Fixation-pattern similarity analysis reveals adaptive changes in face-viewing strategies following aversive learning

Memory Under Stress: From Adaptation to Disorder

Stressful events are ubiquitous in everyday life. Exposure to these stressors initiates the temporally orchestrated release of a multitude of hormones, peptides, and neurotransmitters that target brain areas that have been critically implicated in learning and memory. This review summarizes recent insights on the profound impact of stress on 4 fundamental processes of memory: memory formation, memory contextualization, memory retrieval, and memory flexibility. Stress mediators instigate dynamic alterations in these processes, thereby facilitating efficient responding under stress and the creation of a decontextualized memory representation that can effectively aid coping with novel future threats. While they are generally adaptive, the same stress-related changes may contribute to the rigid behaviors, uncontrollable intrusions, and generalized fear responding seen in anxiety disorders and posttraumatic stress disorder. Drawing on recent discoveries in cognitive neuroscience and psychiatry, this review discusses how stress-induced alterations in memory processes can simultaneously foster adaptation to stressors and fuel psychopathology. The transition from adaptive to maladaptive changes in the impact of stress on memory hinges on the nuanced interplay of stressor characteristics and individual predispositions. Thus, taking individual differences in the cognitive response to stressors into account is essential for any successful treatment of stress-related mental disorders.

The next frontier: Moving human fear conditioning research online

Fear conditioning is a significant area of research that has featured prominently among the topics published in Biological Psychology over the last 50 years. This work has greatly contributed to our understanding of human anxiety and stressor-related disorders. While mainly conducted in the laboratory, recently, there have been initial attempts to conduct fear conditioning experiments online, with around 10 studies published on the subject, primarily in the last two years. These studies have demonstrated the potential of online fear conditioning research, although challenges to ensure that this research meets the same methodological standards as in-person experimentation remain, despite recent progress. We expect that in the coming years new outcome measures will become available online including the measurement of eye-tracking, pupillometry and probe reaction time and that compliance monitoring will be improved. This exciting new approach opens new possibilities for large-scale data collection among hard-to-reach populations and has the potential to transform the future of fear conditioning research.

Inferring danger with minimal aversive experience

Learning about threats is crucial for survival and fundamentally rests upon Pavlovian conditioning. However, Pavlovian threat learning is largely limited to detecting known (or similar) threats and involves first-hand exposure to danger, which inevitably poses a risk of harm. We discuss how individuals leverage a rich repertoire of mnemonic processes that operate largely in safety and significantly expand our ability to recognize danger beyond Pavlovian threat associations. These processes result in complementary memories - acquired individually or through social interactions - that represent potential threats and the relational structure of our environment. The interplay between these memories allows danger to be inferred rather than directly learned, thereby flexibly protecting us from potential harm in novel situations despite minimal prior aversive experience.

Neural signature of delayed fear generalization under stress

Although the generalization of fear to stimuli resembling a threatening stimulus is an adaptive mechanism, fear overgeneralization is maladaptive and thought to play a key role in anxiety-related disorders. Since there is typically a delay between an initial fear experience and a situation in which fear (over)generalization may occur, we assessed delayed fear generalization and its neural signature. Moreover, as stress is known to affect fear learning, we further tested whether acute stress modulates fear generalization. Therefore, we conducted a two-day fear generalization study, with initial fear acquisition on Day 1 and a fear generalization test after a 24-hr delay in the MRI scanner. Prior to fear generalization testing, participants were exposed to a stressor or a control manipulation. Our behavioral data showed the expected generalization of fear. At a neural level, fear generalization was accompanied by increased fear-signaling for stimuli that resembled the conditioned stimulus in the bilateral insula and frontal operculum, whereas activity declined in frontal, hippocampal, and temporal regions, including the ventromedial prefrontal cortex, as stimuli became more similar to the conditioned stimulus. Importantly, stress did not modulate fear generalization, neither on a behavioral nor on a neural level. Interestingly, in an explorative comparison to two other studies that used the same paradigm but tested generalization immediately after acquisition, we observed increased fear generalization in the delayed relative to the immediate generalization test. In sum, our results suggest that stress leaves fear generalization and its neural signature unaffected but that a temporal delay might increase the extent to which fear responses are generalized to stimuli resembling the threatening stimulus.

Generalization of placebo pain relief

ABSTRACT

Efficacy of treatment is heavily dependent on experience and expectations. Moreover, humans can generalize from one experience to a perceptually similar but novel situation. We investigated whether and how this applies to pain relief, using ecologically valid tonic pain stimuli treated by surreptitiously lowering the applied temperature. Using different face cues, participants experienced better treatment from one physician than another. Participants were then tested on 6 additional face cues perceptually lying between both faces. Our data from 2 independent samples (N = 18 and N = 39) show a treatment experience effect, ie, for physically identical treatments, the initially superior physician was reported to deliver stronger pain relief. More importantly, the other faces on the perceptual continuum showed a graded effect of pain relief, indicating placebo generalization. Introducing a paradigm feasible to induce placebo pain relief, we show that the generic learning principle of generalization can explain carryover effects between learned and novel treatment situations.