Enduring influence of early temperament on neural mechanisms mediating attention-emotion conflict in adults

BACKGROUND

Behavioral inhibition, a temperament identified in early childhood, is often associated with dysregulated attention and affective processing, particularly in response to threat. Longitudinal studies find that the manifestation of perturbed attention and affective processing often dissipates with age. Yet, childhood behavioral inhibition continues to predict perturbed brain function into adulthood. This suggests that adults with childhood behavioral inhibition may engage compensatory processes to effectively regulate emotion-related attention. However, it is unknown whether perturbations in brain function reflect compensation for attention bias to emotional stimuli generally, or to threatening contexts more specifically. The present study tests these possibilities.

METHODS

Adults with and without a history of stable childhood behavioral inhibition completed an attention-control task in the context of threatening and nonthreatening stimuli while undergoing functional magnetic resonance imaging. Participants were asked to identify the gender of fearful (threatening) and happy (nonthreatening) faces, while ignoring both the face emotion and overlaid congruent (low attention control, LAC) or incongruent (high attention control, HAC) gender words.

RESULTS

When fearful faces were present, adults with stable childhood behavioral inhibition exhibited more activity in striatum, cingulate, and dorsolateral prefrontal cortex for HAC trials compared with LAC trials, relative to those without behavioral inhibition. When happy faces were present, the opposite activation pattern emerged. No group differences in behavior were observed.

CONCLUSIONS

Among adults, stable childhood behavioral inhibition predicts neural, but not behavioral, responding when attention control is engaged in discrete emotional contexts. This suggests a mechanism by which adults may compensate for the behavioral manifestation of threat-based attention biases.

Antidepressant effects on serotonin 1A/1B receptors in the rat brain using a gene x environment model

A gene-environment (GxE) interaction is implicated in both the pathophysiology and treatment of major depressive disorder (MDD). This study modeled the effects of genetic vulnerability by using the Flinders sensitive line (FSL), a rat model of depression and its control counterpart-the Flinders resistant line (FRL). The effects of environmental vulnerability (e.g., early-life stress) were modeled by using maternal separation. Rats (n=105) were drawn from four groups reflecting experimental crossing of strain (FSL vs. FRL) and early-life stress (high vs. low) to assess the effects of two antidepressants (escitalopram or nortriptyline) compared to vehicle. Quantitative in vitro autoradiography was performed using [(125)I]MPPI (5-HT1A) and [(125)I]CYP (5-HT1B) in prefrontal cortex (PFC) and hippocampus. Stringent, Bonferroni-corrected statistical analyses showed significant strain-by-rearing-by-treatment (three-way) interactions in PFC 5-HT1A and hippocampal 5-HT1B receptors. Either vulnerability reduced serotonergic binding; no additive effects were associated with the two vulnerabilities. Both antidepressants increased hippocampal 5-HT1B receptor binding; however, only nortriptyline selectively increased PFC 5-HT1A receptor binding. Taken together, our findings demonstrate that antidepressant effects on the serotonergic system are shaped by a GxE interaction that depends on antidepressant class and brain region.

Impaired fixation to eyes during facial emotion labelling in children with bipolar disorder or severe mood dysregulation

BACKGROUND

Children with bipolar disorder (BD) or severe mood dysregulation (SMD) show behavioural and neural deficits during facial emotion processing. In those with other psychiatric disorders, such deficits have been associated with reduced attention to eye regions while looking at faces.

METHODS

We examined gaze fixation patterns during a facial emotion labelling task among children with pediatric BD and SMD and among healthy controls. Participants viewed facial expressions with varying emotions (anger, fear, sadness, happiness, neutral) and emotional levels (60%, 80%, 100%) and labelled emotional expressions.

RESULTS

Our study included 22 children with BD, 28 with SMD and 22 controls. Across all facial emotions, children with BD and SMD made more labelling errors than controls. Compared with controls, children with BD spent less time looking at eyes and made fewer eye fixations across emotional expressions. Gaze patterns in children with SMD tended to fall between those of children with BD and controls, although they did not differ significantly from either of these groups on most measures. Decreased fixations to eyes correlated with lower labelling accuracy in children with BD, but not in those with SMD or in controls.

LIMITATIONS

Most children with BD were medicated, which precluded our ability to evaluate medication effects on gaze patterns.

CONCLUSION

Facial emotion labelling deficits in children with BD are associated with impaired attention to eyes. Future research should examine whether impaired attention to eyes is associated with neural dysfunction. Eye gaze deficits in children with BD during facial emotion labelling may also have treatment implications. Finally, children with SMD exhibited decreased attention to eyes to a lesser extent than those with BD, and these equivocal findings are worthy of further study.

Loss aversion and 5HTT gene variants in adolescent anxiety

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Loss aversion is present in adolescents.

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Levels of loss aversion are not modulated by clinical anxiety in adolescents.

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The 5HTT gene modulates levels of loss aversion in clinically anxious patients.

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A subset of anxious adolescents, high 5HTT-expressers, has low lambda and high impulsivity.

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High 5HTT-expression may expose anxious patients to comorbid externalizing disorders.

Loss aversion, a well-documented behavioral phenomenon, characterizes decisions under risk in adult populations. As such, loss aversion may provide a reliable measure of risky behavior. Surprisingly, little is known about loss aversion in adolescents, a group who manifests risk-taking behavior, or in anxiety disorders, which are associated with risk-avoidance. Finally, loss aversion is expected to be modulated by genotype, particularly the serotonin transporter (SERT) gene variant, based on its role in anxiety and impulsivity. This genetic modulation may also differ between anxious and healthy adolescents, given their distinct propensities for risk taking. The present work examines the modulation of loss aversion, an index of risk-taking, and reaction-time to decision, an index of impulsivity, by the serotonin-transporter-gene-linked polymorphisms (5HTTLPR) in healthy and clinically anxious adolescents. Findings show that loss aversion (1) does manifest in adolescents, (2) does not differ between healthy and clinically anxious participants, and (3), when stratified by SERT genotype, identifies a subset of anxious adolescents who are high SERT-expressers, and show excessively low loss-aversion and high impulsivity. This last finding may serve as preliminary evidence for 5HTTLPR as a risk factor for the development of comorbid disorders associated with risk-taking and impulsivity in clinically anxious adolescents.

Neural circuitry of masked emotional face processing in youth with bipolar disorder, severe mood dysregulation, and healthy volunteers

Youth with bipolar disorder (BD) and those with severe, non-episodic irritability (severe mood dysregulation, SMD) show face-emotion labeling deficits. These groups differ from healthy volunteers (HV) in neural responses to emotional faces. It is unknown whether awareness is required to elicit these differences. We compared activation in BD (N=20), SMD (N=18), and HV (N=22) during "Aware" and "Non-aware" priming of shapes by emotional faces. Subjects rated how much they liked the shape. In aware, a face (angry, fearful, happy, neutral, blank oval) appeared (187 ms) before the shape. In non-aware, a face appeared (17 ms), followed by a mask (170 ms), and shape. A Diagnosis-by-Awareness-by-Emotion ANOVA was not significant. There were significant Diagnosis-by-Awareness interactions in occipital regions. BD and SMD showed increased activity for non-aware vs. aware; HV showed the reverse pattern. When subjects viewed angry or neutral faces, there were Emotion-by-Diagnosis interactions in face-emotion processing regions, including the L precentral gyrus, R posterior cingulate, R superior temporal gyrus, R middle occipital gyrus, and L medial frontal gyrus. Regardless of awareness, BD and SMD differ in activation patterns from HV and each other in multiple brain regions, suggesting that BD and SMD are distinct developmental mood disorders.

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.

Neural mechanisms of frustration in chronically irritable children

OBJECTIVE

Irritability is common in children and adolescents and is the cardinal symptom of disruptive mood dysregulation disorder, a new DSM-5 disorder, yet its neural correlates remain largely unexplored. The authors conducted a functional MRI study to examine neural responses to frustration in children with severe mood dysregulation.

METHOD

The authors compared emotional responses, behavior, and neural activity between 19 severely irritable children (operationalized using criteria for severe mood dysregulation) and 23 healthy comparison children during a cued-attention task completed under nonfrustrating and frustrating conditions.

RESULTS

Children in both the severe mood dysregulation and the healthy comparison groups reported increased frustration and exhibited decreased ability to shift spatial attention during the frustration condition relative to the nonfrustration condition. However, these effects of frustration were more marked in the severe mood dysregulation group than in the comparison group. During the frustration condition, participants in the severe mood dysregulation group exhibited deactivation of the left amygdala, the left and right striatum, the parietal cortex, and the posterior cingulate on negative feedback trials, relative to the comparison group (i.e., between-group effect) and to the severe mood dysregulation group's responses on positive feedback trials (i.e., within-group effect). In contrast, neural response to positive feedback during the frustration condition did not differ between groups.

CONCLUSIONS

In response to negative feedback received in the context of frustration, children with severe, chronic irritability showed abnormally reduced activation in regions implicated in emotion, attention, and reward processing. Frustration appears to reduce attention flexibility, particularly in severely irritable children, which may contribute to emotion regulation deficits in this population. Further research is needed to relate these findings to irritability specifically, rather than to other clinical features of severe mood dysregulation.

Impact of negative affectively charged stimuli and response style on cognitive-control-related neural activation: an ERP study

The canonical AX-CPT task measures two forms of cognitive control: sustained goal-oriented control ("proactive" control) and transient changes in cognitive control following unexpected events ("reactive" control). We modified this task by adding negative and neutral International Affective Picture System (IAPS) pictures to assess the effects of negative emotion on these two forms of cognitive control. Proactive and reactive control styles were assessed based on measures of behavior and electrophysiology, including the N2 event-related potential component and source space activation (Low Resolution Tomography [LORETA]). We found slower reaction-times and greater DLPFC activation for negative relative to neutral stimuli. Additionally, we found that a proactive style of responding was related to less prefrontal activation (interpreted to reflect increased efficiency of processing) during actively maintained previously cued information and that a reactive style of responding was related to less prefrontal activation (interpreted to reflect increased efficiency of processing) during just-in-time environmentally triggered information. This pattern of results was evident in relatively neutral contexts, but in the face of negative emotion, these associations were not found, suggesting potential response style-by-emotion interaction effects on prefrontal neural activation.

Punishment insensitivity and impaired reinforcement learning in preschoolers

BACKGROUND

Youth and adults with psychopathic traits display disrupted reinforcement learning. Advances in measurement now enable examination of this association in preschoolers. The current study examines relations between reinforcement learning in preschoolers and parent ratings of reduced responsiveness to socialization, conceptualized as a developmental vulnerability to psychopathic traits.

METHODS

One hundred and fifty-seven preschoolers (mean age 4.7 ± 0.8 years) participated in a substudy that was embedded within a larger project. Children completed the 'Stars-in-Jars' task, which involved learning to select rewarded jars and avoid punished jars. Maternal report of responsiveness to socialization was assessed with the Punishment Insensitivity and Low Concern for Others scales of the Multidimensional Assessment of Preschool Disruptive Behavior (MAP-DB).

RESULTS

Punishment Insensitivity, but not Low Concern for Others, was significantly associated with reinforcement learning in multivariate models that accounted for age and sex. Specifically, higher Punishment Insensitivity was associated with significantly lower overall performance and more errors on punished trials ('passive avoidance').

CONCLUSIONS

Impairments in reinforcement learning manifest in preschoolers who are high in maternal ratings of Punishment Insensitivity. If replicated, these findings may help to pinpoint the neurodevelopmental antecedents of psychopathic tendencies and suggest novel intervention targets beginning in early childhood.

Patterns of neural connectivity during an attention bias task moderate associations between early childhood temperament and internalizing symptoms in young adulthood

BACKGROUND

Biased attention to threat is found in both individuals with anxiety symptoms and children with the childhood temperament of behavioral inhibition (BI). Although perturbed fronto-amygdala function is implicated in biased attention among anxious individuals, no work has examined the neural correlates of attention biases in BI. Work in this area might clarify underlying mechanisms for anxiety in a sample at risk for internalizing disorders. We examined the relations among early childhood BI, fronto-amygdala connectivity during an attention bias task in young adulthood, and internalizing symptoms, assessed in young adulthood.

METHODS

Children were assessed for BI at multiple age points from infancy through age seven. On the basis of a composite of observational and maternal report data, we selected 21 young adults classified as having a history of BI and 23 classified as non-BI for this study (n = 44). Participants completed an event-related functional magnetic resonance imaging attention-bias task involving threat (angry faces) and neutral trials. Internalizing symptoms were assessed by self-report and diagnostic interviews.

RESULTS

The young adults characterized in childhood with BI exhibited greater strength in threat-related connectivity than non-behaviorally inhibited young adults. Between-group differences manifested in connections between the amygdala and two frontal regions: dorsolateral prefrontal cortex and anterior insula. Amygdala-insula connectivity also interacted with childhood BI to predict young adult internalizing symptoms.

CONCLUSIONS

Behavioral inhibition during early childhood predicts differences as young adults in threat and attention-related fronto-amygdala connectivity. Connectivity strength, in turn, moderated the relations between early BI and later psychopathology.

Empathic responsiveness in amygdala and anterior cingulate cortex in youths with psychopathic traits

BACKGROUND

Psychopathic traits are associated with increases in antisocial behaviors such as aggression and are characterized by reduced empathy for others' distress. This suggests that psychopathic traits may also impair empathic pain sensitivity. However, whether psychopathic traits affect responses to the pain of others versus the self has not been previously assessed.

METHOD

We used whole-brain functional magnetic resonance imaging to measure neural activation in 14 adolescents with oppositional defiant disorder or conduct disorder and psychopathic traits, as well as 21 healthy controls matched on age, gender, and intelligence. Activation in structures associated with empathic pain perception was assessed as adolescents viewed photographs of pain-inducing injuries. Adolescents imagined either that the body in each photograph was their own or that it belonged to another person. Behavioral and neuroimaging data were analyzed using random-effects analysis of variance.

RESULTS

Youths with psychopathic traits showed reduced activity within regions associated with empathic pain as the depicted pain increased. These regions included rostral anterior cingulate cortex, ventral striatum (putamen), and amygdala. Reductions in amygdala activity particularly occurred when the injury was perceived as occurring to another. Empathic pain responses within both amygdala and rostral anterior cingulate cortex were negatively correlated with the severity of psychopathic traits as indexed by PCL:YV scores.

CONCLUSIONS

Youths with psychopathic traits show less responsiveness in regions implicated in the affective response to another's pain as the perceived intensity of this pain increases. Moreover, this reduced responsiveness appears to predict symptom severity.

Subliminal attention bias modification training in socially anxious individuals

Anxious individuals demonstrate threat-related attention biases both when threat stimuli are presented within conscious awareness and when presented below awareness threshold. Nevertheless, attention bias modification (ABM) research has rarely utilized sub-awareness protocols in an attempt to modify attention patterns and reduce anxiety. Exploring the potential of subliminal ABM is of interest, as it may target attention processes related to anxiety that are distinct from those engaged by supraliminal ABM. Here we examined the effect of a subliminal ABM training protocol on levels of social anxiety and stress vulnerability. Fifty-one socially anxious students were randomly assigned to either ABM or placebo condition, and completed a pre-training assessment, four training sessions, a social stressor task, and a post-training assessment. Results indicate that the subliminal ABM used here did not induce detectable changes in threat-related attention from pre- to post-training as measured by two independent attention tasks. Furthermore, the ABM and placebo groups did not differ on either self-reported social anxiety post-training or state anxiety following stress induction. Post-hoc auxiliary analyses suggest that ABM may be associated with smaller elevations in state anxiety during the stressor task only for participants who demonstrate attention bias toward threat at baseline. Implications and future research directions are discussed.

Neuroimaging studies of pediatric social anxiety: paradigms, pitfalls and a new direction for investigating the neural mechanisms

Social Anxiety Disorder (SAD) is a common and debilitating condition that typically manifests in adolescence. Here we describe cognitive factors engaged by brain-imaging tasks, which model the peer-based social interactions that evoke symptoms of SAD. We then present preliminary results from the Virtual School paradigm, a novel peer-based social interaction task. This paradigm is designed to investigate the neural mechanisms mediating individual differences in social response flexibility and in participants' responses to uncertainty in social contexts. We discuss the utility of this new paradigm for research on brain function and developmental psychopathology.

Neural traces of stress: cortisol related sustained enhancement of amygdala-hippocampal functional connectivity

Stressful experiences modulate neuro-circuitry function, and the temporal trajectory of these alterations, elapsing from early disturbances to late recovery, heavily influences resilience and vulnerability to stress. Such effects of stress may depend on processes that are engaged during resting-state, through active recollection of past experiences and anticipation of future events, all known to involve the default mode network (DMN). By inducing social stress and acquiring resting-state functional magnetic resonance imaging (fMRI) before stress, immediately following it, and 2 h later, we expanded the time-window for examining the trajectory of the stress response. Throughout the study repeated cortisol samplings and self-reports of stress levels were obtained from 51 healthy young males. Post-stress alterations were investigated by whole brain resting-state functional connectivity (rsFC) of two central hubs of the DMN: the posterior cingulate cortex (PCC) and hippocampus. Results indicate a ’recovery’ pattern of DMN connectivity, in which all alterations, ascribed to the intervening stress, returned to pre-stress levels. The only exception to this pattern was a stress-induced rise in amygdala-hippocampal connectivity, which was sustained for as long as 2 h following stress induction. Furthermore, this sustained enhancement of limbic connectivity was inversely correlated to individual stress-induced cortisol responsiveness (AUCi) and characterized only the group lacking such increased cortisol (i.e., non-responders). Our observations provide evidence of a prolonged post-stress response profile, characterized by both the comprehensive balance of most DMN functional connections and the distinct time and cortisol dependent ascent of intra-limbic connectivity. These novel insights into neuro-endocrine relations are another milestone in the ongoing search for individual markers in stress-related psychopathologies.

Empirical examination of the potential adverse psychological effects associated with pediatric FMRI scanning

BACKGROUND

Over the past decade, the number of functional magnetic resonance imaging (fMRI) studies has increased dramatically. As MRI scans may be anxiety provoking, performing them in a research setting, particularly with children already prone to anxiety, raises questions about ethics as well as methodological feasibility. It is essential to address these questions before expanding the use of this technique to clinical settings, or more widely in the context of pediatric psychopharmacology and biological psychiatry research. The current study investigates the psychological reactions of anxious and non-anxious children and non-anxious adults to an fMRI scan.

METHODS

Eighty-seven anxious children, 140 non-anxious children, and 98 non-anxious adults rated their emotional reactions to an fMRI scan.

RESULTS

Results indicated that anxious and non-anxious children reported no greater anxiety after fMRI scanning than did adults. In addition, no age-related differences in distress were observed. These data demonstrate that anxious children, healthy children, and healthy adults have similar emotional reactions to fMRI scanning.

CONCLUSIONS

The observed findings suggest that the potential for fMRI to produce anxiety should not impede its widespread use in clinical research, psychopharmacology, and biological psychiatry.

Abnormal fusiform activation during emotional-face encoding assessed with functional magnetic resonance imaging

This functional magnetic resonance imaging study shows that children and adults with bipolar disorder (BD), compared with healthy subjects, exhibit impaired memory for emotional faces and abnormal fusiform activation during encoding. Fusiform activation abnormalities in BD were correlated with mania severity and may therefore represent a trait and state BD biomarker.

Maternal over-control moderates the association between early childhood behavioral inhibition and adolescent social anxiety symptoms

Behavioral inhibition (BI) and maternal over-control are early risk factors for later childhood internalizing problems, particularly social anxiety disorder (SAD). Consistently high BI across childhood appears to confer risk for the onset of SAD by adolescence. However, no prior studies have prospectively examined observed maternal over-control as a risk factor for adolescent social anxiety (SA) among children initially selected for BI. The present prospective longitudinal study examines the direct and indirect relations between these early risk factors and adolescent SA symptoms and SAD, using a multi-method approach. The sample consisted of 176 participants initially recruited as infants and assessed for temperamental reactivity to novel stimuli at age 4 months. BI was measured via observations and parent-report across multiple assessments between the ages of 14 months and 7 years. Maternal over-control was assessed observationally during parent-child interaction tasks at 7 years. Adolescents (ages 14-17 years) and parents provided independent reports of adolescent SA symptoms. Results indicated that higher maternal over-control at 7 years predicted higher SA symptoms and lifetime rates of SAD during adolescence. Additionally, there was a significant interaction between consistently high BI and maternal over-control, such that patterns of consistently high BI predicted higher adolescent SA symptoms in the presence of high maternal over-control. High BI across childhood was not significantly associated with adolescent SA symptoms when children experienced low maternal over-control. These findings have the potential to inform prevention and early intervention programs by identifying particularly at-risk youth and specific targets of treatment.

Learning to attend to threat accelerates and enhances memory consolidation

Practice on a procedural task involves within-session learning and between-session consolidation of learning, with the latter requiring a minimum of about four hours to evolve due to involvement of slower cellular processes. Learning to attend to threats is vital for survival and thus may involve faster memory consolidation than simple procedural learning. Here, we tested whether attention to threat modulates the time-course and magnitude of learning and memory consolidation effects associated with skill practice. All participants (N = 90) practiced in two sessions on a dot-probe task featuring pairs of neutral and angry faces followed by target probes which were to be discriminated as rapidly as possible. In the attend-threat training condition, targets always appeared at the angry face location, forming an association between threat and target location; target location was unrelated to valence in a control training condition. Within each attention training condition, duration of the between-session rest interval was varied to establish the time-course for emergence of consolidation effects. During the first practice session, we observed robust improvement in task performance (online, within-session gains), followed by saturation of learning. Both training conditions exhibited similar overall learning capacities, but performance in the attend-threat condition was characterized by a faster learning rate relative to control. Consistent with the memory consolidation hypothesis, between-session performance gains (delayed gains) were observed only following a rest interval. However, rest intervals of 1 and 24 hours yielded similar delayed gains, suggesting accelerated consolidation processes. Moreover, attend-threat training resulted in greater delayed gains compared to the control condition. Auxiliary analyses revealed that enhanced performance was retained over several months, and that training to attend to neutral faces resulted in effects similar to control. These results provide a novel demonstration of how attention to threat can accelerate and enhance memory consolidation effects associated with skill acquisition.

The role of serotonin in the neurocircuitry of negative affective bias: serotonergic modulation of the dorsal medial prefrontal-amygdala 'aversive amplification' circuit

Serotonergic medications can mitigate the negative affective biases in disorders such as depression or anxiety, but the neural mechanism by which this occurs is largely unknown. In line with recent advances demonstrating that negative affective biases may be driven by specific medial prefrontal-amygdala circuitry, we asked whether serotonin manipulation can alter affective processing within a key dorsal medial prefrontal-amygdala circuit: the putative human homologue of the rodent prelimbic-amygdala circuit or 'aversive amplification' circuit. In a double-blind, placebo-controlled crossover pharmaco-fMRI design, subjects (N=19) performed a forced-choice face identification task with word distractors in an fMRI scanner over two separate sessions. On one session subjects received dietary depletion of the serotonin precursor tryptophan while on the other session they received a balanced placebo control diet. Results showed that dorsal medial prefrontal responding was elevated in response to fearful relative to happy faces under depletion but not placebo. This negative bias under depletion was accompanied by a corresponding increase in positive dorsal medial prefrontal-amygdala functional connectivity. We therefore conclude that serotonin depletion engages a prefrontal-amygdala circuit during the processing of fearful relative to happy face stimuli. This same 'aversive amplification' circuit is also engaged during anxiety induced by shock anticipation. As such, serotonergic projections may inhibit engagement of the 'aversive amplification' circuit and dysfunction in this projection may contribute to the negative affective bias in mood and anxiety disorders. These findings thus provide a promising explanation for the role of serotonin and serotonergic medications in the neurocircuitry of negative affective bias.

Dissociable roles of ventromedial prefrontal cortex (vmPFC) and rostral anterior cingulate cortex (rACC) in value representation and optimistic bias

Optimistic bias (OB) is seen when individuals underestimate their probability of experiencing negative life events and overestimate their probability of experiencing positive life events. A reduced OB has been linked with increased depression symptoms. However, given the relevance of this information to mood and anxiety disorders, little is currently known regarding the neurobiology of OB. In the current study, we examine the neural basis of OB in healthy individuals (n=33) during probability estimation of future positive and negative events occurring to themselves relative to other, comparable individuals. In line with previous work, subjects showed significant OB; they considered themselves significantly more likely to experience future positive and significantly less likely to experience future negative events relative to comparable others. Positive, relative to negative events, un-modulated by subjects' probability estimates, were associated with significantly greater activity within the ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC). Moreover, responses within both regions to positive events negatively related to the healthy subjects' self reports of depression symptoms. However, there was no significant modulation of activity in either region by the subject's OB, objectified as the level to which they thought the event was more likely [positive events] or less likely [negative events] to occur to them relative to comparable others. In contrast, activity within the rostral anterior cingulate cortex (rACC) was positively modulated by OB for positive events and activity within the anterior insula and dorsomedial prefrontal cortex (dmPFC) was negatively modulated by OB for negative events. However, there was no significant relationship between responsiveness within these regions and self reports of depression symptoms. The data are discussed with reference to current models of vmPFC, rACC and anterior insula functioning.