Neural differentiation of emotional faces as a function of interpersonal violence among adolescent girls

Interpersonal violence (IV) is associated with altered neural threat processing and risk for psychiatric disorder. Representational similarity analysis (RSA) is a multivariate approach examining the extent to which differences between stimuli correspond to differences in multivoxel activation patterns to these stimuli within each ROI. Using RSA, we examine overlap in neural patterns between threat and neutral faces in youth with IV. Participants were female adolescents aged 11-17 who had a history of IV exposure (n = 77) or no history of IV, psychiatric diagnoses, nor psychiatric medications (n = 37). Participants completed a facial emotion processing task during fMRI. Linear mixed models indicated that increasing hippocampal differentiation of fear and neutral faces was associated with increasing IV severity. Increased neural differentiation of these facial stimuli in the left and right hippocampus was associated with increasing physical abuse severity. Increased differentiation by the dACC correlated with increasing physical assault severity. RSA for most ROIs were not significantly associated with univariate activity, except for a positive association between amygdala RSA and activity to fear faces. Differences in statistically significant ROIs for physical assault and physical abuse may highlight distinct effects of trauma type on encoding of threat vs. neutral faces. Null associations between RSA and univariate activation in most ROIs suggest unique contributions of RSA for understanding IV compared to traditional activation. Implications include understanding mechanisms of risk in IV and trauma-specific treatment selection. Future work should replicate these findings in longitudinal studies and identify sensitive periods for neural alterations in RSA.

Decoding neural reactivation of threat during fear learning, extinction, and recall in a randomized clinical trial of L-DOPA among women with PTSD

BACKGROUND

Laboratory paradigms are widely used to study fear learning in posttraumatic stress disorder (PTSD). Recent basic science models demonstrate that, during fear learning, patterns of activity in large neuronal ensembles for the conditioned stimuli (CS) begin to reinstate neural activity patterns for the unconditioned stimuli (US), suggesting a direct way of quantifying fear memory strength for the CS. Here, we translate this concept to human neuroimaging and test the impact of post-learning dopaminergic neurotransmission on fear memory strength during fear acquisition, extinction, and recall among women with PTSD in a re-analysis of previously reported data.

METHODS

Participants (N = 79) completed a context-dependent fear acquisition and extinction task on day 1 and extinction recall tests 24 h later. We decoded activity patterns in large-scale functional networks for the US, then applied this decoder to activity patterns toward the CS on day 1 and day 2.

RESULTS

US decoder output for the CS+ increased during acquisition and decreased during extinction in networks traditionally implicated in human fear learning. The strength of US neural reactivation also predicted individuals skin conductance responses. Participants randomized to receive L-DOPA (n = 43) following extinction on day 1 demonstrated less US neural reactivation on day 2 relative to the placebo group (n = 28).

CONCLUSION

These results support neural reactivation as a measure of memory strength between competing memories of threat and safety and further demonstrate the role of dopaminergic neurotransmission in the consolidation of fear extinction memories.

States of epistemic curiosity interfere with memory for incidental scholastic facts

Curiosity can be a powerful motivator to learn and retain new information. Evidence shows that high states of curiosity elicited by a specific source (i.e., a trivia question) can promote memory for incidental stimuli (non-target) presented close in time. The spreading effect of curiosity states on memory for other information has potential for educational applications. Specifically, it could provide techniques to improve learning for information that did not spark a sense of curiosity on its own. Here, we investigated how high states of curiosity induced through trivia questions affect memory performance for unrelated scholastic facts (e.g., scientific, English, or historical facts) presented in close temporal proximity to the trivia question. Across three task versions, participants viewed trivia questions closely followed in time by a scholastic fact unrelated to the trivia question, either just prior to or immediately following the answer to the trivia question. Participants then completed a surprise multiple-choice memory test (akin to a pop quiz) for the scholastic material. In all three task versions, memory performance was poorer for scholastic facts presented after trivia questions that had elicited high versus low levels of curiosity. These results contradict previous findings showing curiosity-enhanced memory for incidentally presented visual stimuli and suggest that target information that generates a high-curiosity state interferes with encoding complex and unrelated scholastic facts presented close in time.

Latent-state and model-based learning in PTSD

Post-traumatic stress disorder (PTSD) is characterized by altered emotional and behavioral responding following a traumatic event. In this article, we review the concepts of latent-state and model-based learning (i.e., learning and inferring abstract task representations) and discuss their relevance for clinical and neuroscience models of PTSD. Recent data demonstrate evidence for brain and behavioral biases in these learning processes in PTSD. These new data potentially recast excessive fear towards trauma cues as a problem in learning and updating abstract task representations, as opposed to traditional conceptualizations focused on stimulus-specific learning. Biases in latent-state and model-based learning may also be a common mechanism targeted in common therapies for PTSD. We highlight key knowledge gaps that need to be addressed to further elaborate how latent-state learning and its associated neurocircuitry mechanisms function in PTSD and how to optimize treatments to target these processes.

Decoding context memories for threat in large-scale neural networks

Humans are often tasked with determining the degree to which a given situation poses threat. Salient cues present during prior events help bring online memories for context, which plays an informative role in this process. However, it is relatively unknown whether and how individuals use features of the environment to retrieve context memories for threat, enabling accurate inferences about the current level of danger/threat (i.e. retrieve appropriate memory) when there is a degree of ambiguity surrounding the present context. We leveraged computational neuroscience approaches (i.e. independent component analysis and multivariate pattern analyses) to decode large-scale neural network activity patterns engaged during learning and inferring threat context during a novel functional magnetic resonance imaging task. Here, we report that individuals accurately infer threat contexts under ambiguous conditions through neural reinstatement of large-scale network activity patterns (specifically striatum, salience, and frontoparietal networks) that track the signal value of environmental cues, which, in turn, allows reinstatement of a mental representation, primarily within a ventral visual network, of the previously learned threat context. These results provide novel insight into distinct, but overlapping, neural mechanisms by which individuals may utilize prior learning to effectively make decisions about ambiguous threat-related contexts as they navigate the environment.

Does social rigidity predict cognitive rigidity? Profiles of socio-cognitive polarization

Recent research has proposed a relationship between rigid political ideologies and underlying 'cognitive styles'. However, there remain discrepancies in how both social and cognitive rigidity are defined and measured. Problem-solving, or the ability to generate novel ideas by exploring unusual reasoning paths and challenging rigid perspectives around us, is often used to operationalize cognitive flexibility. Thus, we hypothesized a relation between forms of social rigidity, including Socio-cognitive polarization (i.e., a factor capturing conservative political ideology, absolutism/intolerance of ambiguity, and xenophobia), bullshit receptivity (i.e., overestimating pseudo-profound statements), overclaiming (tendency to self-enhance), and cognitive rigidity (i.e., problem-solving). Our results showed differences in performance on problem-solving tasks between four latent profiles of social rigidity identified in our sample. Specifically, those low in socio-cognitive polarization, bullshit, and overclaiming (i.e., less rigid) performed the best on problem-solving. Thus, we conclude that social and cognitive rigidity may share an underlying socio-cognitive construct, wherein those who are more socially rigid are also more likely to be also cognitively rigid when processing non-social information.

Pattern separation of fear extinction memory

While fear generalizes widely, extinction is stimulus-specific. Using a hybrid conditioning/episodic memory paradigm, subjects encoded nonrepeating category exemplars during fear conditioning and extinction. Twenty-four hours later, a surprise memory test included old, similar, and novel category exemplars. Results showed strong dissociation between pattern completion (generalization) and pattern separation (discrimination) in episodic memory for items encoded during fear conditioning versus extinction, respectively. These data suggest that directly threat-conditioned stimuli are better recognized at the expense of mnemonic precision, whereas discrimination is enhanced for extinguished stimuli. Overly precise extinction memory may be a contributing factor to fear relapse.

Consensus design of a calibration experiment for human fear conditioning

Fear conditioning is a widely used laboratory model to investigate learning, memory, and psychopathology across species. The quantification of learning in this paradigm is heterogeneous in humans and psychometric properties of different quantification methods can be difficult to establish. To overcome this obstacle, calibration is a standard metrological procedure in which well-defined values of a latent variable are generated in an established experimental paradigm. These intended values then serve as validity criterion to rank methods. Here, we develop a calibration protocol for human fear conditioning. Based on a literature review, series of workshops, and survey of N = 96 experts, we propose a calibration experiment and settings for 25 design variables to calibrate the measurement of fear conditioning. Design variables were chosen to be as theory-free as possible and allow wide applicability in different experimental contexts. Besides establishing a specific calibration procedure, the general calibration process we outline may serve as a blueprint for calibration efforts in other subfields of behavioral neuroscience that need measurement refinement.

Counterconditioning reduces contextual renewal in a novel context but not in the acquisition context

As extinction is a context-dependent form of learning, conditioned responses tend to return when the conditioned stimulus (CS) is encountered outside the extinction context, known as contextual renewal. Counterconditioning is a technique that may lead to a more persistent reduction of the conditioned response. However, the effects of aversive-to-appetitive counterconditioning on contextual renewal in rodent studies are mixed. Further, research in humans is sparse, particularly direct statistical comparisons between counterconditioning and standard extinction techniques within the same study. Using a causal associative learning framework (the allergist task) implemented online, we compared the effectiveness of counterconditioning to standard extinction in preventing the renewal of judgements on the allergic properties of different food items (CSs). In a between-subjects design, 328 participants first learned that particular food items (CSs) lead to an allergic reaction in a specific restaurant (context A). Next, one CS was extinguished (no allergic reaction) while another CS was counterconditioned (positive outcome) in restaurant B. Causal judgements of the allergic properties of food items occurred in either the response acquisition context (ABA group, N = 112), the response reduction context where extinction and counterconditioning had occurred (ABB group, N = 107), or a novel context (ABC group, N = 109). Results showed that counterconditioning, compared to extinction, diminished the renewal of causal judgements to the CS in a novel context (ABC group). Still, casual judgements returned for both counter-conditioned and extinguished CSs in the response acquisition context (ABA group). Counterconditioning and extinction were similarly effective at preventing recovery of causal judgements in the response reduction context (ABB group); however, only in context B did participants choose the counter-conditioned CS as less likely to cause an allergic reaction in comparison to the extinguished CS. These findings indicate scenarios in which counterconditioning is more effective than standard extinction at diminishing the return of threat associations, with implications for improving the generalization of safety learning.

Aerobic exercise in the treatment of PTSD: An examination of preclinical and clinical laboratory findings, potential mechanisms, clinical implications, and future directions

Posttraumatic stress disorder (PTSD) is associated with heightened emotional responding, avoidance of trauma related stimuli, and physical health concerns (e.g., metabolic syndrome, type 2 diabetes, cardiovascular disease). Existing treatments such as exposure-based therapies (e.g., prolonged exposure) aim to reduce anxiety symptoms triggered by trauma reminders, and are hypothesized to work via mechanisms of extinction learning. However, these conventional gold standard psychotherapies do not address physical health concerns frequently presented in PTSD. In addition to widely documented physical and mental health benefits of exercise, emerging preclinical and clinical evidence supports the hypothesis that precisely timed administration of aerobic exercise can enhance the consolidation and subsequent recall of fear extinction learning. These findings suggest that aerobic exercise may be a promising adjunctive strategy for simultaneously improving physical health while enhancing the effects of exposure therapies, which is desirable given the suboptimal efficacy and remission rates. Accordingly, this review 1) encompasses an overview of preclinical and clinical exercise and fear conditioning studies which form the basis for this claim; 2) discusses several plausible mechanisms for enhanced consolidation of fear extinction memories following exercise, and 3) provides suggestions for future research that could advance the understanding of the potential importance of incorporating exercise into the treatment of PTSD.

Aerobic exercise after extinction learning reduces return of fear and enhances memory of items encoded during extinction learning

Fear conditioning paradigms are widely used in laboratory settings to discover treatments that enhance memory consolidation and various fear processes (extinction learning, limit return of fear) that are relevant targets of exposure-based therapies. However, traditional lab-based paradigms often use the exact same conditioned stimuli for acquisition and extinction (typically differentiated with a context manipulation), whereas the opposite is true in clinical settings, as exposure therapy rarely (if ever) uses precisely the exact same stimuli from an individual's learning history. Accordingly, this study utilized a novel three-day category-based fear conditioning protocol (that uses categories of non-repeating objects [animals and tools] as conditioned stimuli during fear conditioning and extinction) to determine if aerobic exercise enhances the consolidation of extinction learning (reduces return of fear) and memory (for items encoded during extinction) during subsequent tests of extinction recall. Participants (n=40) completed a fear acquisition (day 1), fear extinction (day 2), and extinction recall (day 3) protocol. On day 1, participants completed a fear acquisition task in which they were trained to associate a category of conditioned stimuli (CS+) with the occurrence of an unconditioned stimulus (US). On day 2, participants were administered a fear extinction procedure during which CS+ and CS- categorical stimuli were presented in absence of the occurrence of the US. After completing the task, participants were randomly assigned to either receive moderate-intensity aerobic exercise (EX) or a light-intensity control (CON) condition. On day 3, participants completed fear recall tests (during which day 1, day 2, and novel CS+ and CS- stimuli were presented). Fear responding was assessed via threat expectancy ratings and skin conductance responses (SCR). During the fear recall tests, the EX group reported significantly lower threat expectancy ratings to the CS+ and CS- and exhibited greater memory of CS+ and CS- stimuli that were previously presented during day 2. There were no significant group differences for SCR. These results suggests that administration of moderate-intensity aerobic exercise following extinction learning contributes to reduced threat expectancies during tests of fear recall and enhanced memory of items encoded during extinction.

Test–retest reliability of human threat conditioning and generalization across a 1‐to‐2‐week interval

Given the increasing use of threat conditioning and generalization for clinical-translational research efforts, establishing test-retest reliability of these paradigms is necessary. Specifically, it is an empirical question whether the same participant evinces a similar generalization gradient of conditioned responses across two sessions with the identical contingencies and stimuli. Here, 46 human volunteers participated in an identical auditory threat acquisition and generalization protocol at two sessions separated by 1-to-2 weeks. Skin conductance responses (SCR) and trial-by-trial shock risk ratings served as primary measures. We used linear mixed effects modeling to test differential threat responses and generalization gradients, and Generalizability (G) theory coefficients as our primary formal assessment of test-retest reliability of intraindividual stability and change across time. Results showed largely invariant differential conditioning and generalization gradients across time. G coefficients indicated fair reliability for acquisition and generalization SCR. In contrast, risk rating reliabilities were mixed, and reliability was particularly low for acquisition risk ratings. Our findings generally support reliability of the threat conditioning and generalization paradigm for shorter test-retest intervals and highlight their utility for assessments of behavioral interventions in mental health research, but challenges remain and further work is needed. Threat conditioning and generalization tasks are increasingly used for translational efforts to improve behavioral interventions, and thus test-retest reliability for these tasks needs to be established. Our results support the test-retest reliability of threat conditioning and generalization over a relatively short (1-to-2 week) interval, but this depends on the measure used (physiological vs. self-report). Overall, these tasks could be appropriate for repeated testing over the course of a short-duration intervention study, but more research is needed, particularly in regard to longer-duration studies.

Large-scale neural network computations and multivariate representations during approach-avoidance conflict decision-making

Many real-world situations require navigating decisions for both reward and threat. While there has been significant progress in understanding mechanisms of decision-making and mediating neurocircuitry separately for reward and threat, there is limited understanding of situations where reward and threat contingencies compete to create approach-avoidance conflict (AAC). Here, we leverage computational learning models, independent component analysis (ICA), and multivariate pattern analysis (MVPA) approaches to understand decision-making during a novel task that embeds concurrent reward and threat learning and manipulates congruency between reward and threat probabilities. Computational modeling supported a modified reinforcement learning model where participants integrated reward and threat value into a combined total value according to an individually varying policy parameter, which was highly predictive of decisions to approach reward vs avoid threat during trials where the highest reward option was also the highest threat option (i.e., approach-avoidance conflict). ICA analyses demonstrated unique roles for salience, frontoparietal, medial prefrontal, and inferior frontal networks in differential encoding of reward vs threat prediction error and value signals. The left frontoparietal network uniquely encoded degree of conflict between reward and threat value at the time of choice. MVPA demonstrated that delivery of reward and threat could accurately be decoded within salience and inferior frontal networks, respectively, and that decisions to approach reward vs avoid threat were predicted by the relative degree to which these reward vs threat representations were active at the time of choice. This latter result suggests that navigating AAC decisions involves generating mental representations for possible decision outcomes, and relative activation of these representations may bias subsequent decision-making towards approaching reward or avoiding threat accordingly.

Insight Problem Solving Ability Predicts Reduced Susceptibility to Fake News, Bullshit, and Overclaiming

The information humans are exposed to has grown exponentially. This has placed increased demands upon our information selection strategies resulting in reduced fact-checking and critical-thinking time. Prior research shows that problem solving (traditionally measured using the Cognitive Reflection Test-CRT) negatively correlates with believing in false information. We argue that this result is specifically related to insight problem solving. Solutions via insight are the result of parallel processing, characterized by filtering external noise, and, unlike cognitively controlled thinking, it does not suffer from the cognitive overload associated with processing multiple sources of information. We administered the Compound Remote Associate Test (problems used to investigate insight problem solving) as well as the CRT, 20 fake and real news headlines, the bullshit, and overclaiming scales to a sample of 61 participants. Results show that insight problem solving predicts better identification of fake news and bullshit (over and above traditional measures i.e., the CRT), and is associated with reduced overclaiming. These results have implications for understanding individual differences in susceptibility to believing false information.

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

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

Tag and capture: how salient experiences target and rescue nearby events in memory

The long-term fate of a memory is not exclusively determined by the events occurring at the moment of encoding. Research at the cellular, circuit, and behavioral levels is beginning to reveal how neurochemical activations in the moments surrounding an event can retroactively and proactively rescue weak memory for seemingly mundane experiences. We review emerging evidence showing enhancement of weakly formed memories encoded minutes to hours before or after a related motivationally relevant experience. We discuss proposed neurobiological mechanisms for strengthening weak memories formed in temporal proximity to a strong event, and how this knowledge could be leveraged to improve memory for information that is prone to forgetting.

Rewarded Extinction Increases Amygdalar Connectivity and Stabilizes Long-Term Memory Traces in the vmPFC

Neurobiological evidence in rodents indicates that threat extinction incorporates reward neurocircuitry. Consequently, incorporating reward associations with an extinction memory may be an effective strategy to persistently attenuate threat responses. Moreover, while there is considerable research on the short-term effects of extinction strategies in humans, the long-term effects of extinction are rarely considered. In a within-subjects fMRI study with both female and male participants, we compared counterconditioning (CC; a form of rewarded-extinction) to standard extinction at recent (24 h) and remote (approximately one month) retrieval tests. Relative to standard extinction, rewarded extinction diminished 24-h relapse of arousal and threat expectancy, and reduced activity in brain regions associated with the appraisal and expression of threat (e.g., thalamus, insula, periaqueductal gray). The retrieval of reward-associated extinction memory was accompanied by functional connectivity between the amygdala and the ventral striatum, whereas the retrieval of standard-extinction memories was associated with connectivity between the amygdala and ventromedial prefrontal cortex (vmPFC). One month later, the retrieval of both standard-extinction and rewarded-extinction was associated with amygdala-vmPFC connectivity. However, only rewarded extinction created a stable memory trace in the vmPFC, identified through overlapping multivariate patterns of fMRI activity from extinction to 24-h and one-month retrieval. These findings provide new evidence that reward may generate a more stable and enduring memory trace of attenuated threat in humans.SIGNIFICANCE STATEMENT Prevalent treatments for pathologic fear and anxiety are based on the principles of Pavlovian extinction. Unfortunately, extinction forms weak memories that only temporarily inhibit the retrieval of threat associations. Thus, to increase the translational relevance of extinction research, it is critical to investigate whether extinction can be augmented to form a more enduring memory, especially after long intervals. Here, we used a multiday fMRI paradigm in humans to compare the short-term and long-term neurobehavioral effects of aversive-to-appetitive counterconditioning (CC), a form of augmented extinction. Our results provide novel evidence that including an appetitive stimulus during extinction can reduce short-term threat relapse and stabilize the memory trace of extinction in the ventromedial prefrontal cortex (vmPFC), for at least one month after learning.

Laboratory models of post-traumatic stress disorder: The elusive bridge to translation

Post-traumatic stress disorder (PTSD) is a debilitating mental illness composed of a heterogeneous collection of symptom clusters. The unique nature of PTSD as arising from a precipitating traumatic event helps simplify cross-species translational research modeling the neurobehavioral effects of stress and fear. However, the neurobiological progress on these complex neural circuits informed by animal models has yet to produce novel, evidence-based clinical treatment for PTSD. Here, we provide a comprehensive overview of popular laboratory models of PTSD and provide concrete ideas for improving the validity and clinical translational value of basic research efforts in humans. We detail modifications to simplified animal paradigms to account for myriad cognitive factors affected in PTSD, which may contribute to abnormalities in regulating fear. We further describe new avenues for integrating different areas of psychological research underserved by animal models of PTSD. This includes incorporating emerging trends in the cognitive neuroscience of episodic memory, emotion regulation, social-emotional processes, and PTSD subtyping to provide a more comprehensive recapitulation of the human experience to trauma in laboratory research.

A Preliminary Test of Novelty-Facilitated Extinction in Individuals With Pathological Anxiety

Studies with rodents and healthy humans suggest that replacing the expected threat with a novel outcome improves extinction and reduces the return of conditioned fear more effectively than threat omission alone. Because of the potential clinical implications of this finding for exposure-based anxiety treatments, this study tested whether the same was true in individuals with pathological anxiety (i.e., met DSM-5 diagnostic criteria for an anxiety disorder and/or obsessive-compulsive disorder (OCD). In this preliminary test of novelty-facilitated extinction, 51 unmedicated individuals with pathological anxiety were randomized to standard extinction (n = 27) or novelty-facilitated extinction (n = 24). Participants returned 24 h later to test extinction recall and fear reinstatement. Skin conductance responses (SCR) were the dependent measure of conditioned fear. Participants in both groups learned the fear association but variably extinguished it. Novelty did not facilitate extinction in this preliminary trial. Findings underscore the importance of translating paradigms from healthy humans to clinical samples, to ensure that new treatment ideas based on advances in basic neuroscience are relevant to patients.

Neural reinstatement reveals divided organization of fear and extinction memories in the human brain

Neurobiological research in rodents has revealed that competing experiences of fear and extinction are stored as distinct memory traces in the brain. This divided organization is adaptive for mitigating overgeneralization of fear to related stimuli that are learned to be safe while also maintaining threat associations for unsafe stimuli. The mechanisms involved in organizing these competing memories in the human brain remain unclear. Here, we used a hybrid form of Pavlovian conditioning with an episodic memory component to identify overlapping multivariate patterns of fMRI activity associated with the formation and retrieval of fear versus extinction. In healthy adults, distinct regions of the medial prefrontal cortex (PFC) and hippocampus showed selective reactivation of fear versus extinction memories based on the temporal context in which these memories were encoded. This dissociation was absent in participants with posttraumatic stress disorder (PTSD) symptoms. The divided neural organization of fear and extinction may support flexible retrieval of context-appropriate emotional memories, while their disorganization may promote overgeneralization and increased fear relapse in affective disorders.

Fear conditioning and extinction in obsessive-compulsive disorder: A systematic review

Laboratory experiments using fear conditioning and extinction protocols help lay the groundwork for designing, testing, and optimizing innovative treatments for anxiety-related disorders. Yet, there is limited basic research on fear conditioning and extinction in obsessive-compulsive disorder (OCD). This is surprising because exposure-based treatments based on associative learning principles are among the most popular and effective treatment options for OCD. Here, we systematically review and critically assess existing aversive conditioning and extinction studies of OCD. Across 12 studies, there was moderate evidence that OCD is associated with abnormal acquisition of conditioned responses that differ from comparison groups. There was relatively stronger evidence of OCD's association with impaired extinction processes. This included multiple studies finding elevated conditioned responses during extinction learning and poorer threat/safety discrimination during recall, although a minority of studies yielded results inconsistent with this conclusion. Overall, the conditioning model holds value for OCD research, but more work is necessary to clarify emerging patterns of results and increase clinical translational utility to the level seen in other anxiety-related disorders. We detail limitations in the literature and suggest next steps, including modeling OCD with more complex conditioning methodology (e.g., semantic/conceptual generalization, avoidance) and improving individual-differences assessment with dimensional techniques.

Emotional learning retroactively enhances item memory but distorts source attribution

An adaptive memory system should prioritize information surrounding a powerful learning event that may prove useful for predicting future meaningful events. The behavioral tagging hypothesis provides a mechanistic framework to interpret how weak experiences persist as durable memories through temporal association with a strong experience. Memories are composed of multiple elements, and different mnemonic aspects of the same experience may be uniquely affected by mechanisms that retroactively modulate a weakly encoded memory. Here, we investigated how emotional learning affects item and source memory for related events encoded close in time. Participants encoded trial-unique category exemplars before, during, and after Pavlovian fear conditioning. Selective retroactive enhancements in 24-h item memory were accompanied by a bias to misattribute items to the temporal context of fear conditioning. The strength of this source memory bias correlated with participants' retroactive item memory enhancement, and source misattribution to the emotional context predicted whether items were remembered overall. In the framework of behavioral tagging: Memory attribution was biased to the temporal context of the stronger event that provided the putative source of memory stabilization for the weaker event. We additionally found that fear conditioning selectively and retroactively enhanced stimulus typicality ratings for related items, and that stimulus typicality also predicted overall item memory. Collectively, these results provide new evidence that items related to emotional learning are misattributed to the temporal context of the emotional event and judged to be more representative of their semantic category. Both processes may facilitate memory retrieval for related events encoded close in time.

Elemental and configural threat learning bias extinction generalization

Emotional experiences often contain a multitude of details that may be represented in memory as individual elements or integrated into a single representation. How details associated with a negative emotional event are represented in memory can have important implications for extinction strategies designed to reduce emotional responses. For example, is extinguishing one cue associated with an aversive outcome sufficient to reduce learned behavior to other cues present at the time of learning that were not directly extinguished? Here, we used a between-subjects multi-day threat conditioning and extinction task to assess whether participants generalize extinction from one cue to unextinguished cues. On Day 1, one group of participants learned that a compound conditioned stimulus, composed of a tone and colored square, predicted an uncomfortable shock to the wrist (Compound group). A second group learned that the tone and square separately predicted shock (Separate group). On Day 2, participants in both groups were exposed to the tone in the absence of shocks (cue extinction). On Day 3, we tested whether extinction generalized from the extinguished to the unextinguished cue, as well as to a compound composed of both cues. Results showed that configural and elemental learning had unique and opposite effects on extinction generalization. Subjects who initially learned that a compound cue predicted shock successfully generalized extinction learning from the tone to the square, but exhibited threat relapse to the compound cue. In contrast, subjects who initially learned that each cue individually predicted shock did not generalize extinction learning from the tone to the square, but threat responses to the compound were low. These results highlight the importance of whether details of an aversive event are represented as integrated or separated memories, as these representations affect the success or limits of extinction generalization.

The Effect of Dopaminergic Replacement Therapy on Creative Thinking and Insight Problem-Solving in Parkinson's Disease Patients

Parkinson's disease (PD) patients receiving dopaminergic treatment may experience bursts of creativity. Although this phenomenon is sometimes recognized among patients and their clinicians, the association between dopamine replacement therapy (DRT) in PD patients and creativity remains underexplored. It is unclear, for instance, whether DRT affects creativity through convergent or divergent thinking, idea generation, or a general lack of inhibition. It is also unclear whether DRT only augments pre-existing creative attributes or generates creativity de novo. Here, we tested a group of PD patients when “on” and “off” dopaminergic treatment on a series of tests of creative problem-solving (Alternative Uses Task, Compound Remote Associates, Rebus Puzzles), and related their performance to a group of matched healthy controls as well as to their pre-PD creative skills and measures of inhibition/impulsivity. Results did not provide strong evidence that DRT improved creative thinking in PD patients. Rather, PD patients “on” medication showed less flexibility in divergent thinking, generated fewer ideas via insight, and showed worse performance in convergent thinking overall (by making more errors) than healthy controls. Pre-PD creative skills predicted enhanced flexibility and fluency in divergent thinking when PD patients were “on” medication. However, results on convergent thinking were mixed. Finally, PD patients who exhibited deficits in a measure of inhibitory control showed weaker convergent thinking while “on” medication, supporting previous evidence on the importance of inhibitory control in creative problem-solving. Altogether, results do not support the hypothesis that DRT promotes creative thinking in PD. We speculate that bursts of artistic production in PD are perhaps conflated with creativity due to lay conceptions of creativity (i.e., an art-bias).

The impact of prior and ongoing threat on the false alarm threshold for facial discrimination

BACKGROUND AND OBJECTIVES

Perceptual adaptations that facilitate rapid responses to threats can also lead to false alarms, or the failure to discriminate safe stimuli from signals of threat. We examined the impact of varying degrees of threat on false alarms in the perceptual discrimination of faces along the dimension of emotion (Experiment 1) or identity (Experiment 2).

METHODS

Participants first trained to discriminate between a target and nontarget face. Next, we tested their ability to identify the target in randomized presentations of the target, the nontarget, and nine novel stimuli morphed in 10% increments of similarity from the target to the nontarget. The task was completed under one of three randomized conditions: 1) Ongoing-Threat paired the target with an aversive outcome in both phases; 2) Prior-Threat paired the target with an aversive outcome in the training phase only; and 3) No-Threat paired the target with a neutral outcome in the training phase only.

RESULTS

In Experiment 1 (N = 90), Ongoing-Threat lowered the false alarm threshold for facial discrimination based on anger intensity compared to Prior-Threat and No-Threat. In Experiment 2 (N = 90), Ongoing-Threat and Prior-Threat each lowered the false alarm threshold for identity-based discrimination compared to No-Threat.

LIMITATIONS

The experiment did not measure generalization of threat responses.

CONCLUSION

Associating a facial expression or identity with threat leads to faster but less accurate discrimination of faces with similar features, particularly under conditions of ongoing threat. These experiments provide an avenue for examining the parameters that impact false alarms, which play a key role in anxiety disorders.

Generalization of conditioned fear along a dimension of increasing positive valence

The amount of fear evoked by potential threats is oftentimes proportional to the overlap in shared features with known threats. An adaptive learning system should therefore extract relevant features from threat stimuli to successfully detect other novel threats in the environment. But what if the most relevant feature of a threat stimulus is emotionally positive? Here, we used Pavlovian fear conditioning to ask whether people extract positive emotional features of a fear conditioned stimulus (CS) to selectively generalize to other stimuli that contain positive features. In a between subjects design, we first paired a picture of a face expressing either a slight amount of happiness or fear with an electrical shock to the wrist. We then tested fear generalization to modified face stimuli of the same identity expressing more or less happiness or fear. Both groups exhibited biased physiological arousal (a peak shift) to a face stimulus with the most exaggerated emotional expression, regardless of valence. Fear generalization diminished to unreinforced happy faces over the course of testing, whereas arousal was maintained to unreinforced fearful faces throughout testing. Finally, subjects fear conditioned to a slightly happy face were accurate at retrospectively identifying the correct CS, whereas subjects fear conditioned to a fearful face retrospectively misidentified a more fearful face as the threat CS. These findings suggest that positive emotional features extracted from a known threat can guide biased fear generalization, but that generalization is maintained by a dimension of increasing fear which also produces retrospective biases in threat intensity estimation.

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.

Thought suppression inhibits the generalization of fear extinction

A challenge for translating fear extinction research into clinical treatments for stress and anxiety disorders is that extinction learning tends not to generalize beyond the treatment context. This may be because the hippocampus limits the expression of extinction memories. Consequently, downregulating the hippocampus may help to promote the generalization of extinction learning. One nonpharmacological strategy to downregulate hippocampal activity in humans is motivated forgetting, in which a participant deliberately attempts to suppress the encoding and/or retrieval of episodic memories. Here, we evaluated whether this strategy could facilitate extinction generalization by augmenting extinction training with thought suppression. Participants were threat conditioned using two conditioned stimulus (CS) categories paired with an electrical shock. Subsequently, during extinction training, one CS category was accompanied by thought suppression. Participants were tested for extinction generalization 24h later with conceptual variations of the extinguished stimuli. Contrary to our prediction, we found that extinction training paired with thought suppression resulted in enhanced shock expectancy (i.e., worse generalization) relative to standard extinction. We conclude that thought suppression during memory encoding likely acts as an inhibitory cue that blocks the acquisition of extinction memories, and therefore may not be a viable tactic to promote extinction generalization in the treatment of anxiety disorders.

Contextual reinstatement promotes extinction generalization in healthy adults but not PTSD

For episodic memories, reinstating the mental context of a past experience improves retrieval of memories formed during that experience. Does context reinstatement serve a similar role for implicit, associative memories such as fear and extinction? Here, we used a fear extinction paradigm to investigate whether the retrieval of extinction (safety) memories is associated with reactivation of the mental context from extinction memory formation. In a two-day Pavlovian conditioning, extinction, and renewal protocol, we collected functional MRI data while healthy adults and adults with PTSD symptoms learned that conditioned stimuli (CSs) signaled threat through association with an electrical shock. Following acquisition, conceptually related exemplars from the CS category no longer signaled threat (i.e., extinction). Critically, during extinction only, task-irrelevant stimuli were presented between each CS trial to serve as "context tags" for subsequent identification of the possible reinstatement of this extinction context during a test of fear renewal the next day. We found that healthy adults exhibited extinction context reinstatement, as measured via multivariate pattern analysis of fMRI data, in the medial temporal lobe that related to behavioral performance, such that greater reinstatement predicted CSs being rated as safe instead of threatening. Moreover, context reinstatement positively correlated with univariate activity in the ventromedial prefrontal cortex and hippocampus, regions which are thought to be important for extinction learning. These relationships were not observed in the PTSD symptom group. These findings provide new evidence of a contextual reinstatement mechanism that helps resolve competition between the retrieval of opposing associative memories of threat and safety in the healthy adult brain that is dysregulated in PTSD.

Neural correlates of conceptual-level fear generalization in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) may develop when mechanisms for making accurate distinctions about threat relevance have gone awry. Generalization across conceptually related objects has been hypothesized based on clinical observation in PTSD, but the neural mechanisms remain unexplored. Recent trauma-exposed military veterans (n = 46) were grouped into PTSD (n = 23) and non-PTSD (n = 23). Participants learned to generalize fear across conceptual categories (animals or tools) of semantically related items that were partially reinforced by shock during functional magnetic resonance imaging. Conditioned fear learning was quantified by shock expectancy and skin conductance response (SCR). Relative to veteran controls, PTSD subjects exhibited a stronger neural response associated with fear generalization to the reinforced object category in the striatum, anterior cingulate cortex, amygdala, occipitotemporal cortex, and insula (Z > 2.3; p < 0.05; whole-brain corrected). Based on SCR, both groups generalized the shock contingency to the reinforced conceptual category, but learning was not significantly different between groups. We found that PTSD was associated with an enhanced neural response in fronto-limbic, midline, and occipitotemporal regions to a learned representation of threat that is based on previously established conceptual knowledge of the relationship between basic-level exemplars within a semantic category. Behaviorally, veterans with PTSD were somewhat slower to differentiate threat and safety categories as compared with trauma-exposed veteran controls owing in part to an initial overgeneralized behavioral response to the safe category. These results have implications for understanding how fear spreads across semantically related concepts in PTSD.

Behavioral and neural processes in counterconditioning: Past and future directions

Counterconditioning refers both to the technique and putative process by which behavior is modified through a new association with a stimulus of an opposite valence. Similar to extinction, counterconditioning is considered a form of inhibition that interferes with the expression of the originally learned response without erasing it. But whereas interest in extinction continues to rise, counterconditioning has received far less attention. Here, we provide an in-depth review of counterconditioning research and detail whether counterconditioning is any more effective than extinction at preventing relapse of the originally learned behavior. We consider the clinical implications of counterconditioning, describe recent neurobiological and neuroimaging research in this area, and consider future avenues in need of further investigation.

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.

Threat-induced modulation of hippocampal and striatal memory systems during navigation of a virtual environment

The brain is composed of multiple memory systems that mediate distinct types of navigation. The hippocampus is important for encoding and retrieving allocentric spatial cognitive maps, while the dorsal striatum mediates procedural memories based on stimulus-response (S-R) associations. These memory systems are differentially affected by emotional arousal. In particular, rodent studies show that stress typically impairs hippocampal spatial memory while it spares or sometimes enhances striatal S-R memory. The influence of emotional arousal on these separate navigational memory systems has received less attention in human subjects. We investigated the effect of dynamic changes in anticipatory anxiety on hippocampal spatial and dorsal striatal S-R memory systems while participants attempted to solve a virtual eight-arm radial maze. In Experiment 1, participants completed a hippocampus-dependent spatial version of the eight-arm radial maze that required allocentric spatial memory to successfully navigate the environment. In Experiment 2, participants completed a dorsal striatal S-R version of the maze where no allocentric spatial cues were present, requiring the use of S-R navigation. Anticipatory anxiety was modulated via threat of receiving an unpleasant electrical shock to the wrist during memory retrieval. Results showed that threat of shock was associated with more errors and increased use of non-spatial navigational strategies in the hippocampal spatial task, but did not influence memory performance in the striatal S-R task. Findings indicate a dissociation regarding the influence of anticipatory anxiety on memory systems that has implications for understanding how fear and anxiety contribute to memory-related symptoms in human psychopathologies.

Threat learning promotes generalization of episodic memory

The ability to generalize from and distinguish between aversive memories and novel experiences is critical to survival. Previous research has revealed mechanisms underlying generalization of threat-conditioned defensive responses, but little is known about generalization of episodic memory for threatening events. Here we tested if aversive learning influences generalization of episodic memory for threatening events in human adults. Subjects underwent Pavlovian threat-conditioning in which objects from one category were paired with a shock and objects from a different category were unpaired. The next day, subjects underwent a recognition memory test that included old, highly similar, and entirely novel items from the shock-paired and shock-unpaired object categories. Results showed that items highly similar to those from the object category previously paired with shock were mistaken for old items more often than items from the shock-unpaired category. This finding indicates that threat learning promotes generalization of episodic memory, and is consistent with the idea that threat generalization is an active process that may be adaptive for avoiding a myriad of potential threats following an emotional experience. Enhanced generalization of aversive episodic memories may be maladaptive, however, when old threat memories are inappropriately reactivated in harmless situations, exemplified in a number of stress- and anxiety-related disorders. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Emotional enhancement of memory for neutral information: The complex interplay between arousal, attention, and anticipation

It can be challenging to explain why certain mundane details circumstantial to an emotional event are nonetheless remembered long after the experience. Here, we examined how attention selectively shapes memory for neutral objects that happen to coincide with either an unexpected or anticipated emotional event. Pictures of neutral objects were presented for 2 s and terminated with either a high-intensity shock, a low-intensity shock, or no shock. Recognition memory was tested 24 -hs later in a surprise test. Results showed no effect of shock intensity on memory for attended objects when shocks were unpredictable (Experiment 1). Similarly, there was no effect of shock intensity for attended objects when shock delivery was signaled before the object appeared (Experiment 2). There was a reduction in memory for unattended objects paired with an anticipated high-intensity shock (Experiment 3). Finally, subjects recognized slightly more attended objects paired with a high-intensity shock if shock intensity was signaled one second after the object was encoded (Experiment 4). We conclude that simply pairing objects with high-intensity shocks is insufficient to drive episodic memory enhancements for neutral information. But anticipation of an impending source of arousal can induce bidirectional effects: attending to an impending emotional event interferes with encoding of neutral information, but encoding an object just prior to anticipation of an emotional event can sometimes benefit memory. Overall, these results highlight a complex interplay between arousal, attention, and anticipation on emotion-induced memory for neutral information.

Viewing Adaptive Social Choice Through the Lens of Associative Learning

Because humans live in a dynamic and evolving social world, modeling the factors that guide social behavior has remained a challenge for psychology. In contrast, much progress has been made on understanding some of the more basic elements of human behavior, such as associative learning and memory, which has been successfully modeled in other species. Here we argue that applying an associative learning approach to social behavior can offer valuable insights into the human moral experience. We propose that the basic principles of associative learning-conserved across a range of species-can, in many situations, help to explain seemingly complex human behaviors, including altruistic, cooperative, and selfish acts. We describe examples from the social decision-making literature using Pavlovian learning phenomena (e.g., extinction, cue competition, stimulus generalization) to detail how a history of positive or negative social outcomes influences cognitive and affective mechanisms that shape moral choice. Examining how we might understand social behaviors and their likely reliance on domain-general mechanisms can help to generate testable hypotheses to further understand how social value is learned, represented, and expressed behaviorally.

Episodic memory and Pavlovian conditioning: ships passing in the night

Research on emotional learning and memory is traditionally approached from one of two directions: episodic memory and classical conditioning. These approaches differ substantially in methodology and intellectual tradition. Here, we offer a new approach to the study of emotional memory in humans that involves integrating theoretical knowledge and experimental techniques from these seemingly distinct fields. Specifically, we describe how subtle modifications to traditional Pavlovian conditioning procedures have provided new insight into how emotional experiences are selectively prioritized in long-term episodic memory. We also speculate on future directions and undeveloped lines of research where some of the knowledge and principles of classical conditioning might advance our understanding of how emotion modifies episodic memory, and vice versa.

A reminder before extinction strengthens episodic memory via reconsolidation but fails to disrupt generalized threat responses

A reminder can temporarily renew flexibility of consolidated memories, referred to as reconsolidation. Pavlovian threat-conditioning studies suggest that a reminder can renew flexibility of threat responses but that episodic memories remain stable. In contrast, outside the threat-conditioning domain, studies testing memory for word lists or stories find that a reminder can renew flexibility of episodic memory. This discrepancy in findings leaves it unclear if episodic memories reconsolidate, or only Pavlovian responses. Here we unite the different approaches in the field and show that a reminder can retroactively strengthen episodic memory for Pavlovian threat-conditioned events, but that, in contrast to threat-conditioning studies with simple sensory stimuli, extinction after a reminder fails to prevent recovery of generalized threat responses. Our results indicate the episodic memories also reconsolidate, allowing strengthening of relevant memories. These findings also suggest that generalized threat responses and episodic memories are less susceptible to be modified by reminder-interventions procedures.

Stress promotes generalization of older but not recent threat memories

Stress broadly affects the ability to regulate emotions and may contribute to generalization of threat-related behaviors to harmless stimuli. Behavioral generalization also tends to increase over time as memory precision for recent events gives way to more gist-like representations. Thus, acute stress coupled with a delay in time from a negative experience may be a strong predictor of the transition from normal to generalized fear expression. Here, we investigated the effect of a single-episode acute stressor on generalization of aversive learning when stress is administered either immediately after an aversive learning event or following a delay. In a between-subjects design, healthy adult volunteers underwent threat (fear) conditioning using a tone-conditioned stimulus paired with an electric shock to the wrist and another tone not paired with shock. Behavioral generalization was tested to a range of novel tones either on the same day (experiment 1) or 24 h later (experiment 2) and was preceded by either an acute stress induction or a control task. Anticipatory sympathetic arousal [i.e., skin conductance responses (SCRs)] and explicit measures of shock expectancy served as dependent measures. Stress administered shortly after threat conditioning did not affect behavioral generalization. In contrast, stress administered following a delay led to heightened arousal and increased generalization of SCRs and explicit measures of shock expectancy. These findings show that acute stress increases generalization of older but not recent threat memories and have clinical relevance to understanding overgeneralization characteristics of anxiety and stress-related disorders.

Context conditioning in humans using commercially available immersive Virtual Reality

Despite a wealth of knowledge on how humans and nonhuman animals learn to associate meaningful events with cues in the environment, far less is known about how humans learn to associate these events with the environment itself. Progress on understanding spatiotemporal contextual processes in humans has been slow in large measure by the methodological constraint of generating and manipulating immersive spatial environments in well-controlled laboratory settings. Fortunately, immersive Virtual Reality (iVR) technology has improved appreciably and affords a relatively straightforward methodology to investigate the role of context on learning, memory, and emotion while maintaining experimental control. Here, we review context conditioning literature in humans and describe challenges to study contextual learning in humans. We then provide details for a novel context threat (fear) conditioning paradigm in humans using a commercially available VR headset and a cross-platform game engine. This paradigm resulted in the acquisition of subjective threat, threat-conditioned defensive responses, and explicit threat memory. We make the paradigm publicly available and describe obstacles and solutions to optimize future studies of context conditioning using iVR. As computer technology advances to replicate the sensation of realistic environments, there are increasing opportunities to bridge the translational gap between rodent and human research on how context modulates cognition, which may ultimately lead to more optimal treatment strategies for anxiety- and stress-related disorders.

Associative Learning of Social Value in Dynamic Groups

Although humans live in societies that regularly demand engaging with multiple people simultaneously, little is known about social learning in group settings. In two experiments, we combined a Pavlovian learning framework with dyadic economic games to test whether blocking mechanisms support value-based social learning in the gain (altruistic dictators) and loss (greedy robbers) domains. Subjects first learned about an altruistic dictator, who subsequently made altruistic splits collectively with a partner. Results revealed that because the presence of the dictator already predicted the outcome, subjects did not learn to associate value with the partner. This social blocking effect was not observed in the loss domain: A kind robber's partner, who could steal all the subjects' money but stole little, acquired highly positive value-which biased subjects' subsequent behavior. These findings reveal how Pavlovian mechanisms support efficient social learning, while also demonstrating that violations of social expectations can attenuate how readily these mechanisms are recruited.

Do salient features overshadow learning of other features in category learning?

Hundreds of associative learning experiments have examined how animals learn to predict an aversive outcome, such as a shock, loud sound, or puff of air in the eye. In this study, we reversed this pattern and examined the role of an aversive stimulus, shock, as a feature of a complex stimulus composed of several features, rather than as an outcome. In particular, we used a category learning paradigm in which multiple features predicted category membership and asked whether a salient, aversive feature would reduce learning of other category features through cue competition. Three experiments compared a condition in which 1 category had among its 6 features a painful "sting" (shock) and the other category a distinctive sound (the critical features) to a control condition in which the sting and sound were represented by much less salient (and not aversive) visual depictions. Subjects learned the categories and then were tested on their knowledge of all 6 features as predictors of the category label. Surprisingly, the experiments consistently found that the salient, aversive critical features did not reduce learning of other features relative to the control. Bayesian statistics gave positive evidence for this null result. Equally surprisingly, in a fourth experiment, a nonaversive salient feature (brightly colored patterns) increased learning of other features compared to the control. We explain the results in terms of attentional strategies that may apply in a category learning context. (PsycINFO Database Record

Threat intensity widens fear generalization gradients

Research in nonhuman animals reveals threat-sensitive generalization of defensive behavior that favors widespread generalization when threat intensity is high and limited generalization (i.e., specificity) when threat intensity is low. Here, we used Pavlovian fear conditioning to systematically investigate whether threat intensity widens behavioral generalization gradients to stimuli that decreasingly resemble a learned threat cue. Using a between-subjects design, volunteers underwent fear conditioning with a tone paired with either a high-intensity or low-intensity aversive stimulus prior to a test of fear generalization to novel tones. Results showed no effect of threat intensity on initial acquisition of conditioned fear. However, volunteers who underwent fear conditioning with a high-intensity aversive stimulus exhibited widespread generalization of autonomic arousal (skin conductance responses) as compared to volunteers who received a low-intensity aversive stimulus. These results show a transition from normal (selective) to overgeneralized fear as threat intensity increases, and have implications for understanding overgeneralization characteristic of trauma- and stress-related disorders. (PsycINFO Database Record

Racial stereotypes impair flexibility of emotional learning

Flexibility of associative learning can be revealed by establishing and then reversing cue-outcome discriminations. Here, we used functional MRI to examine whether neurobehavioral correlates of reversal-learning are impaired in White and Asian volunteers when initial learning involves fear-conditioning to a racial out-group. For one group, the picture of a Black male was initially paired with shock (threat) and a White male was unpaired (safe). For another group, the White male was a threat and the Black male was safe. These associations reversed midway through the task. Both groups initially discriminated threat from safety, as expressed through skin conductance responses (SCR) and activity in the insula, thalamus, midbrain and striatum. After reversal, the group initially conditioned to a Black male exhibited impaired reversal of SCRs to the new threat stimulus (White male), and impaired reversals in the striatum, anterior cingulate cortex, midbrain and thalamus. In contrast, the group initially conditioned to a White male showed successful reversal of SCRs and successful reversal in these brain regions toward the new threat. These findings provide new evidence that an aversive experience with a racial out-group member impairs the ability to flexibly and appropriately adjust fear expression towards a new threat in the environment.

Compound stimulus extinction reduces spontaneous recovery in humans

Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and nonextinguished CSB. Recovery of conditioned skin conductance responses to CSA was reduced 24 h after compound extinction, as compared with a group who received an equal number of extinction trials to the CSA alone.

Novelty-facilitated extinction: providing a novel outcome in place of an expected threat diminishes recovery of defensive responses

BACKGROUND

Experimental extinction serves as a model for psychiatric treatments based on associative learning. However, the effects of extinction are often transient, as evidenced by postextinction return of defensive behaviors. From a therapeutic perspective, an inherent problem with extinction may be that mere omission of threat is not sufficient to reduce future threat uncertainty. The current study tested an augmented form of extinction that replaced, rather than merely omitted, expected threat outcomes with novel nonthreat outcomes, with the goal of reducing postextinction return of defensive behaviors.

METHODS

Thirty-two healthy male Sprague-Dawley rats and 47 human adults underwent threat conditioning to a conditioned stimulus paired with an electrical shock. Subjects then underwent a standard extinction protocol with shock omitted or an augmented extinction protocol wherein the shock was replaced by a surprising tone. Tests of postextinction recovery occurred 24 hours later in the absence of the tone.

RESULTS

Replacing the shock with a novel nonthreat outcome, as compared with shock omission, reduced postextinction recovery (freezing in rats and anticipatory skin conductance responses in humans) when tested 24 hours later. Self-reported intolerance of uncertainty was positively correlated with recovery following standard extinction in humans, providing new evidence that postextinction recovery is related to sensitivity to future threat uncertainty.

CONCLUSIONS

These findings provide cross-species evidence of a novel strategy to enhance extinction that may have broad implications for how to override associative learning that has become maladaptive and offer a simple technique that could be straightforwardly adapted and implemented in clinical situations.

Categories, concepts, and conditioning: how humans generalize fear

During the past century, Pavlovian conditioning has served as the predominant experimental paradigm and theoretical framework to understand how humans learn to fear and avoid real or perceived dangers. Animal models for translational research offer insight into basic behavioral and neurophysiological factors mediating the acquisition, expression, inhibition, and generalization of fear. However, it is important to consider the limits of traditional animal models when applied to humans. Here, we focus on the question of how humans generalize fear. We propose that to understand fear generalization in humans requires taking into account research on higher-level cognition such as category-based induction, inferential reasoning, and representation of conceptual knowledge. Doing so will open the door for productive avenues of new research.

Emotional learning selectively and retroactively strengthens memories for related events

Neurobiological models of long-term memory propose a mechanism by which initially weak memories are strengthened through subsequent activation that engages common neural pathways minutes to hours later. This synaptic tag-and-capture model has been hypothesized to explain how inconsequential information is selectively consolidated following salient experiences. Behavioural evidence for tag-and-capture is provided by rodent studies in which weak early memories are strengthened by future behavioural training. Whether a process of behavioural tagging occurs in humans to transform weak episodic memories into stable long-term memories is unknown. Here we show, in humans, that information is selectively consolidated if conceptually related information, putatively represented in a common neural substrate, is made salient through an emotional learning experience. Memory for neutral objects was selectively enhanced if other objects from the same category were paired with shock. Retroactive enhancements as a result of emotional learning were observed following a period of consolidation, but were not observed in an immediate memory test or for items strongly encoded before fear conditioning. These findings provide new evidence for a generalized retroactive memory enhancement, whereby inconsequential information can be retroactively credited as relevant, and therefore selectively remembered, if conceptually related information acquires salience in the future.

Spatial proximity amplifies valence in emotional memory and defensive approach-avoidance

In urban areas, people often have to stand or move in close proximity to others. The egocentric distance to stimuli is a powerful determinant of defensive behavior in animals. Yet, little is known about how spatial proximity to others alters defensive responses in humans. We hypothesized that the valence of social cues scales with egocentric distance, such that proximal social stimuli have more positive or negative valence than distal stimuli. This would predict enhanced defensive responses to proximal threat and reduced defensive responses to proximal reward. We tested this hypothesis across four experiments using 3-D virtual reality simulations. Results from Experiment 1 confirmed that proximal social stimuli facilitate defensive responses, as indexed by fear-potentiated startle, relative to distal stimuli. Experiment 2 revealed that interpersonal defensive boundaries flexibly increase with aversive learning. Experiment 3 examined whether spatial proximity enhances memory for aversive experiences. Fear memories for social threats encroaching on the body were more persistent than those acquired at greater interpersonal distances, as indexed by startle. Lastly, Experiment 4 examined how egocentric distance influenced startle responses to social threats during defensive approach and avoidance. Whereas fear-potentiated startle increased with proximity when participants actively avoided receiving shocks, startle decreased with proximity when participants tolerated shocks to receive monetary rewards, implicating opposing gradients of distance on threat versus reward. Thus, proximity in egocentric space amplifies the valence of social stimuli that, in turn, facilitates emotional memory and approach-avoidance responses. These findings have implications for understanding the consequences of increased urbanization on affective interpersonal behavior.

Stimulus Typicality Determines How Broadly Fear Is Generalized

The ability to represent knowledge at the category level promotes the transfer of learning. How this ability integrates with basic forms of conditioned learning is unknown but could explain why conditioned fear is overgeneralized after aversive experiences. We examined the impact of stimulus typicality—an important determinant of category-based induction—on fear learning and generalization. Typicality is known to affect the strength of categorical arguments; a premise involving typical exemplars (e.g., sparrow) is believed to apply to other members, whereas a premise about atypical exemplars (e.g., penguin) generalizes more narrowly to similar items. We adopted this framework to human fear conditioning and found that fear conditioned to typical exemplars generalized more readily to atypical members than vice versa, despite equal feature overlap across conditions. These findings have implications for understanding why some fearful events lead to broad overgeneralization of fear whereas others are regarded as isolated episodes.