Reactivity to unpredictable threat as a treatment target for fear-based anxiety disorders

Disorder-specific versus transdiagnostic cognitive mechanisms in anxiety and depression: Machine-learning-based prediction of symptom severity

INTRODUCTION

Psychiatric evaluation of anxiety and depression is currently based on self-reported symptoms and their classification into discrete disorders. Yet the substantial overlap between these disorders as well as their within-disorder heterogeneity may contribute to the mediocre success rates of treatments. The proposed research examines a new framework for diagnosis that is based on alterations in underlying cognitive mechanisms. In line with the Research Domain Criteria (RDoC) approach, the current study directly compares disorder-specific and transdiagnostic cognitive patterns in predicting the severity of anxiety and depression symptoms.

METHODS

The sample included 237 individuals exhibiting differing levels of anxiety and depression symptoms, as measured by the STAI-T and BDI-II. Random Forest regressors were used to analyze their performance on a battery of six computerized cognitive-behavioral tests targeting selective and spatial attention, expectancy, interpretation, memory, and cognitive control biases.

RESULTS

Unique anxiety-specific biases were found, as well as shared anxious-depressed bias patterns. These cognitive biases exhibited relatively high fitting rates when predicting symptom severity (questionnaire scores common range 0-60, MAE = 6.03, RMSE = 7.53). Interpretation and expectancy biases exhibited the highest association with symptoms, above all other individual biases.

LIMITATIONS

Although internal validation methods were applied, models may suffer from potential overfitting due to sample size limitations.

CONCLUSION

In the context of the ongoing dispute regarding symptom-centered versus transdiagnostic approaches, the current study provides a unique comparison of these two views, yielding a novel intermediate approach. The results support the use of mechanism-based dimensional diagnosis for adding precision and objectivity to future psychiatric evaluations.

Transdiagnostic Fear and Anxiety: Prospective Prediction Using the No-Threat, Predictable Threat, and Unpredictable Threat Task

Background

Fear and anxiety are distinct dimensions of psychopathology that may be characterized by differences in dimensional threat reactivity. Heightened response to predictable threat is hypothesized to underlie fear symptomatology, whereas increased response to unpredictable threat may underlie anxiety. Despite widespread acceptance of this model, these purported associations have rarely been tested, and the prognostic value of predictable and unpredictable threat responding is unclear. Here we examined multilevel indicators of predictable and unpredictable threat response as cross-sectional correlates and prospective predictors of transdiagnostic fear and anxiety.

Methods

Fifty-two individuals with varying levels of internalizing psychopathology (31 female) performed the no-threat, predictable threat, and unpredictable threat task. Transdiagnostic fear and anxiety were assessed at baseline (time 1) and approximately 1.5 years later (time 2). We used event-related potential, the stimulus-preceding negativity, as a measure of threat anticipation and startle eyeblink as a measure of defensive reactivity during the no-threat, predictable threat, and unpredictable threat task. These probes were assessed as cross-sectional correlates and prospective predictors of fear and anxiety.

Results

Participants with larger time 1 stimulus-preceding negativities to predictable threat were characterized by greater time 1 fear. Larger time 1 stimulus-preceding negativities to unpredictable threat were associated with greater increases in time 2 anxiety. Heightened time 1 startle to predictable threat predicted larger increases in time 2 fear.

Conclusions

Results validate predictable and unpredictable threat responding as dimensional correlates of transdiagnostic fear versus anxiety and suggest that psychophysiological measures of predictable and unpredictable threat response hold promise as prospective predictors of trajectories of fear and anxiety.

The Role of Serotonin in Fear Learning and Memory: A Systematic Review of Human Studies

Fear is characterized by distinct behavioral and physiological responses that are essential for the survival of the human species. Fear conditioning (FC) serves as a valuable model for studying the acquisition, extinction, and expression of fear. The serotonin (5-hydroxytryptamine, 5-HT) system is known to play a significant role in emotional and motivational aspects of human behavior, including fear learning and expression. Accumulating evidence from both animal and human studies suggests that brain regions involved in FC, such as the amygdala, hippocampus, and prefrontal cortex, possess a high density of 5-HT receptors, implicating the crucial involvement of serotonin in aversive learning. Additionally, studies exploring serotonin gene polymorphisms have indicated their potential influence on FC. Therefore, the objective of this work was to review the existing evidence linking 5-HT with fear learning and memory in humans. Through a comprehensive screening of the PubMed and Web of Science databases, 29 relevant studies were included in the final review. These studies investigated the relationship between serotonin and fear learning using drug manipulations or by studying 5-HT-related gene polymorphisms. The results suggest that elevated levels of 5-HT enhance aversive learning, indicating that the modulation of serotonin 5-HT2A receptors regulates the expression of fear responses in humans. Understanding the role of this neurochemical messenger in associative aversive learning can provide insights into psychiatric disorders such as anxiety and post-traumatic stress disorder (PTSD), among others.

Identifying Transdiagnostic Mechanisms in Mental Health Using Computational Factor Modeling

Most psychiatric disorders do not occur in isolation, and most psychiatric symptom dimensions are not uniquely expressed within a single diagnostic category. Current treatments fail to work for around 25% to 40% of individuals, perhaps due at least in part to an overreliance on diagnostic categories in treatment development and allocation. In this review, we describe ongoing efforts in the field to surmount these challenges and precisely characterize psychiatric symptom dimensions using large-scale studies of unselected samples via remote, online, and "citizen science" efforts that take a dimensional, mechanistic approach. We discuss the importance that efforts to identify meaningful psychiatric dimensions be coupled with careful computational modeling to formally specify, test, and potentially falsify candidate mechanisms that underlie transdiagnostic symptom dimensions. We refer to this approach, i.e., where symptom dimensions are identified and validated against computationally well-defined neurocognitive processes, as computational factor modeling. We describe in detail some recent applications of this method to understand transdiagnostic cognitive processes that include model-based planning, metacognition, appetitive processing, and uncertainty estimation. In this context, we highlight how computational factor modeling has been used to identify specific associations between cognition and symptom dimensions and reveal previously obscured relationships, how findings generalize to smaller in-person clinical and nonclinical samples, and how the method is being adapted and optimized beyond its original instantiation. Crucially, we discuss next steps for this area of research, highlighting the value of more direct investigations of treatment response that bridge the gap between basic research and the clinic.

Startle responses in Duchenne muscular dystrophy: a novel biomarker of brain dystrophin deficiency

Duchenne muscular dystrophy (DMD) is characterized by loss of dystrophin in muscle, however patients also have variable degree of intellectual disability and neurobehavioural co-morbidities. In contrast to muscle, in which a single full-length dystrophin isoform (Dp427) is produced, multiple isoforms are produced in the brain, and their deficiency accounts for the variability of CNS manifestations, with increased risk of comorbidities in patients carrying mutations affecting the 3' end of the gene, which disrupt expression of shorter Dp140 and Dp71 isoforms. A mouse model (mdx mouse) lacks Dp427 in muscle and CNS and exhibits exaggerated startle responses to threat, linked to the deficiency of dystrophin in limbic structures such as the amygdala, which normalize with postnatal brain dystrophin-restoration therapies. A pathological startle response is not a recognized feature of DMD, and its characterization has implications for improved clinical management and translational research. To investigate startle responses in DMD, we used a novel fear-conditioning task in an observational study of 56 males aged 7-12 years (31 affected boys, mean age 9.7 ± 1.8 years; 25 controls, mean age 9.6 ± 1.4 years). Trials of two neutral visual stimuli were presented to participants: one 'safe' cue presented alone; one 'threat' cue paired with an aversive noise to enable conditioning of physiological startle responses (skin conductance response and heart rate). Retention of conditioned physiological responses was subsequently tested by presenting both cues without the aversive noise in an 'Extinction' phase. Primary outcomes were the initial unconditioned skin conductance and change in heart rate responses to the aversive 'threat' and acquisition and retention of conditioned responses after conditioning. Secondary and exploratory outcomes were neuropsychological measures and genotype associations. The mean unconditioned skin conductance response was greater in the DMD group than controls [mean difference 3.0 µS (1.0, 5.1); P = 0.004], associated with a significant threat-induced bradycardia only in the patient group [mean difference -8.7 bpm (-16.9, -0.51); P = 0.04]. Participants with DMD found the task more aversive than controls, with increased early termination rates during the Extinction phase (26% of DMD group versus 0% of controls; P = 0.007). This study provides the first evidence that boys with DMD show similar increased unconditioned startle responses to threat to the mdx mouse, which in the mouse respond to brain dystrophin restoration. Our study provides new insights into the neurobiology underlying the complex neuropsychiatric co-morbidities in DMD and defines an objective measure of this CNS phenotype, which will be valuable for future CNS-targeted dystrophin-restoration studies.

Aversive response to uncertainty as a mediator for the effect of a mindfulness intervention on symptoms of anxiety

THEORETICAL BACKGROUND

Intolerance of uncertainty plays a central role in anxiety and research suggests that it's an important treatment target. Investigating response to uncertainty using other dimensions than self-report, such as physiological responses, can further the effort to understand the role of uncertainty in anxiety more fully. Mindfulness interventions have become increasingly interesting in their application to anxiety, as they foster acceptance of unpleasant aspects of experience. The aims of the study were to examine whether a mindfulness intervention reduced response to uncertainty and anxiety symptoms, and to examine the associations between intolerance of uncertainty, physiological response to uncertainty, mindfulness and anxiety.

METHODS

Participants were 117 students who completed a two-week mindfulness or audiobook control intervention. At pre- and post-intervention assessments, measures of anxiety, mindfulness, and intolerance of uncertainty were completed and a threat-of-shock task assessing startle responding to unpredictable shock was administered.

RESULTS

Findings showed a significant effect of the intervention for social anxiety symptoms. Furthermore, intolerance of uncertainty mediated the effect of the intervention on symptoms for social anxiety and worry. No such effects were found for physiological response to uncertainty.

CONCLUSION

The study adds to the understanding of the role of response to uncertainty in anxiety as well as to its mechanistic role in the context of mindfulness practice. Implications and possible explanations for the non-significant main effects of the intervention on anxiety symptoms and physiological response to uncertainty are discussed.

Uncertain in the face of change: Lack of contingency shift awareness during extinction is associated with higher fear-potentiated startle and PTSD symptoms in children

Intolerance of uncertainty is a transdiagnostic risk factor for fear-related disorders and is associated with higher levels of anxiety in children and adolescents. It is unclear how uncertainty relates to development of psychopathology in children who have experienced trauma in early life. The present study used a fear-potentiated startle paradigm in children to examine associations between uncertainty (assessed as unawareness of a change in reinforcement during fear extinction) and symptoms of anxiety and posttraumatic stress disorder (PTSD), as well as startle potentiation to threat and safety cues. Results showed that unaware children had strong positive associations between trauma exposure and PTSD symptoms, whereas aware children did not. Uncertainty interacted with anxiety in that children who were both unaware and had higher anxiety displayed higher fear-potentiated startle to safety cues and did not show discrimination between threat and safety during fear conditioning. These results suggest that anxious children who persist in associating a threat cue with an aversive event during extinction, after repeated presentations of the no longer reinforced conditioned stimulus, may express psychophysiological phenotypes related to PTSD.

Sustained threat and phasic fear in the laboratory and cognitive-emotional processes of anxiety in everyday life - An ambulatory assessment study

Fear is a phasic state of apprehension to an imminent threat, whereas anxiety is a more sustained state of expecting a potential threat leading to tension and worry. The NPU-threat test is a laboratory startle paradigm allowing a reliable and valid assessment of both, fear- and anxiety-potentiated reactions. It is suggested to differentiate between anxiety disorders, but little is known on associations with everyday life experiences of cognitive-emotional processes regarding anxiety in non-clinical samples. In the present project, the NPU-threat test was applied in three studies with (1) unselected healthy individuals, (2) participants with extreme manifestations of trait anxiety (low vs. high) and (3) individuals preparing for a high-stakes exam. Self-reported states of emotionality and worry were assessed during a four-day ambulatory assessment (AA). Overall, NPU-threat test measures did not significantly differ between studies, while the AA dependent measures were sufficiently sensitive to capture differences between groups. However, there was no significant association between psychophysiological measures of the NPU-threat test and AA state measures across participants. In participants recruited for low vs. high trait anxiety we found an association with AA worry and emotionality, but no interaction with potentiated startle. The present findings do not support the idea of a link between our laboratory biomarker and adaptive regulation of cognitive-emotional states in everyday life in healthy individuals. We speculate that an association between laboratory physiological measures and everyday experience of anxious states may be detectable in clinical samples.

Event-related potentials to acoustic startle probes during unpredictable threat are associated with individual differences in intolerance of uncertainty

Individual differences in sensitivity to unpredictable threat may be a critical mechanism for internalizing psychopathology phenotypes. The present study examined whether the startle probe-elicited N100 and P300 during unpredictable threat - two event-related potentials indexing early and elaborative attentional processing of unpredictable threat - may be endophenotypes for internalizing psychopathology, including fear and distress/misery disorders and intolerance of uncertainty (IU), a clinical trait that is transdiagnostically associated with internalizing disorders. A large sample of adult siblings (N = 375) completed the no, predictable, and unpredictable threat task, during which the N100 and P300 were recorded. Relative to the no threat condition, N100 was more strongly enhanced in anticipation of unpredictable than predictable threat while P300 was suppressed to both predictable and unpredictable threat. While neither N100 enhancement nor P300 suppression to unpredictable threat was associated with fear or distress/misery disorders, they were negatively linked to inhibitory IU (a facet of IU). Thus, individuals high in inhibitory IU showed reduced attentional engagement with the threatening context when it was unpredictable. Further, N100 enhancement and, to a lesser degree, P300 suppression to unpredictable threat showed familial aggregation - a key criterion for determining whether a biomarker is an endophenotype. In sum, N100 enhancement and P300 suppression to unpredictable threat may be endophenotypes for dimensional measures of internalizing psychopathology.

Neural and Self-report Measures of Sensitivity to Uncertainty as Predictors of COVID-Related Negative Affect

The COVID-19 pandemic has been a period of unprecedented uncertainty. Research indicates individuals differ in their response to uncertainty and these differences are mediated by anterior insula (aINS) function. Those most sensitive to uncertainty are likely vulnerable to negative affect in the context of the pandemic. The current study was designed to directly test this question using both neural and self-reported measures of sensitivity to uncertainty. Fifty-nine volunteers completed a task designed to probe neural response to anticipation of predictable (P-) and unpredictable (U-) threat-of-electric-shock during functional magnetic resonance imaging and a self-report measure of intolerance of uncertainty (IU). Approximately two years later, during the peak of the pandemic, participants reported their emotional reactions to the COVID-19 crisis. Multilevel mixed models revealed that greater aINS activation to U-threat and greater self-reported IU were independent predictors of increased COVID-related negative affect. These findings were significant when adjusting for biological sex and depression and anxiety symptom severity. The results add to a growing literature demonstrating that individual differences in response to uncertainty have a robust impact on mood and functioning. Results also highlight that individuals highly sensitive to uncertainty may be at increased risk for poor mental health during the ongoing pandemic.

Ethnic differences in behavioral and physiological indicators of sensitivity to threat

The clinical presentation of anxiety may differ between Hispanics/Latinx (H/L) and non-H/L, although findings on ethnic differences in self-reported anxiety symptoms have been mixed. Fewer studies have focused on ethnic differences in quick and relatively automatic laboratory-assessed indicators of anxiety symptoms, which have the potential to be more objective indicators than self-report. Therefore, the present study examined ethnic differences in two laboratory-assessed indicators of threat sensitivity (an important transdiagnostic mechanism of anxiety): attentional bias to threat and electromyography startle reactivity to threat. White H/L (n = 117) and White non-H/L (n = 168) adults who were matched on demographics and lifetime psychopathology (including anxiety) completed a dot-probe task to assess attentional bias to threat and the No-Predictable-Unpredictable threat (NPU) task to assess startle reactivity to threat. Results indicated that H/L displayed less Slow OrientationRB (β = -0.27, p = 0.032, R2β∗ = 0.02), and increased Slow DisengagementRB (β = 0.31, p = 0.016, R2β∗ = 0.02) compared to non-H/L. H/L exhibited blunted overall startle compared to non-H/L (β = -0.30, p = 0.014, R2β∗ = 0.02), but groups did not differ in startle reactivity to either predictable or unpredictable threat. In summary, H/L and non-H/L may differ in their experience and presentation of anxiety symptoms and such differences may vary across indicators of sensitivity to threat.

The novel vasopressin receptor (V1aR) antagonist SRX246 reduces anxiety in an experimental model in humans: a randomized proof-of-concept study

RATIONALE

Arginine vasopressin (AVP) is a neuropeptide that modulates both physiological and emotional responses to threat. Until recently, drugs that target vasopressin receptors (V1a) in the human central nervous system were unavailable. The development of a novel V1a receptor antagonist, SRX246, permits the experimental validation of vasopressin's role in the regulation of anxiety and fear in humans.

OBJECTIVES

Here, we examined the effects of SRX246 in a proof-of-concept translational paradigm of fear (phasic response to imminent threat) and anxiety (prolonged response to potential threat).

METHODS

Healthy volunteers received both SRX246 and placebo in a randomized, double-blind, counter-balanced order separated by a 5-7-day wash-out period. Threat consisted of unpleasant electric shocks. The "NPU" threat test probed startle reactivity during predictable threat (i.e., fear-potentiated startle) and unpredictable threat (i.e., anxiety-potentiated startle).

RESULTS

As predicted, SRX246 decreased anxiety-potentiated startle independent of fear-potentiated startle.

CONCLUSIONS

As anxiety-potentiated startle is elevated in anxiety and trauma-associated disorders and decreased by traditional anxiolytics such as SSRIs and benzodiazepines, the V1a receptor is a promising novel treatment target.

Decreased defensive reactivity to interoceptive threat after successful exposure-based psychotherapy in patients with panic disorder

Panic disorder (PD) is characterized by a dysfunctional defensive responding to panic-related body symptoms that is assumed to contribute to the persistence of panic symptomatology. The present study aimed at examining whether this dysfunctional defensive reactivity to panic-related body symptoms would no longer be present following successful cognitive behavior therapy (CBT) but would persist when patients show insufficient symptom improvement. Therefore, in the present study, effects of CBT on reported symptoms and defensive response mobilization during interoceptive challenge were investigated using hyperventilation as a respiratory symptom provocation procedure. Changes in defensive mobilization to body symptoms in the course of CBT were investigated in patients with a primary diagnosis of PD with or without agoraphobia by applying a highly standardized hyperventilation task prior to and after a manual-based CBT (n = 38) or a waiting period (wait-list controls: n = 20). Defensive activation was indexed by the potentiation of the amygdala-dependent startle eyeblink response. All patients showed a pronounced defensive response mobilization to body symptoms at baseline. After treatment, no startle reflex potentiation was found in those patients who showed a clinically significant improvement. However, wait-list controls and treatment non-responders continued to show increased defensive responses to actually innocuous body symptoms after the treatment/waiting period. The present results indicate that the elimination of defensive reactivity to actually innocuous body symptoms might be a neurobiological correlate and indicator of successful CBT in patients with PD, which may help to monitor and optimize CBT outcomes.

Responding to uncertain threat: A potential mediator for the effect of mindfulness on anxiety

Mindfulness-based interventions have gained extensive support for their application in the treatment of anxiety. However, their mechanisms remain largely unexplored. Excessive reactivity to uncertainty plays a central role in anxiety, and may represent a mechanism for the effect of mindfulness on anxiety, as mindfulness training fosters an open and accepting stance towards all aspects of experience. The present study sought to investigate both (i) self-reported intolerance of uncertainty (IU) as well as (ii) physiological and subjective responding to uncertain threat in a threat-of-shock paradigm, the NPU-threat test, as mediators for the relationship between mindfulness and anxiety in a cross-sectional study of healthy participants (N = 53). The results indicated that IU mediated the effect of mindfulness on some anxiety symptoms. In contrast, scores of physiological as well as subjective responses to uncertain threat from the NPU-threat test were largely unrelated to mindfulness, anxiety, or the IU self-report measure. The results provide initial evidence that reactions to uncertainty may play a role in the mindfulness-anxiety relationship and suggest that studies are needed to address how methodological variations of the NPU-threat test affect perceived levels of uncertainty and uncertainty-related anxiety.

A way forward for anxiolytic drug development: Testing candidate anxiolytics with anxiety-potentiated startle in healthy humans

This review introduces a research strategy that may radically transform the pursuit of new anxiolytics, via the use of human models of anxiety in healthy individuals. Despite enormous investments in developing novel pharmacological treatments for anxiety disorders, pharmacotherapy for these conditions remains suboptimal. Most candidate anxiolytics from animal studies fail in clinical trials. We propose an additional screening step to help select candidate anxiolytics before launching clinical trials. This intermediate step moves the evidence for the potential anxiolytic property of candidate drugs from animals to humans, using experimental models of anxiety in healthy individuals. Anxiety-potentiated startle is a robust translational model of anxiety. The review of its face, construct, and predictive validity as well as its psychometric properties in humans establishes it as a promising tool for anxiolytic drug development. In conclusion, human models of anxiety may stir a faster, more efficient path for the development of clinically effective anxiolytics.

Threat-induced anxiety during goal pursuit disrupts amygdala-prefrontal cortex connectivity in posttraumatic stress disorder

To investigate how unpredictable threat during goal pursuit impacts fronto-limbic activity and functional connectivity in posttraumatic stress disorder (PTSD), we compared military veterans with PTSD (n = 25) vs. trauma-exposed control (n = 25). Participants underwent functional magnetic resonance imaging (fMRI) while engaged in a computerized chase-and-capture game task that involved optimizing monetary rewards obtained from capturing virtual prey while simultaneously avoiding capture by virtual predators. The game was played under two alternating contexts-one involving exposure to unpredictable task-irrelevant threat from randomly occurring electrical shocks, and a nonthreat control condition. Activation in and functional connectivity between the amygdala and ventromedial prefrontal cortex (vmPFC) was tested across threat and nonthreat task contexts with generalized psychophysiological interaction (gPPI) analyses. PTSD patients reported higher anxiety than controls across contexts. Better task performance represented by successfully avoiding capture by predators under threat compared with nonthreat contexts was associated with stronger left amygdala-vmPFC functional connectivity in controls and greater vmPFC activation in PTSD patients. PTSD symptom severity was negatively correlated with vmPFC activation in trauma-exposed controls and with right amygdala-vmPFC functional connectivity across all participants in the threat relative to nonthreat contexts. The findings showed that veterans with PTSD have disrupted amygdala-vmPFC functional connectivity and greater localized vmPFC processing under threat modulation of goal-directed behavior, specifically related to successfully avoiding loss of monetary rewards. In contrast, trauma survivors without PTSD relied on stronger threat-modulated left amygdala-vmPFC functional connectivity during goal-directed behavior, which may represent a resilience-related functional adaptation.

Modeling anxiety in healthy humans: a key intermediate bridge between basic and clinical sciences

Animal models of anxiety disorders are important for elucidating neurobiological defense mechanisms. However, animal models are limited when it comes to understanding the more complex processes of anxiety that are unique to humans (e.g., worry) and to screen new treatments. In this review, we outline how the Experimental Psychopathology approach, based on experimental models of anxiety in healthy subjects, can mitigate these limitations and complement research in animals. Experimental psychopathology can bridge basic research in animals and clinical studies, as well as guide and constrain hypotheses about the nature of psychopathology, treatment mechanisms, and treatment targets. This review begins with a brief review of the strengths and limitations of animal models before discussing the need for human models of anxiety, which are especially necessary to probe higher-order cognitive processes. This can be accomplished by combining anxiety-induction procedures with tasks that probe clinically relevant processes to identify neurocircuits that are potentially altered by anxiety. The review then discusses the validity of experimental psychopathology and introduces a methodological approach consisting of five steps: (1) select anxiety-relevant cognitive or behavioral operations and associated tasks, (2) identify the underlying neurocircuits supporting these operations in healthy controls, 3) examine the impact of experimental anxiety on the targeted operations in healthy controls, (4) utilize findings from step 3 to generate hypotheses about neurocircuit dysfunction in anxious patients, and 5) evaluate treatment mechanisms and screen novel treatments. This is followed by two concrete illustrations of this approach and suggestions for future studies.

The effect of trait anxiety on attentional mechanisms in combined context and cue conditioning and extinction learning

Sensory processing and attention allocation are shaped by threat, but the role of trait-anxiety in sensory processing as a function of threat predictability remains incompletely understood. Therefore, we measured steady-state visual evoked potentials (ssVEPs) as an index of sensory processing of predictable and unpredictable threat cues in 29 low (LA) and 29 high (HA) trait-anxious participants during a modified NPU-paradigm followed by an extinction phase. Three different contextual cues indicated safety (N), predictable (P) or unpredictable threat (U), while foreground cues signalled shocks in the P-condition only. All participants allocated increased attentional resources to the central P-threat cue, replicating previous findings. Importantly, LA individuals exhibited larger ssVEP amplitudes to contextual threat (U and P) than to contextual safety cues, while HA individuals did not differentiate among contextual cues in general. Further, HA exhibited higher aversive ratings of all contexts compared to LA. These results suggest that high trait-anxious individuals might be worse at discriminating contextual threat stimuli and accordingly overestimate the probability and aversiveness of unpredictable threat. These findings support the notion of aberrant sensory processing of unpredictable threat in anxiety disorders, as this processing pattern is already evident in individuals at risk of these disorders.

Psychophysiological Markers of Fear and Anxiety

PURPOSE OF REVIEW

The purpose of this paper is to provide a current review of the recent literature (2015-2018) on psychophysiological markers of fear and anxiety.

RECENT FINDING

Relative to healthy controls, fear-based disorders are characterised by heightened physiological reactivity to circumscribe threat salient stimuli, whereas anxiety-related disorders are associated with a more blunted pattern of physiological reactivity. Fear and anxiety disorders are marked by abnormal patterns of physiological reactivity, characterised by hyper- and hypo-reactivity in response to stimuli varying in threat salience.

If or when? Uncertainty's role in anxious anticipation

Uncertainty is often associated with subjective distress and a potentiated anxiety response. Occurrence uncertainty, or the inability to predict if a threat will occur, has rarely been compared experimentally with temporal uncertainty, or the inability to predict when a threat will occur. The current study aimed to (a) directly compare the anxiogenic effects of anticipating these two types of uncertain threat, as indexed by the eyeblink startle response, and (b) assess the relationship between startle response to occurrence and temporal uncertainty and individual differences in self-reported intolerance of uncertainty and anxiety. The findings indicated that anticipation during occurrence uncertainty elicited a larger startle response than anticipating a certain threat, but anticipation during temporal uncertainty was superior at potentiating startle blink overall. Additional analyses of the effects of order and habituation further highlighted temporal uncertainty's superiority in eliciting greater startle responding. This suggests that, while uncertainty is physiologically anxiety provoking, some level of certainty that the threat will occur enhances the robustness of the physiological anxiety response. However, self-reported anxiety was equivalent for temporal and occurrence uncertainty, suggesting that, while defensive responding may be more affected by temporal uncertainty, people perceive both types of uncertainty as anxiogenic. Individual differences in the intolerance of uncertainty and other anxiety measures were not related to anticipatory startle responsivity during any of the conditions.

Hypervigilance during anxiety and selective attention during fear: Using steady-state visual evoked potentials (ssVEPs) to disentangle attention mechanisms during predictable and unpredictable threat

Anxiety is induced by unpredictable threat, and presumably characterized by enhanced vigilance. In contrast, fear is elicited by imminent threat, and leads to phasic responses with selective attention. In order to investigate attention mechanisms and defensive responding during fear and anxiety, we employed an adaptation of the NPU-threat test and measured cortical (steady-state visual evoked potentials, ssVEPs), physiological (heart rate, HR), and subjective responses (ratings) to predictable (fear-related) and unpredictable (anxiety-related) threat in 42 healthy participants. An aversive unconditioned stimulus (US, loud noise) was 100% predicted by a cue (predictable P-cue) in one context (predictable P-context), but appeared unpredictably within a different context (unpredictable U-context, U-cue), while it was never delivered in a neutral safe context (N-cue, N- context). In response to predictable threat (P-cue), increased ssVEP amplitudes and accelerated HR were found. Both predictable and unpredictable contexts yielded increased ssVEP amplitudes compared to the safe context. Interestingly, in the unpredictable context participants showed longer-lasting visuocortical activation than in the predictable context, supporting the notion of heightened vigilance during anxiety. In parallel, HR decelerated to both threat contexts indicating fear bradycardia to these threatening contexts as compared to the safe context. These results support the idea of hypervigilance in anxiety-like situations reflected in a long-lasting facilitated processing of sensory information, in contrast to increased selective attention to specific imminent threat during fear. Thus, this study further supports the defense-cascade model with vigilance and orienting in the post-encounter phase of threat (anxiety), while selective attention and defensive mobilization in the circa-strike phase of threat (fear).

Preliminary evidence that reactivity to uncertain threat is an endophenotype for alcohol use disorder

BACKGROUND

Having an exaggerated reactivity to threats that are uncertain (U-threat) may facilitate the initiation and maintenance of excessive alcohol use in some individuals. This abnormality may not just be a concomitant for alcohol use disorder (AUD), but also an endophenotype for AUD.

METHOD

The aim of the current study was therefore to provide a preliminary test of whether U-threat is an endophenotype for AUD using several of the endophenotype criteria outlined by Gottesman and Gould (2003). Specifically, the study examined whether heightened U-threat reactivity is evidenced in those with: 1) current AUD; 2) remitted AUD (early and sustained remission examined separately); and 3) at-risk for AUD by virtue of having a positive family history of AUD. Participants (N = 147) completed a well-validated threat-of-shock task and startle eyeblink potentiation was collected as an index of aversive responding. Individuals and all available first-degree family members were diagnosed using structured clinical interviews.

RESULTS

Individuals at-risk for AUD, with current AUD, and AUD in remission (both early and sustained) all displayed exaggerated reactivity to U-threat, but not predictable threat, compared with non-AUD controls. Moreover, there were no significant differences between the at-risk and any of the AUD groups indicating that exaggerated reactivity to U-threat is relatively state-independent and present regardless of current AUD disease status.

CONCLUSIONS

The findings together highlight that exaggerated reactivity to U-threat may be a promising endophenotype for AUD that can aid in the refinement of mechanistic AUD disease models.