Transitional and translational studies of risk for anxiety

Peer facilitation of emotion regulation in adolescence

Emotion regulation is particularly important for adolescents as they undergo normative developmental changes in affective systems and experience heightened risk for psychopathology. Despite a high need for emotion regulation during adolescence, commonly studied emotion regulation strategies like cognitive reappraisal are less beneficial for adolescents than adults because they rely on neural regions that are still developing during this period (i.e., lateral prefrontal cortex). However, adolescence is also marked by increased valuation of peer relationships and sensitivity to social information and cues. In the present review, we synthesize research examining emotion regulation and peer influence across development to suggest that sensitivity to peers during adolescence could be leveraged to improve emotion regulation for this population. We first discuss developmental trends related to emotion regulation at the level of behavior and brain in adolescents, using cognitive reappraisal as an exemplar emotion regulation strategy. Next, we discuss social influences on adolescent brain development, describing caregiver influence and increasing susceptibility to peer influence, to describe how adolescent sensitivity to social inputs represents both a window of vulnerability and opportunity. Finally, we conclude by describing the promise of social (i.e., peer-based) interventions for enhancing emotion regulation in adolescence.

The Neurobiology of Infant Attachment-Trauma and Disruption of Parent-Infant Interactions

Current clinical literature and supporting animal literature have shown that repeated and profound early-life adversity, especially when experienced within the caregiver-infant dyad, disrupts the trajectory of brain development to induce later-life expression of maladaptive behavior and pathology. What is less well understood is the immediate impact of repeated adversity during early life with the caregiver, especially since attachment to the caregiver occurs regardless of the quality of care the infant received including experiences of trauma. The focus of the present manuscript is to review the current literature on infant trauma within attachment, with an emphasis on animal research to define mechanisms and translate developmental child research. Across species, the effects of repeated trauma with the attachment figure, are subtle in early life, but the presence of acute stress can uncover some pathology, as was highlighted by Bowlby and Ainsworth in the 1950s. Through rodent neurobehavioral literature we discuss the important role of repeated elevations in stress hormone corticosterone (CORT) in infancy, especially if paired with the mother (not when pups are alone) as targeting the amygdala and causal in infant pathology. We also show that following induced alterations, at baseline infants appear stable, although acute stress hormone elevation uncovers pathology in brain circuits important in emotion, social behavior, and fear. We suggest that a comprehensive understanding of the role of stress hormones during infant typical development and elevated CORT disruption of this typical development will provide insight into age-specific identification of trauma effects, as well as a better understanding of early markers of later-life pathology.

Amygdala hyperreactivity to faces conditioned with a social-evaluative meaning- a multiplex, multigenerational fMRI study on social anxiety endophenotypes

Social anxiety disorder (SAD) runs in families, but the neurobiological pathways underlying the genetic susceptibility towards SAD are largely unknown. Here, we employed an endophenotype approach, and tested the hypothesis that amygdala hyperreactivity to faces conditioned with a social-evaluative meaning is a candidate SAD endophenotype. We used data from the multiplex, multigenerational Leiden Family Lab study on Social Anxiety Disorder (eight families, n = 105) and investigated amygdala activation during a social-evaluative conditioning paradigm with high ecological validity in the context of SAD. Three neutral faces were repeatedly presented in combination with socially negative, positive or neutral sentences. We focused on two endophenotype criteria: co-segregation of the candidate endophenotype with the disorder within families, and heritability. Analyses of the fMRI data were restricted to the amygdala as a region of interest, and association analyses revealed that bilateral amygdala hyperreactivity in response to the conditioned faces co-segregated with social anxiety (SA; continuous measure) within the families; we found, however, no relationship between SA and brain activation in response to more specific fMRI contrasts. Furthermore, brain activation in a small subset of voxels within these amygdala clusters was at least moderately heritable. Taken together, these findings show that amygdala engagement in response to conditioned faces with a social-evaluative meaning qualifies as a neurobiological candidate endophenotype of social anxiety. Thereby, these data shed light on the genetic vulnerability to develop SAD.

Corticolimbic circuit structure moderates an association between early life stress and later trait anxiety

Childhood adversity is associated with a wide range of negative behavioral and neurodevelopmental consequences. However, individuals vary substantially in their sensitivity to such adversity. Here, we examined how individual variability in structural features of the corticolimbic circuit, which plays a key role in emotional reactivity, moderates the association between childhood adversity and later trait anxiety in 798 young adult university students. Consistent with prior research, higher self-reported childhood adversity was significantly associated with higher self-reported trait anxiety. However, this association was attenuated in participants with higher microstructural integrity of the uncinate fasciculus and greater thickness of the orbitofrontal cortex. These structural properties of the corticolimbic circuit may capture a neural profile of relative resiliency to early life stress, especially against the negative effects of childhood adversity on later trait anxiety.

Microstructural integrity of white matter moderates an association between childhood adversity and adult trait anger

Amongst a number of negative life sequelae associated with childhood adversity is the later expression of a higher dispositional tendency to experience anger and frustration to a wide range of situations (i.e., trait anger). We recently reported that an association between childhood adversity and trait anger is moderated by individual differences in both threat-related amygdala activity and executive control-related dorsolateral prefrontal cortex (dlPFC) activity, wherein individuals with relatively low amygdala and high dlPFC activity do not express higher trait anger even when having experienced childhood adversity. Here, we examine possible structural correlates of this functional dynamic using diffusion magnetic resonance imaging data from 647 young adult men and women volunteers. Specifically, we tested whether the degree of white matter microstructural integrity as indexed by fractional anisotropy modulated the association between childhood adversity and trait anger. Our analyses revealed that higher microstructural integrity of multiple pathways was associated with an attenuated link between childhood adversity and adult trait anger. Amongst these pathways was the uncinate fasciculus (UF; ΔR ²  = 0.01), which not only provides a major anatomical link between the amygdala and prefrontal cortex but also is associated with individual differences in regulating negative emotion through top-down cognitive reappraisal. These findings suggest that higher microstructural integrity of distributed white matter pathways including but not limited to the UF may represent an anatomical foundation serving to buffer against the expression of childhood adversity as later trait anger, which is itself associated with multiple negative health outcomes.

A descriptive analysis of gut microbiota composition in differentially reared infant rhesus monkeys (Macaca mulatta) across the first 6 months of life

The gastrointestinal microbiome is recognized as a critical component in host immune function, physiology, and behavior. Early life experiences that alter diet and social contact also influence these outcomes. Despite the growing number of studies in this area, no studies to date have examined the contribution of early life experiences on the gut microbiome in infants across development. Such studies are important for understanding the biological and environmental factors that contribute to optimal gut microbial colonization and subsequent health. We studied infant rhesus monkeys (Macaca mulatta) across the first 6 months of life that were pseudo-randomly assigned to one of two different rearing conditions at birth: mother-peer-reared (MPR), in which infants were reared in social groups with many other adults and peers and nursed on their mothers, or nursery-reared (NR), in which infants were reared by human caregivers, fed formula, and given daily social contact with peers. We analyzed the microbiome from rectal swabs (total N = 97; MPR = 43, NR = 54) taken on the day of birth and at postnatal Days 14, 30, 90, and 180 using 16S rRNA gene sequencing. Bacterial composition differences were evident as early as 14 days, with MPR infants exhibiting a lower abundance of Bifidobacterium and a higher abundance of Bacteroides than NR infants. The most marked differences were observed at 90 days, when Bifidobacterium, Lactobacillus, Streptococcus, Bacteroides, Clostridium, and Prevotella differed across rearing groups. By Day 180, no differences in the relative abundances of the bacteria of interest were observed. These novel findings in developing primate neonates indicate that the early social environment as well as diet influence gut microbiota composition very early in life. These results also lay the groundwork for mechanistic studies examining the effects of early experiences on gut microbiota across development with the ultimate goal of understanding the clinical significance of developmental changes.

Measuring novel antecedents of mental illness: the Questionnaire of Unpredictability in Childhood

Increasing evidence indicates that, in addition to poverty, maternal depression, and other well-established factors, unpredictability of maternal and environmental signals early in life influences trajectories of brain development, determining risk for subsequent mental illness. However, whereas most risk factors for later vulnerability to mental illness are readily measured using existing, clinically available tools, there are no similar measures for assessing early-life unpredictability. Here we validate the Questionnaire of Unpredictability in Childhood (QUIC) and examine its associations with mental health in the context of other indicators of childhood adversity (e.g., traumatic life events, socioeconomic status, and parenting quality). The QUIC was initially validated through administration to a cohort of adult females (N = 116) and then further refined in two additional independent cohorts (male Veterans, N = 95, and male and female adolescents, N = 175). The QUIC demonstrated excellent internal (α = 0.89) and test-retest reliability (r = 92). Scores on the QUIC were positively correlated with other prospective indicators of exposures to unpredictable maternal inputs in infancy and childhood (unpredictable maternal mood and sensory signals), and accuracy of recall also was confirmed with prospective data. Importantly, the QUIC predicted symptoms of anxiety, depression, and anhedonia in the three study cohorts, and these effects persisted after adjusting for other previously established risk factors. The QUIC, a reliable and valid self-report assessment of exposure to unpredictability in the social, emotional, and physical domains during early life, is a brief, comprehensive, and promising instrument for predicting risk for mental illness.

Chronic harsh parenting and anxiety associations with fear circuitry function in healthy adolescents: A preliminary study

Previous studies have reported altered fear circuitry function during fear conditioning in highly anxious individuals and in adults with a history of severe childhood adversity; less is known regarding younger populations and more common forms of adversity. We investigated fear circuitry functioning in healthy youths with histories of high (HH) or low (LH) chronic harsh parenting and high (HA) or low (LA) anxiety levels. 84 youths aged 13-16 performed an fMRI fear conditioning task. HH displayed decreased selective medial temporal lobe deactivations to CS+> CS- relative to LH. In addition, we found less amygdala-insula connectivity in HH vs LH. Interestingly, we observed distinct patterns of anxiety differences in amygdala-rostral ACC connectivity and subjective fear ratings depending on harsh parenting levels, suggesting a history of harsh parenting is linked with unique neural and behavioral anxious manifestations, which are different from anxiety manifestations in a context of low adversity.

Association between risky behaviors in adolescents and altered psychophysiological emotional responses

Introducción. La psicofisiología de la respuesta emocional en la adolescencia es un factor clave en la comprensión de conductas de riesgo y desadaptación.Objetivo. Comparar especificidades de la reacción psicofisiológica emocional entre adolescentes con y sin conductas de riesgo.Materiales y métodos. Las medidas consistieron en la caracterización de conductas de riesgo (CR), variaciones en la frecuencia cardiaca (FC) electromiografía (EMG), conductancia de la piel (CP) y temperatura durante la presentación de estímulos emocionales visuales, así como la calificación en parámetros de valencia emocional, activación y dominancia de dichos estímulos.Resultados. Se encontraron diferencias significativas entre los adolescentes con CR comparados con aquellos que no las presentaban: se detectaron signos de mayor reacción psicofisiológica a los estímulos emocionales.Conclusiones. El grupo control se caracterizó por una bradicardia inicial más expresiva en comparación con el grupo con CR, ambos grupos mostraron desaceleración cardíaca más pronunciada ante estímulos desagradables, niveles más altos en EMG ante estímulos agradables en el grupo con RB e indicadores más elevados de CP ante los tres tipos de estímulo. Se requiere un estudio de cohorte a fin de comparar los hallazgos actuales en CR frente a la reacción fisiológica emocional entre los grupos de adolescentes.

Adolescent Substance Use and Comorbid Psychopathology: Emotion Regulation Deficits as a Transdiagnostic Risk Factor

Rates of substance use and comorbid psychopathology peak during adolescence, highlighting the need to identify transdiagnostic risk processes that cut across conditions and elucidate early embedded risk factors for comorbidity across development. The current review highlights emotion regulation deficits as a core transdiagnostic risk factor underlying the development of substance use, addiction, and comorbid psychopathology in adolescence. We present the dual systems model of neurological development to highlight adolescence as a critical period of increased risk for emotion regulation difficulties, corresponding risk behaviors, and psychopathology. We describe malfunction in the neurobiological regulation system underlying the relationship between emotion regulation and risk for addiction and comorbidity. We pull from two established developmental theories including both the externalizing pathway and the internalizing pathway to substance use disorders, which together highlight how early embedded risk in the form of emotion regulation deficits can explain mechanisms underlying the development of addiction and comorbid psychiatric disorders.

Allelic Variation of Risk for Anxiety Symptoms Moderates the Relation Between Adolescent Safety Behaviors and Social Anxiety Symptoms

Social anxiety often develops in adolescence, and precedes the onset of depression and substance use disorders. The link between social anxiety and use of behaviors to minimize distress in social situations (i.e., safety behaviors) is strong and for some patients, this link poses difficulty for engaging in, and benefiting from, exposure-based treatment. Yet, little is known about whether individual differences may moderate links between social anxiety and safety behaviors, namely variations in genetic alleles germane to anxiety. We examined the relation between adolescent social anxiety and expressions of safety behaviors, and whether allelic variation for anxiety moderates this relation. Adolescents (n=75; ages 14-17) were recruited from two larger studies investigating measurement of family relationships or adolescent social anxiety. Adolescents completed self-report measures about social anxiety symptoms and use of safety behaviors. They also provided saliva samples to assess allelic variations for anxiety from two genetic polymorphisms (BDNF rs6265; TAQ1A rs1800497). Controlling for adolescent age and gender, we observed a significant interaction between social anxiety symptoms and allelic variation (β=0.37, t=2.41, p=.02). Specifically, adolescents carrying allelic variations for anxiety evidenced a statistically significant and relatively strong positive relation between social anxiety symptoms and safety behaviors (β=0.73), whereas adolescents not carrying allelic variation evidenced a statistically non-significant and relatively weak relation (β=0.22). These findings have important implications for treating adolescent social anxiety, in that we identified an individual difference variable that can be used to identify people who evidence a particularly strong link between use of safety behaviors and expressing social anxiety.

Social scaffolding of human amygdala-mPFCcircuit development

Strong evidence indicates that reciprocal connections between the amygdala and the medial prefrontal cortex (mPFC) support fundamental aspects of emotional behavior in adulthood. However, this circuitry is slow to develop in humans, exhibiting immaturity in childhood. The argument is made that the development of this circuitry in humans is intimately associated with caregiving, such that parental availability during childhood provides important and enduring scaffolding of neuroaffective processes that ultimately form of the nature of the adult phenotype.

Social scaffolding of human amygdala-mPFCcircuit development

Strong evidence indicates that reciprocal connections between the amygdala and the medial prefrontal cortex (mPFC) support fundamental aspects of emotional behavior in adulthood. However, this circuitry is slow to develop in humans, exhibiting immaturity in childhood. The argument is made that the development of this circuitry in humans is intimately associated with caregiving, such that parental availability during childhood provides important and enduring scaffolding of neuroaffective processes that ultimately form of the nature of the adult phenotype.

Neuroimaging and Anxiety: the Neural Substrates of Pathological and Non-pathological Anxiety

Advances in the use of noninvasive neuroimaging to study the neural correlates of pathological and non-pathological anxiety have shone new light on the underlying neural bases for both the development and manifestation of anxiety. This review summarizes the most commonly observed neural substrates of the phenotype of anxiety. We focus on the neuroimaging paradigms that have shown promise in exposing this relevant brain circuitry. In this way, we offer a broad overview of how anxiety is studied in the neuroimaging laboratory and the key findings that offer promise for future research and a clearer understanding of anxiety.

Monoamine-sensitive developmental periods impacting adult emotional and cognitive behaviors

Development passes through sensitive periods, during which plasticity allows for genetic and environmental factors to exert indelible influence on the maturation of the organism. In the context of central nervous system development, such sensitive periods shape the formation of neurocircuits that mediate, regulate, and control behavior. This general mechanism allows for development to be guided by both the genetic blueprint as well as the environmental context. While allowing for adaptation, such sensitive periods are also vulnerability windows during which external and internal factors can confer risk to disorders by derailing otherwise resilient developmental programs. Here we review developmental periods that are sensitive to monoamine signaling and impact adult behaviors of relevance to psychiatry. Specifically, we review (1) a serotonin-sensitive period that impacts sensory system development, (2) a serotonin-sensitive period that impacts cognition, anxiety- and depression-related behaviors, and (3) a dopamine- and serotonin-sensitive period affecting aggression, impulsivity and behavioral response to psychostimulants. We discuss preclinical data to provide mechanistic insight, as well as epidemiological and clinical data to point out translational relevance. The field of translational developmental neuroscience has progressed exponentially providing solid conceptual advances and unprecedented mechanistic insight. With such knowledge at hand and important methodological innovation ongoing, the field is poised for breakthroughs elucidating the developmental origins of neuropsychiatric disorders, and thus understanding pathophysiology. Such knowledge of sensitive periods that determine the developmental trajectory of complex behaviors is a necessary step towards improving prevention and treatment approaches for neuropsychiatric disorders.

Aberrant amygdala functional connectivity at rest in pediatric anxiety disorders

BACKGROUND

Childhood onset of anxiety disorders is associated with greater functional impairment and burden across the lifespan. Recent work suggests that generalized anxiety disorder (GAD) is characterized by dysfunctional connectivity in amygdala-based circuits at rest in adolescents, consistent with adults. However, neural mechanisms underlying a broad spectrum of often-comorbid anxiety disorders in children remains unclear and understudied. The current study examines amygdala functional connectivity at rest in children and adolescents across comorbid anxiety disorders (ADs) including youth with primary diagnoses of GAD and social phobia (SP).

RESULTS

Compared with healthy controls (HCs), AD youth exhibited hyperconnectivity between the right amygdala and the insula and hypoconnectivity between the left amygdala and the ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC). Within the AD group, connectivity was not correlated with anxiety severity and only the amygdala-PCC connectivity was positively correlated with age.

CONCLUSIONS

Our findings indicate that youth with comorbid ADs demonstrate aberrant connectivity in the anterior limbic network (ALN) as well as the PCC at rest. This extends upon previous work suggesting alterations in amygdala circuits underlying fear learning, emotion regulation, and the processing of interoceptive states. Presence of these findings within this young, comorbid sample points to underlying common mechanisms across ADs and illuminates future targets for prevention and intervention in childhood.

Concurrent and lasting effects of emotion regulation on amygdala response in adolescence and young adulthood

This study used functional MRI (fMRI) to examine a novel aspect of emotion regulation in adolescent development: whether age predicts differences in both the concurrent and lasting effects of emotion regulation on amygdala response. In the first, active regulation, phase of the testing session, fMRI data were collected while 56 healthy individuals (age range: 10.50-22.92 years) reappraised aversive stimuli so as to diminish negative responses to them. After a short delay, the second, re-presentation, phase involved passively viewing the aversive images from the reappraisal task. During active regulation, older individuals showed greater drops in negative affect and inverse rostrolateral prefrontal-amygdala connectivity. During re-presentation, older individuals continued to show lasting reductions in the amygdala response to aversive stimuli they had previously reappraised, an effect mediated by rostrolateral PFC. These data suggest that one source of heightened emotionality in adolescence is a diminished ability to cognitively down-regulate aversive reactions.

Looking beyond Fear and Extinction Learning: Considering Novel Treatment Targets for Anxiety

Fear conditioning studies provide valuable insight into how fears are learned and extinguished. Previous work focuses on fear and extinction learning to understand and treat anxiety disorders. However, a cascade of cognitive processes that extend beyond learning may also yield therapeutic targets for anxiety disorders. Throughout this review, we will discuss recent findings of fear generalization, memory consolidation, and reconsolidation. Factors related to effectiveness, efficiency and durability of extinction-based treatments will be addressed. Moreover, adolescence may be a key developmental stage when threat-related perturbations emerge; therefore, targeting interventions during adolescence when these nascent processes are more malleable may alter the trajectory of anxiety disorders.

Risk for anxiety and implications for treatment: developmental, environmental, and genetic factors governing fear regulation

Anxiety disorders are the most common psychiatric disorders, affecting as many as 10% of youth, with diagnoses peaking during adolescence. A core component of these disorders is an unremitting fear in the absence of present threat. One of the most commonly used therapies to treat these disorders is exposure-based cognitive behavioral therapy that identifies the source of the fear and anxiety and then desensitizes the individual to it. This treatment builds on basic principles of fear-extinction learning. A number of patients improve with this therapy, but 40-50% do not. This paper provides an overview of recent empirical studies employing both human imaging and cross-species behavioral genetics to examine how fear regulation varies across individuals and across development, especially during adolescence. These studies have important implications for understanding who may be at risk for anxiety disorders and for whom and when during development exposure-based therapies may be most effective.

Response to learned threat: An FMRI study in adolescent and adult anxiety

OBJECTIVE

Poor threat-safety discrimination reflects prefrontal cortex dysfunction in adult anxiety disorders. While adolescent anxiety disorders are impairing and predict high risk for adult anxiety disorders, the neural correlates of threat-safety discrimination have not been investigated in this population. The authors compared prefrontal cortex function in anxious and healthy adolescents and adults following conditioning and extinction, processes requiring threat-safety learning.

METHOD

Anxious and healthy adolescents and adults (N=114) completed fear conditioning and extinction in the clinic. The conditioned stimuli (CS+) were neutral faces, paired with an aversive scream. Physiological and subjective data were acquired. Three weeks later, 82 participants viewed the CS+ and morphed images resembling the CS+ in an MRI scanner. During scanning, participants made difficult threat-safety discriminations while appraising threat and explicit memory of the CS+.

RESULTS

During conditioning and extinction, the anxious groups reported more fear than the healthy groups, but the anxious adolescent and adult groups did not differ on physiological measures. During imaging, both anxious adolescents and adults exhibited lower activation in the subgenual anterior cingulate cortex than their healthy counterparts, specifically when appraising threat. Compared with their age-matched counterpart groups, anxious adults exhibited reduced activation in the ventromedial prefrontal cortex when appraising threat, whereas anxious adolescents exhibited a U-shaped pattern of activation, with greater activation in response to the most extreme CS+ and CS-.

CONCLUSIONS

Two regions of the prefrontal cortex are involved in anxiety disorders. Reduced subgenual anterior cingulate cortex engagement is a shared feature in adult and adolescent anxiety disorders, but ventromedial prefrontal cortex dysfunction is age-specific. The unique U-shaped pattern of activation in the ventromedial prefrontal cortex in many anxious adolescents may reflect heightened sensitivity to threat and safety conditions. How variations in the pattern relate to later risk for adult illness remains to be determined.

Enhanced sensitivity to learning fearful associations during adolescence

The majority of anxiety disorders emerge during adolescence, yet there is a paucity of research examining factors that contribute to the "storm and stress" of this period. Understanding how juvenile (P23), adolescent (P35), and adult (P90) rats differ on basic fear conditioning tasks may shed light on this issue. In Experiment 1, P23, P35, and P90 rats were given 6 CS-US presentations. There were four training conditions: Delay (i.e., CS co-terminating with the US), Trace 20 and Trace 40 (i.e., an interval of 20s and 40s between the CS and US, respectively), and Unpaired (i.e., explicitly Unpaired presentations of the CS and US). Twenty-four hours after conditioning, freezing was measured to assess fear of the CS in a novel context. At test, there were no age differences in CS-elicited freezing in group Delay, and this condition exhibited significantly higher levels of freezing compared to group Unpaired. However, the adolescent rats were the only age group to exhibit higher levels of freezing following training with the 20s and 40s trace intervals, compared to Unpaired controls. Experiment 2 replicated the finding that adolescent but not adult rats exhibit fear following conditioning with a 20s trace interval, while also demonstrating that both age groups display learning with a shorter trace interval of 5s. Experiment 3 showed that exposure to corticosterone (200 μg/ml) in the drinking water for 1 week prior to conditioning selectively disrupts Trace 20 but not Delay conditioning during adolescence. Lastly, in Experiment 4 the test procedures were changed such that freezing was measured both during the CS and during a stimulus free trace interval. Once again, P35 but not P90 rats exhibited fear following training with a 20s trace interval. Taken together, these findings demonstrate that adolescent rats show a heightened propensity to learn fearful associations, and that this is disrupted following exposure to corticosterone.

Early-life stress affects extinction during critical periods of development: an analysis of the effects of maternal separation on extinction in adolescent rats

Adolescence is a period of heightened susceptibility to anxiety disorders, yet we have little experimental evidence on what factors may lead to psychopathology in adolescence. Preclinical models of extinction are commonly used to study the treatment of anxiety symptoms. Interestingly, recent research has shown that there are fundamental changes in the process of extinction across development, which may have implications for our understanding of psychopathology across the lifespan. Specifically, this research shows that the process of extinction parallels the nonlinear function of prefrontal cortex development, such that extinction behaviour is similar in juvenile and adult rats, but involves different processes in infancy and adolescence (periods of rapid growth and pruning, respectively). Our previous studies have shown that early-life stress accelerates the transition between infant and juvenile extinction systems. In the current series of experiments, we examined whether the same early-life stress, maternal separation (MS), would lead to an earlier transition between the juvenile and adolescent extinction systems, and between the adolescent and adult extinction systems. We show that MS adolescent rats exhibit more adult-like extinction behaviour, and that adolescent-like extinction emerges earlier in development (i.e. in pre-adolescent rats). These results may have important implications for the understanding and treatment of anxiety symptoms in adolescent populations.

Towards the study of functional brain development in depression: an Interactive Specialization approach

Depression is a significant and impairing mood disorder with onset possible as early as age 3 and into adulthood. Given this varying pattern of age of onset, identifying the relationship between brain development and depression across the lifespan has proven elusive. This review identifies some of the factors that may have limited the advancement of our knowledge in this area and discusses how synthesizing established models of depression and normative brain development may help to overcome them. More specifically, it is suggested that current neurobiological models of depression fail to account for the developmental variance associated with early neural network development and the potential influence of experience on this process. The utility of applying an established framework of normative brain development to this topic is described and its potential utility for conceptualizing the influence of depression on brain function across the life span is addressed. Future directions including longitudinal neuroimaging studies of early onset depression and groups at risk for this disorder are proposed.

Rethinking the emotional brain

I propose a reconceptualization of key phenomena important in the study of emotion-those phenomena that reflect functions and circuits related to survival, and that are shared by humans and other animals. The approach shifts the focus from questions about whether emotions that humans consciously feel are also present in other animals, and toward questions about the extent to which circuits and corresponding functions that are present in other animals (survival circuits and functions) are also present in humans. Survival circuit functions are not causally related to emotional feelings but obviously contribute to these, at least indirectly. The survival circuit concept integrates ideas about emotion, motivation, reinforcement, and arousal in the effort to understand how organisms survive and thrive by detecting and responding to challenges and opportunities in daily life.