Social support of virtual characters reduces pain perception

BACKGROUND

Psychosocial factors, such as social support, can reduce pain. Virtual reality (VR) is a powerful tool to decrease pain, but social factors in VR-based pain analgesia have rarely been studied. Specifically, it is unclear whether social support by virtual characters can reduce pain and whether the perceived control behind virtual characters (agency) and varying degrees of social cues impact pain perception.

METHODS

Healthy participants (N = 97) received heat pain stimulation while undergoing four within-subject conditions in immersive VR: (1) virtual character with a low number of social cues (virtual figure) provided verbal support, (2) virtual character with a high number of social cues (virtual human) provided verbal support, (3) no social support (hearing neutral words), (4) no social support. Perceived agency of the virtual characters served as between-subjects factor. Participants in the avatar group were led to believe that another participant controlled the virtual characters. Participants in the agent group were told they interacted with a computer. However, in both conditions, virtual characters were computer-controlled. Pain ratings, psychophysiological measurements and presence ratings were recorded.

RESULTS

Virtual social support decreased pain intensity and pain unpleasantness ratings but had no impact on electrodermal activity nor heart rate. A virtual character with a high number of social cues led to lower pain unpleasantness and higher feelings of presence. Agency had no significant impact.

CONCLUSIONS

Virtual characters providing social support can reduce pain independent of perceived agency. A more human visual appearance can have beneficial effects on social pain modulation by virtual characters.

SIGNIFICANCE

Social influences are important factors in pain modulation. The current study demonstrated analgesic effects through verbal support provided by virtual characters and investigated modulating factors. A more human appearance of a virtual character resulted in a higher reduction of pain unpleasantness. Importantly, agency of the virtual characters had no impact. Given the increasing use of digital health interventions, the findings suggest a positive impact of virtual characters for digital pain treatments.

No influence of threat uncertainty on fear generalization

Fear overgeneralization and perceived uncertainty about future outcomes have been suggested as risk factors for clinical anxiety. However, little is known regarding how they influence each other. In this study, we investigated whether different levels of threat uncertainty influence fear generalization. Three groups of healthy participants underwent a differential fear conditioning protocol followed by a generalization test. All groups learned to associate one female face (conditioned stimulus, CS+) with a female scream (unconditioned stimulus, US), whereas the other face (CS-) was not associated with the scream. In order to manipulate threat uncertainty, one group (low uncertainty, n = 26) received 80%, the second group (moderate uncertainty, n = 32) received 60%, and the third group (high uncertainty, n = 30) 40% CS-US contingency. In the generalization test, all groups saw CS+ and CS- again along with four morphs resembling the CSs in steps of 20%. Subjective (expectancy, valence, and arousal ratings), psychophysiological (skin conductance response, SCR), and visuocortical (steady-state visual evoked potentials, ssVEPs) indices of fear were registered. Participants expected the US according to their reinforcement schedules and the discriminative responses to CS+/CS- increased with more uncertainty in skin conductance. However, acquisition of conditioned fear was not evident in ssVEPs. During the generalization test, we found no effect of threat uncertainty in any of the measured variables, but the strength of generalization for threat expectancy ratings was positively correlated with dispositional intolerance of uncertainty. This study suggests that mere threat uncertainty does not modulate fear generalization.

Context-Dependent Responses to the Spread of COVID-19 Among National and International Students During the First Lockdown: An Online Survey

BACKGROUND

Restrictions to minimize social contact was necessary to prevent the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus but may have impacted individuals' mental well-being. Emotional responses are modulated by contextual information. Living abroad during the coronavirus disease 2019 (COVID-19) pandemic may have boosted the feeling of isolation as the context is unfamiliar.

OBJECTIVES

This study compared the psychological impact of social distancing in national students (living in a familiar context) versus international students (living in an unfamiliar context).

METHODS

During March/April 2020 (first lockdown in the Netherlands), 850 university students completed an online survey. Structural equation modeling (SEM) was conducted to compare how students' responses to the virus were predicted by health anxiety, emotional distress, and personal traits.

RESULTS

Compared with national students, international students showed higher levels in 4 identified factors (COVID-19-related worry, perceived risk of infection, distance from possibly contaminated objects, distance from social situations). The factors were mainly predicted by health anxiety across international students, while emotional distress and individual traits (eg, intolerance of uncertainty) played a role across national students.

CONCLUSIONS

In the familiar context, individual characteristics (traits) predicted the responses to the virus, while the unfamiliar context drove individuals' health-focused responses. Living in a foreign country is associated with psychological burdens and this should be considered by universities for more pronounced social support and clear references to health-related institutions.

Examining the impact of cue similarity and fear learning on perceptual tuning

Past research on the effects of associative aversive learning on discrimination acuity has shown mixed results, including increases, decreases, and no changes in discrimination ability. An animal study found that the type of learning experience determined the direction and extent of learning-induced changes. The current preregistered web-based study aimed to translate these findings to humans. Experiment 1 (N = 245) compared changes in stimulus discrimination between simple learning (only one oriented grating cue), coarse differential conditioning (physically distinct cues), and fine differential conditioning (physically similar cues) as well as to their three respective control groups. The discrimination task consisted of a two-alternative-forced-choice task with oriented grating stimuli. During learning, a specific orientation was paired with unpleasant pictures. Our analysis using generative modeling demonstrated weak to moderate evidence that aversive learning did not alter discrimination acuity in any of the groups. In a follow-up experiment (N = 121), we replicated these findings despite successful learning trajectories in all three groups and a more detailed assessment of discrimination acuity. Contrary to prior assumptions, our findings indicate that aversive learning does not enhance perceptual discrimination, and the presence of additional safety cues does not appear to moderate this effect.

The effect of inherently threatening contexts on visuocortical engagement to conditioned threat

Fear and anxiety are crucial for adaptive responding in life-threatening situations. Whereas fear is a phasic response to an acute threat accompanied by selective attention, anxiety is characterized by a sustained feeling of apprehension and hypervigilance during situations of potential threat. In the current literature, fear and anxiety are usually considered mutually exclusive, with partially separated neural underpinnings. However, there is accumulating evidence that challenges this distinction between fear and anxiety, and simultaneous activation of fear and anxiety networks has been reported. Therefore, the current study experimentally tested potential interactions between fear and anxiety. Fifty-two healthy participants completed a differential fear conditioning paradigm followed by a test phase in which the conditioned stimuli were presented in front of threatening or neutral contextual images. To capture defense system activation, we recorded subjective (threat, US-expectancy), physiological (skin conductance, heart rate) and visuocortical (steady-state visual evoked potentials) responses to the conditioned stimuli as a function of contextual threat. Results demonstrated successful fear conditioning in all measures. In addition, threat and US-expectancy ratings, cardiac deceleration, and visuocortical activity were enhanced for fear cues presented in threatening compared with neutral contexts. These results are in line with an additive or interactive rather than an exclusive model of fear and anxiety, indicating facilitated defensive behavior to imminent danger in situations of potential threat.

VR for Studying the Neuroscience of Emotional Responses

Emotions are frequently considered as the driving force of behavior, and psychopathology is often characterized by aberrant emotional responding. Emotional states are reflected on a cognitive-verbal, physiological-humoral, and motor-behavioral level but to date, human research lacks an experimental protocol for a comprehensive and ecologically valid characterization of such emotional states. Virtual reality (VR) might help to overcome this situation by allowing researchers to study mental processes and behavior in highly controlled but reality-like laboratory settings. In this chapter, we first elucidate the role of presence and immersion as requirements for eliciting emotional states in a virtual environment and discuss different VR methods for emotion induction. We then consider the organization of emotional states on a valence continuum (i.e., from negative to positive) and on this basis discuss the use of VR to study threat processing and avoidance as well as reward processing and approach behavior. Although the potential of VR has not been fully realized in laboratory and clinical settings yet, this technological tool can open up new avenues to better understand the neurobiological mechanisms of emotional responding in healthy and pathological conditions.

Biomarkers of Anxiety Acquisition and Generalization in Virtual Reality Experiments

Abstract. Anxiety disorders are characterized by exaggerated responses to a threatening situation and overgeneralization. Context conditioning has been used for the identification of risk factors. This systematic literature search identifies 16 articles published between 1990 and 2021 on differential anxiety conditioning and generalization in humans. Additionally, we provide example data for individuals suffering from panic attacks with and without depressive symptoms. Successful anxiety acquisition (discrimination between anxiety and safety context) was found on the subjective level of anxiety and US-expectancy, on the physiological level of electrodermal activity, and in the defensive behavior of startle response. Anxiety generalization (discrimination between generalization and safety context) was found on the verbal but not on the physiobehavioral level. In sum, we emphasize the impact of virtual reality on anxiety research. Verbal and physiobehavioral responses serve as reliable biomarkers for anxiety. Few studies found ratings to be the best predictor for anxiety generalization. Genetic predisposition or personality traits might foster overgeneralization.

Investigating sustained attention in contextual threat using steady‐state VEPs evoked by flickering video stimuli

Anxiety is characterized by anxious anticipation and heightened vigilance to uncertain threat. However, if threat is not reliably indicated by a specific cue, the context in which threat was previously experienced becomes its best predictor, leading to anxiety. A suitable means to induce anxiety experimentally is context conditioning: In one context (CTX+), an unpredictable aversive stimulus (US) is repeatedly presented, in contrast to a second context (CTX-), in which no US is ever presented. In this EEG study, we investigated attentional mechanisms during acquisition and extinction learning in 38 participants, who underwent a context conditioning protocol. Flickering video stimuli (32 s clips depicting virtual offices representing CTX+/-) were used to evoke steady-state visual evoked potentials (ssVEPs) as an index of visuocortical engagement with the contexts. Analyses of the electrocortical responses suggest a successful induction of the ssVEP signal by video presentation in flicker mode. Furthermore, we found clear indices of context conditioning and extinction learning on a subjective level, while cortical processing of the CTX+ was unexpectedly reduced during video presentation. The differences between CTX+ and CTX- diminished during extinction learning. Together, these results indicate that the dynamic sensory input of the video presentation leads to disruptions in the ssVEP signal, which is greater for motivationally significant, threatening contexts.

Responsivity of the Striatal Dopamine System to Methylphenidate-A Within-Subject I-123-β-CIT-SPECT Study in Male Children and Adolescents With Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Methylphenidate (MPH) is the first-line pharmacological treatment of attention-deficit/hyperactivity disorder (ADHD). MPH binds to the dopamine (DA) transporter (DAT), which has high density in the striatum. Assessments of the striatal dopamine transporter by single positron emission computed tomography (SPECT) in childhood and adolescent patients are rare but can provide insight on how the effects of MPH affect DAT availability. The aim of our within-subject study was to investigate the effect of MPH on DAT availability and how responsivity to MPH in DAT availability is linked to clinical symptoms and cognitive functioning.

METHODS

Thirteen adolescent male patients (9-16 years) with a diagnosis of ADHD according to the DSM-IV and long-term stimulant medication (for at least 6 months) with MPH were assessed twice within 7 days using SPECT after application of I-123-β-CIT to examine DAT binding potential (DAT BP). SPECT measures took place in an on- and off-MPH status balanced for order across participants. A virtual reality continuous performance test was performed at each time point. Further clinical symptoms were assessed for baseline off-MPH.

RESULTS

On-MPH status was associated with a highly significant change (-29.9%) of striatal DAT BP as compared to off-MPH (t = -4.12, p = 0.002). A more pronounced change in striatal DAT BP was associated with higher off-MPH attentional and externalizing symptom ratings (Pearson r = 0.68, p = 0.01). Striatal DAT BP off-MPH, but not on-MPH, was associated with higher symptom ratings (Pearson r = 0.56, p = 0.04).

CONCLUSION

Our findings corroborate previous reports from mainly adult samples that MPH changes striatal DAT BP availability and suggest higher off-MPH DAT BP, likely reflecting low baseline DA levels, as a marker of symptom severity.

The skin conductance response indicating pain relief is independent of self or social influence on pain

Pain relief is defined as the ease of pain and is thus highly relevant for clinical applications and everyday life. Given that pain relief is based on the cessation of an aversive pain experience, it is reasonable to assume that pain relief learning would also be shaped by factors that alter subjective and physiological pain responses, such as social presence or a feeling of control. To date, it remains unclear whether and how factors that shape autonomic pain responses might affect pain relief learning. Here, we investigated how pain relief learning is shaped by two important factors known to modulate pain responses, i.e. social influence and controllability of pain. Skin conductance responses (SCRs) were recorded while participants learned to associate a formerly neutral stimulus with pain relief under three different pain conditions. In the social‐influence condition (N = 34), the pain stimulation could be influenced by another person’s decisions. In the self‐influence condition (N = 31), the participants themselves could influence the pain stimulation. Finally, in the no‐influence condition (N = 32), pain stimulation was simply delivered without any influence. According to our results, the SCRs elicited by the stimulus that was associated with pain relief were significantly smaller compared to the SCRs elicited by a neutral control stimulus, indicating pain relief learning. However, there was no significant difference in the pain relief learning effect across the groups. These results suggest that physiological pain relief learning in humans is not significantly influenced by social influence and pain controllability.

The contents of this page will be shown on the eTOC on the online version only. It will not be published as part of the article PDF. Subjective and physiological pain responses can be altered by social support or pain controllability. Pain relief strongly depends on the perceived pain, but we found that it is less influenceable. Neither social nor self‐influence changed the magnitude of physiological pain‐relief responses. We conclude that pain relief is a basic mechanism not easily influenced by circumstantial manipulations.

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 shapes visual discrimination in a web-based classical conditioning task

Threat detection plays a vital role in adapting behavior to changing environments. A fundamental function to improve threat detection is learning to differentiate between stimuli predicting danger and safety. Accordingly, aversive learning should lead to enhanced sensory discrimination of danger and safety cues. However, studies investigating the psychophysics of visual and auditory perception after aversive learning show divergent findings, and both enhanced and impaired discrimination after aversive learning have been reported. Therefore, the aim of this web-based study is to examine the impact of aversive learning on a continuous measure of visual discrimination. To this end, 205 participants underwent a differential fear conditioning paradigm before and after completing a visual discrimination task using differently oriented grating stimuli. Participants saw either unpleasant or neutral pictures as unconditioned stimuli (US). Results demonstrated sharpened visual discrimination for the US-associated stimulus (CS+), but not for the unpaired conditioned stimuli (CS-). Importantly, this finding was irrespective of the US's valence. These findings suggest that associative learning results in increased stimulus salience, which facilitates perceptual discrimination in order to prioritize attentional deployment.

Reducing Generalization of Conditioned Fear: Beneficial Impact of Fear Relevance and Feedback in Discrimination Training

Anxiety patients over-generalize fear, possibly because of an incapacity to discriminate threat and safety signals. Discrimination trainings are promising approaches for reducing such fear over-generalization. Here we investigated the efficacy of a fear-relevant vs. a fear-irrelevant discrimination training on fear generalization and whether the effects are increased with feedback during training. Eighty participants underwent two fear acquisition blocks, during which one face (conditioned stimulus, CS+), but not another face (CS-), was associated with a female scream (unconditioned stimulus, US). During two generalization blocks, both CSs plus four morphs (generalization stimuli, GS1-GS4) were presented. Between these generalization blocks, half of the participants underwent a fear-relevant discrimination training (discrimination between CS+ and the other faces) with or without feedback and the other half a fear-irrelevant discrimination training (discrimination between the width of lines) with or without feedback. US expectancy, arousal, valence ratings, and skin conductance responses (SCR) indicated successful fear acquisition. Importantly, fear-relevant vs. fear-irrelevant discrimination trainings and feedback vs. no feedback reduced generalization as reflected in US expectancy ratings independently from one another. No effects of training condition were found for arousal and valence ratings or SCR. In summary, this is a first indication that fear-relevant discrimination training and feedback can improve the discrimination between threat and safety signals in healthy individuals, at least for learning-related evaluations, but not evaluations of valence or (physiological) arousal.

International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020)

Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

Generalization of Conditioned Contextual Anxiety and the Modulatory Effects of Anxiety Sensitivity

Anxiety patients overgeneralize fear responses, possibly because they cannot distinguish between cues never been associated with a threat (i.e., safe) and threat-associated cues. However, as contexts and not cues are discussed as the relevant triggers for prolonged anxiety responses characterizing many anxiety disorders, we speculated that it is rather overgeneralization of contextual anxiety, which constitutes a risk factor for anxiety disorders. To this end, we investigated generalization of conditioned contextual anxiety and explored modulatory effects of anxiety sensitivity, a risk factor for anxiety disorders. Fifty-five participants underwent context conditioning in a virtual reality paradigm. On Day 1 (acquisition), participants received unpredictable mildly painful electric stimuli (unconditioned stimulus, US) in one virtual office (anxiety context, CTX+), but never in a second office (safety context, CTX-). Successful acquisition of conditioned anxiety was indicated by aversive ratings and defensive physiological responses (i.e., SCR) to CTX+ vs CTX-. On Day 2 (generalization), participants re-visited both the anxiety and the safety contexts plus three generalization contexts (G-CTX), which were gradually dissimilar to CTX+ (from 75 to 25%). Generalization of conditioned anxiety was evident for ratings, but less clear for physiological responses. The observed dissociation between generalization of verbal and physiological responses suggests that these responses depend on two distinct context representations, likely elemental and contextual representations. Importantly, anxiety sensitivity was positively correlated with the generalization of reported contextual anxiety. Thus, this study demonstrates generalization gradients for conditioned contextual anxiety and that anxiety sensitivity facilitates such generalization processes suggesting the importance of generalization of contextual anxiety for the development of anxiety disorders.

Conjunctive and Elemental Representations of a Context in Humans

The dual-process theory assumes that contexts are encoded in an elemental and in a conjunctive representation. However, this theory was developed from animal studies, and we still have to explore if and how elemental and conjunctive representations contribute to, for example, contextual anxiety in humans. Therefore, 28 participants underwent differential context conditioning in a newly developed flip-book paradigm. Virtual rooms were presented similar to a flip-book, that is, as a stream of 49 consecutive screenshots creating the impression of walking through the rooms. This allowed registration of event-related brain potentials triggered by specific screenshots. During two acquisition phases, two rooms were shown in this way for six times each. In one room, the anxiety context (CTX+), mildly painful electric stimuli (unconditioned stimuli [USs]) were administered unpredictably after 12 distinct screenshots, which became threat elements, whereas 12 selected comparable screenshots became nonthreat elements (elemental representation); all screenshots represented the anxiety context (conjunctive representation). In the second room, the safety context (CTX-), no USs were applied; thus, all screenshots created the safety context whereby 12 preselected screenshots represented safety elements. Increased US expectancy ratings for threat versus nonthreat or safety elements reflected elemental representation. Conjunctive representation was evident in differential ratings (arousal and contingency) and increased P100 and early posterior negativity amplitudes for threat and nonthreat CTX+ versus safety CTX- screenshots. These differences disappeared during two test phases without US delivery indicating successful extinction. In summary, we revealed the first piece of evidence for the simultaneous contributions of elemental and conjunctive representation during context conditioning in humans.

The Influence of Methylphenidate on Hyperactivity and Attention Deficits in Children With ADHD: A Virtual Classroom Test

Objective: This study compares the performance in a continuous performance test within a virtual reality classroom (CPT-VRC) between medicated children with ADHD, unmedicated children with ADHD, and healthy children. Method:N = 94 children with ADHD (n = 26 of them received methylphenidate and n = 68 were unmedicated) and n = 34 healthy children performed the CPT-VRC. Omission errors, reaction time/variability, commission errors, and body movements were assessed. Furthermore, ADHD questionnaires were administered and compared with the CPT-VRC measures. Results: The unmedicated ADHD group exhibited more omission errors and showed slower reaction times than the healthy group. Reaction time variability was higher in the unmedicated ADHD group compared with both the healthy and the medicated ADHD group. Omission errors and reaction time variability were associated with inattentiveness ratings of experimenters. Head movements were correlated with hyperactivity ratings of parents and experimenters. Conclusion: Virtual reality is a promising technology to assess ADHD symptoms in an ecologically valid environment.

Navigating the garden of forking paths for data exclusions in fear conditioning research

In this report, we illustrate the considerable impact of researcher degrees of freedom with respect to exclusion of participants in paradigms with a learning element. We illustrate this empirically through case examples from human fear conditioning research, in which the exclusion of 'non-learners' and 'non-responders' is common - despite a lack of consensus on how to define these groups. We illustrate the substantial heterogeneity in exclusion criteria identified in a systematic literature search and highlight the potential problems and pitfalls of different definitions through case examples based on re-analyses of existing data sets. On the basis of these studies, we propose a consensus on evidence-based rather than idiosyncratic criteria, including clear guidelines on reporting details. Taken together, we illustrate how flexibility in data collection and analysis can be avoided, which will benefit the robustness and replicability of research findings and can be expected to be applicable to other fields of research that involve a learning element.

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

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

Contextual Fear Conditioning and Fear Generalization in Individuals With Panic Attacks

Context conditioning is characterized by unpredictable threat and its generalization may constitute risk factors for panic disorder (PD). Therefore, we examined differences between individuals with panic attacks (PA; N = 21) and healthy controls (HC, N = 22) in contextual learning and context generalization using a virtual reality (VR) paradigm. Successful context conditioning was indicated in both groups by higher arousal, anxiety and contingency ratings, and increased startle responses and skin conductance levels (SCLs) in an anxiety context (CTX+) where an aversive unconditioned stimulus (US) occurred unpredictably vs. a safety context (CTX−). PA compared to HC exhibited increased differential responding to CTX+ vs. CTX− and overgeneralization of contextual anxiety on an evaluative verbal level, but not on a physiological level. We conclude that increased contextual conditioning and contextual generalization may constitute risk factors for PD or agoraphobia contributing to the characteristic avoidance of anxiety contexts and withdrawal to safety contexts and that evaluative cognitive process may play a major role.

Generalization of appetitive conditioned responses

A stimulus (conditioned stimulus, CS) associated with an appetitive unconditioned stimulus (US) acquires positive properties and elicits appetitive conditioned responses (CR). Such associative learning has been examined extensively in animals with food as the US, and results are used to explain psychopathologies (e.g., substance‐related disorders or obesity). Human studies on appetitive conditioning exist, too, but we still know little about generalization processes. Understanding these processes may explain why stimuli not associated with a drug, for instance, can elicit craving. Forty‐seven hungry participants underwent an appetitive conditioning protocol during which one of two circles with different diameters (CS+) became associated with an appetitive US (chocolate or salty pretzel, according to participants’ preference) but never the other circle (CS−). During generalization, US were delivered twice and the two CS were presented again plus four circles (generalization stimuli, GS) with gradually increasing diameters from CS− to CS+. We found successful appetitive conditioning as reflected in appetitive subjective ratings (positive valence, higher contingency) and physiological responses (startle attenuation and larger skin conductance responses) to CS+ versus CS−, and, importantly, both measures confirmed generalization as indicated by generalization gradients. Small changes in CS‐US contingency during generalization may have weakened generalization processes on the physiological level. Considering that appetitive conditioned responses can be generalized to non‐US‐associated stimuli, a next important step would be to investigate risk factors that mediate overgeneralization.

Numerous studies demonstrated overgeneralization of conditioned fear as a pathological marker for anxiety disorders as well as stress‐related disorders. Appetitive conditioning is crucially involved in mental disorders such as eating or substance‐related and addictive disorders. Thus far, the generalization processes of appetitive conditioned responses remain unexplored. In this study, we demonstrate for the first time a generalization gradient of appetitive conditioned responses. Our study contributes and extends the understanding of generalization processes by explaining, for instance, why craving can be elicited by stimuli that share physical properties with a stimulus signaling the drug.

Human BDNF rs6265 polymorphism as a mediator for the generalization of contextual anxiety

The Met allele of the human brain-derived neurotrophic factor (BDNF) gene might be a risk factor for anxiety disorders and is associated with reduced hippocampal volume. Notably, hippocampus plays a crucial role in contextual learning and generalization. The role of the BDNF gene variation in human context-conditioning and generalization is still unknown. We investigated 33 carriers of the Met allele (18 females) and 32 homozygous carriers of the Val allele (15 females) with a virtual-reality context-conditioning paradigm. Electric stimulations (unconditioned stimulus, US) were unpredictably delivered in one virtual office (CTX+), but never in another virtual office (CTX-). During generalization, participants revisited CTX+ and CTX- and a generalization office (G-CTX), which was a mix of the other two. Rating data indicated successful conditioning (more negative valence, higher arousal, anxiety and contingency ratings for CTX+ than CTX-), and generalization of conditioned anxiety by comparable ratings for G-CTX and CTX+. The startle data indicated discriminative learning for Met allele carriers, but not for Val homozygotes. Moreover, a trend effect suggests that startle responses of only the Met carriers were slightly potentiated in G-CTX versus CTX-. In sum, the BDNF polymorphism did not affect contextual learning and its generalization on a verbal level. However, the physiological data suggest that Met carriers are characterized by fast discriminative contextual learning and a tendency to generalize anxiety responses to ambiguous contexts. We propose that such learning may be related to reduced hippocampal functionality and the basis for the risk of Met carriers to develop anxiety disorders.

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).

Don't fear 'fear conditioning': Methodological considerations for the design and analysis of studies on human fear acquisition, extinction, and return of fear

The so-called 'replicability crisis' has sparked methodological discussions in many areas of science in general, and in psychology in particular. This has led to recent endeavours to promote the transparency, rigour, and ultimately, replicability of research. Originating from this zeitgeist, the challenge to discuss critical issues on terminology, design, methods, and analysis considerations in fear conditioning research is taken up by this work, which involved representatives from fourteen of the major human fear conditioning laboratories in Europe. This compendium is intended to provide a basis for the development of a common procedural and terminology framework for the field of human fear conditioning. Whenever possible, we give general recommendations. When this is not feasible, we provide evidence-based guidance for methodological decisions on study design, outcome measures, and analyses. Importantly, this work is also intended to raise awareness and initiate discussions on crucial questions with respect to data collection, processing, statistical analyses, the impact of subtle procedural changes, and data reporting specifically tailored to the research on fear conditioning.

Kontextkonditionierung in virtueller Realität als Modell für pathologische Angst

Zur experimentellen Untersuchung von Furcht, die sich auf spezifische Reize bezieht, eignet sich die Hinweisreizkonditionierung. Die Kontextkonditionierung dagegen ist wahrscheinlich ein Modell für Angst, die länger anhaltend und nicht reizbezogen ist. Kontextkonditionierung kann am Menschen in Analogie zu Tierstudien mittels virtueller Realität (VR) untersucht werden. Unser VR-Paradigma realisiert virtuelle Räume als Kontexte, wobei die Probanden im Angstkontext unvorhersehbare, leicht schmerzhafte elektrische Reize appliziert bekommen, im Sicherheitskontext dagegen nicht. Für die Validität des Paradigmas spricht, dass die Probanden den virtuellen Angstkontext als angstauslösend bewerten, ihn vermeiden und im Angstkontext potenzierte Schreckreaktionen zeigen. Unsere Folgestudien haben nachgewiesen, dass Risikofaktoren für Angststörungen die Kontextkonditionierung modulieren. Personen mit hoher Ängstlichkeit erlernen die Kontextkonditionierung schneller und zeigen im Angstkontext stärkere Angstreaktionen. Auch Personen, die genetische Risikofaktoren für Angststörungen haben, scheinen Kontextkonditionierungen besonders effektiv zu lernen, zumindest bei Betrachtung der potenzierten Schreckreaktion als Indikator für den Lernerfolg. Diese Befunde legen nahe, dass Kontextkonditionierungen bei Risikopersonen zur Entstehung von Angststörungen (z. B. Panikstörung, posttraumatische Belastungsstörung) beitragen.

Effects of context preexposure and delay until anxiety retrieval on generalization of contextual anxiety

Animal studies suggest that time delay between acquisition and retrieval of contextual anxiety increases generalization. Moreover, such generalization is prevented by preexposure to the context (CTX), presumably due to an improved representation of such context. We investigated whether preexposure and time-passing modulate generalization of contextual anxiety, in humans. On Day 1, 42 participants (preexposure group) explored two virtual offices, while 41 participants (no-preexposure group) explored a virtual stadium. On Day 2 (24 h later), all participants learned to associate one office (CTX+) with unpredictable unconditioned stimuli (USs), and another office (CTX-) with safety. On Day 3, either 24 h (recent test) or 2 wk (remote test) later, participants revisited CTX- and CTX+ without USs, as well as a generalization context (G-CTX). Results revealed successfully conditioned anxiety and anxiety generalization for ratings (G-CTX was as aversive as CTX+ was), while safety generalization was found for startle responses (G-CTX elicited startle attenuation as CTX- did). Time between learning and testing enhanced generalization as reflected by comparable startle responses to all three offices in the remote test. Contextual preexposure facilitated extinction of explicit conditioned anxiety assessed with ratings. These results suggest that memory trace of a context degrades with passage of time in humans like in animals and, consequently, anxiety generalization enhances. After context preexposure, high cognitive processes seem to be crucially involved in facilitating extinction (or safety) learning.

Converging evidence for an impact of a functional NOS gene variation on anxiety-related processes

Being a complex phenotype with substantial heritability, anxiety and related phenotypes are characterized by a complex polygenic basis. Thereby, one candidate pathway is neuronal nitric oxide (NO) signaling, and accordingly, rodent studies have identified NO synthase (NOS-I), encoded by NOS1, as a strong molecular candidate for modulating anxiety and hippocampus-dependent learning processes. Using a multi-dimensional and -methodological replication approach, we investigated the impact of a functional promoter polymorphism (NOS1-ex1f-VNTR) on human anxiety-related phenotypes in a total of 1019 healthy controls in five different studies. Homozygous carriers of the NOS1-ex1f short-allele displayed enhanced trait anxiety, worrying and depression scores. Furthermore, short-allele carriers were characterized by increased anxious apprehension during contextual fear conditioning. While autonomous measures (fear-potentiated startle) provided only suggestive evidence for a modulatory role of NOS1-ex1f-VNTR on (contextual) fear conditioning processes, neural activation at the amygdala/anterior hippocampus junction was significantly increased in short-allele carriers during context conditioning. Notably, this could not be attributed to morphological differences. In accordance with data from a plethora of rodent studies, we here provide converging evidence from behavioral, subjective, psychophysiological and neuroimaging studies in large human cohorts that NOS-I plays an important role in anxious apprehension but provide only limited evidence for a role in (contextual) fear conditioning.

Emotion regulation in heavy smokers: experiential, expressive and physiological consequences of cognitive reappraisal

Emotion regulation dysfunctions are assumed to contribute to the development of tobacco addiction and relapses among smokers attempting to quit. To further examine this hypothesis, the present study compared heavy smokers with non-smokers (NS) in a reappraisal task. Specifically, we investigated whether non-deprived smokers (NDS) and deprived smokers (DS) differ from non-smokers in cognitive emotion regulation and whether there is an association between the outcome of emotion regulation and the cigarette craving. Sixty-five participants (23 non-smokers, 22 NDS, and 20 DS) were instructed to down-regulate emotions by reappraising negative or positive pictorial scenarios. Self-ratings of valence, arousal, and cigarette craving as well as facial electromyography and electroencephalograph activities were measured. Ratings, facial electromyography, and electroencephalograph data indicated that both NDS and DS performed comparably to nonsmokers in regulating emotional responses via reappraisal, irrespective of the valence of pictorial stimuli. Interestingly, changes in cigarette craving were positively associated with regulation of emotional arousal irrespective of emotional valence. These results suggest that heavy smokers are capable to regulate emotion via deliberate reappraisal and smokers’ cigarette craving is associated with emotional arousal rather than emotional valence. This study provides preliminary support for the therapeutic use of reappraisal to replace maladaptive emotion-regulation strategies in nicotine addicts.

When does pleasure start after the end of pain? The time course of relief

Painful events are suggested to elicit two opponent responses: a negatively valenced and a positively valenced process triggered by their onset and termination, respectively. Consequently, stimuli (conditioned stimulus, CS) associated with pain onset (unconditioned stimulus, US) provoke defensive responses like startle potentiation, while stimuli associated with pain termination elicit appetitive responses like startle attenuation. Here we summarize four studies elucidating the time course of the relief following the termination of a painful US. In these studies, the timing of a relief-associated stimulus (reliefCS) presented after a painful US was varied from immediately (Study1), 3 seconds (Study4), or 6 seconds (Study2 and 3) after the US. Responses to these relief CSs were compared also with responses to a stimulus presented before the US (fearCS), and a third stimulus (safetyCS) that was never associated with the US. The synopsis of these studies reveals that the timing of the reliefCS is crucial to turn a defensive response into an appetitive response. Namely, the reliefCS immediately following the US-induced startle potentiation and negative valence (Study1); 3 seconds later, the startle response was slightly less potentiated and the ratings a little less negative (Study4); finally, the reliefCS presented 6 seconds after the US caused startle attenuation (Study2 and 3) and positively valenced ratings (Study3). In sum, the observed time course of relief closely follows the predictions of opponent process theory. This means that relief may be a reinforcer that elicits conditioned appetitive behavior, but its reinforcing properties strongly depend on its temporal relation to the aversive event.

Generalization of Contextual Fear in Humans

Enhanced fear responses to cues, which were not associated with the threat but share perceptual characteristics with the threat signal, indicate generalization of conditioned fear. Here, we investigated for the first time generalization processes in contextual fear conditioning. Thirty-two participants were guided through two virtual offices (acquisition phases). Mildly painful electric shocks (unconditioned stimulus, US) were unpredictably delivered in one office (anxiety context, CTX+), but never in the other office (safety context, CTX-). During the generalization test, participants were guided through CTX+, CTX-, and the generalization context (G-CTX), which contained features of both the CTX+ and the CTX-, but no US was delivered. We found successful contextual fear conditioning (i.e., the CTX+ compared to the CTX- elicited potentiated startle responses and was rated with more negative valence, higher arousal and higher anxiety). Importantly, implicit and explicit responses dissociated in the generalization test. Thus, participants rated the G-CTX as more arousing and anxiogenic than the CTX- indicating anxiety generalization, but they showed enhanced startle responses to the CTX+ only, while the G-CTX and the CTX- did not differ. In summary, healthy participants on an explicit level responded to the generalization context like to the anxiety context, but on an implicit level responded to the generalization context like to the safety context. Possibly, this dissociation suggests distinct and specific generalization processes underlying contextual fear.

Appetitive vs. Aversive conditioning in humans

In classical conditioning, an initially neutral stimulus (conditioned stimulus, CS) becomes associated with a biologically salient event (unconditioned stimulus, US), which might be pain (aversive conditioning) or food (appetitive conditioning). After a few associations, the CS is able to initiate either defensive or consummatory responses, respectively. Contrary to aversive conditioning, appetitive conditioning is rarely investigated in humans, although its importance for normal and pathological behaviors (e.g., obesity, addiction) is undeniable. The present study intents to translate animal findings on appetitive conditioning to humans using food as an US. Thirty-three participants were investigated between 8 and 10 am without breakfast in order to assure that they felt hungry. During two acquisition phases, one geometrical shape (avCS+) predicted an aversive US (painful electric shock), another shape (appCS+) predicted an appetitive US (chocolate or salty pretzel according to the participants' preference), and a third shape (CS-) predicted neither US. In a extinction phase, these three shapes plus a novel shape (NEW) were presented again without US delivery. Valence and arousal ratings as well as startle and skin conductance (SCR) responses were collected as learning indices. We found successful aversive and appetitive conditioning. On the one hand, the avCS+ was rated as more negative and more arousing than the CS- and induced startle potentiation and enhanced SCR. On the other hand, the appCS+ was rated more positive than the CS- and induced startle attenuation and larger SCR. In summary, we successfully confirmed animal findings in (hungry) humans by demonstrating appetitive learning and normal aversive learning.

Brain activity associated with illusory correlations in animal phobia

Anxiety disorder patients were repeatedly found to overestimate the association between disorder-relevant stimuli and aversive outcomes despite random contingencies. Such an illusory correlation (IC) might play an important role in the return of fear after extinction learning; yet, little is known about how this cognitive bias emerges in the brain. In a functional magnetic resonance imaging study, 18 female patients with spider phobia and 18 healthy controls were exposed to pictures of spiders, mushrooms and puppies followed randomly by either a painful electrical shock or nothing. In advance, both patients and healthy controls expected more shocks after spider pictures. Importantly, only patients with spider phobia continued to overestimate this association after the experiment. The strength of this IC was predicted by increased outcome aversiveness ratings and primary sensory motor cortex activity in response to the shock after spider pictures. Moreover, increased activation of the left dorsolateral prefrontal cortex (dlPFC) to spider pictures predicted the IC. These results support the theory that phobia-relevant stimuli amplify unpleasantness and sensory motor representations of aversive stimuli, which in turn may promote their overestimation. Hyper-activity in dlPFC possibly reflects a pre-occupation of executive resources with phobia-relevant stimuli, thus complicating the accurate monitoring of objective contingencies and the unlearning of fear.

Is there a negative interpretation bias in depressed patients? An affective startle modulation study

BACKGROUND/AIMS

Scientists proposed that patients with depression favour negative interpretations when appraising ambiguity. As self-report measures seem prone to response bias, implicit measures of emotional valence should be additionally used.

METHODS

A total of 16 patients with depression and 19 controls underwent an acoustic imagery task comprising neutral and negative words, as well as ambiguous words that could be understood either way. Affective startle modulation and direct interrogation were used to assess implicit and explicit emotional valence, respectively. We expected a negative bias for ambiguous words in the patient group, resulting in augmented startle magnitudes and preference for negative interpretations of the ambiguous words in the interrogation.

RESULTS

Surprisingly, both groups preferred neutral interpretations and showed augmented startle magnitudes to ambiguous words. Furthermore, both groups displayed an emotional startle potentiation for negative words.

CONCLUSION

In summary, our results do not confirm a negative interpretation bias or a blunted emotional response in patients with major depression. The mismatch between self-report and affective startle reaction to ambiguous targets might reflect defensive mobilization or attention effects.

Delay and trace fear conditioning in a complex virtual learning environment-neural substrates of extinction

Extinction is an important mechanism to inhibit initially acquired fear responses. There is growing evidence that the ventromedial prefrontal cortex (vmPFC) inhibits the amygdala and therefore plays an important role in the extinction of delay fear conditioning. To our knowledge, there is no evidence on the role of the prefrontal cortex in the extinction of trace conditioning up to now. Thus, we compared brain structures involved in the extinction of human delay and trace fear conditioning in a between-subjects-design in an fMRI study. Participants were passively guided through a virtual environment during learning and extinction of conditioned fear. Two different lights served as conditioned stimuli (CS); as unconditioned stimulus (US) a mildly painful electric stimulus was delivered. In the delay conditioning group (DCG) the US was administered with offset of one light (CS+), whereas in the trace conditioning group (TCG) the US was presented 4 s after CS+ offset. Both groups showed insular and striatal activation during early extinction, but differed in their prefrontal activation. The vmPFC was mainly activated in the DCG, whereas the TCG showed activation of the dorsolateral prefrontal cortex (dlPFC) during extinction. These results point to different extinction processes in delay and trace conditioning. VmPFC activation during extinction of delay conditioning might reflect the inhibition of the fear response. In contrast, dlPFC activation during extinction of trace conditioning may reflect modulation of working memory processes which are involved in bridging the trace interval and hold information in short term memory.

Medial prefrontal cortex stimulation modulates the processing of conditioned fear

The extinction of conditioned fear depends on an efficient interplay between the amygdala and the medial prefrontal cortex (mPFC). In rats, high-frequency electrical mPFC stimulation has been shown to improve extinction by means of a reduction of amygdala activity. However, so far it is unclear whether stimulation of homologues regions in humans might have similar beneficial effects. Healthy volunteers received one session of either active or sham repetitive transcranial magnetic stimulation (rTMS) covering the mPFC while undergoing a 2-day fear conditioning and extinction paradigm. Repetitive TMS was applied offline after fear acquisition in which one of two faces (CS+ but not CS-) was associated with an aversive scream (UCS). Immediate extinction learning (day 1) and extinction recall (day 2) were conducted without UCS delivery. Conditioned responses (CR) were assessed in a multimodal approach using fear-potentiated startle (FPS), skin conductance responses (SCR), functional near-infrared spectroscopy (fNIRS), and self-report scales. Consistent with the hypothesis of a modulated processing of conditioned fear after high-frequency rTMS, the active group showed a reduced CS+/CS- discrimination during extinction learning as evident in FPS as well as in SCR and arousal ratings. FPS responses to CS+ further showed a linear decrement throughout both extinction sessions. This study describes the first experimental approach of influencing conditioned fear by using rTMS and can thus be a basis for future studies investigating a complementation of mPFC stimulation to cognitive behavioral therapy (CBT).

Pain predictability reverses valence ratings of a relief-associated stimulus

Relief from pain is positively valenced and entails reward-like properties. Notably, stimuli that became associated with pain relief elicit reward-like implicit responses too, but are explicitly evaluated by humans as aversive. Since the unpredictability of pain makes pain more aversive, this study examined the hypotheses that the predictability of pain also modulates the valence of relief-associated stimuli. In two studies, we presented one conditioned stimulus (_FORWARDCS+) before a painful unconditioned stimulus (US), another stimulus (_BACKWARDCS+) after the painful US, and a third stimulus (CS−) was never associated with the US. In Study 1, _FORWARDCS+ predicted half of the USs while the other half was delivered unwarned and followed by _BACKWARDCS+. In Study 2, all USs were predicted by _FORWARDCS+ and followed by _BACKWARDCS+. In Study 1 both _FORWARDCS+ and _BACKWARDCS+ were rated as negatively valenced and high arousing after conditioning, while _BACKWARDCS+ in Study 2 acquired positive valence and low arousal. Startle amplitude was significantly attenuated to _BACKWARDCS+ compared to _FORWARDCS+ in Study 2, but did not differ among CSs in Study 1. In summary, predictability of aversive events reverses the explicit valence of a relief-associated stimulus.

Contextual fear conditioning in virtual reality is affected by 5HTTLPR and NPSR1 polymorphisms: effects on fear-potentiated startle

The serotonin (5-HT) and neuropeptide S (NPS) systems are discussed as important genetic modulators of fear and sustained anxiety contributing to the etiology of anxiety disorders. Sustained anxiety is a crucial characteristic of most anxiety disorders which likely develops through contextual fear conditioning. This study investigated if and how genetic alterations of the 5-HT and the NPS systems as well as their interaction modulate contextual fear conditioning; specifically, function polymorphic variants in the genes coding for the 5-HT transporter (5HTT) and the NPS receptor (NPSR1) were studied. A large group of healthy volunteers was therefore stratified for 5HTTLPR (S+ vs. LL carriers) and NPSR1 rs324981 (T+ vs. AA carriers) polymorphisms resulting in four genotype groups (S+/T+, S+/AA, LL/T+, LL/AA) of 20 participants each. All participants underwent contextual fear conditioning and extinction using a virtual reality (VR) paradigm. During acquisition, one virtual office room (anxiety context, CXT+) was paired with an unpredictable electric stimulus (unconditioned stimulus, US), whereas another virtual office room was not paired with any US (safety context, CXT−). During extinction no US was administered. Anxiety responses were quantified by fear-potentiated startle and ratings. Most importantly, we found a gene × gene interaction on fear-potentiated startle. Only carriers of both risk alleles (S+/T+) exhibited higher startle responses in CXT+ compared to CXT−. In contrast, anxiety ratings were only influenced by the NPSR1 polymorphism with AA carriers showing higher anxiety ratings in CXT+ as compared to CXT−. Our results speak in favor of a two level account of fear conditioning with diverging effects on implicit vs. explicit fear responses. Enhanced contextual fear conditioning as reflected in potentiated startle responses may be an endophenotype for anxiety disorders.

Enhanced discrimination between threatening and safe contexts in high-anxious individuals

Trait anxiety, a stable personality trait associated with increased fear responses to threat, is regarded as a risk factor for the development and maintenance of anxiety disorders. Although the effect of trait anxiety has been examined with regard to explicit threat cues, little is known about the effect of trait anxiety on contextual threat learning. To assess this issue, extreme groups of low and high trait anxiety underwent a contextual fear conditioning protocol using virtual reality. Two virtual office rooms served as the conditioned contexts. One virtual office room (CXT+) was paired with unpredictable electrical stimuli. In the other virtual office room, no electrical stimuli were delivered (CXT-). High-anxious participants tended to show faster acquisition of startle potentiation in the CXT+ versus the CXT- than low-anxious participants. This enhanced contextual fear learning might function as a risk factor for anxiety disorders that are characterized by sustained anxiety.