Social exclusion influences conditioned fear acquisition and generalization: A mediating effect from the medial prefrontal cortex

Sleep debt-induced anxiety and addiction to substances of abuse: A narrative review

Substance Use Disorder (SUD) has been conceptualized as an outcome of a dysregulated reward system. However, individuals with SUD suffer from anxiety with an intensity depending on the abstinence period length. This review discusses the role of anxiety as a major contributor to the initiation and perpetuation of SUD, and its dependence on an up-regulated defense-antireward system. In addition, it is discussed that sleep debt, and its psychosocial consequences, promote anxiety, contributing to SUD generation and maintenance. Healthy sleep patterns can be disrupted by diverse medical conditions and negative psychosocial interactions, resulting in accumulated sleep debt and anxiety. Within this narrative review, we discuss the interplay between the motivation-reward and defense-antireward systems, framing the progression from recreational drug use to addiction. This interplay is nuanced by sleep debt-induced anxiety and its psychosocial consequences as contributory vulnerability factors in the genesis of addiction.

Trait self-compassion enhances activation in the medial prefrontal cortex during fear extinction: An fNIRS study

Fear acquisition and fear extinction are the most widely used experimental models to study anxiety related disorders, with the medial prefrontal cortex (mPFC) playing an important role in this process. Previous research suggests that trait self-compassion is associated with lower anxiety, but the neural mechanisms underlying this relationship remain unclear. Women generally exhibit lower self-compassion than men, making them more vulnerable to fear and anxiety. In this study, female participants were divided into two groups - high and low trait self-compassion, based on their scores on the Self-Compassion Scale-Short Form (SCS-SF). Both groups completed fear acquisition and fear extinction tasks, during which conditioned responses (CRs) were measured using self-reported unconditioned stimulus (US) expectancy ratings, skin conductance response (SCR), and functional near-infrared spectroscopy (fNIRS). The results showed that in the fear acquisition phase, all participants successfully acquired fear, showing greater responses to threat stimuli than safety stimuli. However, participants with high trait self-compassion exhibited lower SCR than those with low trait self-compassion. In the fear extinction phase, compared to individuals with low trait self-compassion, individuals with high trait self-compassion exhibited more effective fear extinction learning, characterized by lower US expectancy ratings, lower SCR, and higher mPFC activation. Moreover, trait self-compassion was significantly correlated with the behavioral extinction ability and the mPFC activation during the late phase of fear extinction, and behavioral extinction ability was significantly correlated with mPFC activation. The findings of this study suggest individuals with high trait self-compassion have better physiological flexibility during fear acquisition and fear extinction, and may through enhancing mPFC activation to facilitate fear extinction. The results provide new insights into the pathological mechanisms of anxiety.

The impact of anger on intertemporal decision-making in individuals with internet addiction: an fNIRS study

Intertemporal decision-making is the choice between an immediate smaller reward (SS) and a delayed larger reward (LL). Intertemporal decision-making depends on the interaction of the cognitive and emotional systems, and the latter is particularly vital. According to the Appraisal Tendency Frame (ATF) theory, anger influences intertemporal decision-making by increasing an individual's sense of certainty and control. This study examined whether anger affects intertemporal decision-making in individuals with internet addiction (IA) in this manner and investigated its neural mechanisms. Nineteen individuals with IA and 20 healthy controls were recruited. All subjects performed the Monetary choice task under anger and neutral emotions while functional near-infrared spectroscopy (fNIRS) equipment simultaneously recorded the hemodynamics in the prefrontal cortex (PFC). Individuals with IA showed a more considerable delay discount and lower brain activations in the orbitofrontal cortex (OFC) and left dorsolateral prefrontal cortex (L-dlPFC) compared to HC. Moreover, individuals with IA made more LL choices in the angry condition than in the neutral emotion, yet there was no difference in HC. The brain activation in L-dlPFC of individuals with IA tends to increase in the angry condition compared to the neutral condition. These findings revealed that impairment of intertemporal decision-making in individuals with individuals with IA might be related to the dysfunction of OFC and L-dlPFC. Our work also provided initial footing for the applicability of the appraisal tendency frame theory to individuals with IA, and L-dlPFC might play a role in the effects of anger on intertemporal decision-making.

Loneliness and the persistence of fear: Perceived social isolation reduces evaluative fear extinction

Loneliness has been linked to a host of harmful physical and mental health outcomes, detrimental effects that may stem from increases in threat-responding caused by altered fear learning in lonely individuals. In particular, the heightened threat-vigilance that is a hallmark of loneliness may augment the processes by which fear learning occurs, ultimately resulting in a greater number of perceived threatening cues in the environment. However, almost no research has examined how loneliness alters fear learning processes in humans. Here, we investigated the effect of loneliness on fear learning during an evaluative learning procedure in which participants (n = 782) were taught to associate fearful, positive, or neutral control stimuli with neutral images. Results showed that reduced extinction of evaluative fear associations occurred in high (vs. low) lonely individuals, but there was no difference in extinction of evaluative appetitive (also known as positive or reward) associations, suggesting this effect is specific to fear learning. In addition to shedding light on the link between loneliness and poor health, these results represent an important step forward in the growing understanding of the powerful impact of social bonds on fear learning processes.

Sleep deprivation increases the generalization of perceptual and concept-based fear: An fNIRS study

Insufficient sleep can initiate or exacerbate anxiety by triggering excessive fear generalization. In this study, a de novo paradigm was developed and used to examine the neural mechanisms governing the effects of sleep deprivation on processing perceptual and concept-based fear generalizations. A between-subject design was adopted, wherein a control group (who had a typical night's sleep) and a one-night sleep deprivation group completed a fear acquisition task at 9:00 PM on the first day and underwent a generalization test the following morning at 7:00 AM. In the fear acquisition task, navy blue and olive green were used as perceptual cues (P+ and P-, respectively), while animals and furniture items were used as conceptual cues (C+ and C-, respectively). Generalization was tested for four novel generalized categories (C+P+, C+P-, C-P+, and C-P-). Shock expectancy ratings, skin conductance responses, and functional near-infrared spectroscopy were recorded during the fear acquisition and generalization processes. Compared with the group who had a typical night's sleep, the sleep deprived group showed higher shock expectancy ratings (especially for P+ and C-), increased oxygenated hemoglobin in the dorsolateral prefrontal cortex, and increased activation in the triangular inferior frontal gyrus during the generalization test. These findings suggest that sleep deprivation increases the generalization of threat memories, thus providing insights into the overgeneralization characteristics of anxiety and fear-related disorders.

Exaggerated sensitivity to threat and reduced medial prefrontal engagement during threat generalization in reactive aggressive adolescents

Aggressive adolescents tend to exhibit abnormal fear acquisition and extinction, and reactive aggressive adolescents are often more anxious. However, the relationship between fear generalization and reactive aggression (RA) remains unknown. According to Reactive-Proactive Aggression Questionnaire (RPQ) scores, 61 adolescents were divided into two groups, namely, a high RA group (N = 30) and a low aggression (LA) group (N = 31). All participants underwent three consecutive phases of the Pavlovian conditioning paradigm (i.e., habituation, acquisition, and generalization), and neural activation of the medial prefrontal cortex (mPFC) was assessed by functional near-infrared spectroscopy (fNIRS). The stimuli were ten circles with varying sizes, including two conditioned stimuli (CSs) and eight generalization stimuli (GSs). A scream at 85 dB served as the auditory unconditioned stimulus (US). The US expectancy ratings of both CSs and GSs were higher in the RA group than in the LA group. The fNIRS results showed that CSs and GSs evoked lower mPFC activation in the RA group compared to the LA group during fear generalization. These findings suggest that abnormalities in fear acquisition and generalization are prototypical dysregulations in adolescents with RA. They provide neurocognitive evidence for dysregulated fear learning in the mechanisms underlying adolescents with RA, highlighting the need to develop emotional regulation interventions for these individuals.

Intolerance of uncertainty affects the behavioral and neural mechanisms of higher generalization

Intolerance of uncertainty (IU) is associated with several anxiety disorders. In this study, we employed rewards and losses as unconditioned positive and negative stimuli, respectively, to explore the effects of an individual's IU level on positive and negative generalizations using magnetic resonance imaging technology. Following instrumental learning, 48 participants (24 high IU; 24 low IU) were invited to complete positive and negative generalization tasks; their behavioral responses and neural activities were recorded by functional magnetic resonance imaging. The behavior results demonstrated that participants with high IUs exhibited higher generalizations to both positive and negative cues as compared with participants having low IUs. Neuroimaging results demonstrated that they exhibited higher activation levels in the right anterior insula and the default mode network (i.e. precuneus and posterior cingulate gyrus), as well as related reward circuits (i.e. caudate and right putamen). Therefore, higher generalization scores and the related abnormal brain activation may be key markers of IU as a vulnerability factor for anxiety disorders.

Effects of an open-label placebo intervention on reactions to social exclusion in healthy adults: a randomized controlled trial

Social exclusion, that is being left out by others, can have adverse consequences for individuals' psychological well-being. Even short-term experiences of social exclusion strongly threaten basic psychological needs and cause so-called social pain. Prior research suggests an overlap between the experience of social and physical pain that, amongst others, is reflected by the effectiveness of physical pain treatments in alleviating social pain. Drawing upon these prior findings, we here explore whether open-label placebos, which have previously been found to be effective in reducing physical pain, can alleviate social pain following social exclusion. Seventy-four healthy participants were randomly assigned to one of four conditions in a 2 × 2 between-subjects design: First, they either received an open-label placebo intervention or no treatment. Second, they either experienced inclusion or exclusion by their co-players in the interactive ball-tossing game Cyberball. We find that excluded participants in the open-label placebo condition experienced significantly less hurt feelings compared to those in the control condition (Cohen's d = 0.77). There was no effect of treatment for need threat. The findings suggest new possibilities to alleviate social pain, which is of particular interest in the context of preventing destructive and maladaptive behaviors in situations where functional coping strategies are unavailable.

Impact of observational and direct learning on fear conditioning generalization in humans

Humans gain knowledge about threats not only from their own experiences but also from observing others' behavior. A neutral stimulus is associated with a threat stimulus for several times and the neutral stimulus will evoke fear responses, which is known as fear conditioning. When encountering a new event that is similar to one previously associated with a threat, one may feel afraid and produce fear responses. This is called fear generalization. Previous studies have mostly focused on fear conditioning and generalization based on direct learning, but few have explored how observational fear learning affects fear conditioning and generalization. To the best of our knowledge, no previous study has focused on the neural correlations of fear conditioning and generalization based on observational learning. In the present study, 58 participants performed a differential conditioning paradigm in which they learned the associations between neutral cues (i.e., geometric figures) and threat stimuli (i.e., electric shock). The learning occurred on their own (i.e., direct learning) and by observing other participant's responses (i.e., observational learning); the study used a within-subjects design. After each learning condition, a fear generalization paradigm was conducted by each participant independently while their behavioral responses (i.e., expectation of a shock) and electroencephalography (EEG) recordings or responses were recorded. The shock expectancy ratings showed that observational learning, compared to direct learning, reduced the differentiation between the conditioned threatening stimuli and safety stimuli and the increased shock expectancy to the generalization stimuli. The EEG indicated that in fear learning, threatening conditioned stimuli in observational and direct learning increased early discrimination (P1) and late motivated attention (late positive potential [LPP]), compared with safety conditioned stimuli. In fear generalization, early discrimination, late motivated attention, and orienting attention (alpha-event-related desynchronization [alpha-ERD]) to generalization stimuli were reduced in the observational learning condition. These findings suggest that compared to direct learning, observational learning reduces differential fear learning and increases the generalization of fear, and this might be associated with reduced discrimination and attentional function related to generalization stimuli.

Attachment voices promote safety learning in humans: A critical role for P2

Humans have evolved to seek the proximity of attachment figures during times of threat in order to obtain a sense of safety. In this context, we examined whether or not the voice of an intimate partner (termed "attachment voice") could reduce fear-learning of conditioned stimuli (CS+) and enhance learning of safety signals (CS-). Although the ability to learn safety signals is vital for human survival, few studies have explored how attachment voices affect safety learning. To test our hypothesis, we recruited thirty-five young couples and performed a classic Pavlovian conditioning experiment, recording behavioral and electroencephalographic (EEG) data. The results showed that compared with a stranger's voice, the voices of the partners reduced expectancy of the unconditioned stimulus (a shock) during fear-conditioning, as well as the magnitude of P2 event-related potentials within the EEG responses, provided the voices were safety signals. Additionally, behavioral and EEG responses to the CS+ and CS- differed more when the participants heard their partner's voice than when they heard the stranger's voice. Thus, attachment voices, even as pure vowel sounds without any semantic information, enhanced acquisition of conditioned safety (CS-). These findings may provide implications for investigating other new techniques to improve clinical treatments for fear- and anxiety-related disorders and for psychological interventions against the mental health effects of the public health emergency.

Influence of Perceptual and Conceptual Information on Fear Generalization: A Behavioral and Event-Related Potential Study

Learned fear can be generalized through both perceptual and conceptual information. This study investigated how perceptual and conceptual similarities influence this generalization process. Twenty-three healthy volunteers completed a fear-generalization test as brain activity was recorded in the form of event-related potentials (ERPs). Participants were exposed to a de novo fear acquisition paradigm with four categories of conditioned stimuli (CS): two conceptual cues (animals and furniture); and two perceptual cues (blue and purple shapes). Animals (C+) and purple shapes (P+) were paired with the unconditioned stimulus (US), whereas furniture (C-) and blue shapes (P-) never were. The generalized stimuli were thus blue animals (C+P+, determined danger), blue furniture (C-P+, perceptual danger), purple animals (C+P-, conceptual danger), and purple furniture (C-P-, determined safe). We found that perceptual cues elicited larger fear responses and shorter reaction times than did conceptual cues during fear acquisition. This suggests that a perceptually related pathway might evoke greater fear than a conceptually based route. During generalization, participants were more afraid of C+ exemplars than of C- exemplars. Furthermore, C+ trials elicited greater N400 amplitudes. Thus, participants appear able to use conceptually based cues to infer the value of the current stimuli. Additionally, compared with C+ exemplars, we found an enhanced late positive potential effect in response to C- exemplars, which seems to reflect a late inhibitory process and might index safety learning. These findings may offer new insights into the pathological mechanism of anxiety disorders.

The Arousal Effect of Exclusionary and Inclusionary Situations on Social Affiliation Motivation and Its Subsequent Influence on Prosocial Behavior

Given the negative costs of exclusion and the relevance of belongingness for humans, the experience of exclusion influences social affiliation motivation, which in turn is a relevant predictor of prosocial behavior. Skin conductance is a typical measure of the arousal elicited by emotions. Hence, we argued that both inclusion and exclusion will increase skin conductance level due to the increase of either positive affect or anger affects, respectively. Moreover, we argued that emotional arousal is also related to social affiliation motivation and prosocial behavior. A total of 48 students were randomly allocated to either an inclusionary or exclusionary condition and their skin conductance levels were recorded during an experiment in which they completed an online questionnaire and played the game “Cyberball.” Results indicated that (a) individuals who perceived high exclusion felt angrier than individuals perceiving high inclusion, who feel positive affect; (b) no differences were evidenced in terms of skin conductance between exclusion and inclusion situations; (c) over-aroused individuals were less motivated to affiliate; and (d) individuals with lower affiliation motivation behaved in a less prosocial way. The results were congruent to the argument that behaving prosocially may be a way to gain the desired affiliation.