Tom Smeets

True or false? Memory is differentially affected by stress-induced cortisol elevations and sympathetic activity at consolidation and retrieval

Adrenal stress hormones released in response to acute stress may yield memory-enhancing effects when released post-learning and impairing effects at memory retrieval, especially for emotional memory material. However, so far these differential effects of stress hormones on the various memory phases for neutral and emotional memory material have not been demonstrated within one experiment. This study investigated whether, in line with their effects on true memory, stress and stress-induced adrenal stress hormones affect the encoding, consolidation, and retrieval of emotional and neutral false memories. Participants (N=90) were exposed to a stressor before encoding, during consolidation, before retrieval, or were not stressed and then were subjected to neutral and emotional versions of the Deese-Roediger-McDermott word list learning paradigm. Twenty-four hours later, recall of presented words (true recall) and non-presented critical lure words (false recall) was assessed. Results show that stress exposure resulted in superior true memory performance in the consolidation stress group and reduced true memory performance in the retrieval stress group compared to the other groups, predominantly for emotional words. These memory-enhancing and memory-impairing effects were strongly related to stress-induced cortisol and sympathetic activity measured via salivary alpha-amylase levels. Neutral and emotional false recall, on the other hand, was neither affected by stress exposure, nor related to cortisol and sympathetic activity following stress. These results demonstrate the importance of stress-induced hormone-related activity in enhancing memory consolidation and in impairing memory retrieval, in particular for emotional memory material.

The Effectiveness of Tailored Feedback and Action Plans in an Intervention Addressing Multiple Health Behaviors

Purpose. Examine the effects of three iterative tailored feedback letters addressing smoking; physical activity; and fruit, vegetable, and fat intake, and test the additional effects of providing feedback on action plans. Design. A tailored, print-based intervention was developed and tested in a randomized control trial with a posttest after 9 months. Setting. A total of 2827 respondents agreed to participate. They were recruited from a random sample of 35,000 addresses obtained through the Dutch national telephone company. Subjects. The mean age was 49 years, and 55% were female. Intervention. The experimental group received three printed tailored letters, and the control group received three printed generic letters. Respondents from the experimental group randomly received either a third letter with tailored information or tailored information and action-planning feedback. Measures. The questionnaire assessed physical activity; smoking; consumption of fruit, vegetables and fat; motivational determinants; action plans; and demographics. Results. Tailored information resulted in more improvement over time than generic information for the intake of fruit, vegetables, and fat and for physical activity. No differences between the conditions were found for smoking because of high cessation rates in all conditions. Action-planning feedback did not increase the effects. Conclusions. Tailored lifestyle information can be effective for adults in changing nutrition behavior and physical activity.

Self-reported trauma, cortisol levels, and aggression in psychopathic and non-psychopathic prison inmates

The relationship between self-reported traumatic childhood experiences, cortisol levels, aggression, and psychopathy was investigated in prison inmates (n=47) and healthy controls (n=27). Besides questionnaires, a brief salivary diurnal profile was measured. Results show that criminals (both psychopaths and non-psychopaths) demonstrate more traumatic childhood experiences than the control group. Within the group of criminals, psychopaths showed the lowest diurnal cortisol concentrations, whereas the non-psychopaths demonstrated highest daily average cortisol (DAC) scores. High levels of aggression were related to traumatic childhood experiences in non-psychopaths and control participants, but not in psychopaths. Although psychopathic offenders demonstrated low levels of cortisol, high levels of childhood traumatic experiences and high levels of aggression, cortisol was not a mediating factor between childhood traumatic experiences and aggression. Implications of the finding that psychopathic offenders displayed lower and non-psychopaths showed higher daily cortisol levels are discussed.

Social cognition under stress: Differential effects of stress-induced cortisol elevations in healthy young men and women

Humans as social beings often have to perform complex social cognitive tasks while under stress (e.g., during a social conflict). Previous research has established that the brain regions responsible for social cognitive tasks are target regions for stress hormones. However, little experimental research has been done testing the acute effects of stress on social cognition. Here, we investigated whether stress exposure and the ensuing glucocorticoid (i.e., cortisol) elevations affect social cognition. Thirty-two men and 32 women were exposed to either a psychosocial stress or a non-stressful control test before assessing their social cognition using the Reading the Mind in the Eyes Test (RMET) and the Movie for the Assessment of Social Cognition (MASC). Results showed differential effects of stress-induced cortisol responses among men and women for the MASC, but not the RMET. Among men, high cortisol responders displayed elevated MASC scores compared with low cortisol responders. Moreover, for stressed men a positive association between the magnitude of the cortisol responses to the stressor and MASC scores emerged. Among women, enhanced MASC scores were found for low cortisol responders relative to high cortisol responders and non-stressed controls. A strong negative association between cortisol reactivity and MASC scores was found among women. These results imply sex specific effects of glucocorticoids on social cognition and partially support the idea of sex differences in biobehavioral stress responses, with men engaging in fight-or-flight responses while women may react to stress with tending and befriending behavior.

Stress selectively and lastingly promotes learning of context-related high arousing information

The secretion of adrenal stress hormones in response to acute stress is known to affect learning and memory, particularly for emotionally arousing memory material. Here, we investigated whether stress-induced modulation of learning and memory performance depends on (i) the conceptual relatedness between the material to be learned/remembered and the stressor and (ii) the timing of stress exposure versus learning phase. Participants learned stressor-related and stressor-unrelated words of varying arousal 1h prior to, immediately following, or 2h after exposure to the Trier Social Stress Test (all groups n=16). Twenty-four hours later, delayed free recall was assessed. Cortisol and alpha-amylase were sampled to evaluate if concurrent stress-induced raised glucocorticoid levels and high adrenergic activity are implicated in modulating learning performance. Our results demonstrate that immediate and delayed post-stress learning selectively enhanced the learning and delayed recall of stressor-related high arousing words. This enhancing effect was strongly associated with concurrent stress-induced cortisol and sympathetic activity. Our data suggest that when to-be-learned information is conceptually related to a stressor and considered important (i.e., arousing) by the individual, learning under stressful circumstances results in improved memorability afterwards.

Adaptive Memory: Survival Processing Increases Both True and False Memory in Adults and Children.

Research has shown that processing information in a survival context can enhance the informations memorability. The current study examined whether survival processing can also decrease the susceptibility to false memories and whether the survival advantage can be found in children. In Experiment 1, adults rated semantically related words in a survival, moving, or pleasantness scenario. Even though the survival advantage was demonstrated for true recall, there also was an unexpected increase in false memories in the survival condition. Similarly, younger and older children in Experiment 2 displayed superior true recall but also higher rates of false memories in a survival condition. Experiment 3 showed that in adults false memories were also more likely to occur in the survival condition when categorized lists instead of Deese-Roediger-McDermott (DRM)-like word lists were used. In all three experiments, no survival recall advantage was found when net accuracy scores that take the total output into account were used. These findings question whether survival processing is an adaptive memory strategy per se, as such processing not only enriches true recall but simultaneously amplifies the vulnerability to false memories.

Picturing survival memories: Enhanced memory after fitness-relevant processing occurs for verbal and visual stimuli

Recent studies have shown that processing words according to a survival scenario leads to superior retention relative to control conditions. Here, we examined whether a survival recall advantage could be elicited by using pictures. Furthermore, in Experiment 1, we were interested in whether survival processing also results in improved memory for details. Undergraduates rated the relevance of pictures in a survival, moving, or pleasantness scenario and were subsequently given a surprise free recall test. We found that survival processing yielded superior retention. We also found that distortions occurred more often in the survival condition than in the pleasantness condition. In Experiment 2, we directly compared the survival recall effect between pictures and words. A comparable survival recall advantage was found for pictures and words. The present findings support the idea that memory is enhanced by processing information in terms of fitness value, yet at the same time, the present results suggest that this may increase the risk for memory distortions.

A randomized trial on mineralocorticoid receptor blockade in men: effects on stress responses, selective attention, and memory

Corticosteroids, released in high amounts after stress, exert their effects via two different receptors in the brain: glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs). GRs have a role in normalizing stress-induced effects and promoting consolidation, while MRs are thought to be important in determining the threshold for activation of the hypothalamic–pituitary–adrenal (HPA) axis. We investigated the effects of MR blockade on HPA axis responses to stress and stress-induced changes in cognitive function. In a double-blind, placebo-controlled study, 64 healthy young men received 400 mg of the MR antagonist spironolactone or placebo. After 1.5 h, they were exposed to either a Trier Social Stress Test or a non-stressful control task. Responses to stress were evaluated by hormonal, subjective, and physiological measurements. Afterwards, selective attention, working memory, and long-term memory performance were assessed. Spironolactone increased basal salivary cortisol levels as well as cortisol levels in response to stress. Furthermore, spironolactone significantly impaired selective attention, but only in the control group. The stress group receiving spironolactone showed impaired working memory performance. By contrast, long-term memory was enhanced in this group. These data support a role of MRs in the regulation of the HPA axis under basal conditions as well as in response to stress. The increased availability of cortisol after spironolactone treatment implies enhanced GR activation, which, in combination with MR blockade, presumably resulted in a decreased MR/GR activation ratio. This condition influences both selective attention and performance in various memory tasks.

Context-dependent enhancement of declarative memory performance following acute psychosocial stress

Studies on how acute stress affects learning and memory have yielded inconsistent findings, with some studies reporting enhancing effects while others report impairing effects. Recently, Joëls et al. [Joëls, M., Pu, Z., Wiegert, O., Oitzl, M.S., Krugers, H.J., 2006. Learning under stress: how does it work? Trends in Cognitive Sciences, 10, 152-158] argued that stress will enhance memory only when the memory acquisition phase and stressor share the same spatiotemporal context (i.e., context-congruency). The current study tested this hypothesis by looking at whether context-congruent stress enhances declarative memory performance. Undergraduates were assigned to a personality stress group (n=16), a memory stress group (n=18), or a no-stress control group (n=18). While being exposed to the acute stressor or a control task, participants encoded personality- and memory-related words and were tested for free recall 24h later. Relative to controls, stress significantly enhanced recall of context-congruent words, but only for personality words. This suggests that acute stress may strengthen the consolidation of memory material when the stressor matches the to-be-remembered information in place and time.

Introducing the Maastricht Acute Stress Test (MAST): a quick and non-invasive approach to elicit robust autonomic and glucocorticoid stress responses

Stress-related research has employed several procedures to activate the human stress system. Two of the most commonly used laboratory paradigms are the Trier Social Stress Test (TSST) and the Cold Pressor Test (CPT). We combined their most stressful features to create a simple laboratory stress test capable of eliciting strong autonomic and glucocorticoid stress responses. In comparison with the CPT and its variations, our stress tool (labeled the Maastricht Acute Stress Test; MAST) was found to yield superior salivary cortisol responses, while being equally effective in eliciting subjective stress reactions and (systolic and diastolic) blood pressure increases (study 1; N=80). In study 2 (N=20), we directly compared the effectiveness of the MAST and TSST and found that both methods elicited similar subjective, salivary alpha-amylase, and salivary cortisol stress responses. Finally, we developed and evaluated an appropriate no-stress control version of the MAST that was similar to the stress version, although it did not comprise stressful components (study 3; N=40). Collectively, our results confirm the effectiveness of the MAST in terms of subjective, autonomic, and--most importantly--glucocorticoid stress responses. Thus, as a brief and simple stress protocol, the MAST holds considerable promise for future research.