Learning not to fear : extinction, erasure, and the recovery of fear memories

Much of the progress in understanding the mechanisms underlying the formation and persistence of fear memories comes from studies of Pavlovian conditioning and extinction. Recently, considerable interest has been turn to strategies that facilitate the development and persistence of extinction. This interest has been particularly fueled by the fact that the findings may have important clinical implications by identifying the conditions during which extinction may permanently prevent the recovery of learned fears. The overall aim of this thesis was to identify the temporal factors that drive fear extinction learning (Study I) and to investigate different approaches to preventing the return of fear that occurs after extinction (Study II-IV). More specifically, we assessed the effects of initiating extinction training within the consolidation (Study II) or reconsolidation (Study III) time window and the effects of optimizing safety learning during fear extinction through social observation (Study IV). In Study I, we evaluated two critical accounts of extinction by separately manipulating the number of non-reinforced trials and the cumulated non-reinforced exposure time during extinction training. Our data did not support that extinction is driven by the cumulative duration of non-reinforced exposure, but rather the number of trials appeared critical. In fact, many extinction trials with a duration shorter than the acquisition trial duration facilitated extinction learning, but this effect did not predict the recovery of fear. In Study II, we found that extinction training initiated within, but not outside, the consolidation time window yielded less extinction of both fear-potentiated startle and shock expectancy ratings, while selectively preventing the return of fear-potentiated startle during a subsequent reinstatement test. Contrary, in Study III, extinction training initiated within the reconsolidation time window did not prevent the recovery of fear, as measured by reinstatement of fear-potentiated startle or skin conductance responses, using either fear-relevant or fear-irrelevant stimuli. Finally, as an alternative approach to preventing the return of fear, in Study IV, we capitalized on the fact that much of what we learn about the environment comes through social forms of learning such as through observation of other individuals. Therefore, we assessed the effects of vicarious safety learning on the decrement of conditioned fear during extinction training and its effects on the subsequent return of fear. We found that vicarious extinction efficiently reduced conditioned fear responses during extinction and blocked the subsequent return of fear, as measured by skin conductance responses during a subsequent reinstatement test. In sum, the studies in this thesis demonstrate an intricate relation between extinction learning and the return of fear and highlight that extinction represents a highly complex phenomenon that most probably is determined by multiple factor

Data from: Social learning of fear and safety is determined by the demonstrator’s racial group

Social learning offers an efficient route through which humans and other animals learn about potential dangers in the environment. Such learning inherently relies on the transmission of social information and should imply selectivity in what to learn from whom. Here, we conducted two observational learning experiments to assess how humans learn about danger and safety from members (‘demonstrators’) of another social group than their own. We show that both fear and safety learning from a racial in-group demonstrator was more potent than learning from a racial out-group demonstrator

Vic_Race_Experiment1

Vic_Race_Experiment

Vic-Race_Ext_Experiment2

Vic-Race_Ext_Experiment

Social threat learning transfers to decision making in humans

In today’s world, mass-media and online social networks present us with unprecedented exposure to second-hand, vicarious experiences and thereby the chance of forming associations between previously innocuous events (e.g., being in a subway station) and aversive outcomes (e.g., footage or verbal reports from a violent terrorist attack) without direct experience. Such social threat, or fear, learning can have dramatic consequences, as manifested in acute stress symptoms and maladaptive fears. However, most research has so far focused on socially acquired threat responses that are expressed as increased arousal rather than active behavior. In three experiments (n = 120), we examined the effect of indirect experiences on behaviors by establishing a link between social threat learning and instrumental decision making. We contrasted learning from direct experience (i.e., Pavlovian conditioning) (experiment 1) against two common forms of social threat learning - social observation (experiment 2) and verbal instruction (experiment 3) - and how this learning transferred to subsequent instrumental decision making using behavioral experiments and computational modeling. We found that both types of social threat learning transfer to decision making in a strong and surprisingly inflexible manner. Notably, computational modeling indicated that the transfer of observational and instructed threat learning involved different computational mechanisms. Our results demonstrate the strong influence of others’ expressions of fear on one’s own decisions and have important implications for understanding both healthy and pathological human behaviors resulting from the indirect exposure to threatening events

In Your Face: Risk of Punishment Enhances Cognitive Control and Error-Related Activity in the Corrugator Supercilii Muscle.

Cognitive control is needed when mistakes have consequences, especially when such consequences are potentially harmful. However, little is known about how the aversive consequences of deficient control affect behavior. To address this issue, participants performed a two-choice response time task where error commissions were expected to be punished by electric shocks during certain blocks. By manipulating (1) the perceived punishment risk (no, low, high) associated with error commissions, and (2) response conflict (low, high), we showed that motivation to avoid punishment enhanced performance during high response conflict. As a novel index of the processes enabling successful cognitive control under threat, we explored electromyographic activity in the corrugator supercilii (cEMG) muscle of the upper face. The corrugator supercilii is partially controlled by the anterior midcingulate cortex (aMCC) which is sensitive to negative affect, pain and cognitive control. As hypothesized, the cEMG exhibited several key similarities with the core temporal and functional characteristics of the Error-Related Negativity (ERN) ERP component, the hallmark index of cognitive control elicited by performance errors, and which has been linked to the aMCC. The cEMG was amplified within 100 ms of error commissions (the same time-window as the ERN), particularly during the high punishment risk condition where errors would be most aversive. Furthermore, similar to the ERN, the magnitude of error cEMG predicted post-error response time slowing. Our results suggest that cEMG activity can serve as an index of avoidance motivated control, which is instrumental to adaptive cognitive control when consequences are potentially harmful

The influence of work-related chronic stress on the regulation of emotion and on functional connectivity in the brain.

Despite mounting reports about the negative effects of chronic occupational stress on cognitive and emotional functions, the underlying mechanisms are unknown. Recent findings from structural MRI raise the question whether this condition could be associated with a functional uncoupling of the limbic networks and an impaired modulation of emotional stress. To address this, 40 subjects suffering from burnout symptoms attributed to chronic occupational stress and 70 controls were investigated using resting state functional MRI. The participants' ability to up- regulate, down-regulate, and maintain emotion was evaluated by recording their acoustic startle response while viewing neutral and negatively loaded images. Functional connectivity was calculated from amygdala seed regions, using explorative linear correlation analysis. Stressed subjects were less capable of down-regulating negative emotion, but had normal acoustic startle responses when asked to up-regulate or maintain emotion and when no regulation was required. The functional connectivity between the amygdala and the anterior cingulate cortex correlated with the ability to down-regulate negative emotion. This connectivity was significantly weaker in the burnout group, as was the amygdala connectivity with the dorsolateral prefrontal cortex and the motor cortex, whereas connectivity from the amygdala to the cerebellum and the insular cortex were stronger. In subjects suffering from chronic occupational stress, the functional couplings within the emotion- and stress-processing limbic networks seem to be altered, and associated with a reduced ability to down-regulate the response to emotional stress, providing a biological substrate for a further facilitation of the stress condition

Time course of Error main effect Post-response.

<p>The cEMG was amplified directly within 0–99 ms following error responses (<i>p</i><.05). Error bars denote SE.</p