Excitatory strength of expressive faces: effects of happy and fear expressions and context on the extinction of a conditioned fear response

In a recent study, Orr and Lanzetta (1984) showed that the excitatory properties of fear facial expressions previously described (Lanzetta & Orr, 1981; Orr & Lanzetta, 1980) do not depend on associative mechanisms; even in the absence of reinforcement, fear faces intensify the emotional reaction to a previously conditioned stimulus and disrupt extinction of an acquired fear response. In conjunction with the findings on acquisition, the failure to obtain extinction suggests that fear faces have some of the functional properties of "prepared" (fear-relevant) stimuli. In the present study we compared the magnitude of conditioned fear responses to happy and fear faces when a potent danger signal, the shock electrodes, are attached or unattached. If fear faces are functionally analogous to prepared stimuli, then, even in the absence of veridical support for an expectation of shock, they should retain excitatory strength, whereas happy faces should not. The results are consistent with this view of fear expressions. In the absence of reinforcement, and with shock electrodes removed, conditioned fear responses and basal levels of arousal were of greater magnitude for the fear-face condition than for the happy-face condition.     

认知重评阻断条件化恐惧记忆的习得与表达——对恐惧反应的长程抑制作用

情绪调节是人类特有的、并能有效控制个体情绪反应的行为方式,认知重评是其中最有效的调节策略之一。恐惧记忆是参与情绪障碍形成的重要病理机制,且已习得的恐惧反应难消退、易复发。为了考察认知重评能否起到长久抑制恐惧反应的效应,本研究利用条件化恐惧范式,第一天进行条件化恐惧习得训练,并在习得后间隔24 h及31天进行恐惧记忆的表达及自发恢复测试。实验1中,随机将被试分为两组,要求其在恐惧习得过程中进行认知重评或自然感受;在实验2,同样随机将被试分为两组,但要求其在恐惧记忆表达过程中进行认知重评或自然感受。结果发现,习得阶段进行认知重评显著降低了恐惧记忆的习得、表达及自发恢复过程中的SCR水平。同样,表达阶段进行认知重评也降低了此阶段的恐惧水平,且显著抑制了恐惧记忆的自发恢复。结果提示,在面对应激时,个体如果能够成功地利用想象进行认知重评,就有可能避免应激事件对个体的心理或精神造成伤害。     

Different mechanisms of fear extinction dependent on length of time since fear acquisition

Fear extinction is defined as a decline in conditioned fear responses (CRs) following nonreinforced exposure to a feared conditioned stimulus (CS). Behavioral evidence indicates that extinction is a form of inhibitory learning: Extinguished fear responses reappear with the passage of time (spontaneous recovery), a shift of context (renewal), and unsignaled presentations of the unconditioned stimulus (reinstatement). However, there also is evidence to suggest that extinction is an "unlearning" process corresponding to depotentiation of potentiated synapses within the amygdala. Because depotentiation is induced more readily at short intervals following LTP induction and is not inducible at all at a sufficient delay, it may be that extinction initiated shortly following fear acquisition preferentially engages depotentiation/"unlearning," whereas extinction initiated at longer delays recruits a different mechanism. We investigated this possibility through a series of behavioral experiments examining the recoverability of conditioned fear following extinction. Consistent with an inhibitory learning mechanism of extinction, rats extinguished 24-72 h following acquisition exhibited moderate to strong reinstatement, renewal, and spontaneous recovery. In contrast, and consistent with an erasure mechanism, rats extinguished 10 min to 1 h after acquisition exhibited little or no reinstatement, renewal, or spontaneous recovery. These data support a model in which different neural mechanisms are recruited depending on the temporal delay of fear extinction.     

Individual differences in cortisol responses to fear and frustration during middle childhood

The purpose of this study was to examine individual differences in the activation and regulation of the hypothalamic-pituitary-adrenal (HPA) axis in prepubertal children after exposure to two different stress modalities and to evaluate the utility of an individual differences approach to the examination of HPA axis functioning. After a 30-min controlled baseline period, 73 7-year-olds (40 boys and 33 girls) were randomly assigned to a validity check condition or one of two experimental tasks designed to elicit fear or frustration. This was followed by a 60-min controlled regulation phase. A total of 17 saliva samples were collected, including 12 poststress samples at 5-min intervals. There was a significant stress modality effect, with children exposed to the fear condition reaching peak cortisol levels at 25 min poststress and those exposed to the frustration condition reaching peak levels at 45 min poststress. There was no difference in peak cortisol levels between the stress modalities. Individual variability across conditions was significant, with participants reaching peak levels as early as 10 min poststress and as late as 60 min poststress. Our data suggest that analysis of individual curves prior to making group-level comparisons may improve the explanatory power of HPA axis behavior models.     

The effects on arousal of frustration and aggressive films

In two two-by-two factorial experiments, subjects were either frustrated or not, and then were shown either a film depicting aggression or a neutral film. In the first experiment, performance on a digit-symbol test was measured before and immediately after the manipulations. Subjects who had either been frustrated or who had watched the aggressive movie performed better on the second digit-symbol test than did subjects who had experienced neither or both of these manipulations. In the second experiment, blood pressure was measured before and immediately after the manipulations. On various indices of arousal, the most arousal was shown for subjects who had been frustrated and who had watched the aggressive film. Subjects who had not been frustrated and who had not watched the aggressive film showed the least arousal, and subjects who had experienced one or the other of these manipulations were in between. Given that performance on the digit-symbol test has been shown to be an inverted U function of arousal, both of these experiments support the notion that the effects on arousal of frustration and aggressive movies are additive. This is directly counter to the idea that movies involving aggression are tension reducing for either frustrated or nonfrustrated subjects.     

The interaction between response effects during the acquisition of response priming

In three experiments we investigated the role of associative learning in the acquisition of response priming by effect stimuli, by examining their interaction during response-effect learning. Having replicated the ability of visual effect stimuli to prime their associated responses, we paired a response with a compound consisting of visual and auditory effects before assessing the ability of the auditory effect stimulus to prime the response. This priming was reduced if the visual stimulus had been pre-trained as an effect of the response. By contrast, priming by the visual effect stimulus was potentiated when the auditory effect had been pre-trained. We interpret these interactions in terms of contemporary associative learning theory derived from studies of conditioning.     

Failure to overcome 'innate' fear: a developmental test of the non-associative model of fear acquisition

The non-associative, Darwinian theory of fear acquisition proposes that some individuals fail to overcome biologically-relevant fears (e.g. height) because they (1) do not have sufficient safe exposure to the relevant stimuli early in life or (2) are poor habituators who have difficulty 'learning not to fear'. These two hypotheses were tested in a longitudinal birth cohort study. Study 1 found evidence for reduced exposure to height stimuli in childhood for individuals with a fear of heights compared to study members without fear. Study 2 found evidence for higher levels of stress reactivity (a proxy for habituation) in childhood and adolescence among 18-year-old height phobics compared to study members with dental phobia and those with no fear. The results were discussed in relation to recent findings suggesting that some evolutionary-relevant fears may appear in the absence of traumatic 'learning' experiences. The merits of adding a fourth, non-associative pathway to Rachman's [Rachman, S. (1977)]. The conditioning theory of fear acquisition: a critical examination. Behaviour Research and Therapy, 15, 375-387) three pathways model of fear acquisition were briefly considered.     

Mother knows best: effects of maternal modelling on the acquisition of fear and avoidance behaviour in toddlers

The present study was conducted to investigate the influence of parental modelling on the acquisition of fear and avoidance towards novel, fear-relevant stimuli in a sample of 30 toddlers. The toddlers were shown a rubber snake and spider, which were alternately paired with either negative or positive facial expressions by their mothers. Both stimuli were presented again after a 1- and a 10-min delay, while mothers maintained a neutral expression. The children showed greater fear expressions and avoidance of the stimuli following negative reactions from their mothers. This was true for both genders although the degree of modelled avoidance was greater in girls than in boys. The strong observational learning results are consistent with views that modelling constitutes a mechanism by which fear may be acquired early in life.