Developmental differences in aversive conditioning, extinction, and reinstatement: A study with children, adolescents, and adults

Functional connectivity between the nucleus accumbens and amygdala underlies avoidance learning during adolescence: Implications for developmental psychopathology

BACKGROUND

Reward and threat processes work together to support adaptive learning during development. Adolescence is associated with increasing approach behavior (e.g., novelty-seeking, risk-taking) but often also coincides with emerging internalizing symptoms, which are characterized by heightened avoidance behavior. Peaking engagement of the nucleus accumbens (NAcc) during adolescence, often studied in reward paradigms, may also relate to threat mechanisms of adolescent psychopathology.

METHODS

47 typically developing adolescents (9.9-22.9 years) completed an aversive learning task during functional magnetic resonance imaging, wherein visual cues were paired with an aversive sound or no sound. Task blocks involved an escapable aversively reinforced stimulus (CS+r), the same stimulus without reinforcement (CS+nr), or a stimulus that was never reinforced (CS-). Parent-reported internalizing symptoms were measured using Revised Child Anxiety and Depression Scales.

RESULTS

Functional connectivity between the NAcc and amygdala differentiated the stimuli, such that connectivity increased for the CS+r (p = .023) but not for the CS+nr and CS-. Adolescents with greater internalizing symptoms demonstrated greater positive functional connectivity for the CS- (p = .041).

CONCLUSIONS

Adolescents show heightened NAcc-amygdala functional connectivity during escape from threat. Higher anxiety and depression symptoms are associated with elevated NAcc-amygdala connectivity during safety, which may reflect poor safety versus threat discrimination.

Late positive potential reveals sustained threat contingencies despite extinction in adolescents but not adults

BACKGROUND

Major theories link threat learning processes to anxiety symptoms, which typically emerge during adolescence. While this developmental stage is marked by substantial maturation of the neural circuity involved in threat learning, research directly examining adolescence-specific patterns of neural responding during threat learning is scarce. This study compared adolescents and adults in acquisition and extinction of conditioned threat responses assessed at the cognitive, psychophysiological, and neural levels, focusing on the late positive potential (LPP), an event-related potential (ERP) component indexing emotional valence.

METHOD

Sixty-five adults and 63 adolescents completed threat acquisition and extinction, 24 h apart, using the bell conditioning paradigm. Self-reported fear, skin conductance responses (SCR), and ERPs were measured.

RESULTS

Developmental differences emerged in neural and psychophysiological responses during threat acquisition, with adolescents displaying heightened LPP responses to threat and safety cues as well as heightened threat-specific SCR compared to adults. During extinction, SCR suggested comparable reduction in conditioned threat responses across groups, while LPP revealed incomplete extinction only among adolescents. Finally, age moderated the link between anxiety severity and LPP-assessed extinction, whereby greater anxiety severity was associated with reduced extinction among younger participants.

CONCLUSIONS

In line with developmental theories, adolescence is characterized by a specific age-related difficulty adapting to diminishing emotional significance of prior threats, contributing to heightened vulnerability to anxiety symptoms. Further, LPP appears to be sensitive to developmental differences in threat learning and may thus potentially serve as a useful biomarker in research on adolescents, threat learning, and anxiety.

A multi-modal assessment of fear conditioning in adolescent anorexia nervosa

OBJECTIVE

Anorexia nervosa (AN) is a pernicious psychiatric disorder which is principally characterized by a fear of weight gain. Notwithstanding the centrality of fear in the psychopathology of AN, controlled assessments of negative valence systems are lacking. Herein we assess fear conditioning in adolescent females with AN.

METHOD

Adolescent girls (Mage = 14.6 years, ±1.57) with DSM-5 diagnoses of AN (N = 25) and age-matched control girls (Mage = 14.8 years, ±1.46) with no DSM-5 diagnoses (N = 25) completed structured clinical interviews and participated in a classical three-phase Pavlovian fear conditioning paradigm. Participants with comorbid anxiety disorders were excluded. Skin conductance response (SCR) was measured, alongside self-reported fear, valence, and fear expectancy ratings.

RESULTS

Both groups demonstrated significant differential acquisition across all four measures. Regarding group comparisons, no differences emerged for self-reported fear, valence, and fear expectancy ratings during acquisition, although for SCR, those with AN demonstrated reduced physiological arousal relative to controls. Both groups demonstrated significant differential extinction for unconditioned stimuli (US) expectancy, self-report fear, and self-report valence. No statistically significant group differences were evident during extinction to the conditioned stimuli (CS)+, on any outcome measure. However, controls reported more positive valence to the CS- than those with AN.

CONCLUSIONS

Contrary to our hypotheses, our preliminary assessment did not find support for elevated fear responding among adolescent girls with AN with regards to fear acquisition or extinction. These data suggest that AN in adolescent girls may not be associated with a heightened propensity to acquire fear, but conversely, may suggest that exposure treatments for AN may be helpful, since extinction learning is intact in AN.

PUBLIC SIGNIFICANCE

AN is characterized by fear-related symptoms, including food and weight-related fear, and behavioral avoidance, yet controlled studies assessing fear learning are limited. Our preliminary assessment of adolescent AN indicates no abnormalities in fear learning among adolescents with AN. These findings may inform existing mechanistic models of AN psychopathology, and the development of exposure-based treatments for AN.

Do single-case experimental designs lead to randomised controlled trials of cognitive behavioural therapy interventions for adolescent anxiety and related disorders recommended in the National Institute of Clinical Excellence guidelines? A systematic review

Background

Although Cognitive Behavioural Therapy (CBT) is effective for 60% of adolescents with anxiety disorders, only 36% are in remission post-intervention. This indicates that more effective treatments are needed which should be reflected in the NICE guidelines. We hypothesised that Single-case experimental designs (SCEDs) may provide a framework for accelerating the development of novel interventions. The primary purpose of this review was to investigate whether SCEDs are currently followed by randomised controlled trials (RCTs) of CBT intervention for adolescent anxiety disorders named in the NICE guidelines. The secondary objective was to investigate whether using SCEDs prior to RCTs could be a helpful approach.

Method

For the primary search of SCEDs five databases were used (PsycINFO, PubMed, PsycArticles, Web of Science and ProQuest). Nineteen articles met eligibility criteria including a total of 107 participants. For the secondary search of RCTs named in the NICE guidelines for adolescent anxiety disorders 53 articles met inclusion criteria and were included in the systematic review.

Results

The 19 SCED studies included in the review were conducted with participants with a diverse range of anxiety disorders and across a range of CBT formats. Two of the SCEDs were followed by RCTs, but neither of these were named in the NICE guidelines for anxiety disorders. All of the SCEDs identified were rated as low quality with none meeting the criteria for the highest or second highest quality rating. From the secondary searches, none of the RCTs named in the NICE guide were preceded by SCEDs.

Conclusions

It was concluded that currently SCEDs were not followed by RCTs of CBT interventions named in the NICE guidelines for adolescent anxiety disorders. However, it was suggested that SCEDs may provide an important framework for the development of more effective interventions for adolescents with anxiety.

Calibrating your own fears: Feasibility of a remote fear conditioning paradigm with semi-subjective stimulus calibration and differences in fear learning

Fear conditioning studies have occurred mostly in the laboratory, but recently researchers have started to adapt fear conditioning procedures for remote application. Standardization of aversive stimulus material not causing unnecessarily strong discomfort remains an issue especially relevant to research without experimental supervision. The present study introduces a novel semi-subjective method to calibrate aversive sounds in a remotely conducted fear conditioning paradigm. To demonstrate feasibility and proof of concept, 165 participants completed the paradigm, calibrating the loudness of an aversive sound without the guidance of an experimental instructor. This study also aimed to replicate existing findings of participant groups that differed in their early CS-UCS contingency awareness. Participants were classified as Accurate (UCS more likely after the CS+ than CS-), Poor (UCS more likely after the CS- than CS+, or UCS unlikely after either CS), and Threat Biased (UCS equally likely after the CS+ and CS-). Results indicated both the feasibility and efficacy of the paradigm, with participants showing typical patterns of fear learning. Threat Biased participants showed significantly higher uncertainty towards safety signals. There were no differences between the groups in terms of personality traits, thus questioning whether these attributes mediate differences in fear learning and the emergence of anxiety disorders. Using semi-subjective sound calibration appears to be functional, and future studies may consider implementing the new method when remotely administering fear conditioning paradigms.

Conditioning induced placebo-like and nocebo-like effects of thermal discomfort in adults but not in youth

Introduction

Conditioning can be used to modulate the perception of pain, in the form of placebo and nocebo effects. Previous studies show inconsistent results as to whether adolescents show similar, weaker, or non-significant conditioned placebo and nocebo effects compared to effects found in adults. There are suggestions that such differences (if any) may dependent on the cues used in the thermal conditioning paradigms. Therefore, in this current study, we utilized novel, neutral 3D-shaped visual cues to implicitly induce conditioned placebo-like and nocebo-like effects in adolescents and adults.

Methods

During the conditioning paradigm, distinct cues (Fribbles) were paired with low and high temperatures in 24 adults and 20 adolescents (mean age = 25.5 years). In the testing phase, these conditioned cues as well as a neutral (unconditioned) cue were presented with moderate temperatures.

Results

Thermal discomfort of moderate temperatures was lower when presented with the conditioned low heat cue (placebo-like effect) and higher when thermal stimuli were presented with the high heat cue (nocebo-like effect) compared to the neutral cue. The effects were driven by adults, as neither the placebo-like nor the nocebo-like effect was significant in adolescents. The difference between adolescents and adults was not explained by differences in temperature or discomfort levels, as adults and adolescents had comparable calibrated temperatures and levels of discomfort during heat stimuli.

Conclusion

Our findings suggest that thermal perception in adolescents is less influenced by conditioning to an engaging novel visual cue, compared to adults. Our work may have implications for better understanding the scope and limitations of conditioning as a key mechanism of placebo and nocebo effects in youth.

Fear learning and extinction predicts anxiety in daily life: a study of Pavlovian conditioning and ecological momentary assessment

BACKGROUND

The association between anxious mood and aberrant fear learning mechanisms has not been fully elucidated. Studying how fear conditioning and extinction constructs relate to anxiety symptoms and reactivity to stressful and benign moments in everyday life provides a powerful addition to experimental paradigms.

METHOD

Fifty-one young adults completed laboratory-based differential conditioning and extinction tasks with (CS + ) and without (CS-) an aversive unconditional stimulus (US). Electrodermal skin conductance responses were measured during each phase, followed by ecological momentary assessment (EMA) tapping anxiety and stressors six times daily for seven days (2, 142 moments).

RESULTS

Conditioned electrodermal reactivity to the CS + and overgeneralisation to the CS- were associated with greater change in anxiety (measured via EMA), across non-stressful situations, remaining the same across stressful situations. Likewise, during extinction when the CS + is now safe, more electrodermal reactivity to the CS + was associated with more anxiety change across non-stressful situations and remained the same across stressful situations. Also, during extinction when threat is absent, more electrodermal reactivity at the late stage of the CS- was associated with less momentary anxiety change in response to stressful situations; more electrodermal activity at the late stage of the CS + was associated with more anxiety change across non-stressful situations and remained the same across stressful situations.

CONCLUSIONS

Sampling 'in vivo' emotion and stress experiences, study findings revealed links between conditioned electrodermal reactivity and overgeneralisation to safe stimuli and heightened anxious reactivity during non-stressful (i.e. safe) moments in daily life, coupled with less change in response to actual stressors.

Sensitivity and specificity in affective and social learning in adolescence

Adolescence is a period of heightened affective and social sensitivity. In this review we address how this increased sensitivity influences associative learning. Based on recent evidence from human and rodent studies, as well as advances in computational biology, we suggest that, compared to other age groups, adolescents show features of heightened Pavlovian learning but tend to perform worse than adults at instrumental learning. Because Pavlovian learning does not involve decision-making, whereas instrumental learning does, we propose that these developmental differences might be due to heightened sensitivity to rewards and threats in adolescence, coupled with a lower specificity of responding. We discuss the implications of these findings for adolescent mental health and education.

Extinction Learning Across Development: Neurodevelopmental Changes and Implications for Pediatric Anxiety Disorders

Alterations in extinction learning relate to the development and maintenance of anxiety disorders across the lifespan. While exposure therapy, based on principles of extinction, can be highly effective for treating anxiety, many patients do not show sufficient improvement following treatment. In particular, evidence suggests that exposure therapy does not work sufficiently for up to 40% of children who receive this evidence-based treatment.Importantly, fear learning and extinction, as well as the neural circuitry supporting these processes, undergo dynamic changes across development. An improved understanding of developmental changes in extinction learning and the associated neural circuitry may help to identify targets to improve treatment response in clinically anxious children and adolescents. In this chapter, we provide a brief overview of methods used to study fear learning and extinction in developmental populations. We then review what is currently known about the developmental changes that occur in extinction learning and related neural circuitry. We end this chapter with a discussion of the implications of these neurodevelopmental changes for the characterization and treatment of pediatric anxiety disorders.

Optimising exposure for adolescents with public speaking anxiety: Affect labelling or positive coping statements?

Cognitive Behavioural Therapy (CBT) is the first line treatment for anxiety disorders in youth however many adolescents do not benefit. Behavioural exposure is believed to be the critical ingredient of CBT and research with adults has shown that labelling affect, but not positive coping statements, enhances exposure outcomes. However, many CBT protocols for young people involve using positive coping statements alongside exposure. We compared the effects of exposure with positive coping statements, affect labelling, and neutral statements on fear responses in adolescents (age 13-14 years) with public speaking anxiety as they delivered a series of speeches in front of a pre-recorded classroom audience. Self-rated anxiety, heart rate, and observer ratings of expressed anxiety were assessed pre-test, immediate post-test and at 1-week follow-up. Neither affect labelling nor positive coping statements enhanced exposure on any measure from pre-test to 1-week follow-up. While there was an initial advantage of exposure with positive coping statements for post-speech self-reported anxiety, this effect was not maintained, and there was a significant increase in anxiety from immediate post-test to 1-week follow-up in this condition, compared to the other conditions. The short-term benefits from generating positive coping statements may explain why this is often employed in the treatment of anxiety problems in young people, but also indicate that it may not confer any advantage in the longer term. These intriguing findings highlight the urgent need for further attention to improve understanding of how to optimise exposure in young people and maximise treatment outcomes.

Differential Patterns of Delayed Emotion Circuit Maturation in Abused Girls With and Without Internalizing Psychopathology

OBJECTIVE

Childhood abuse represents one of the most potent risk factors for developing psychopathology, especially in females. Evidence suggests that exposure to early-life adversity may be related to advanced maturation of emotion processing neural circuits. However, it remains unknown whether abuse is related to early circuit maturation and whether maturation patterns depend on the presence of psychopathology.

METHODS

A multisite sample of 234 girls (ages 8-18 years) completed clinical assessment, maltreatment histories, and high-resolution T1-weighted structural MRI. Girls were stratified by abuse history and internalizing disorder diagnosis into typically developing (no abuse/no diagnosis), resilient (abuse/no diagnosis), and susceptible (abuse/current diagnosis) groups. Machine learning models of normative brain development were aggregated in a stacked generalization framework trained to predict chronological age using gray matter volume in whole-brain, emotion, and language circuit parcellations. Brain age gap estimations (BrainAGEs; predicted age minus true chronological age) were calculated as indices of relative circuit maturation.

RESULTS

Childhood abuse was related to reduced BrainAGE (delayed maturation) specific to emotion circuits. Delayed emotion circuit BrainAGE was further related to increased hyperarousal symptoms. Childhood physical neglect was associated with increased whole-brain BrainAGE (advanced maturation). Neural contributors to emotion circuit BrainAGE differed in girls with and without an internalizing diagnosis, especially in the lateral prefrontal, parietal, and insular cortices and the hippocampus.

CONCLUSIONS

Abuse exposure in girls is associated with a delayed structural maturation pattern specific to emotion circuitry, a potentially adaptive mechanism enhancing threat generalization. Physical neglect, on the other hand, is associated with a broader brain-wide pattern of advanced structural maturation. The differential influence of fronto-parietal cortices and the hippocampus on emotion circuit maturity in resilient girls may represent neurodevelopmental markers of reduced psychiatric risk following abuse.

Fear learning, avoidance, and generalization are more context-dependent for adults than adolescents

This study examined developmental differences in contextual and perceptual generalization of fear and avoidance learning. Adults (N = 39) and adolescents (N = 44) completed differential fear acquisition wherein each conditional stimulus (CS) appeared in a background context. In the dangerous context, one stimulus (CS+) predicted an aversive sound, and the other stimulus (CS-) did not. In the safe context, the aversive sound was never administered with either CS. During fear generalization, participants were presented with three generalization stimuli (GSs), ranging on a perceptual continuum from threat to safety stimuli, in both contexts. Participants then completed avoidance conditioning and avoidance generalization phases, allowing them to actively avoid the upcoming aversive sound by pressing an avoidance button. Developmental differences emerged in threat perception, physiological arousal, avoidance behavior, and eye movements during contextual fear learning and generalization. Adolescents showed less discrimination between stimuli and contexts than adults, resulting primarily from their elevated fear responses to safety and generalized stimuli. Developmental differences in fear learning should be further explored in future research, as they could explain why adolescence is a sensitive developmental period for anxiety.

MicroRNAs in the Onset of Schizophrenia

Mounting evidence implicates microRNAs (miRNAs) in the pathology of schizophrenia. These small noncoding RNAs bind to mRNAs containing complementary sequences and promote their degradation and/or inhibit protein synthesis. A single miRNA may have hundreds of targets, and miRNA targets are overrepresented among schizophrenia-risk genes. Although schizophrenia is a neurodevelopmental disorder, symptoms usually do not appear until adolescence, and most patients do not receive a schizophrenia diagnosis until late adolescence or early adulthood. However, few studies have examined miRNAs during this critical period. First, we examine evidence that the miRNA pathway is dynamic throughout adolescence and adulthood and that miRNAs regulate processes critical to late neurodevelopment that are aberrant in patients with schizophrenia. Next, we examine evidence implicating miRNAs in the conversion to psychosis, including a schizophrenia-associated single nucleotide polymorphism in MIR137HG that is among the strongest known predictors of age of onset in patients with schizophrenia. Finally, we examine how hemizygosity for DGCR8, which encodes an obligate component of the complex that synthesizes miRNA precursors, may contribute to the onset of psychosis in patients with 22q11.2 microdeletions and how animal models of this disorder can help us understand the many roles of miRNAs in the onset of schizophrenia.

The Effectiveness of Psychological Therapies for Anxiety Disorders in Adolescents: A Meta-Analysis

Anxiety disorders are common in adolescence but outcomes for adolescents are unclear and we do not know what factors moderate treatment outcome for this age group. We conducted meta-analyses to establish the effectiveness of psychological therapies for adolescent anxiety disorders in (i) reducing anxiety disorder symptoms, and (ii) remission from the primary anxiety disorder, compared with controls, and examine potential moderators of treatment effects. The protocol was registered with PROSPERO (CRD42018091744). Electronic databases (Web of Science, MEDLINE, Psycinfo, EMBASE) were searched from January 1990 to December 2019. 2511 articles were reviewed, those meeting strict criteria were included. Random effects meta-analyses were conducted. Analyses of symptom severity outcomes comprised sixteen studies (CBT k = 15, non-CBT k = 1; n = 766 adolescents), and analyses of diagnostic remission outcomes comprised nine (CBT k = 9; n = 563 adolescents). Post-treatment, those receiving treatment were significantly more likely to experience reduced symptom severity (SMD = 0.454, 95% CI 0.22–0.69) and remission from the primary anxiety disorder than controls (RR = 7.94, 95% CI 3.19–12.7) (36% treatment vs. 9% controls in remission). None of the moderators analysed were statistically significant. Psychological therapies targeting anxiety disorders in adolescents are more effective than controls. However, with only just over a third in remission post-treatment, there is a clear need to develop more effective treatments for adolescents, evaluated through high-quality randomised controlled trials incorporating active controls and follow-up data.

Safety learning during development: Implications for development of psychopathology

Fear and safety learning are necessary adaptive behaviors that develop over the course of maturation. While there is a large body of literature regarding the neurobiology of fear and safety learning in adults, less is known regarding safety learning during development. Given developmental changes in the brain, there are corresponding changes in safety learning that are quantifiable; these may serve to predict risk and point to treatment targets for fear and anxiety-related disorders in children and adolescents. For healthy, typically developing youth, the main developmental variation observed is reduced discrimination between threat and safety cues in children compared to adolescents and adults, while lower expression of extinction learning is exhibited in adolescents compared to adults. Such distinctions may be related to faster maturation of the amygdala relative to the prefrontal cortex, as well as incompletely developed functional circuits between the two. Fear and anxiety-related disorders, childhood maltreatment, and behavioral problems are all associated with alterations in safety learning for youth, and this dysfunction may proceed into adulthood with corresponding abnormalities in brain structure and function-including amygdala hypertrophy and hyperreactivity. As impaired inhibition of fear to safety may reflect abnormalities in the developing brain and subsequent psychopathology, impaired safety learning may be considered as both a predictor of risk and a treatment target. Longitudinal neuroimaging studies over the course of development, and studies that query change with interventions are needed in order to improve outcomes for individuals and reduce long-term impact of developmental psychopathology.

Optimising Exposure for Children and Adolescents with Anxiety, OCD and PTSD: A Systematic Review

Cognitive behavioural therapy is an effective treatment for anxiety disorders in children and young people; however, many do not benefit. Behavioural exposure appears to be the critical ingredient in the treatment of anxiety disorders. Research with adults has identified innovative strategies to optimise exposure-based treatments, yet it is not clear how to optimise the effects of exposure for children and young people. This review was a preliminary exploration of the association between potential optimisation strategies and treatment procedures and outcomes for the treatment of child anxiety symptoms/disorders. We searched Psych-Info and Medline databases using a systematic search strategy and identified 29 articles. We found preliminary evidence that some specific strategies may enhance the effects of exposure, such as dropping safety behaviours, parents and therapists discouraging avoidance, and the use of homework. However, not one significant finding was replicated by another study for the same timepoint using the same methodology. To a large degree, this lack of replication reflects a limited number of studies combined with a lack of consistency across studies around conceptualisations, methodological approaches, and outcome measures making it difficult to make meaningful comparisons between studies and draw firm conclusions. Examination is needed of a wide range of theoretically-driven potential optimisation strategies using methodologically robust, preclinical studies with children and young people. Furthermore, the methods used in future research must enable comparisons across studies and explore developmental differences in the effects of particular optimisation strategies.

Annual Research Review: Immersive virtual reality and digital applied gaming interventions for the treatment of mental health problems in children and young people: the need for rigorous treatment development and clinical evaluation

BACKGROUND

Mental health problems in children and young people are common and can lead to poor long-term outcomes. Despite the availability of effective psychological interventions for mental health disorders, only a minority of affected children and young people access treatment. Digital interventions, such as applied games and virtual reality (VR), that target mental health problems in children and young people may hold a key to increasing access to, engagement with, and potentially the effectiveness of psychological treatments. To date, several applied games and VR interventions have been specifically developed for children and young people. This systematic review aims to identify and synthesize current data on the experience and effectiveness of applied games and VR for targeting mental health problems in children and young people (defined as average age of 18 years or below).

METHODS

Electronic systematic searches were conducted in Medline, PsycINFO, CINAHL, and Web of Science.

RESULTS

Nineteen studies were identified that examined nine applied games and two VR applications, and targeted symptoms of anxiety, depression, and phobias using both quantitative and qualitative methodologies. Existing evidence is at a very early stage and studies vary extensively in key methodological characteristics. For applied games, the most robust evidence is for adolescent depressive symptoms (medium clinical effect sizes). Insufficient research attention has been given to the efficacy of VR interventions in children and young people.

CONCLUSIONS

The evidence to date is at a very early stage. Despite the enthusiasm for applied games and VR, existing interventions are limited in number and evidence of efficacy, and there is a clear need for further co-design, development, and evaluation of applied games and VR before they are routinely offered as treatments for children and young people with mental health problems.

Potentiated perceptual neural responses to learned threat during Pavlovian fear acquisition and extinction in adolescents

Adolescents' experience of heightened anxiety and increased vulnerability to develop anxiety disorders is believed to partly result from blunted fear extinction processes. However, whether this anxiety is mediated by adolescent-specific differences in perceptual responses to learned threat is not known. To investigate this, we used EEG to examine reinforcement-dependent changes in early visual event-related potentials in adolescents (N = 28, 13-14 years) and adults (N = 23, 25-26 years old) during a differential Pavlovian fear conditioning task, with one conditioned stimulus (CS+) paired with an aversive sound (unconditioned stimulus [US]) on 50% of trials, and another (CS-) never paired with the US. An immediate extinction phase followed, where both CSs were presented alone. We found age-dependent dissociations between explicit and implicit measures of fear learning. Specifically, both adolescents and adults demonstrated successful fear conditioning and extinction according to their explicit awareness of changes in CS contingencies and their evaluative CS ratings, and their differential skin conductance responses. However, for the first time we show age differences at the neural level in perceptual areas. Only adolescents showed greater visual P1 and N1 responses to the CS+ compared to the CS- during acquisition, a dissociation that for the N1 was maintained during extinction. We suggest that the adolescent perceptual hyper-responsivity to learned threat and blunted extinction reported here could be an adaptive mechanism to protect adolescents from harm. However, this hyper-responsivity may also confer greater vulnerability to experience pathological levels of anxiety at this developmental stage.

Pavlovian Learning Processes in Pediatric Anxiety Disorders: A Critical Review

Deficits in associative and Pavlovian learning are thought to lie at the center of anxiety-related disorders. However, the majority of studies have been carried out in adult populations. The aim of this review was to critically examine the behavioral and neuroimaging literature on Pavlovian learning in pediatric anxiety disorders. We conclude that although there is evidence for deficits in Pavlovian processes (e.g., heightened reactivity to safety cues in anxious samples), the extant literature suffers from key methodological and theoretical issues. We conclude with theoretical and methodological recommendations for future research in order to further elucidate the role of Pavlovian learning in the etiology, maintenance, and treatment of pediatric anxiety disorders.

Does the assessment of different combinations of within-phase subjective measures influence electrodermal responding and between-phase subjective ratings during fear conditioning and extinction experiments?

The type and number of dependent measures assessed have varied between fear conditioning and extinction experiments and it remains unclear whether methodological differences influence results. Measuring skin conductance responses (SCRs) and between-phase subjective ratings between four conditions; Con condition had no within-phase ratings; US Exp condition included within-phase US expectancy ratings only; CS Eval condition included within-phase CS evaluations only and All Meas condition included both. All Meas condition exhibited larger SCRs compared to other conditions during acquisition, extinction, and return of differential responding at test. Differential SCRs did not extinguish in CS Eval and Con conditions, and CS Eval condition exhibited smaller CS- SCRs than other conditions throughout phases. US Exp condition revealed differential conditioning, successful extinction, and no return of differential SCRs. Between-phase ratings were not affected by within-phase ratings. Researchers should consider assessing different combinations of within-phase subjective ratings depending on the aims of their research.

Comparing neural correlates of conditioned inhibition between children with and without anxiety disorders - A preliminary study

Cognitive-behavioral therapy (CBT), a first-line treatment for pediatric anxiety disorders, is based on principles of threat learning and extinction. However, CBT does not work sufficiently for up to 40% of clinically anxious youth. The neural and behavioral correlates of conditioned inhibition might provide promising targets for attempts to improve CBT response. During conditioned inhibition, threat and safety cues appear together, forming a safety compound. Here, we test whether this safety compound elicits a reduced fear response compared to pairing the threat cue with a novel cue (novel compound). The current pilot study compares behavioral, physiological, and neural correlates of conditioned inhibition between children with (n = 17, Mage = 13.09, SDage = 3.05) and without (n = 18, Mage = 14.49, SDage = 2.38) anxiety disorders. Behavioral and physiological measures did not differ between children with and without anxiety disorders during fear acquisition. During testing, children with anxiety disorders showed overall higher skin conductance response and expected to hear the aversive sound following the novel compound more often than children without anxiety disorders. Children with anxiety disorders showed more activity in the right ventromedial prefrontal cortex (vmPFC) to the safety versus novel compound. Children without anxiety disorders showed the opposite pattern - more right vmPFC activity to the novel versus safety compound (F(1,31) = 5.40, p = 0.03). No group differences manifested within the amygdala, dorsal anterior cingulate cortex, or hippocampus. These pilot findings suggest a feasible approach for examining conditioned inhibition in pediatric anxiety disorders. If replicated in larger samples, findings may implicate perturbed conditioned inhibition in pediatric anxiety disorders and provide targets for CBT.

Learning About Safety: Conditioned Inhibition as a Novel Approach to Fear Reduction Targeting the Developing Brain

Adolescence is a peak time for the onset of psychiatric disorders, with anxiety disorders being the most common and affecting as many as 30% of youths. A core feature of anxiety disorders is difficulty regulating fear, with evidence suggesting deficits in extinction learning and corresponding alterations in frontolimbic circuitry. Despite marked changes in this neural circuitry and extinction learning throughout development, interventions for anxious youths are largely based on principles of extinction learning studied in adulthood. Safety signal learning, based on conditioned inhibition of fear in the presence of a cue that indicates safety, has been shown to effectively reduce anxiety-like behavior in animal models and attenuate fear responses in healthy adults. Cross-species evidence suggests that safety signal learning involves connections between the ventral hippocampus and the prelimbic cortex in rodents or the dorsal anterior cingulate cortex in humans. Particularly because this pathway follows a different developmental trajectory than fronto-amygdala circuitry involved in traditional extinction learning, safety cues may provide a novel approach to reducing fear in youths. In this review, the authors leverage a translational framework to bring together findings from studies in animal models and humans and to bridge the gap between research on basic neuroscience and clinical treatment. The authors consider the potential application of safety signal learning for optimizing interventions for anxious youths by targeting the biological state of the developing brain. Based on the existing cross-species literature on safety signal learning, they propose that the judicious use of safety cues may be an effective and neurodevelopmentally optimized approach to enhancing treatment outcomes for youths with anxiety disorders.

A legacy of fear: Physiological evidence for intergenerational effects of trauma exposure on fear and safety signal learning among African Americans

OBJECTIVE

To determine the influence of maternal trauma and posttraumatic stress disorder (PTSD) symptoms on children's physiological response to threat and safety signals during a fear conditioning task in trauma-exposed mothers and children.

METHOD

Participants were African American mother-child dyads (N = 137; children aged 8-13 years). Mothers' trauma history and PTSD symptoms were assessed; Latent Class Analysis (LCA) was conducted from these measures to identify distinct classes. Children reported violence exposure and completed a differential fear conditioning task using fear-potentiated startle (FPS) responses to conditioned danger (CS+) and safety (CS-) signals.

RESULTS

Four classes of maternal trauma history and PTSD symptoms emerged: 1) Lower Trauma, 2) Moderate Trauma, 3) High Sexual Abuse, and 4) High Trauma and PTSD Symptoms. Children's FPS to CS + and CS- were tested with maternal class as the between-subjects factor. FPS to the danger signal was not significantly different across maternal classes, but FPS to safety (CS-) was significantly higher for the Lower Trauma and High Trauma and PTSD Symptoms classes than either the Moderate Trauma or the High Sexual Abuse classes.

CONCLUSIONS

Results indicate that maternal trauma impacts children's ability to modulate fear responses in the presence of a safety signal, independent of the children's own trauma exposure. To our knowledge, this is the first study to demonstrate that children's fear inhibition is impacted by maternal trauma exposure. Prior studies have linked fear inhibition to mental health outcomes, highlighting the need to understand intergenerational modulation of fear learning and physiology.

Impact of ADCYAP1R1 genotype on longitudinal fear conditioning in children: interaction with trauma and sex

Dysregulated fear conditioned responses have been associated with PTSD in adults, with increased fear-potentiated startle (FPS) serving as a potential intermediate phenotype for PTSD risk. This phenotype has also been associated with stress-related ADCYAP1R1 gene variants in adult women. However, FPS and genotype have not yet been examined during development. The aim of this study was to examine developmental changes in fear conditioning, and to see whether these changes were impacted by genotype and trauma. Differential fear conditioning using FPS was tested in n = 63 children ages 8-13 at two visits (V1, V2) 1 year apart. Startle response was measured using electromyograph recordings of the eyeblink muscle. The rs2267735 SNP of the ADCYAP1R1 gene was extracted from genome-wide (GWAS) analyses. Trauma exposure was assessed using the Violence Exposure Scale-Revised (VEX-R). We found significant Visit by Genotype interactions, with CC genotype increasing FPS from V1 to V2. At V2 there was a Genotype by Violence interaction, with higher FPS in the CC vs G allele groups among those with higher violence exposure (F = 17.46, p = 0.0002). Females with the CC genotype had higher FPS compared to G allele females (F = 12.09, p = 0.002); there were no effects of genotype in males. This study showed Gene × Environment × Development and Gene × Sex effects of ADCYAP1R1 in a high-risk pediatric population. Those with the CC genotype and high levels of violence exposure, as well as females with the CC genotype, showed the greatest conditioned fear responses in adolescence.

Deficits in opioid receptor-mediated prediction error contribute to impaired fear extinction during adolescence

Adolescent-onset anxiety disorders are more common and costly than those that emerge later in life. Unfortunately, nearly half of adolescents undergoing cognitive behavioural therapies, including exposure therapies, show significant symptom relapse. Such poor treatment outcomes are consistent with preclinical work examining fear extinction, in which adolescents show persistent fear to extinguished cues. Both extinction and exposure are dependent on the generation of prediction error (i.e., the difference between the expected and actual outcome of a cue presentation), a process which involves the opioid system. We investigated the contribution of prediction error signalling to extinction during adolescence using the opioid receptor antagonist naloxone. We demonstrated that unlike in juvenile and adult rats, fear expression during extinction training and test in adolescent rats was unaffected by naloxone, suggesting that adolescent rats are impaired in using prediction error signalling to extinguish fear under typical conditions. However, in two circumstances where adolescents exhibit good extinction retention, opioid receptor blockade impaired extinction retention, suggesting that the recruitment of prediction error signalling mechanisms promotes extinction in this age group, just as it does in adults. Importantly, additional extinction training may be required to enable prediction error mechanisms to be recruited during adolescence.

Puberty drives fear learning during adolescence

Risk for adverse outcomes, including the onset of mental illness, increases during adolescence. This increase may be linked to both new exposures, such as violence at home or in the community, or to physiological changes driven by puberty. There are significant sex differences in adolescent risk, for instance, anxiety disorders are significantly more prevalent in girls than boys. Fear learning is linked to mental health and may develop during adolescence, but the role of puberty in adolescent-specific change has not yet been systematically evaluated. We conducted a longitudinal study of fear learning that tested fear-potentiated startle (FPS) in 78 children (40 girls) aged 8-16 years. Participants completed two to three visits that included a differential fear conditioning task and self-report of both pubertal status and violence exposure. We tested for effects of sex, pubertal status, and violence exposure on FPS over time with latent growth curve models. We also examined the association between FPS and later anxiety symptoms. We found significant changes in FPS to the threat cue, but not the safety cue, across visits. Higher pubertal status was significantly associated with increased FPS to threat cues at each visit, whereas sex and violence exposure were not. FPS to threat during the baseline visit also predicted later anxiety symptoms. These findings suggest that puberty drives increased fear response to threat cues similarly for girls and boys, and that this effect may not be significantly impacted by individual differences in violence exposure during early adolescence.

Under the influence of the environment: Children's responding invigorated and biased by predictive cues

Cues that signal motivationally significant consequences can elevate responding and bias choice. A task known as Pavlovian-to-instrumental transfer (PIT) has been used to assess the influence of these cues on independently trained responses and to study the effect of drug-related and food-related cues on behavior in adult populations, but it has not yet been employed in children. This study aimed to develop a simple computer task to study PIT in children. Participants, aged 7-11 years, observed a screen in which different pairings of distinct cartoon images and specific outcomes were presented (images of foods and drinks in Experiment 1 and images of pets in Experiment 2). After this, the participants pressed two keys, each consistently reinforced with one of the two outcomes. Finally, the children pressed both keys in the absence of any outcome, and each cartoon image was presented periodically so that the effect of these cues on behavior could be measured. Experiment 1 showed that the cartoons' presentations biased responding toward the key that was trained with the same outcome as the cartoon being presented, that is, outcome-specific PIT. Experiment 2 replicated this finding and also showed that a cartoon trained with an outcome different from that reinforcing the responses elevated performance of both responses relative to a cartoon that was not paired with any outcome in training, that is, general PIT. These findings are consistent with those reported in the adult population and might be a useful tool to study the early development of maladaptive behaviors.

A study on classification features of depressive symptoms in adolescents

Although extensive literature has addressed depression among adolescents, few studies have emphasized the classification features of depressive symptoms in adolescents. To gain insight into the hierarchy and heterogeneity of depression in adolescents based on symptoms, 5086 adolescents completed the Chinese version of the Center for Epidemiological Studies Depression Scale (CES-D). Using Latent Class Analysis (LCA), we identified different subgroups of adolescents based on depressive symptoms. Multivariate logistic regression analysis was implemented to examine the relations between latent classes and demographic covariates. Four latent classes of individuals with depressive symptoms displaying a pattern of hierarchical organization were identified. The four classes were ordered by the degree of severity, ranging from the students reporting the highest number of depressive symptoms to the lowest number: "probable clinical depression", "subthreshold depression", "mild depression" and "low depression", accounting for 8.2%, 19.2%, 41.8% and 30.8% of total sample respectively. Further analyses revealed that compared to the "mild depression" class, the rest of three classes differed significantly across age groups and only child (vs. sibling) status. In conclusion, classifying the groups of adolescents based on features of depressive symptoms is potentially useful for understanding risk factors and developing tailored prevention and intervention programs for this age group.

Mechanisms linking childhood adversity with psychopathology: Learning as an intervention target

Exposure to childhood adversity is common and a powerful risk factor for many forms of psychopathology. In this opinion piece, we argue for greater translation of knowledge about the developmental processes that are influenced by childhood adversity into targeted interventions to prevent the onset of psychopathology. Existing evidence has consistently identified several neurodevelopmental pathways that serve as mechanisms linking adversity with psychopathology. We highlight three domains in which these mechanisms are well-established and point to clear targets for intervention: 1) threat-related social information processing biases; 2) heightened emotional reactivity and difficulties with emotion regulation; and 3) disruptions in reward processing. In contrast to these established pathways, knowledge of how childhood adversity influences emotional learning mechanisms, including fear and reward learning, is remarkably limited. We see the investigation of these mechanisms as a critical next step for the field that will not only advance understanding of developmental pathways linking childhood adversity with psychopathology, but also provide clear targets for behavioral interventions. Knowledge of the mechanisms linking childhood adversity with psychopathology has advanced rapidly, and the time has come to translate that knowledge into clinical interventions to prevent the onset of mental health problems in children who have experienced adversity.

Development of Prefrontal Cortical Connectivity and the Enduring Effect of Learned Value on Cognitive Control

Inhibitory control, the capacity to suppress an inappropriate response, is a process employed for guiding action selection in the service of goal-directed behavior. Under neutral circumstances, inhibitory control success improves from childhood to adulthood and has been associated with developmental shifts in functional activation and connectivity of the PFC. However, the ability to exercise inhibitory control is challenged in certain contexts by including appetitive cues, a phenomenon that may be particularly pronounced in youths. Here, we examine the magnitude and temporal persistence of learned value's influence on inhibitory control in a cross-sectional sample of 8- to 25-year-olds. Participants first underwent conditioning of a motor approach response to two initially neutral cues, with one cue reinforced with monetary reward and the other with no monetary outcome. Subsequently, during fMRI, participants reencountered these cues as no-go targets in a nonreinforced go/no-go paradigm. Although the influence of learned value increasingly disrupted inhibitory control with increasing age, in young adults this pattern remitted over the course of the task, whereas during adolescence the impairing effect of reward history persisted. Successful no-go performance to the previously rewarded target was related to greater recruitment of the right inferior frontal gyrus and age-related increase in functional connectivity between the inferior frontal gyrus and the ventromedial PFC for the previously rewarded no-go target over the control target. Together, results indicate the complex influence of value on goals over development relies upon the increased coordination of distinct higher-order regions in the PFC.

The need for standards in the design of differential fear conditioning and extinction experiments in youth: A systematic review and recommendations for research on anxiety

Fear extinction studies in youth have yielded mixed results due to developmental processes and variations in design, methodology and dependent measures. This systematic review focused on studies with healthy youth between 2 and 17 years of age to identify experimental parameters of studies documenting extinction effects. Thirty-five studies met inclusion criteria and the following themes emerged (a) some studies employed parameters and task demands that are complex and require active participant involvement whereas others involved simple stimulus configurations and passive participant involvement, and (b) variation exists among dependent measures in units of measurement, timing and type of measurement. The review identified that studies using geometric shape conditioned stimuli (CS) paired with a tone unconditioned stimulus (US) (e.g., metal scraping on slate), as well as face CSs with a scream US produced the most reliable extinction effects, although the latter combination may be associated with higher drop-out than shape CSs and a tone US. The most commonly used and effective dependent measures for revealing extinction effects were skin conductance responses (SCR) and subjective ratings (SR) of CS valence, fearfulness and arousal. Fear potentiated startle (FPS) blink reflexes were also an effective but less commonly used measure. It is recommended that future studies use shape CSs and the metal scraping on slate US in studies involving children and either shape CSs and the metal scraping on slate US or face CSs paired with a scream US with adolescents. It is also recommended that US expectancy ratings and CS evaluations are assessed trial-by-trial and between-phase, and that startle-eliciting stimuli to measure startle blink reflexes are delivered on every second trial per CS so that SCR and FPS can be examined. However, further research is required to determine whether increased participant involvement due to providing trial-by-trial and between-phase ratings of the CSs and US differentially influences responding, particularly in children relative to adolescents and adults.

State-of-the-art and future directions for extinction as a translational model for fear and anxiety

Through advances in both basic and clinical scientific research, Pavlovian fear conditioning and extinction have become an exemplary translational model for understanding and treating anxiety disorders. Discoveries in associative and neurobiological mechanisms underlying extinction have informed techniques for optimizing exposure therapy that enhance the formation of inhibitory associations and their consolidation and retrieval over time and context. Strategies that enhance formation include maximizing prediction-error correction by violating expectancies, deepened extinction, occasional reinforced extinction, attentional control and removal of safety signals/behaviours. Strategies that enhance consolidation include pharmacological agonists of NMDA (i.e. d-cycloserine) and mental rehearsal. Strategies that enhance retrieval include multiple contexts, retrieval cues, and pharmacological blockade of contextual encoding. Stimulus variability and positive affect are posited to influence the formation and the retrieval of inhibitory associations. Inhibitory regulation through affect labelling is considered a complement to extinction. The translational value of extinction will be increased by more investigation of elements central to extinction itself, such as extinction generalization, and interactions with other learning processes, such as instrumental avoidance reward learning, and with other clinically relevant cognitive-emotional processes, such as self-efficacy, threat appraisal and emotion regulation, will add translational value. Moreover, framing fear extinction and related processes within a developmental context will increase their clinical relevance.This article is part of a discussion meeting issue 'Of mice and mental health: facilitating dialogue between basic and clinical neuroscientists'.

A novel paradigm to study interpersonal threat-related learning and extinction in children using virtual reality

Disruptions in fear-extinction learning are centrally implicated in a range of stress-related disorders, including anxiety and posttraumatic stress disorder. Given that these disorders frequently begin in childhood/adolescence, an understanding of fear-extinction learning in children is essential for (1) detecting the source of developmental susceptibility, (2) identifying mechanisms leading to pathology, and (3) informing the development and/or more judicious application of treatments for youth. Here, we offer and validate a novel virtual reality paradigm to study threat-related learning and extinction in children that models real-world cues, environments, and fear-inducing events that children are likely to experience, and are linked to the development of fear- and stress-related pathologies. We found that our paradigm is well tolerated in children as young as 6 years, that children show intact fear and extinction learning, and show evidence of divergence in subjective, physiological, and behavioral measures of conditioned fear. The paradigm is available for use in 3-D and in 2-D (e.g., for the MRI scanner) upon request at www.tnp2lab.org.