Self-relevant threat contexts enhance early processing of fear-conditioned faces

Enhanced late positive potential to conditioned threat cue during delayed extinction in anxious youth

BACKGROUND

Deficits in threat learning relate to anxiety symptoms. Since several anxiety disorders arise in adolescence, impaired adolescent threat learning could contribute to adolescent changes in risk for anxiety. This study compared threat learning among anxious and non-anxious youth using self-reports, peripheral psychophysiology measures, and event-related potentials. Because exposure therapy, the first-line treatment for anxiety disorders, is largely based on principles of extinction learning, the study also examined the link between extinction learning and treatment outcomes among anxious youth.

METHODS

Clinically anxious (n = 28) and non-anxious (n = 33) youth completed differential threat acquisition and immediate extinction. They returned to the lab a week later to complete a threat generalization test and a delayed extinction task. Following these two experimental visits, anxious youth received exposure therapy for 12 weeks.

RESULTS

Anxious as compared to non-anxious youth demonstrated elevated cognitive and physiological responses across acquisition and immediate extinction learning, as well as greater threat generalization. In addition, anxious youth showed enhanced late positive potential response to the conditioned threat cue compared to the safety cue during delayed extinction. Finally, aberrant neural response during delayed extinction was associated with poorer treatment outcomes.

CONCLUSIONS

The study emphasizes differences between anxious and non-anxious youth in threat learning processes and provides preliminary support for a link between neural processing during delayed extinction and exposure-based treatment outcome in pediatric anxiety.

Motivated attention and task relevance in the processing of cross-modally associated faces: Behavioral and electrophysiological evidence

It has repeatedly been shown that visually presented stimuli can gain additional relevance by their association with affective stimuli. Studies have shown effects of associated affect in event-related potentials (ERP) like the early posterior negativity (EPN), late positive complex (LPC), and even earlier components as the P1 or N170. However, findings are mixed as to the extent associated affect requires directed attention to the emotional quality of a stimulus and which ERP components are sensitive to task instructions during retrieval. In this preregistered study ( https://osf.io/ts4pb ), we tested cross-modal associations of vocal affect-bursts (positive, negative, neutral) to faces displaying neutral expressions in a flash-card-like learning task, in which participants studied face-voice pairs and learned to correctly assign them to each other. In the subsequent EEG test session, we applied both an implicit ("old-new") and explicit ("valence-classification") task to investigate whether the behavior at retrieval and neurophysiological activation of the affect-based associations were dependent on the type of motivated attention. We collected behavioral and neurophysiological data from 40 participants who reached the preregistered learning criterium. Results showed EPN effects of associated negative valence after learning and independent of the task. In contrast, modulations of later stages (LPC) by positive and negative associated valence were restricted to the explicit, i.e., valence-classification, task. These findings highlight the importance of the task at different processing stages and show that cross-modal affect can successfully be associated to faces.

Early neural potentiation to centrally and peripherally presented fear-conditioned faces

For humans, it is vitally important to rapidly detect and process threatening signals regardless of whether stimuli occur at fixation or in the periphery. However, it is unknown whether eccentricity affects early neuronal electrophysiological responses to fear-conditioned stimuli. We examined early event-related potentials (ERPs) of the electroencephalogram (EEG) to fear-conditioned faces to address this question. Participants (N = 80) were presented with faces, either paired with an aversive (CS+) or neutral sound (CS-), at central or peripheral positions. We ensured constant central fixation using online eye-tracking but directed attention to either centrally or peripherally presented faces. Manipulation checks showed successful fear-conditioning (i.e., on average lower ratings in valence and higher ratings in arousal and perceived threat) and successful shifts of visuospatial attention indexed by high task performance and pre-stimulus alpha lateralization of the EEG spectra. We observed a generally increased P1 to fear-conditioned faces regardless of presentation location. An N170 difference between fear-conditioned and neutral stimuli was found but was restricted to the central location and depended on the effectivity of fear-conditioning. A similar effect was observed for the early posterior negativity (EPN). Trait anxiety was not related to differential ERP responses to CS+ versus CS- faces for any ERP component. These findings suggest that the P1 indexes early responses to centrally and peripherally presented fear-conditioned faces. Subsequent stages are modulated by the spatial location of the stimuli. This suggests different stages of neural processing of fear-conditioned faces depending on their spatial location. Finally, our results question the hypothesis that trait anxiety in healthy participants is related to altered visual processing of fear-conditioned faces.

No trait anxiety influences on early and late differential neuronal responses to aversively conditioned faces across three different tasks

The human brain's ability to quickly detect dangerous stimuli is crucial in selecting appropriate responses to possible threats. Trait anxiety has been suggested to moderate these processes on certain processing stages. To dissociate such different information-processing stages, research using classical conditioning has begun to examine event-related potentials (ERPs) in response to fear-conditioned (CS +) faces. However, the impact of trait anxiety on ERPs to fear-conditioned faces depending on specific task conditions is unknown. In this preregistered study, we measured ERPs to faces paired with aversive loud screams (CS +) or neutral sounds (CS −) in a large sample (N = 80) under three different task conditions. Participants had to discriminate face-irrelevant perceptual information, the gender of the faces, or the CS category. Results showed larger amplitudes in response to aversively conditioned faces for all examined ERPs, whereas interactions with the attended feature occurred for the P1 and the early posterior negativity (EPN). For the P1, larger CS + effects were observed during the perceptual distraction task, while the EPN was increased for CS + faces when deciding about the CS association. Remarkably, we found no significant correlations between ERPs and trait anxiety. Thus, fear-conditioning potentiates all ERP amplitudes, some processing stages being further modulated by the task. However, the finding that these ERP differences were not affected by individual differences in trait anxiety does not support theoretical accounts assuming increased threat processing or reduced threat discrimination depending on trait anxiety.

Alpha-2 Adrenoreceptor Antagonist Yohimbine Potentiates Consolidation of Conditioned Fear

BACKGROUND

Hyperconsolidation of aversive associations and poor extinction learning have been hypothesized to be crucial in the acquisition of pathological fear. Previous animal and human research points to the potential role of the catecholaminergic system, particularly noradrenaline and dopamine, in acquiring emotional memories. Here, we investigated in a between-participants design with 3 groups whether the noradrenergic alpha-2 adrenoreceptor antagonist yohimbine and the dopaminergic D2-receptor antagonist sulpiride modulate long-term fear conditioning and extinction in humans.

METHODS

Fifty-five healthy male students were recruited. The final sample consisted of n = 51 participants who were explicitly aware of the contingencies between conditioned stimuli (CS) and unconditioned stimuli after fear acquisition. The participants were then randomly assigned to 1 of the 3 groups and received either yohimbine (10 mg, n = 17), sulpiride (200 mg, n = 16), or placebo (n = 18) between fear acquisition and extinction. Recall of conditioned (non-extinguished CS+ vs CS-) and extinguished fear (extinguished CS+ vs CS-) was assessed 1 day later, and a 64-channel electroencephalogram was recorded.

RESULTS

The yohimbine group showed increased salivary alpha-amylase activity, confirming a successful manipulation of central noradrenergic release. Elevated fear-conditioned bradycardia and larger differential amplitudes of the N170 and late positive potential components in the event-related brain potential indicated that yohimbine treatment (compared with a placebo and sulpiride) enhanced fear recall during day 2.

CONCLUSIONS

These results suggest that yohimbine potentiates cardiac and central electrophysiological signatures of fear memory consolidation. They thereby elucidate the key role of noradrenaline in strengthening the consolidation of conditioned fear associations, which may be a key mechanism in the etiology of fear-related disorders.

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.

Learning dynamics of electrophysiological brain signals during human fear conditioning

Electrophysiological studies in rodents allow recording neural activity during threats with high temporal and spatial precision. Although fMRI has helped translate insights about the anatomy of underlying brain circuits to humans, the temporal dynamics of neural fear processes remain opaque and require EEG. To date, studies on electrophysiological brain signals in humans have helped to elucidate underlying perceptual and attentional processes, but have widely ignored how fear memory traces evolve over time. The low signal-to-noise ratio of EEG demands aggregations across high numbers of trials, which will wash out transient neurobiological processes that are induced by learning and prone to habituation. Here, our goal was to unravel the plasticity and temporal emergence of EEG responses during fear conditioning. To this end, we developed a new sequential-set fear conditioning paradigm that comprises three successive acquisition and extinction phases, each with a novel CS+/CS- set. Each set consists of two different neutral faces on different background colors which serve as CS+ and CS-, respectively. Thereby, this design provides sufficient trials for EEG analyses while tripling the relative amount of trials that tap into more transient neurobiological processes. Consistent with prior studies on ERP components, data-driven topographic EEG analyses revealed that ERP amplitudes were potentiated during time periods from 33-60 ms, 108-200 ms, and 468-820 ms indicating that fear conditioning prioritizes early sensory processing in the brain, but also facilitates neural responding during later attentional and evaluative stages. Importantly, averaging across the three CS+/CS- sets allowed us to probe the temporal evolution of neural processes: Responses during each of the three time windows gradually increased from early to late fear conditioning, while long-latency (460-730 ms) electrocortical responses diminished throughout fear extinction. Our novel paradigm demonstrates how short-, mid-, and long-latency EEG responses change during fear conditioning and extinction, findings that enlighten the learning curve of neurophysiological responses to threat in humans.

Neurophysiological responses to safety signals and the role of cardiac vagal control

BACKGROUND

Deficits in safety signal learning are well-established in fear-related disorders (e.g., PTSD, phobias). The current study used a fear conditioning paradigm to test associations among eye blink startle and event-related brain potential (ERP) latency measures of safety signal learning, as well as the role of cardiac vagal control (a measure of top-down inhibition necessary for safety learning).

METHODS

Participants were 49 trauma-exposed women ages 17 to 28 years. Eyeblink startle response and ERP amplitudes/latencies were derived for conditioned stimuli associated (CS+) and not associated (CS-) with an aversive unconditioned stimulus. ERPs included the P100 and late positive potential (LPP), which index early visual processing and sustained emotional encoding, respectively. Cardiac vagal control was assessed with resting heart rate variability (HRV).

RESULTS

P100 and LPP latencies for the CS- (safety signal stimulus) were significantly negatively associated with startle to the CS-, but not the CS + . LPP CS- latencies were significantly negatively associated with PTSD Intrusion scores, and this relationship was moderated by vagal control, such that the effect was only present among those with low HRV.

CONCLUSIONS

ERP-based markers of safety signal learning were associated with startle response to the CS- (but not CS+) and PTSD symptoms, indicating that these markers may have relevance for fear-related disorders. Cardiac vagal control indexed by HRV is a moderating factor in these associations and may be relevant to safety signal learning.

Neural indices of orienting, discrimination, and conflict monitoring after contextual fear and safety learning

Investigations of fear conditioning have recently begun to evaluate contextual factors that affect attention-related processes. However, much of the extant literature does not evaluate how contextual fear learning influences neural indicators of attentional processes during goal-directed activity. The current study evaluated how early attention for task-relevant stimuli and conflict monitoring were affected when presented within task-irrelevant safety and threat contexts after fear learning. Participants (N = 72) completed a Flanker task with modified context before and after context-dependent fear learning. Flanker stimuli were presented in the same threat and safety contexts utilized in the fear learning task while EEG was collected. Results indicated increased early attention (N1) to flankers appearing in threat contexts and later increased neural indicators (P2) of attention to flankers appearing in safety contexts. Results of this study indicate that contextual fear learning modulates early attentional processes for task-relevant stimuli that appear in the context of safety and threat. Theoretical and clinical implications are discussed.

Extinction-resistant attention to long-term conditioned threat is indexed by selective visuocortical alpha suppression in humans

Previous electrophysiological studies in humans have shown rapid modulations of visual attention after conditioned threat vs. safety cues (<500 ms post-stimulus), but it is unknown whether this attentional prioritization is sustained throughout later time windows and whether it is robust to extinction. To investigate sustained visual attention, we assessed visuocortical alpha suppression in response to conditioned and extinguished threat. We reanalysed data from N = 87 male participants that had shown successful long-term threat conditioning and extinction in self reports and physiological measures in a two-day conditioning paradigm. The current EEG time-frequency analyses on recall test data on Day 2 revealed that previously threat-conditioned vs. safety cues evoked stronger occipital alpha power suppression from 600 to 1200 ms. Notably, this suppression was resistant to previous extinction. The present study showed for the first time that threat conditioning enhances sustained modulation of visuocortical attention to threat in the long term. Long-term stability and extinction resistance of alpha suppression suggest a crucial role of visuocortical attention mechanisms in the maintenance of learned fears.

Threat-conditioned contexts modulate the late positive potential to faces-A mobile EEG/virtual reality study

In everyday life, the motivational value of faces is bound to the contexts in which faces are perceived. Electrophysiological studies have demonstrated that inherent negatively valent contexts modulate cortical face processing as assessed with ERP components. However, it is not well understood whether learned (rather than inherent) and three-dimensional aversive contexts similarly modulate the neural processing of faces. Using full immersive virtual reality (VR) and mobile EEG techniques, 25 participants underwent a differential fear conditioning paradigm, in which one virtual room was paired with an aversive noise burst (threat context) and another with a nonaversive noise burst (safe context). Subsequently, avatars with neutral or angry facial expressions were presented in the threat and safe contexts while EEG was recorded. Analysis of the late positive potential (LPP), which presumably indicates motivational salience, revealed a significant interaction of context (threat vs. safe) and face type (neutral vs. angry). Neutral faces evoked increased LPP amplitudes in threat versus safe contexts, while angry faces evoked increased early LPP amplitudes regardless of context. In addition to indicating that threat-conditioned contexts alter the processing of ambiguous faces, the present study demonstrates the successful integration of EEG and VR with particular relevance for affective neuroscience research.

Testing neurophysiological markers related to fear-potentiated startle

Fear-potentiated startle (FPS) paradigms provide insight into fear learning mechanisms that contribute to impairment among individuals with posttraumatic stress symptoms (PTSS). Electrophysiology also has provided insight into these mechanisms through the examination of event-related potentials (ERPs) such as the P100 and LPP. It remains unclear, however, whether the P100 and LPP may be related to fear learning processes within the FPS paradigm. To this end, we tested differences in ERP amplitudes for conditioned stimuli associated (CS+) and not associated (CS-) with an aversive unconditioned stimulus (US) during fear acquisition. Participants included 54 female undergraduate students (mean age = 20.26). The FPS response was measured via electromyography of the orbicularis oculi muscle. EEG data were collected during the FPS paradigm. While the difference between CS+ and CS- P100 amplitude was not significant, LPP amplitudes were significantly enhanced following the CS+ relative to CS-. Furthermore, the LPP difference wave (CS+ minus CS-) was associated with FPS scores for the CS- during the later portion of fear acquisition. These findings suggest that conditioned stimuli may have altered emotional encoding (LPP) during the FPS paradigm. Thus, the LPP may be a promising neurophysiological marker that is related to fear learning processes.