Looking under the hood of the dot-probe task: an fMRI study in anxious youth

Behavioral and neural stability of attention bias to threat in healthy adolescents

Considerable translational research on anxiety examines attention bias to threat and the efficacy of attention training in reducing symptoms. Imaging research on the stability of brain functions engaged by attention bias tasks could inform such research. Perturbed fronto-amygdala function consistently arises in attention bias research on adolescent anxiety. The current report examines the stability of the activation and functional connectivity of these regions on the dot-probe task. Functional magnetic resonance imaging (fMRI) activation and connectivity data were acquired with the dot-probe task in 39 healthy youth (f=18, Mean Age=13.71years, SD=2.31) at two time points, separated by approximately nine weeks. Intraclass-correlations demonstrate good reliability in both neural activation for the ventrolateral PFC and task-specific connectivity for fronto-amygdala circuitry. Behavioral measures showed generally poor test-retest reliability. These findings suggest potential avenues for future brain imaging work by highlighting brain circuitry manifesting stable functioning on the dot-probe attention bias task.

Imaging the neural effects of cognitive bias modification training

Cognitive bias modification (CBM) was first developed as an experimental tool to examine the causal role of cognitive biases, and later developed into complementary interventions in experimental psychopathology research. CBM involves the "re-training" of implicit biases by means of multiple trials of computerized tasks, and has been demonstrated to change anxious, depressive and drug-seeking behavior, including clinically relevant effects. Recently, the field has progressed by combining CBM with neuroimaging techniques, which provides insight into neural mechanisms underlying how CBM affects implicit biases in anxiety, depression, and addiction, and potentially other pathologies. This narrative literature review summarizes the state of the art of studies on the neural effects of CBM and provides directions for future research in the field. A total of 13 published studies were found and discussed: n=9 in anxiety, n=2 in depressive behavior, and n=2 in addiction.

Individual variation in the neural processes of motor decisions in the stop signal task: the influence of novelty seeking and harm avoidance personality traits

Personality traits contribute to variation in human behavior, including the propensity to take risk. Extant work targeted risk-taking processes with an explicit manipulation of reward, but it remains unclear whether personality traits influence simple decisions such as speeded versus delayed responses during cognitive control. We explored this issue in an fMRI study of the stop signal task, in which participants varied in response time trial by trial, speeding up and risking a stop error or slowing down to avoid errors. Regional brain activations to speeded versus delayed motor responses (risk-taking) were correlated to novelty seeking (NS), harm avoidance (HA) and reward dependence (RD), with age and gender as covariates, in a whole brain regression. At a corrected threshold, the results showed a positive correlation between NS and risk-taking responses in the dorsomedial prefrontal, bilateral orbitofrontal, and frontopolar cortex, and between HA and risk-taking responses in the parahippocampal gyrus and putamen. No regional activations varied with RD. These findings demonstrate that personality traits influence the neural processes of executive control beyond behavioral tasks that involve explicit monetary reward. The results also speak broadly to the importance of characterizing inter-subject variation in studies of cognition and brain functions.

Neural correlates of attention biases, behavioral inhibition, and social anxiety in children: An ERP study

Behavioral inhibition (BI) is a biologically-based temperament characterized by vigilance toward threat. Over time, many children with BI increasingly fear social circumstances and display maladaptive social behavior. BI is also one of the strongest individual risk factors for developing social anxiety disorder. Although research has established a link between BI and anxiety, its causal mechanism remains unclear. Attention biases may underlie this relation. The current study examined neural markers of the BI-attention-anxiety link in children ages 9-12 years (N=99, Mean=9.97, SD=0.97). ERP measures were collected as children completed an attention-bias (dot-probe) task with neutral and angry faces. P2 and N2 amplitudes were associated with social anxiety and attention bias, respectively. Specifically, augmented P2 was related to decreased symptoms of social anxiety and moderated the relation between BI and social anxiety, suggesting that increasing attention mobilization may serve as a compensatory mechanism that attenuates social anxiety in individuals with high BI. The BI by N2 interaction found that larger N2 related to threat avoidance with increasing levels of BI, consistent with over-controlled socio-emotional functioning. Lastly, children without BI (BN) showed an augmented P1 to probes replacing angry faces, suggesting maintenance of attentional resources in threat-related contexts.

Vigilance in the laboratory predicts avoidance in the real world: A dimensional analysis of neural, behavioral, and ecological momentary data in anxious youth

Vigilance and avoidance of threat are observed in anxious adults during laboratory tasks, and are posited to have real-world clinical relevance, but data are mixed in anxious youth. We propose that vigilance-avoidance patterns will become evident in anxious youth through a focus on individual differences and real-world strategic avoidance. Decreased functional connectivity between the amygdala and prefrontal cortex (PFC) could play a mechanistic role in this link. 78 clinically anxious youth completed a dot-probe task to assess vigilance to threat while undergoing fMRI. Real-world avoidance was assessed using Ecological Momentary Assessment (EMA) of self-reported suppression and distraction during negative life events. Vigilance toward threat was positively associated with EMA distraction and suppression. Functional connectivity between a right amygdala seed region and dorsomedial and right dorsolateral PFC regions was inversely related to EMA distraction. Dorsolateral PFC-amygdalar connectivity statistically mediated the relationship between attentional vigilance and real-world distraction. Findings suggest anxious youth showing attentional vigilance toward threat are more likely to use suppression and distraction to regulate negative emotions. Reduced PFC control over limbic reactivity is a possible neural substrate of this pattern. These findings lend ecological validity to laboratory vigilance assessments and suggest PFC-amygdalar connectivity is a neural mechanism bridging laboratory and naturalistic contexts.

Individual Differences in Anticipatory Somatosensory Cortex Activity for Shock is Positively Related with Trait Anxiety and Multisensory Integration

Anxiety is associated with an exaggerated expectancy of harm, including overestimation of how likely a conditioned stimulus (CS+) predicts a harmful unconditioned stimulus (US). In the current study we tested whether anxiety-associated expectancy of harm increases primary sensory cortex (S1) activity on non-reinforced (i.e., no shock) CS+ trials. Twenty healthy volunteers completed a differential-tone trace conditioning task while undergoing fMRI, with shock delivered to the left hand. We found a positive correlation between trait anxiety and activity in right, but not left, S1 during CS+ versus CS− conditions. Right S1 activity also correlated with individual differences in both primary auditory cortices (A1) and amygdala activity. Lastly, a seed-based functional connectivity analysis demonstrated that trial-wise S1 activity was positively correlated with regions of dorsolateral prefrontal cortex (dlPFC), suggesting that higher-order cognitive processes contribute to the anticipatory sensory reactivity. Our findings indicate that individual differences in trait anxiety relate to anticipatory reactivity for the US during associative learning. This anticipatory reactivity is also integrated along with emotion-related sensory signals into a brain network implicated in fear-conditioned responding.

The neurobiology of dispositional negativity and attentional biases to threat: Implications for understanding anxiety disorders in adults and youth

When extreme, anxiety can become debilitating. Anxiety disorders, which often first emerge early in development, are common and challenging to treat, yet the neurocognitive mechanisms that confer increased risk have only recently begun to come into focus. Here we review recent work highlighting the importance of neural circuits centered on the amygdala. We begin by describing dispositional negativity, a core dimension of childhood temperament and adult personality and an important risk factor for the development of anxiety disorders and other kinds of stress-sensitive psychopathology. Converging lines of epidemiological, neurophysiological, and mechanistic evidence indicate that the amygdala supports stable individual differences in dispositional negativity across the lifespan and contributes to the etiology of anxiety disorders in adults and youth. Hyper-vigilance and attentional biases to threat are prominent features of the anxious phenotype and there is growing evidence that they contribute to the development of psychopathology. Anatomical studies show that the amygdala is a hub, poised to govern attention to threat via projections to sensory cortex and ascending neuromodulatory systems. Imaging and lesion studies demonstrate that the amygdala plays a key role in selecting and prioritizing the processing of threat-related cues. Collectively, these observations provide a neurobiologically-grounded framework for understanding the development and maintenance of anxiety disorders in adults and youth and set the stage for developing improved intervention strategies.

From anxious youth to depressed adolescents: Prospective prediction of 2-year depression symptoms via attentional bias measures

Anxious youth are at heightened risk for subsequent development of depression; however, little is known regarding which anxious youth are at the highest prospective risk. Biased attentional patterns (e.g., vigilance and avoidance of negative cues) are implicated as key mechanisms in both anxiety and depression. Aberrant attentional patterns may disrupt opportunities to effectively engage with, and learn from, threatening aspects of the environment during development and/or treatment, compounding risk over time. Sixty-seven anxious youth (ages 9-14; 36 female) completed a dot-probe task to assess baseline attentional patterns provoked by fearful-neutral face pairs. The time course of attentional patterns both during and after threat was assessed via eye-tracking and pupilometry. Self-reported depressive and anxiety symptoms were assessed 2 years after the conclusion of a larger psychotherapy treatment trial. Eye-tracking patterns indicating threat avoidance predicted greater 2-year depression scores, over and above baseline and posttreatment symptoms. Sustained, postthreat pupillary avoidance (reflecting preferential neural engagement with the neutral relative to the previously threatening location) predicted additional variance in depression scores, suggesting sustained avoidance in the wake of threat further exacerbated risk. Identical eye-tracking and pupil indices were not predictive of anxiety at 2 years. These biobehavioral markers imply that avoidant attentional processing in the context of anxiety may be a gateway to depression across a key maturational window. Excessive avoidance of threat could interfere with acquisition of adaptive emotion regulation skills during development, culminating in the broad behavioral deactivation that typifies depression. Prevention efforts explicitly targeting avoidant attentional patterns may be warranted.

Disrupted prefrontal activity during emotion processing in complicated grief: An fMRI investigation

Complicated Grief, marked by a persistent and intrusive grief lasting beyond the expected period of adaptation, is associated with a relative inability to disengage from idiographic loss-relevant stimuli (O'Connor and Arizmendi, 2014). In other populations, functional magnetic resonance imaging (fMRI) studies investigating the neural networks associated with this bias consistently implicate the anterior cingulate cortex (ACC) during emotion regulation. In the present study, twenty-eight older adults were categorized into three groups based on grief severity: Complicated Grief (n=8), Non-Complicated Grief (n=9), and Nonbereaved, married controls (n=11). Using a block design, all participants completed 8 blocks (20 stimuli per block) of the ecStroop task during fMRI data acquisition. Differences in neural activity during grief-related (as opposed to neutral) stimuli across groups were examined. Those with Complicated Grief showed an absence of increased rostral ACC (rACC) and fronto-cortical recruitment relative to Nonbereaved controls. Activity in the orbitofrontal cortex (x=6, y=54, z=-10) was significantly elevated in the Non-Complicated Grief group when compared to Nonbereaved controls. Post hoc analysis evidenced activity in the dorsal ACC in the Complicated Grief and Nonbereaved groups late in the task. These findings, supported by behavioral data, suggest a relative inability to recruit the regions necessary for successful completion of this emotional task in those with Complicated Grief. This deficit was not observed in recruitment of the orbitofrontal cortex and the rACC during processing of idiographic semantic stimuli in Non-Complicated Grief.

Frontolimbic functioning during threat-related attention: Relations to early behavioral inhibition and anxiety in children

Children with behavioral inhibition (BI), a temperament characterized by biologically-based hyper-vigilance to novelty, display threat-related attention biases (AB) that shape developmental trajectories of risk for anxiety. Here we explore the relations between BI, neural function, and anxiety. Fifty-six 9-12-year-olds (23 behaviorally inhibited) performed the dot-probe task while undergoing fMRI. AB scores were not associated with BI group or parent-rated anxiety symptoms. Trials requiring attention orienting away from threat engaged an executive and threat-attention network (dlPFC, vlPFC, mPFC, and amygdala). Within that network, behaviorally inhibited children showed greater activation in the right dlPFC. Heightened dlPFC activation related to increased anxiety, and BI levels accounted for the direct relation between dlPFC activation and anxiety. Behaviorally inhibited children may engage the executive attention system during threat-related processing as a compensatory mechanism. We provide preliminary evidence that the link between PFC functioning and anxiety might be attributed to early-emerging temperamental vulnerabilities present before the emergence of clinical anxiety.

An integrative review of attention biases and their contribution to treatment for anxiety disorders

Models of exposure therapy, one of the key components of cognitive behavioral therapy for anxiety disorders, suggest that attention may play an important role in the extinction of fear and anxiety. Evidence from cognitive research suggests that individual differences may play a causal role in the onset and maintenance of anxiety disorders and so it is also likely to influence treatment. We review the evidence concerning attention and treatment outcomes in anxiety disorders. The evidence reviewed here suggests that that attention biases assessed at pre-treatment might actually predict improved response to treatment, and in particular that prolonged engagement with threat as measured in tasks such as the dot probe is associated with greater reductions in anxious symptoms following treatment. We examine this research within a fear learning framework, considering the possible role of individual differences in attention in the extinction of fear during exposure. Theoretical, experimental and clinical implications are discussed, particularly with reference to the potential for attention bias modification programs in augmenting treatment, and also with reference to how existing research in this area might inform best practice for clinicians.

A neurobehavioral account for individual differences in resilience to chronic military stress

BACKGROUND

Military training is a chronic stressful period that often induces stress-related psychopathology. Stress vulnerability and resilience depend on personality trait anxiety, attentional threat bias and prefrontal-limbic dysfunction. However, how these neurobehavioral elements interact with regard to the development of symptoms following stress remains unclear.

METHOD

Fifty-five healthy combat soldiers undergoing intensive military training completed functional magnetic resonance imaging (fMRI) testing while performing the dot-probe task (DPT) composed of angry (threat) and neutral faces. Participants were then stratified according to their bias tendency to avoidance (n = 25) or vigilance (n = 30) groups, categorized as high or low trait anxiety and assessed for post-stress symptom severity.

RESULTS

Avoidance compared to vigilance tendency was associated with fewer post-trauma symptoms and increased hippocampal response to threat among high anxious but not low anxious individuals. Importantly, mediation analysis revealed that only among high anxious individuals did hippocampal activity lead to lower levels of symptoms through avoidance bias tendency. However, in the whole group, avoidance bias was modulated by the interplay between the hippocampus and the dorsal anterior cingulate cortex (dACC).

CONCLUSIONS

Our results provide a neurobehavioral model to explain the resilience to post-trauma symptoms following chronic exposure. The model points to the importance of considering threat bias tendency in addition to personality traits when investigating the brain response and symptoms of trauma. Such a multi-parametric approach that accounts for individual behavioral sensitivities may also improve brain-driven treatments of anxiety, possibly by targeting the interplay between the hippocampus and the dACC.

Neurobiology of Pediatric Anxiety Disorders

While the fear-based anxiety disorders (i.e., generalized anxiety disorder, social phobia and separation anxiety disorder) are among the most common psychiatric conditions in children and adolescents, only recently has an integrated understanding of the neurobiology of these disorders developed. In this regard, both structural and functional neuroimaging studies have demonstrated neuroanatomic and functional abnormalities within the amygdala and prefrontal cortex in youth with fear-based anxiety disorders, and have also suggested altered functional connectivity among components of the anterior limbic network (ALN), as well as alterations in neurochemistry within the anterior cingulate cortex. Additionally, several prefrontal structures and regions (e.g., medial prefrontal cortex) appear to be dysregulated in youth who are at risk of developing anxiety disorders (e.g., youth with inhibited temperament, behavioral inhibition, etc.). Finally, emerging data raise the possibility that functional activity within these amygdala-prefrontal networks may be affected by successful psychopharmacologic and psychotherapeutic treatment and may predict outcome.