to blocked reward in regions implicated in animal models of reactive aggression, including the amygdala, midbrain periaqueductal grey (PAG), insula and prefrontal cortex. Our findings suggest that frustration may serve an energizing function, translating unfulfilled motivation into aggressive-like surges via a cortical, amygdala and PAG network.

Overlapping and distinct representations of advantageous and disadvantageous inequality

Advantageous inequality (AI) aversion, or paying at a personal cost to achieve equal reward distribution, represents a unique feature of human behavior. Here, we show that individuals have strong preferences for fairness in both disadvantageous (DI) and advantageous inequality (AI) situations, such that they alter others' payoff at a personal financial cost. At the neural level, we found that both types of inequality activated the putamen, orbitofrontal cortex, and insula, regions implicated in motivation. Individual difference analyses found that those who spent more money to increase others' payoff had stronger activity in putamen when they encountered AI and less functional connectivity between putamen and both orbitofrontal cortex and anterior insula. Conversely, those who spent more money to reduce others' payoff had stronger activity in amygdala in response to DI and less functional connectivity between amygdala and ventral anterior cingulate cortex. These dissociations suggest that both types of inequality are processed by similar brain areas, yet modulated by different neural pathways. Hum Brain Mapp 35:3290–3301, 2014. © 2013 Wiley Periodicals, Inc.