Socially Evaluated Cold Pressor Test Research Articles

Non-instrumental information seeking is resistant to acute stress

Previous research has shown that people intrinsically value non-instrumental information, which cannot be used to change the outcome of events, but only provides an early resolution of uncertainty. This is true even for information about rather inconsequential events, such as the outcomes of small lotteries. Here we investigated whether participants’ willingness to pay for non-instrumental information about the outcome of simple coin-flip lotteries with guaranteed winnings was modulated by acute stress. Stress was induced using the Socially Evaluated Cold Pressor Test (SECPT), and information-seeking choices were compared to a warm water control group. Our results neither support the hypothesis that stress decreases information-seeking by directing cognitive resources away from the relevance of the lotteries, nor the opposite hypothesis that stress increases information-seeking by driving anxiety levels up. Instead, we found that despite successful stress induction, as evidenced by increased saliva cortisol levels in the SECPT group, information valuation was remarkably stable. This finding is in line with recent findings that experimentally increased state anxiety did not modulate non-instrumental information seeking. Together, these results suggest that the aversiveness of “not knowing” is a stable cognitive state and not easily modulated by situational context, such as acute stress.

Psychological distress modulates dorsal anterior cingulate cortex responses to salient stimuli in obsessive-compulsive disorder

BackgroundPatients with obsessive-compulsive disorder (OCD) experience an exacerbation of symptoms under psychological distress. The neurobiological underpinnings of this effect of stress remain elusive. Here, we induced psychological distress to explore its effect on neural reactivity of the salience network during a symptom provocation task. MethodsTwenty-three patients with OCD and twenty-three healthy volunteers underwent functional magnetic resonance imaging scanning after stress induction and a control condition in a cross-over design. Psychological distress was induced using the socially evaluated cold pressor test (SECPT) and neural responses were measured during a symptom provocation task. ResultsOCD participants showed a blunted cortisol response to the stressor. We found a group by stress interaction effect in the dorsal anterior cingulate cortex (dACC), such that psychological distress reduced dACC reactivity to emotionally salient pictures in OCD participants, whereas it increased dACC reactivity in healthy controls. LimitationsA considerable proportion of OCD participants was on medication, and the neuroimaging session was conducted more than 1 h after the initial stressor. ConclusionsConsidering this timeline, we speculate that the blunted dACC reactivity towards emotionally salient pictures in OCD participants may reflect impaired emotion regulation in the aftermath of stress.

Time of day differences in appetite and gut hormone responses to meal and stress challenges in adults with normal-weight and obesity

BackgroundLifestyle factors like time of eating and stress exposure may impact physiology to promote excess weight gain. To understand behavioral and physiological mechanisms underlying these potential effects, we compared appetite and gut hormone responses to a series of meal and stress challenges beginning in the morning and the afternoon, in adults with normal-weight and obesity. MethodThirty-two adults (16 with normal-weight, 16 with obesity) underwent the same test protocol on different days, each following an 8 h fast. On one day the protocol began in the morning (AM condition); on the other day it began in the late afternoon (PM condition). On each day they first received a standardized liquid meal (9:00am/4:00pm), then a stress test (Socially-Evaluated Cold Pressor Test, 11:10am/6:10pm), then an ad libitum buffet meal (11:40am/6:40pm). Appetite and stress ratings were obtained, and blood was drawn for measures of ghrelin, PYY, GLP-1, insulin, glucose, cortisol and leptin. Acetaminophen was administered as a tracer to assess gastric emptying of the liquid meal. ResultsAcross all three challenges, AUC cortisol was lower in the PM vs. AM condition (all p<.001), and AUC insulin and leptin were higher in the obesity vs. normal-weight group (all p<.001). For the standardized liquid meal only, AUC hunger, desire to eat and ghrelin were greater in the PM vs. AM condition (all p<0.05), and AUC ghrelin was lower in the obesity vs. normal-weight group, even when controlling for baseline values (p<0.05). AUC glucose was higher in the evening for the normal-weight group only (condition x group interaction p<0.05). Post-liquid meal gastric emptying as indexed by AUC acetaminophen was slower in the PM vs. AM (p<.01). For the stress test, AUC cortisol was lower in the PM than the AM condition even when controlling for baseline values (p<.05). AUC leptin was lower in the evening in the obesity group only (condition x group interaction p<0.01). PYY showed an acute decrease post-stressor in the normal-weight but not the obesity group (p<.05). Post-stress ad libitum buffet meal intake was similar in the evening and morning conditions, and higher in the obesity group (p<0.05). Only among the obesity group in the evening condition, higher stressor-associated stress and cortisol were associated with greater meal-associated appetite (p<0.05). ConclusionsNormal-weight individuals and those with obesity may be at risk of evening overeating as a result of differential appetite and gut hormone responses following meal intake and stress exposure.

Acute social and somatic stress alters cortical metaplasticity probed with non-invasive brain stimulation in humans

Studying the neuronal mechanisms that govern the cortical adaptations to acute stress is critical for understanding the development of neuropsychiatric diseases. Homeostatic plasticity stabilizes the neural activity in which a previous synaptic event drives subsequent synaptic plasticity. In this study, we evaluated the effect of acute stress induced with the socially evaluated cold pressor test (SECPT) on cortical metaplasticity in humans using a non-invasive brain stimulation protocol.After being exposed to the SECPT and control stress conditions, 30 healthy participants were tested for cortical metaplasticity assessed with changes in the amplitude of the motor evoked potential (MEP) induced by a single-pulse transcranial magnetic stimulation (TMS). Cortical metaplasticity was induced by combining priming with cathodal tDCS (cTDCS) followed by a sub-threshold 1-Hz repetitive stimulation (rTMS) test session.Our results showed that SECPT induced cardiovascular adaptations (increase in systolic, diastolic blood pressure, and heart rate), indicating that SECPT effectively induced acute stress. Also, in our experiments stimulation of subjects with 1-Hz rTMS after they had undergone the SECPT condition induced inhibition of MEP whereas 1-Hz rTMS administered after the control condition induced a facilitatory (physiologic) response pattern.Here we observed that acute stress impairs homeostatic metaplasticity. The dysfunctional regulation of cortical plastic changes after stress could play a pivotal role in the pathogenesis of neurological and psychiatric diseases.

Examining the effect of stress induction on auditory working memory performance for emotional and non-emotional stimuli in female students

BackgroundTheoretical frameworks have shown that stress might influence working memory in different ways. Previous research has investigated the effect of stress on female's working memory but there is lack of evidence regarding the impact of emotional aspects. ObjectivesThis study examined the effect of stress induction on auditory working memory (AWM) performance among university students for emotional (positive and negative) and non-emotional (neutral) stimuli. MethodsA sample of 102 female students at the Universities of Isfahan, Iran was selected using convenience sampling in 2018. Participants completed the demographic information sheets, then, they were randomly assigned into the experimental and control groups. The stress was induced by the Socially Evaluated Cold Pressor Test (SECPT). An n-back task was presented pre and post of stress induction, to evaluate the AWM performance (accuracy and reaction time). The research data were analyzed using mixed-model ANOVA. ResultsBoth accuracy and reaction time (RT) scores were found to be enhanced for positive words in the experimental condition. However, accuracy and RT indices were found to be worsening for negative words in the experimental condition. ConclusionsThis study supports the idea that stress influences AWM performance depend on emotionally-valenced stimuli, which may help us to better understand the underlying mechanisms of memory processing.

Twenty-five years later: A systematic review of the methodological changes in the Trier Social Stress Test and its confounding variables

The neuro-physiological response to stress has far-reaching implications for learning and memory processes. Here, we examined whether and how the stress-induced release of cortisol, following the socially-evaluated cold pressor test, influenced the acquisition of preferences in an evaluative conditioning (EC) procedure. We found that when the stressor preceded the evaluation phase, cortisol responders showed decreased evaluative conditioning effects. By contrast, impairing effects of a stressor-induced cortisol release before encoding were not found. Moreover, explicit memory was not found to be affected by the stressor or its timing. Implications of the timing-dependent effects of stress-induced cortisol release on EC and the relation between stress and associative memory are discussed.

Associations between Attention and Implicit Associative Learning in Healthy Adults: The Role of Cortisol and Salivary Alpha-Amylase Responses to an Acute Stressor.

In this study, we investigated the associations between implicit associative learning with the cortisol and salivary alpha-amylase (sAA) stress response to an acute stressor as well as their associations with attention. Eighty one healthy adults (25 male) participated and either performed the socially evaluated cold-pressor test (SECPT) or a warm-water control task (WWT). Either prior to or immediately after the SECPT/WWT, participants implicitly learned digit-symbol pairs. A not-previously announced recall test was conducted about 20 min after the SECPT/WWT. Attention was assessed by means of a Stroop task at nine time points over the course of the experiment. Memory recall performance was not significantly associated with the acquisition time point (pre or post stressor) and did not significantly differ between the responder groups (i.e., non-responders, sAA-and-cortisol responders, only sAA responders, and only cortisol responders). Attentional performance increased throughout the experiment (i.e., reaction times in the Stroop task decreased). No differences in the attentional time course were found between the responder groups. However, some associations were found (puncorrected < 0.05) that did not pass the multiple comparison adjusted alpha level of αadjusted = 0.002, indicating different associations between attention and implicit learning between the responder groups. We conclude that the associations of sAA and cortisol responses with implicit learning are complex and are related to each other. Further studies in which both (sAA and cortisol responses) are selectively (de-) activated are needed. Furthermore, different learning tasks and less—potentially stressful—attentional assessments should be used in future research. Moreover, field studies are needed in which the associations between acute stress and implicit associative learning are investigated in everyday life.

Acute stress affects implicit but not explicit motor imagery: A pilot study

Motor imagery (MI) is the capacity to mentally perform one or a set of movements without concomitant overt action. MI training has been show to enhance the subsequent motor performance. While the benefits of MI to manage stress have been extensively documented, the reverse impact of stress on MI received far less attention. The present study thus aimed to evaluate whether acute stress might influence MI abilities. Thirty participants were assigned either to a stress or a control group. The Socially Evaluated Cold Pressor Test (SECPT) was used to induce stress, with heart rate, electrodermal activity, salivary cortisol, and self-report perceived levels of stress being monitored during the experiment. Stress induction was followed by both implicit (laterality judgment) and explicit (sequential pointing) MI tasks. Main results showed a deleterious impact of stress on implicit MI, while explicit MI was not altered. These exploratory findings provide a deeper understanding of stress effects on cognition, and practically support that under stressful conditions, as during a sport competition or rehabilitation contexts, explicit MI should be prioritized.

The timing-dependent effects of stress-induced cortisol release on evaluative conditioning

The neuro-physiological response to stress has far-reaching implications for learning and memory processes. Here, we examined whether and how the stress-induced release of cortisol, following the socially-evaluated cold pressor test, influenced the acquisition of preferences in an evaluative conditioning (EC) procedure. We found that when the stressor preceded the evaluation phase, cortisol responders showed decreased evaluative conditioning effects. By contrast, impairing effects of a stressor-induced cortisol release before encoding were not found. Moreover, explicit memory was not found to be affected by the stressor or its timing. Implications of the timing-dependent effects of stress-induced cortisol release on EC and the relation between stress and associative memory are discussed.

Evidence for impaired extinction learning in humans after distal stress exposure.

Stressful or traumatic events can be risk factors for anxiety or trauma- and stressor-related disorders. In this regard, it has been shown that stress affects aversive learning and memory processes. In rodents, stress exposure 10days prior to fear acquisition impairs fear extinction. However, in humans the effect of distal stress on fear conditioning is sparse. Therefore, we examined the influence of distal stress on fear memory in humans in two studies. In Study 1, participants underwent either socially evaluated cold-pressor test (SECPT) or sham procedure 10days or 40min before a fear conditioning paradigm (four groups, N=78). In Study 2, context effects were examined by conducting SECPT and sham procedures 10days prior conditioning either in the later fear conditioning context or in another context (three groups, N=69). During acquisition phase, one geometrical shape (conditioned stimulus, CS+) was paired with painful electric shocks (unconditioned stimulus, US), but never a second shape (CS-). Extinction phase was identical to acquisition, but without US delivery. Importantly, for Study 1 these phases were conducted on one day, while for Study 2 on two separated days. Successful fear acquisition was indicated by aversive ratings and startle potentiation to CS+ versus CS- in both studies. Interestingly, participants stressed 10days earlier showed impaired extinction on the implicit level (startle potentiation to CS+ vs. CS-) in Study 1 and only in the acquisition context on the explicit level (aversive ratings for CS+ vs. CS-) in Study 2. In sum, distal stress may strengthen later acquired fear memories and thereby impair fear extinction. This finding could have clinical implications, showing that prior stress exposure sensitizes later aversive processing and impairs therapy.

How acute stress may enhance subsequent memory for threat stimuli outside the focus of attention: DLPFC-amygdala decoupling

Stress-related disorders, e.g., anxiety and depression, are characterized by decreased top-down control for distracting information, as well as a memory bias for threatening information. However, it is unclear how acute stress biases mnemonic encoding and leads to prioritized storage of threat-related information even if outside the focus of attention. In the current study, healthy adults (N = 53, all male) were randomly assigned to stress induction using the socially evaluated cold-pressor test (SECPT) or a control condition. Participants performed a task in which they were required to identify a target letter within a string of letters that were either identical to the target and thereby facilitating detection (low distractor load) or mixed with other letters to complicate the search (high load). Either a fearful or neutral face was presented on the background, outside the focus of attention. Twenty-four hours later, participants were asked to perform a surprise recognition memory test for those background faces. Stress induction resulted in increased cortisol and negative subjective mood ratings. Stress did not affect visual search performance, however, participants in the stress group showed stronger memory compared to the control group for fearful faces in the low attentional load condition. Critically, the stress induced memory bias was accompanied by decoupling between amygdala and DLFPC during encoding, which may represent a mechanism for decreased ability to filter task-irrelevant threatening background information. The current study provides a potential neural account for how stress can produce a negative memory bias for threatening information even if presented outside the focus of attention. Despite of an adaptive advantage for survival, such tendencies may ultimately also lead to generalized fear, a possibility requiring additional investigation.

Stress-related cortisol responsivity modulates prospective memory.

It is known that there is inter-individual variation in behavioural and physiological stress reactions to the same stressor. The present study aimed to examine the impact of cortisol responsivity on performance in a complex real life-like prospective memory (PM) paradigm by a re-analysis of data published previously, with a focus on the taxonomy of cognitive dimensions of PM. Twenty-one male subjects were stressed with the Socially Evaluated Cold Pressor Test (SECPT) before the planning of intentions. Another group of 20 males underwent a control procedure. Salivary cortisol was measured to assess the intensity of the biological stress response. Additionally, participants rated the subjective experience of stress on a 5-point rating scale. Stressed participants were post-hoc differentiated in high (n=11) and low cortisol responders (n=10). Cortisol niveau differed significantly between the two groups, whereas subjective stress ratings did not. PM performance of low cortisol responders was stable across time and the PM performance of controls declined. High cortisol responders showed a nominally weaker PM retrieval across the early trails and significantly improved only on the last trial. The data demonstrate for the first time that participants with a low cortisol responsivity may benefit from stress exposure before the planning phase of PM. PM performance of high cortisol responders shows a more inconsistent pattern, which may be interpreted in the sense of a recency effect in PM retrieval. Alternatively, high cortisol responses may have a deteriorating effect on PM retrieval, which disappeared on the last trials of the task as a result of the decrease of cortisol levels across time. Importantly, the data also demonstrate that the intensity of cortisol responses does not necessarily correspond to the intensity of the mental experience of stress.

Lost in translation? The potential psychobiotic Lactobacillus rhamnosus (JB-1) fails to modulate stress or cognitive performance in healthy male subjects

BackgroundPreclinical studies have identified certain probiotics as psychobiotics – live microorganisms with a potential mental health benefit. Lactobacillus rhamnosus (JB-1) has been shown to reduce stress-related behaviour, corticosterone release and alter central expression of GABA receptors in an anxious mouse strain. However, it is unclear if this single putative psychobiotic strain has psychotropic activity in humans. Consequently, we aimed to examine if these promising preclinical findings could be translated to healthy human volunteers. ObjectivesTo determine the impact of L. rhamnosus on stress-related behaviours, physiology, inflammatory response, cognitive performance and brain activity patterns in healthy male participants. MethodsAn 8week, randomized, placebo-controlled, cross-over design was employed. Twenty-nine healthy male volunteers participated. Participants completed self-report stress measures, cognitive assessments and resting electroencephalography (EEG). Plasma IL10, IL1β, IL6, IL8 and TNFα levels and whole blood Toll-like 4 (TLR-4) agonist-induced cytokine release were determined by multiplex ELISA. Salivary cortisol was determined by ELISA and subjective stress measures were assessed before, during and after a socially evaluated cold pressor test (SECPT). ResultsThere was no overall effect of probiotic treatment on measures of mood, anxiety, stress or sleep quality and no significant effect of probiotic over placebo on subjective stress measures, or the HPA response to the SECPT. Visuospatial memory performance, attention switching, rapid visual information processing, emotion recognition and associated EEG measures did not show improvement over placebo. No significant anti-inflammatory effects were seen as assessed by basal and stimulated cytokine levels. ConclusionsL. rhamnosus was not superior to placebo in modifying stress-related measures, HPA response, inflammation or cognitive performance in healthy male participants. These findings highlight the challenges associated with moving promising preclinical studies, conducted in an anxious mouse strain, to healthy human participants. Future interventional studies investigating the effect of this psychobiotic in populations with stress-related disorders are required.

Acute stress selectively impairs learning to act.

Stress interferes with instrumental learning. However, choice is also influenced by non-instrumental factors, most strikingly by biases arising from Pavlovian associations that facilitate action in pursuit of rewards and inaction in the face of punishment. Whether stress impacts on instrumental learning via these Pavlovian associations is unknown. Here, in a task where valence (reward or punishment) and action (go or no-go) were orthogonalised, we asked whether the impact of stress on learning was action or valence specific. We exposed 60 human participants either to stress (socially-evaluated cold pressor test) or a control condition (room temperature water). We contrasted two hypotheses: that stress would lead to a non-selective increase in the expression of Pavlovian biases; or that stress, as an aversive state, might specifically impact action production due to the Pavlovian linkage between inaction and aversive states. We found support for the second of these hypotheses. Stress specifically impaired learning to produce an action, irrespective of the valence of the outcome, an effect consistent with a Pavlovian linkage between punishment and inaction. This deficit in action-learning was also reflected in pupillary responses; stressed individuals showed attenuated pupillary responses to action, hinting at a noradrenergic contribution to impaired action-learning under stress.

Acute social stress before the planning phase improves memory performance in a complex real life-related prospective memory task

Successful execution of intentions, but also the failure to recall are common phenomena in everyday life. The planning, retention, and realization of intentions are often framed as the scientific concept of prospective memory. The current study aimed to examine the influence of acute stress on key dimensions of complex “real life” prospective memory. To this end, we applied a prospective memory task that involved the planning, retention, and performance of intentions during a fictional holiday week. Forty healthy males participated in the study. Half of the subjects were stressed with the Socially Evaluated Cold Pressor Test (SECPT) before the planning of intentions, and the other half of the participants underwent a control procedure at the same time. Salivary cortisol was used to measure the effectiveness of the SECPT stress induction. Stressed participants did not differ from controls in planning accuracy. However, when we compared stressed participants with controls during prospective memory retrieval, we found statistically significant differences in PM across the performance phase. Participants treated with the SECPT procedure before the planning phase showed improved prospective memory retrieval over time, while performance of controls declined. Particularly, there was a significant difference between the stress and control group for the last two days of the holiday week. Interestingly, control participants showed significantly better performance for early than later learned items, which could be an indicator of a primacy effect. This differential effect of stress on performance was also found in time- and event-dependent prospective memory.Our results demonstrate for the first time, that acute stress induced before the planning phase may improve prospective memory over the time course of the performance phase in time- and event-dependent prospective memory. Our data thus indicate that prospective memory can be enhanced by acute stress.

Stress induced by the socially evaluated cold-pressor test cause equivalent deficiencies of sensory gating in male subjects with schizophrenia and healthy controls

It is known that patients with schizophrenia show a deficiency in the prepulse inhibition reflex (PPI). These patients display abnormalities in autonomic nervous system and hypothalamic–pituitary–adrenal function and may have an altered sensitivity to stress. To date, no studies have been carried out to determine the effect of acute stress on the PPI. We investigated whether there was a differential response in reactivity to acute stress caused by the socially evaluated cold-pressor test (SECPT) in a sample of 58 chronic male patients with schizophrenia and 28 healthy control subjects. PPI, salivary cortisol and heart rate (HR) were measured. The patients were evaluated in two sessions (with and without the SECPT) 72h apart and basal measurements were carried out and 30min post-startle probe. We found an increase in salivary cortisol levels and the HR with SECPT condition in both groups and a significantly lower PPI% in patients with schizophrenia. The most relevant findings of this study are that the impairment of the PPI is increased by stress. Stress-induced increase in cortisol in both groups, mainly in healthy control group which allows us to hypothesize that at least such deterioration may be due to the hypercortisolemia caused by the SECPT.

Acute Stress Dysregulates the LPP ERP Response to Emotional Pictures and Impairs Sustained Attention: Time-Sensitive Effects.

Stress can increase emotional vigilance at the cost of a decrease in attention towards non-emotional stimuli. However, the time-dependent effects of acute stress on emotion processing are uncertain. We tested the effects of acute stress on subsequent emotion processing up to 40 min following an acute stressor. Our measure of emotion processing was the late positive potential (LPP) component of the visual event-related potential (ERP), and our measure of non-emotional attention was the sustained attention to response task (SART). We also measured cortisol levels before and after the socially evaluated cold pressor test (SECPT) induction. We found that the effects of stress on the LPP ERP emotion measure were time sensitive. Specifically, the LPP ERP was only altered in the late time-point (30–40 min post-stress) when cortisol was at its highest level. Here, the LPP no longer discriminated between the emotional and non-emotional picture categories, most likely because neutral pictures were perceived as emotional. Moreover, compared to the non-stress condition, the stress-condition showed impaired performance on the SART. Our results support the idea that a limit in attention resources after an emotional stressor is associated with the brain incorrectly processing non-emotional stimuli as emotional and interferes with sustained attention.

The influence of acute stress on attention mechanisms and its electrophysiological correlates.

For the selection of relevant information out of a continuous stream of information, which is a common definition of attention, two core mechanisms are assumed: a competition-based comparison of the neuronal activity in sensory areas and the top-down modulation of this competition by frontal executive control functions. Those control functions are thought to bias the processing of information toward the intended goals. Acute stress is thought to impair these frontal functions through the release of cortisol. In the present study, subjects had to detect a luminance change of a stimulus and ignore more salient but task irrelevant orientation changes. Before the execution of this task, subjects underwent a socially evaluated cold pressor test (SECPT) or a non-stressful control situation. The SECPT revealed reliable stress response with a significant increase of cortisol and alpha-amylase. Stressed subjects showed higher error rates than controls, particularly in conditions which require top-down control processing to bias the less salient target feature against the more salient and spatially separated distracter. By means of the EEG, subjects who got stressed showed a reduced allocation to the relevant luminance change apparent in a modulation of the N1pc. The following N2pc, which reflects a re-allocation of attentional resources, supports the error pattern. There was only an N2pc in conditions, which required to bias the less salient luminance change. Moreover, this N2pc was decreased as a consequence of the induced stress. These results allow the conclusion that acute stress impairs the intention-based attentional allocation and enhances the stimulus-driven selection, leading to a strong distractibility during attentional information selection.

The socially evaluated cold-pressor test (SECPT) for groups: Effects of repeated administration of a combined physiological and psychological stressor

The combined administration of physiological (cold pressor) and psychological (social-evaluative threat) stressors, as in the socially evaluated cold pressor test (SECPT; Schwabe et al., 2008) activates the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. Thus far, the SECPT has been administered exclusively to individual participants, which requires substantial personal effort and time. Therefore, the aim of the present study was to investigate whether and to what extent cardiovascular parameters (SNS) and salivary cortisol concentrations (HPA axis) are affected over the course of repeated SECPT administration in a group design. The SECPT was conducted in groups of seven or more persons and repeated twice with a 24-h interval between each administration. During the stress test, the participants (n=61) were videotaped and observed continuously while they immersed their hands into ice-cold (1 °C, experimental group) or room-temperature (20 °C, control group) water. Blood pressure, heart rate, salivary cortisol concentration, and subjective stress perception were measured. All of these parameters increased significantly during each of the three stress exposures; in contrast, they remained constant in the control group. Moreover, the heart rate response towards the stressor decreased significantly over the course of the repeated stress exposures and salivary cortisol concentration of the experimental group was elevated before the third SECPT administration. Our results indicate that the group SECPT activates the SNS and the HPA, leading to increased blood pressure, heart rate, and cortisol concentration. Moreover, the repeated administration leads to habituation exclusively of heart rate.

Stress Sensitizes the Brain: Increased Processing of Unpleasant Pictures after Exposure to Acute Stress

A key component of acute stress is a surge in vigilance that enables a prioritized processing of highly salient information to promote the organism's survival. In this study, we investigated the neural effects of acute stress on emotional picture processing. ERPs were measured during a deep encoding task, in which 40 male participants categorized 50 unpleasant and 50 neutral pictures according to arousal and valence. Before picture encoding, participants were subjected either to the Socially Evaluated Cold Pressor Test (SECPT) or to a warm water control procedure. The exposure to the SECPT resulted in increased subjective and autonomic (heart rate and blood pressure) stress responses relative to the control condition. Viewing of unpleasant relative to neutral pictures evoked enhanced late positive potentials (LPPs) over centro-parietal scalp sites around 400 msec after picture onset. Prior exposure to acute stress selectively increased the LPPs for unpleasant pictures. Moreover, the LPP magnitude for unpleasant pictures following the SECPT was positively associated with incidental free recall performance 24 hr later. The present results suggest that acute stress sensitizes the brain for increased processing of cues in the environment, particularly priming the processing of unpleasant cues. This increased processing is related to later long-term memory performance.