Generalisation of fear and avoidance along a semantic continuum

Directly conditioned fear and avoidance readily generalises to dissimilar but conceptually related stimuli. Here, for the first time, we examined the conceptual/semantic generalisation of both fear and avoidance using real words (synonyms). Participants were first exposed to a differential fear conditioning procedure in which one word (e.g., “broth”; CS+) was followed with brief electric shock [unconditioned stimulus (US)] and another was not (e.g., “assist”; CS–). Next, an instrumental conditioning phase taught avoidance in the presence the CS+ but not the CS–. During generalisation testing, synonyms of the CS+ (e.g., “soup”; GCS+) and CS– (e.g., “help”; GCS–) were presented in the absence of shock. Conditioned fear and avoidance, measured via skin conductance responses, behavioural avoidance and US expectancy ratings, generalised to the semantically related, but not to the semantically unrelated, synonyms. Findings have implications for how natural language categories and concepts mediate the expansion of fear and avoidance repertoires in clinical contexts.     

The time course of attentional bias to cues of threat and safety

It is well known that relative to neutral stimuli, attention is biased towards processing stimuli that convey threat. In a previous study in which a particular stimulus (e.g. a blue diamond) was associated with the delivery of an electrical shock, the presence of the fear-conditioned stimulus interfered with the execution of voluntary eye movements to other locations. Here, we show that this effect not only occurs early in time, but remains present long after the fear-conditioned stimulus was removed from the screen. In a subsequent experiment, we associated the presence of a particular stimulus with safety, that is, when this stimulus was present it was certain that no electrical shock would be delivered. The presence of the safety signalling stimulus also interfered with the execution of voluntary saccades, but only when the time between stimulus and cue presentation was relatively long. The results indicate that both signals of threat and signals of safety interfere with execution of a saccade long after the source of threat or safety has been removed. However, only threatening stimuli affect saccade execution early in time, suggesting that threatening stimuli drive selection exogenously.     

Noradrenergic enhancement of associative fear memory in humans

Ample evidence in animals and humans supports the noradrenergic modulation in the formation of emotional memory. However, in humans the effects of stress on emotional memory are traditionally investigated by declarative memory tests (e.g., recall, recognition) for non-associative emotional stimuli (e.g., stories, pictures). Given that anxiety disorders are thought to originate from associative learning processes and are characterized by distressing emotional responses, the existing literature seems to be inconclusive for the understanding of these disorders. Here, we tested whether noradrenaline strengthens the emotional expression of associative fear memory by using a differential fear conditioning procedure in humans. Stimulation of the noradrenergic system by the administration of yohimbine HCl (20 mg) during memory formation did not directly augment the differential startle fear response 48 h later. Yet, the other retention tests uncovered that the administration of yohimbine HCl contrary to placebo pill extensively delayed the process of extinction learning and generated a superior recovery of fear (i.e., reinstatement and reacquisition). Conversely, the yohimbine HCl manipulation did not affect the skin conductance responding and the US expectancy ratings, emphasizing the concept of multiple memory systems. To our knowledge this is the first demonstration in humans that increased noradrenaline release during or shortly after a stressful event strengthens the formation of associative fear memory traces. The present findings suggest that noradrenaline may play an important role in the etiology and maintenance of anxiety disorders.     

非条件刺激降低再评估对条件性恐惧消退的影响

诸多情绪障碍治疗的关键在于促进条件性恐惧反应的消退, 研究证明非条件刺激再评估能够引起恐惧反应的变化。本研究将非条件刺激降低再评估范式应用于消退训练, 以主观预期值、皮电反应作为恐惧反应指标, 考察恐惧习得后非条件刺激强度降低对条件性恐惧消退的影响, 并运用评价性条件作用探讨非条件刺激再评估的作用机制。结果表明：在消退阶段, 降低组对条件刺激的皮电反应显著低于控制组。同时评价性条件作用结果显示：经过非条件刺激再评估, 降低组较控制组对条件刺激的评价更为正性。说明非条件刺激降低再评估有效改变条件刺激的负性效价, 降低个体的恐惧反应、促进恐惧消退。     

情绪记忆的神经基础

情绪记忆具有强烈、持久的特点,在记忆中具有优势地位。杏仁核是情绪记忆的关键脑区,其外侧核被认为是情绪回路建立的中心部位。恐惧条件反射是情绪记忆,特别是情绪回路研究的有效手段。情绪记忆的编码,储存与提取受到杏仁核与各相关脑区共同影响,其中激素调节在这些过程中发挥重要作用。文中结合最新的研究成果对情绪记忆的神经机制进行讨论     

Constraints on enhanced extinction resulting from extinction treatment in the presence of an added excitor

Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects extinguished on the target CS alone, Experiments 1 and 2 found across a range of parameters that any appreciable effect of facilitated extinction due to the concurrent excitor was submerged by generalization decrement going from extinction to testing. In Experiment 3 we used different durations for the target and concurrent stimuli in order to discourage configuring and an ABC renewal design to increase sensitivity, and observed diminished renewal resulting from extinction in the presence of a second excitor. Our findings suggest that there are distinct limits to the observation of enhanced extinction in the presence of an excitor and identifies some of the sources of these limitations.     

The Effect of Counterconditioning on Evaluative Responses and Harm Expectancy in a Fear Conditioning Paradigm

In fear conditioning, extinction targets harm expectancy as well as the fear response, but it often fails to eradicate the negative affective value that is associated with the conditioned stimulus. In the present study, we examined whether counterconditioning can serve to reduce evaluative responses within fear conditioning. The sample consisted of 70 nonselected students, 12 of whom were men. All participants received acquisition with human face stimuli as the conditioned stimuli and an unpleasant white noise as the unconditioned stimulus. After acquisition, one third of the sample was allocated to an extinction procedure. The other participants received counterconditioning with either a neutral stimulus (neutral tone) or a positive stimulus (baby laugh). Results showed that counterconditioning (with both neutral and positive stimuli), in contrast to extinction, successfully reduced evaluative responses. This effect was found on an indirect measure (affective priming task), but not on self-report. Counterconditioning with a positive stimulus also tended to enhance the reduction of conditioned skin conductance reactivity. The present data suggest that counterconditioning procedures might be a promising approach in diminishing evaluative learning and even expectancy learning in the context of fear conditioning.     

Depth of processing and recall of threat material in fearful and nonfearful individuals

Abstract

Although many studies have examined the nature of memory distortions in anxious individuals, few have considered biases in specific memory processes, such as encoding or retrieval. To investigate whether the presentation of threat material facilitates encoding biases, spider fearful (n=63), blood fearful (n=73), and nonfearful (n=75) participants encoded spider related, blood related, and neutral words as a function of three levels of processing (i.e., structural, semantic, and self referent). Participants subsequently completed either a free recall or a recognition task. All participants demonstrated a partial depth of processing effect, such that they recalled more words encoded in the self referent condition than in the other two conditions, but groups did not differ in their recall of stimuli as a function of word type. Relative to participants in the other groups, spider fearful participants had fewer spider related intrusions in the recall condition, and they made fewer errors in responding to structural and semantic encoding questions when spider related words were presented. These results contribute to an increasingly large body of literature suggesting that anxious individuals are not characterized by a memory bias toward threat, and they raise the possibility that individuals with spider fears process threat-relevant information differently than individuals with blood fears.     

Transfer of conditioned fear and avoidance: Concurrent measurement of arousal and operant responding

A reversal design was employed for the analysis of transfer of fear and avoidance through equivalence classes. Two 5-member equivalence classes (A1-B1-C1-D1-E1 and A2-B2-C2-D2-E2) were established. Then B1 and C1 were paired with shock (CS+) and served as S^Ds in avoidance training (B2 and C2 were trained as CS-/S^∆s for avoidance). Further avoidance training followed with D1 and E1 (as S^Ds) and D2 and E2 (as S^∆s), with the first presentation of each of these stimuli serving as the first transfer test. Afterwards, aversive conditioning contingencies were reversed: B2 and D2 were paired with shock and trained as S^Ds for avoidance, B1 and D1 were presented without shock (CS-/S^∆s). Transfer was tested again with C1, E1, C2 and E2. This reversal was implemented to allow for the within-subject replication of transfer effects upon changes in the function of only a subset of each class's elements. Avoidance (key presses) and conditioned fear (skin conductance and heart rate) were simultaneously measured. Results show a clear transfer effect for avoidance, with between- and within-subject replications. For physiological measures, transfer effects in the first test could only be imputed on the basis of group-based inferential statistical analysis. Evidence for between-subject replication was weaker, with only a limited proportion of participants meeting the individual criterion for transfer.     

Post-extinction conditional stimulus valence predicts reinstatement fear: Relevance for long-term outcomes of exposure therapy

Exposure therapy for anxiety disorders is translated from fear conditioning and extinction. While exposure therapy is effective in treating anxiety, fear sometimes returns after exposure. One pathway for return of fear is reinstatement: unsignaled unconditional stimuli following completion of extinction. The present study investigated the extent to which valence of the conditional stimulus (CS+) after extinction predicts return of CS+ fear after reinstatement. Participants (N = 84) engaged in a differential fear conditioning paradigm and were randomised to reinstatement or non-reinstatement. We hypothesised that more negative post-extinction CS+ valence would predict higher CS+ fear after reinstatement relative to non-reinstatement and relative to extinction retest. Results supported the hypotheses and suggest that strategies designed to decrease negative valence of the CS+ may reduce the return of fear via reinstatement following exposure therapy.     

The transfer of respondent eliciting and extinction functions through stimulus equivalence classes

Two studies investigated the transfer of respondent elicitation through equivalence classes. In Experiment 1, match-to-sample procedures were used to teach 8 subjects two four-member equivalence classes. One member of one class was then paired with electric shock, and one member of the other class was presented without shock. All remaining stimuli were then presented. Using skin conductance as the measure of conditioning, transfer of conditioning was demonstrated in 6 of the 8 subjects. In Experiment 2, similar procedures were used to replicate the results of Experiment 1 and investigate the transfer of extinction. Following equivalence training and conditioning to all members of one class, one member was then presented in extinction. When the remaining stimuli from this class were then presented, they failed to elicit skin conductance. In the final phase of the experiment, the stimulus that was previously presented in extinction was reconditioned. Test trials with other members of the class revealed that they regained elicitation function. These results demonstrate that both respondent elicitation and extinction can transfer through stimulus classes. The clinical and applied significance of the results is discussed.     

Fear conditioning in posttraumatic stress disorder: evidence for delayed extinction of autonomic, experiential, and behavioural responses

Aversive conditioning has been proposed as an important factor involved in the etiology of posttraumatic stress disorder (PTSD). However, it is not yet fully understood exactly which learning mechanisms are characteristic for PTSD. PTSD patients (n=36), and healthy individuals with and without trauma exposure (TE group, n=21; nTE group, n=34), underwent a differential fear conditioning experiment consisting of habituation, acquisition, and extinction phases. An electrical stimulus served as the unconditioned stimulus (US), and two neutral pictures as conditioned stimuli (CS+, paired; CS-, unpaired). Conditioned responses were quantified by skin conductance responses (SCRs), subjective ratings of CS valence and US-expectancy, and a behavioural test. In contrast to the nTE group, PTSD patients showed delayed extinction of SCRs to the CS+. Online ratings of valence and US-expectancy as well as the behavioural test confirmed this pattern. These findings point to a deficit in extinction learning and highlight the role of affective valence appraisals and cognitive biases in PTSD. In addition, there was some evidence that a subgroup of PTSD patients had difficulties in learning the CS-US contingency, thereby providing preliminary evidence of reduced discrimination learning.     

预期错误在恐惧记忆更新中的作用与机制

依据错误驱动的学习理论,行为预期结果与实际结果之间的不匹配即预期错误(Predictionerror,PE)是学习产生的驱动因素。作为显著性信息中的一种,预期错误和物理显著性、惊讶、新异性等存在信息加工阶段的不同,与记忆更新的关系也有差异。近年来,记忆再巩固干预范式(reconsolidation interference)被证明可用于人类条件性恐惧记忆的更新,其中记忆提取激活阶段所包含的预期错误起到了引发记忆“去稳定”、开启记忆再巩固的关键作用。在促进恐惧记忆更新的行为机制上,PE被认为是记忆去稳定的必要非充分条件。记忆提取必须包含适量的PE,但其引发的是记忆去稳定、消退还是中间状态,还需结合记忆本身性质确定。在促进恐惧记忆更新的神经机制上,杏仁核、导水管周围灰质(PAG)、海马均在PE探测和计算过程中具有重要作用;前额叶皮层(PFC)及其亚区在PE开启记忆再巩固过程中扮演了重要角色。上述过程又受到神经系统中特定神经递质的重要调节,尤其是多巴胺能和谷氨酸能。未来研究应进一步探索基于PE计算模型的量化研究,整合PE与其他边界条件的交互作用,考察不同类型显著性在记忆再巩固中的作用等;并亟...     

分类和概念对恐惧泛化的影响机制

恐惧泛化与多种焦虑障碍的病理基础密切相关。例如创伤后应激障碍个体往往持续地逃避与创伤事件有关的刺激,遭受着创伤痛苦折磨。本文在厘清知觉辨别与恐惧泛化关系的基础上,着力于高级认知过程(分类与概念相似性、典型性和人工概念)对恐惧泛化的影响,回顾了恐惧泛化的相关神经机制,并揭示恐惧泛化对焦虑障碍患者的临床治疗启示。未来研究应将知觉和高级认知维度的恐惧泛化进行整合研究,同时扩充恐惧习得和泛化的神经回路,以促进人类恐惧泛化更深入的研究。     

Intrahippocampal scopolamine impairs both acquisition and consolidation of contextual fear conditioning

Lesions of the dorsal hippocampus have been shown to disrupt both the acquisition and the consolidation of memories associated with contextual fear (fear of the place of conditioning), but do not affect fear conditioning to discrete cues (e.g., a tone). Blockade of central muscarinic cholinergic receptor activation results in selective acquisition deficits of contextual fear conditioning, but reportedly has little effect on consolidation. Here we show for the first time that direct infusion of the muscarinic cholinergic receptor antagonist, scopolamine, into the dorsal hippocampus produces a dose-dependent deficit in both acquisition and consolidation of contextual fear conditioning, while having no impact on simple tone conditioning.     

Time-based prospective memory difficulties in children with ADHD and the role of time perception and working memory

Time-based prospective memory (PM) is the ability to remember to perform an intended action at a given time in the future. It is a competence that is crucial for effective performance in everyday life and may be one of the main causes of problems for individuals who have difficulty in planning and organizing their life, such as children with attention deficit/hyperactivity disorder (ADHD). This study systematically examines different aspects of time-based PM performance in a task that involves taking an action at a given future time in a group of 23 children with ADHD who were compared with a matched group of typically-developing (TD) children. The children were asked to watch a cartoon and then answer a questionnaire about its content (ongoing task). They were also asked to press a key every 2 minutes while watching the cartoon (PM task). The relationships of time perception and verbal working memory with PM performance were examined by administering appropriate tasks. The results showed that the children with ADHD were less accurate than the TD children in the PM task and exhibited less strategic time-monitoring behavior. Time perception was found to predict PM accuracy, whereas working memory was mainly involved in time-monitoring behavior, but this applied more to the TD group than to the ADHD group, suggesting that children with ADHD are less able to use their cognitive resources when meeting a PM request.     

阻碍条件性恐惧记忆消退的原因分析

创伤后应激障碍是个体经历严重应激后形成的一种焦虑障碍,对其治疗的关键是消退由创伤应激导致的条件性恐惧记忆,但目前最有效的暴露疗法并不能真正有效地抑制患者恐惧记忆的表达.对条件性恐惧的动物模型研究发现情绪性增强效应、恐惧记忆二级条件化与再巩固、内侧前额叶皮层功能不足等均能够阻碍条件性恐惧记忆的消退.针对这几个方面可以探索治疗创伤后应激障碍的相应方法.     

Autobiographical memories of anxiety-related experiences

Ninety-nine undergraduate students retrieved three memories associated with each of the five emotional experiences: panic, trauma, worry, social anxiety, and feeling content. Subsequently, they answered 24 questions assessing properties of each memory, including the vividness and perceived accuracy of the memories and sensory, emotional, and anxiety-related experiences during retrieval. Memories were coded for affective tone and specificity. Results indicated that panic-related and trauma-related memories were rated similarly as content memories, but that they generally were associated with more imagery and emotional experiencing than worry-related or social anxiety-related memories. Participants experienced panic and worry symptoms to the greatest degree when they retrieved panic-related and trauma-related memories. All anxiety-related memories were characterized by more negative tone than content memories. Panic-related and trauma-related memories were more specific than worry-related, social anxiety-related, and content memories. These findings can explain partially why individuals with some, but not all, anxiety disorders experience enhanced memory for threatening material.     

Neighborhood Disorder, Fear, and Mistrust: The Buffering Role of Social Ties with Neighbors

This paper proposes that individuals who report that they live in neighborhoods characterized by disorder—by crime, vandalism, graffiti, danger, noise, dirt, and drugs—have high levels of fear and mistrust. It further proposes that an individual's alliances and connections with neighbors can buffer the negative effects of living in a neighborhood characterized by disorder on fear and mistrust. Results from a representative sample of 2482 Illinois residents collected by telephone in 1995 support the propositions. Living in a neighborhood with a lot of perceived disorder significantly affects mistrust and the fear of victimization, adjusting for sociodemographic characteristics. Perceived neighborhood disorder and social ties significantly interact: informal social ties with neighbors reduce the fear- and mistrust-producing effects of disorder. However, formal participation in neighborhood organizations shows little buffering effect.     

Emotional distress and positive and negative memories from military deployment: the influence of PTSD symptoms and time

During military deployment, soldiers are confronted with both negative and positive events. What is remembered and how it affects an individual is influenced by not only the perceived emotion of the event, but also the emotional state of the individual. Here we examined the most negative and most positive deployment memories from a company of 337 soldiers who were deployed together to Afghanistan. We examined how the level of emotional distress of the soldiers and the valence of the memory were related to the emotional intensity, experience of reliving, rehearsal and coherence of the memories, and how the perceived impact of these memories changed over time. We found that soldiers with higher levels of post-traumatic stress disorder (PTSD) symptoms were more affected by both their negative and positive memories, compared with soldiers with lower levels of PTSD symptoms. Emotional intensity of the most negative memory increased over time in the group with highest levels of PTSD symptoms, but dropped in the other groups. The present study adds to the literature on emotion and autobiographical memory and how this relationship interacts with an individual’s present level of emotional distress and the passage of time.