Context conditioning in humans using commercially available immersive Virtual Reality

Itsy bitsy spider: Fear and avoidance (generalization) in a free-exploratory virtual reality paradigm

Most experimental avoidance paradigms lack either control over the experimental situation or simplify real-life avoidance behavior to a great extent, making it difficult to generalize the results to the complex approach-avoidance situations that anxious individuals face in daily life. The current study aimed to examine the usability of our recently developed free-exploratory avoidance paradigm in Virtual Reality (VR) that allows for the assessment of subjective as well as behavioral avoidance in participants with varying levels of spider fear. In a VR escape room, participants searched for cues to decipher a code-locked door. Opening a wooden box marked with a post-it note (conditioned stimulus, CS) resulted in exposure to a virtual crawling spider (unconditioned stimulus, US). Avoidance of the original CS and other objects marked with the CS (generalization stimuli, GSs; EXPgen condition) or non-marked (CONT condition) objects was measured via questionnaires and relative manipulation times in a novel room. We expected a positive linear relationship between US aversiveness (levels of spider fear) and (generalization of) fear and avoidance behaviors. Avoidance learning and generalization was demonstrated on both a subjective and behavioral level. Higher levels of spider fear were, overall, related to more negative emotions in response to the encounter with the spider, higher US expectancies for the GSs, and more self-reported and behavioral avoidance of the original CS and the GSs. Finally, we explored relationships between trait anxiety and intolerance of uncertainty and fear and avoidance (generalization), but no robust associations were observed. In conclusion, we confirmed the expected positive linear relationship between spider fear and (generalization of) fear and avoidance behaviors. Our results suggest that our free-exploratory VR avoidance paradigm is well-suited to investigate avoidance behaviors and the generalization of avoidance.

Altered frontolimbic activity during virtual reality-based contextual fear learning in patients with posttraumatic stress disorder

BACKGROUND

Deficiency in contextual and enhanced responding in cued fear learning may contribute to the development of posttraumatic stress disorder (PTSD). We examined the responses to aversive Pavlovian conditioning with an unpredictable spatial context as conditioned stimulus compared to a predictable context. We hypothesized that the PTSD group would demonstrate less hippocampal and ventromedial prefrontal cortex (vmPFC) activation during acquisition and extinction of unpredictable contexts and an over-reactive amygdala response in the predictable contexts compared to controls.

METHODS

A novel combined differential cue-context conditioning paradigm was applied using virtual reality with spatial contexts that required configural and cue processing. We assessed 20 patients with PTSD, 21 healthy trauma-exposed (TC) and 22 non-trauma-exposed (HC) participants using functional magnetic resonance imaging, skin conductance responses, and self-report measures.

RESULTS

During fear acquisition, patients with PTSD compared to TC showed lower activity in the hippocampi in the unpredictable and higher activity in the amygdalae in the predictable context. During fear extinction, TC compared to patients and HC showed higher brain activity in the vmPFC in the predictable context. There were no significant differences in self-report or skin conductance responses.

CONCLUSIONS

Our results suggest that patients with PTSD differ in brain activation from controls in regions such as the hippocampus, the amygdala, and the vmPFC in the processing of unpredictable and predictable contexts. Deficient encoding of more complex configurations might lead to a preponderance of cue-based predictions in PTSD. Exposure-based treatments need to focus on improving predictability of contextual processing and reducing enhanced cue reactivity.

Measuring human context fear conditioning and retention after consolidation

Fear conditioning is a laboratory paradigm commonly used to investigate aversive learning and memory. In context fear conditioning, a configuration of elemental cues (conditioned stimulus [CTX]) predicts an aversive event (unconditioned stimulus [US]). To quantify context fear acquisition in humans, previous work has used startle eyeblink responses (SEBRs), skin conductance responses (SCRs), and verbal reports, but different quantification methods have rarely been compared. Moreover, preclinical intervention studies mandate recall tests several days after acquisition, and it is unclear how to induce and measure context fear memory retention over such a time interval. First, we used a semi-immersive virtual reality paradigm. In two experiments (N = 23 and N = 28), we found successful declarative learning and memory retention over 7 d but no evidence of other conditioned responses. Next, we used a configural fear conditioning paradigm with five static room images as CTXs in two experiments (N = 29 and N = 24). Besides successful declarative learning and memory retention after 7 d, SCR and pupil dilation in response to CTX onset differentiated CTX+/CTX- during acquisition training, and SEBR and pupil dilation differentiated CTX+/CTX- during the recall test, with medium to large effect sizes for the most sensitive indices (SEBR: Hedge's g = 0.56 and g = 0.69; pupil dilation: Hedge's g = 0.99 and g = 0.88). Our results demonstrate that with a configural learning paradigm, context fear memory retention can be demonstrated over 7 d, and we provide robust and replicable measurement methods to this end.

Parsing neural circuits of fear learning and extinction across basic and clinical neuroscience: Towards better translation

Over the past decades, studies of fear learning and extinction have advanced our understanding of the neurobiology of threat and safety learning. Animal studies can provide mechanistic/causal insights into human brain regions and their functional connectivity involved in fear learning and extinction. Findings in humans, conversely, may further enrich our understanding of neural circuits in animals by providing macroscopic insights at the level of brain-wide networks. Nevertheless, there is still much room for improvement in translation between basic and clinical research on fear learning and extinction. Through the lens of neural circuits, in this article, we aim to review the current knowledge of fear learning and extinction in both animals and humans, and to propose strategies to fill in the current knowledge gap for the purpose of enhancing clinical benefits.

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.

Head-Mounted Display-Based Application for Cognitive Training

Virtual Reality (VR) has had significant advances in rehabilitation, due to the gamification of cognitive activities that facilitate treatment. On the other hand, Immersive Virtual Reality (IVR) produces outstanding results due to the interactive features with the user. This work introduces a VR application for memory rehabilitation by walking through a maze and using the Oculus Go head-mounted display (HMD) technology. The mechanics of the game require memorizing geometric shapes while the player progresses in two modes, autonomous or manual, with two levels of difficulty depending on the number of elements to remember. The application is developed in the Unity 3D video game engine considering the optimization of computational resources to improve the performance in the processing and maintaining adequate benefits for the user, while the generated data is stored and sent to a remote server. The maze task was assessed with 29 subjects in a controlled environment. The obtained results show a significant correlation between participants’ response accuracy in both the maze task and a face–pair test. Thus, the proposed task is able to perform memory assessments.

Quantifying Human Avoidance Behavior in Immersive Virtual Reality

Avoidance behavior is a key symptom of most anxiety disorders and a central readout in animal research. However, the quantification of real-life avoidance behavior in humans is typically restricted to clinical populations, who show actual avoidance of phobic objects. In experimental approaches for healthy participants, many avoidance tasks utilize button responses or a joystick navigation on the screen as indicators of avoidance behavior. To allow the ecologically valid assessment of avoidance behavior in healthy participants, we developed a new automated immersive Virtual Reality paradigm, where participants could freely navigate in virtual 3-dimensional, 360-degrees scenes by real naturalistic body movements. A differential fear conditioning procedure was followed by three newly developed behavioral tasks to assess participants’ avoidance behavior of the conditioned stimuli: an approach, a forced-choice, and a search task. They varied in instructions, degrees of freedom, and high or low task-related relevance of the stimuli. We initially examined the tasks in a quasi-experiment (N = 55), with four consecutive runs and various experimental adaptations. Here, although we observed avoidance behavior in all three tasks after additional reinforcement, we only detected fear-conditioned avoidance behavior in the behavioral forced-choice and search tasks. These findings were largely replicated in a confirmatory experiment (N = 72) with randomized group allocation, except that fear-conditioned avoidance behavior was only manifest in the behavioral search task. This supports the notion that the behavioral search task is sensitive to detect avoidance behavior after fear conditioning only, whereas the behavioral approach and forced-choice tasks are still able to detect “strong” avoidance behavior after fear conditioning and additional reinforcement.

Investigating the efficacy of the reminder-extinction procedure to disrupt contextual threat memories in humans using immersive Virtual Reality

Upon reactivation, consolidated memories can enter a temporary labile state and require restabilisation, known as reconsolidation. Interventions during this reconsolidation period can disrupt the reactivated memory. However, it is unclear whether different kinds of memory that depend on distinct brain regions all undergo reconsolidation. Evidence for reconsolidation originates from studies assessing amygdala-dependent memories using cue-conditioning paradigms in rodents, which were subsequently replicated in humans. Whilst studies providing evidence for reconsolidation of hippocampus-dependent memories in rodents have predominantly used context conditioning paradigms, studies in humans have used completely different paradigms such as tests for wordlists or stories. Here our objective was to bridge this paradigm gap between rodent and human studies probing reconsolidation of hippocampus-dependent memories. We modified a recently developed immersive Virtual Reality paradigm to test in humans whether contextual threat-conditioned memories can be disrupted by a reminder-extinction procedure that putatively targets reconsolidation. In contrast to our hypothesis, we found comparable recovery of contextual conditioned threat responses, and comparable retention of subjective measures of threat memory, episodic memory and exploration behaviour between the reminder-extinction and standard extinction groups. Our result provide no evidence that a reminder before extinction can prevent the return of context conditioned threat memories in humans.

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.

Patients with dorsolateral prefrontal cortex lesions are capable of discriminatory threat learning but appear impaired in cognitive regulation of subjective fear

Humans are able to cognitively regulate emotions by changing their thoughts. Neuroimaging studies show correlations between dorsolateral prefrontal cortex (dlPFC) activity and cognitive regulation of emotions. Here our objective was to investigate whether dlPFC damage is associated with impaired cognitive regulation of emotion. We therefore tested the ability of patients with dlPFC lesions (N = 6) and matched control participants (N = 19) to utilize a laboratory version of cognitive regulation training (CRT) to regulate subjective fear and autonomic threat responses following Pavlovian threat conditioning. We found that patients with dlPFC lesions were able to acquire conditioned threat but seemed impaired in their ability to utilize CRT to cognitively regulate subjective fear to a threatening stimulus. Despite inclusion of a limited number of lesion patients, our results suggest that the dlPFC is important for the cognitive regulation of subjective fear.

The role of hippocampal spatial representations in contextualization and generalization of fear

Using contextual information to predict aversive events is a critical ability that protects from generalizing fear responses to safe contexts. Animal models have demonstrated the importance of spatial context representations within the hippocampal formation in contextualization of fear learning. The ventromedial prefrontal cortex (vmPFC) is known to play an important role in safety learning, possibly also through the incorporation of context information. However, if contextual representations are related to context-dependent expression of fear memory in humans remains unclear. Twenty-one healthy participants underwent functional MRI combined with a cue-context conditioning paradigm within a self-navigated virtual reality environment. The environment included two buildings (Threat and Safe context), which had distinct features outside but were identical inside. Within each context, participants saw two cues (CS+, CS-). The CS+ was consistently (100% reinforcement rate) paired with an electric shock in the Threat context, but never in the Safe context. The CS- was never paired with a shock. We found robust differential skin conductance responses (SCRs; CS+ ​> ​CS-) in the Threat context, but also within the Safe context, indicating fear generalization. Within the Safe context, vmPFC responses to the CS+ were larger than those in the Threat context. We furthermore found environment-specific representations for the two contexts in the training paradigm (i.e., before conditioning took place) in the hippocampus to be related to fear expression and generalization. Namely, participants with a weak context representation (z-score < 1.65) showed stronger fear generalization compared to participants with a strong context representation (z-score > 1.65). Thus, a weak neural representation strength of spatial context may explain overgeneralization of memory to safe contexts. In addition, our findings demonstrate that context-dependent regulation of fear expression engages ventromedial prefrontal pathways suggesting this involves a similar mechanism that is known to be involved in retrieval of extinction memory.

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.

From Extinction Learning to Anxiety Treatment: Mind the Gap

Laboratory models of extinction learning in animals and humans have the potential to illuminate methods for improving clinical treatment of fear-based clinical disorders. However, such translational research often neglects important differences between threat responses in animals and fear learning in humans, particularly as it relates to the treatment of clinical disorders. Specifically, the conscious experience of fear and anxiety, along with the capacity to deliberately engage top-down cognitive processes to modulate that experience, involves distinct brain circuitry and is measured and manipulated using different methods than typically used in laboratory research. This paper will identify how translational research that investigates methods of enhancing extinction learning can more effectively model such elements of human fear learning, and how doing so will enhance the relevance of this research to the treatment of fear-based psychological disorders.

Dispositional negativity, cognition, and anxiety disorders: An integrative translational neuroscience framework

When extreme, anxiety can become debilitating. Anxiety disorders, which often first emerge early in development, are common and challenging to treat, yet the underlying mechanisms have only recently begun to come into focus. Here, we review new insights into the nature and biological bases of dispositional negativity, a fundamental dimension of childhood temperament and adult personality and a prominent risk factor for the development of pediatric and adult anxiety disorders. Converging lines of epidemiological, neurobiological, and mechanistic evidence suggest that dispositional negativity increases the likelihood of psychopathology via specific neurocognitive mechanisms, including attentional biases to threat and deficits in executive control. Collectively, these observations provide an integrative translational framework for understanding the development and maintenance of anxiety disorders in adults and youth and set the stage for developing improved intervention strategies.

The emotional brain: Fundamental questions and strategies for future research

Emotions play a central role in human experience. Over time, methods for manipulating emotion have become increasingly refined and techniques for making sense of the underlying neurobiology have become ever more powerful and precise, enabling new insights into the organization of emotions in the brain. Yet recent years have witnessed a remarkably vigorous debate about the nature and origins of emotion, with leading scientists raising compelling concerns about the canon of facts and principles that has inspired and guided the field for the past quarter century. Here, we consider ways in which recent neuroimaging research informs this dialogue. By focusing attention on the most important outstanding questions about the nature of emotion and the architecture of the emotional brain, we hope to stimulate the kinds of work that will be required to move the field forward. Addressing these questions is critical, not just for understanding the mind, but also for elucidating the root causes of many of its disorders.

The emerging neuroscience of appetitive and drug cue extinction in humans

Fear extinction has been extensively studied in both humans and non-human animals, and this work has contributed greatly to our understanding and treatment of anxiety disorders. Yet other psychopathologies like addiction might be associated with impairments selectively in extinction of non-fear based, appetitive and drug cue associations, and these processes have been underexplored in clinical translational neuroscience. Important questions regarding similarities and differences in the neurobiological mechanisms underlying aversive and appetitive extinction remain unanswered, particularly those pertaining to cross-species evidence for the role of the ventromedial prefrontal cortex and, to some extent, the striatum. Here, we aim to draw attention to the paucity of studies investigating non-fear based extinction in humans, summarize emerging findings from the available literature, and highlight important directions for future research. We argue that closing these gaps in our understanding could help inform the development of more targeted, and perhaps more durable, forms of extinction-based treatments for addiction and related psychopathologies characterized by abnormally persistent appetitive and drug cue associations.

Effects of mixed reality head-mounted glasses during 90 minutes of mental and manual tasks on cognitive and physiological functions

Background

We evaluated the effects of a mixed reality (MR) head-mounted deviceon some cognitiveand physiological functions during 90 min tasks in an attempt to determine their safety for workers.

Methods

A total of 12 volunteers performed 90-min intellectual and manual tasks with and without MR glasses. Balance, Stroop, and memory tests were conducted before, during and after these tasks. Heart rate and electromyographic activity of some muscles were recorded. A survey was used to determine subjective fatigue, pain, or discomfort.

Results

Balance, heart rate, rate of perceived exertion, memory, and attention were unaffected by wearing MR glasses. Electromyographic activity increased with MR glasses for deltoid, biceps brachii, and soleus muscles. Few subjects reported discomfort, pain, or visual fatigue with MR glasses. Some participants reported they lost the notion of time and reality.

Discussion

Accordingly, we concluded that the MR glasses under investigation (Hololens) can be used safely. An appropriate setup and familiarization are needed to optimize use.