The effects of hydrocortisone and yohimbine on human behavior in approach-avoidance conflicts

RATIONALE

Balancing approach of positive and avoidance of negative stimuli is essential when faced with approach-avoidance conflicts, e.g., situations with both positive and negative outcomes. This balance is disturbed in several mental disorders, e.g., excessive avoidance in anxiety disorders, and heightened approach in substance use disorders. Since stress is assumed to impact these disorders' etiology and maintenance, it seems crucial to understand how stress influences behavior in approach-avoidance conflicts. Indeed, some studies suggested altered approach-avoidance behavior under acute stress, but the mechanism underlying these effects is unknown.

OBJECTIVES

Investigate how the pharmacological manipulation of major stress mediators (cortisol and noradrenaline) influences task-based approach-avoidance conflict behavior in healthy individuals.

METHODS

Ninety-six participants (48 women, 48 men) received either 20mg hydrocortisone, 20mg yohimbine, both, or placebo before performing a task targeting foraging under predation in a fully crossed double-blind between-subject design. Moreover, we investigated effects of gender and endogenous testosterone and estradiol levels on approach-avoidance behavior.

RESULTS

While biological stress markers (cortisol concentration, alpha amylase activity) indicated successful pharmacological manipulation, behavior in approach-avoidance conflicts was not affected as expected. Although yohimbine administration affected risky foraging latency under predation, we found no main effect of hydrocortisone or their interaction on behavior. In contrast, we found gender differences for almost all behavioral outcome measures, which might be explained by differences in endogenous testosterone levels.

CONCLUSIONS

The investigated major stress mediators were not sufficient to imitate previously shown stress effects on approach-avoidance conflict behavior. We discuss potential reasons for our findings and implications for future research.

Neuroendocrine response to a psychosocial stress test is not related to schizotypy but cortisol elevation predicts inflexibility of semantic memory retrieval

An altered stress response can contribute to the transition from preclinical psychotic symptoms to the clinical manifestation of schizophrenia and other psychotic disorders. The present study was aimed at testing the hypotheses that (i) the autonomic and neuroendocrine responses under psychosocial stress are dysregulated in individuals with high psychosis proneness (schizotypy); (ii) the magnitude of post-stress autonomic activation and cortisol release predicts alterations in semantic memory retrieval. The study was performed in 73 healthy individuals of both sexes with either high or low schizotypal traits preselected out of 609 individuals using the Schizotypal Personality Questionnaire. A psychosocial stress procedure based on public speech was used as a stress model. We found that individuals with high schizotypy engaged in less adaptive emotional stress-coping strategies than low schizotypy individuals. Yet, the neuroendocrine, immune, and sympathetic activation in response to the stress test was not different between the groups. Irrespective of the exposure to the stressor, individuals with high schizotypy were less fluent when retrieving associations from semantic memory. In addition, we demonstrated that acute psychosocial stress reduced the flexibility of semantic memory retrieval. The post-stress mental inflexibility was reliably predicted by the concomitant elevation of cortisol concentrations in saliva. The present study thus brings novel evidence indicating that the acute psychosocial challenge impairs retrieval flexibility in the semantic domain, which may be due to neuroendocrine activation.

On making (and turning adaptive to) maladaptive aversive memories in laboratory rodents

Fear conditioning and avoidance tasks usually elicit adaptive aversive memories. Traumatic memories are more intense, generalized, inflexible, and resistant to attenuation via extinction- and reconsolidation-based strategies. Inducing and assessing these dysfunctional, maladaptive features in the laboratory are crucial to interrogating posttraumatic stress disorder's neurobiology and exploring innovative treatments. Here we analyze over 350 studies addressing this question in adult rats and mice. There is a growing interest in modeling several qualitative and quantitative memory changes by exposing already stressed animals to freezing- and avoidance-related tests or using a relatively high aversive training magnitude. Other options combine aversive/fearful tasks with post-acquisition or post-retrieval administration of one or more drugs provoking neurochemical or epigenetic alterations reported in the trauma aftermath. It is potentially instructive to integrate these procedures and incorporate the measurement of autonomic and endocrine parameters. Factors to consider when defining the organismic and procedural variables, partially neglected aspects (sex-dependent differences and recent vs. remote data comparison) and suggestions for future research (identifying reliable individual risk and treatment-response predictors) are discussed.

A systematic review of the pharmacological modulation of autobiographical memory specificity

Background

Over-general autobiographical memory (AM) retrieval is proposed to have a causal role in the maintenance of psychological disorders like depression and PTSD. As such, the identification of drugs that modulate AM specificity may open up new avenues of research on pharmacological modeling and treatment of psychological disorders.

Aim

The current review summarizes randomized, placebo-controlled studies of acute pharmacological modulation of AM specificity.

Method

A systematic search was conducted of studies that examined the acute effects of pharmacological interventions on AM specificity in human volunteers (healthy and clinical participants) measured using the Autobiographical Memory Test.

Results

Seventeen studies were identified (986 total participants), of which 16 were judged to have low risk of bias. The presence and direction of effects varied across drugs and diagnostic status of participants (clinical vs. healthy volunteers). The most commonly studied drug-hydrocortisone-produced an overall impairment in AM specificity in healthy volunteers [g = -0.28, CI (-0.53, -0.03), p = 0.03], although improvements were reported in two studies of clinical participants. In general, studies of monoamine modulators reported no effect on specificity.

Conclusion

Pharmacological enhancement of AM specificity is inconsistent, although monaminergic modulators show little promise in this regard. Drugs that reduce AM specificity in healthy volunteers may be useful experimental-pharmacological tools that mimic an important transdiagnostic impairment in psychological disorders.

Systematic review registration

PROSPERO, identifier CRD42020199076, https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020199076.

Interactions of Noradrenergic, Glucocorticoid and Endocannabinoid Systems Intensify and Generalize Fear Memory Traces

Systemic administration of drugs that activate the noradrenergic or glucocorticoid system potentiates aversive memory consolidation and reconsolidation. The opposite happens with the stimulation of endocannabinoid signaling under certain conditions. An unbalance of these interacting neurotransmitters can lead to the formation and maintenance of traumatic memories, whose strength and specificity attributes are often maladaptive. Here we aimed to investigate whether originally low-intensity and precise contextual fear memories would turn similar to traumatic ones in rats systemically administered with adrenaline, corticosterone, and/or the cannabinoid type-1 receptor antagonist/inverse agonist AM251 during consolidation or reconsolidation. The high dose of each pharmacological agent evaluated significantly increased freezing times at test in the conditioning context one and nine days later when given alone post-acquisition or post-retrieval. Their respective low dose produced no relative changes when given separately, but co-treatment of adrenaline with corticosterone or AM251 and the three drugs combined, but not corticosterone with AM251, produced results equivalent to those mentioned initially. Neither the high nor the low dose of adrenaline, corticosterone, or AM251 altered freezing times at test in a novel, neutral context two and ten days later. In contrast, animals receiving the association of their low dose exhibited significantly higher freezing times than controls. Together, the results indicate that newly acquired and destabilized threat memory traces become more intense and generalized after a combined interference acting synergistically and mimicking that reported in patients presenting stress-related psychiatric conditions.

Stress-induced bias of multiple memory systems during retrieval depends on training intensity

Stressful events promote a shift from hippocampus-dependent 'cognitive' learning towards dorsal striatum-dependent 'habit' learning. Beyond modulating the recruitment of multiple memory systems during learning, recent evidence suggests that stress may also affect which of these memory systems is employed during retrieval, thereby affecting the nature of remembering. However, while some studies reported increased reliance on 'habit' memory retrieval after stress, other studies suggested even a bias towards 'cognitive' memory retrieval after stress. In the present experiment, we tested the hypothesis that the nature of the stress effect on the control of memory retrieval depends on the extent of initial training. To this end, participants completed a probabilistic classification learning (PCL) task that can be solved by both the 'cognitive' and the 'habit' memory systems, which is reflected in the engagement of specific behavioral strategies. Critically, participants received either moderate (100 trials) or intensive (200 trials) training in the PCL task. Participants then underwent a stress protocol or a non-stressful control procedure, before they completed a retrieval version of the PCL task. The effectiveness of the stress manipulation was verified by increases in salivary cortisol and autonomic arousal. Our results further revealed that participants who received moderate training showed, during retrieval, a stress-induced shift towards strategies indicative of the dorsal striatal 'habit' memory system. After prolonged training, however, stress did not affect which memory system guided retrieval. The present results indicate that the effect of stress on the engagement of multiple memory systems during retrieval is critically dependent on the extent of initial training and, by inference, on the strength of the multiple memory traces established during learning.

Noradrenergic stimulation increases fear memory expression

Fear responses are typically not limited to the actual threatening stimulus but generalize to other stimuli resembling the threatening stimulus. Although this fear generalization is generally adaptive, fear overgeneralization is maladaptive and assumed to contribute to anxiety disorders. Despite the clinical relevance of fear (over)generalization, how the extent of fear generalization is modulated remains not well understood. Based on the known effects of stress on learning and memory, we tested here the impact of major stress mediators, glucocorticoids and noradrenergic arousal, on fear generalization. In a laboratory-based, placebo-controlled, double-blind, between-subject design, 125 healthy participants first underwent a fear conditioning procedure. About 24 h later, participants received orally either a placebo, hydrocortisone, the α2-adrenoceptor antagonist yohimbine, leading to increased noradrenergic stimulation, or both drugs before a test of fear generalization. Skin conductance responses as well as explicit rating data revealed that yohimbine intake led to enhanced fear memory expression, i.e. an enhanced responding to the CS+ but not to stimuli resembling the CS+. Moreover, neither enhanced safety learning nor a mere enhancement of perceptual discrimination ability could explain this result. In contrast to yohimbine, hydrocortisone had no significant effect on fear memory. These findings suggest that noradrenergic arousal strengthens fear memory expression and have important implications for mental disorders in which the overgeneralization of conditioned fear is prominent.

Stress-induced modulation of multiple memory systems during retrieval requires noradrenergic arousal

Stress has been shown to favor dorsal striatum-dependent 'habit' memory over hippocampus-dependent 'cognitive' memory during learning. Here, we investigated whether stress may modulate the engagement of these 'cognitive' and 'habit' systems also during memory retrieval and if so, whether such a stress-induced shift in the control of memory retrieval depends on noradrenergic activation. To this end, participants acquired a probabilistic classification learning (PCL) task that can be solved by both the 'cognitive' and the 'habit' system, reflected in the distinct behavioral strategies. Twenty-four hours later, participants received either the beta-adrenergic receptor antagonist propranolol or a placebo before they underwent a psychosocial stressor or a non-stressful control manipulation, followed by a retrieval version of the PCL task. Overall, participants showed a practice-dependent shift from 'cognitive' to 'habit' memory. Stressed participants that had received a placebo fell back to a 'cognitive' strategy during retrieval, which was linked to an impairment in retrieval performance. Propranolol blocked this stress-induced shift towards the less efficient strategy. Moreover, our results showed that salivary cortisol was related to the retrieval strategy only when paralleled by increased autonomic arousal. Together, these results indicate that stress effects on the modulation of multiple memory system during retrieval necessitate noradrenergic arousal, with relevant implications for retrieval performance under stress.

Stress-induced cortisol modulates the control of memory retrieval towards the dorsal striatum

Stress can modulate the recruitment of multiple memory systems during learning, favouring dorsal striatal "habit" learning over hippocampal "cognitive" learning. Here, we tested whether stress may also bias the engagement of "cognitive" and "habit" systems during retrieval and thereby affect the nature of remembering. To this end, participants first performed a probabilistic classification learning task that can be solved by both the "cognitive" and the "habit" system. Twenty-four hours later, participants underwent either a stress manipulation or a non-stressful control procedure before they completed a retention test for the previously learned task in the MRI scanner. During this retention test, stress-induced cortisol levels were linked to a relative bias towards behavioural strategies indicative for the "habit" system. At the neural level, stress led to increased dorsal striatal activity during retrieval. Elevated cortisol levels were directly correlated with increased activity in the dorsal striatum and further linked to reduced functional connectivity between the hippocampus and the amygdala, which is assumed to orchestrate the stress-related shift from "cognitive" to "habitual" control. Together, our data suggest that stress may bias the contributions of multiple memory systems also at retrieval, in a manner that promotes dorsal striatal "habit" processes and most likely driven by cortisol.