Acute cortisone administration impairs retrieval of long-term declarative memory in humans

Acute cognitive and behavioral effects of systemic corticosteroids in children treated for inflammatory bowel disease

Systemic corticosteroids are a mainstay of treatment for many pediatric medical conditions. Although their impact on the central nervous system has been well-studied in animal models and adults, less is known about such effects in pediatric populations. The current study investigated acute effects of corticosteroids on memory, executive functions, emotion, and behavior in children and adolescents with inflammatory bowel disease (IBD). Patients 8-17 years with IBD (Crohn's disease, CD; ulcerative colitis, UC) on high-dose prednisone (n = 33) and IBD patients in remission off steroids (n = 33) completed standardized neuropsychological tests and behavior rating scales. In the IBD sample as a whole, few steroid effects were found for laboratory cognitive measures, but steroid-treated patients were rated as exhibiting more problems with emotional, and to a lesser extent with cognitive function in daily life. Steroid effects, assessed by laboratory measures and questionnaires, were more prevalent in CD than UC patients; UC patients on steroids sometimes performed better than controls. Sleep disruption also predicted some outcomes, diminishing somewhat the magnitude of the steroid effects. Corticosteroid therapy can have acute effects on cognition, emotion, and behavior in chronically ill children; the clinical and long-term significance of these effects require further investigation.

Candesartan prevents impairment of recall caused by repeated stress in rats

RATIONALE

Deleterious effects of psychological stress on memory are increasingly important. Overexpression of the AT(1) angiotensin receptors in brain has been found to participate in several negative effects of chronic stress including hypertension and a cognitive impairment.

OBJECTIVE

In this study, we searched for the protective effects the AT(1) angiotensin receptor blockade with candesartan against the adverse effects of repeated stress on recall of aversively and appetitively motivated behaviours in rats.

METHODS

Two groups of male Wistar rats were repeatedly stressed by keeping them daily (2 h/21 days) in tight plastic tubes. The subjects of the group 1 received candesartan (0.1 mg/kg, orally) each day before the stressing procedure. The rats of the group 2 received vehicle. Another two groups of rats (3 and 4) receiving candesartan and vehicle, respectively, were appropriately handled but not stressed. Next day, after ending the repeated stress procedure, all rats were tested in two cognitive paradigms: inhibitory avoidance (IA) and object recognition (OR).

RESULTS

Stressed animals displayed decreased recall of the IA behaviour (p < 0.01) and decreased OR (p < 0.05). These effects were not seen in the animals stressed and concomitantly treated with candesartan. The auxiliary tests designed to control for the possible unspecific contribution of motor (open field) and emotional (elevated "plus" maze) effects of the experimental procedures to results of the cognitive tests showed no such contribution.

CONCLUSION

These data strongly suggest that the AT(1) angiotensin receptor blockade effectively counteracts deleterious effects of stress on recall of aversively and appetitively motivated memories in rats.

Stress eliminates retrieval-induced forgetting--does the oral application of cortisol?

It is well established that stress and glucocorticoids can affect memory. Psychosocial stress has been reported to eliminate retrieval-induced forgetting (RIF), the phenomenon that repeated retrieval of a subset of previously learned material impairs later recall of related, but non-retrieved information. The stress-related reduction of RIF has been found correlated with an increase in salivary cortisol levels. Based on these findings, the current placebo-controlled study examined the effect of an oral dose of 25mg hydrocortisone on the RIF effect in 37 healthy men. Even though participants in the hydrocortisone group showed a marked increase in salivary cortisol, retrieval-induced forgetting was not affected by the pharmacological treatment. Thus, cortisol administration alone in contrast to stress experience does not impair the RIF effect. However, participants with high state anxiety during retrieval practice did not show RIF, whereas participants with low state anxiety did. This finding suggests a role for state anxiety in stress-related elimination of retrieval-induced forgetting, perhaps indicative of a memory-modulating sympathetic nervous system effect.

Hydrocortisone infusion exerts dose- and sex-dependent effects on attention to emotional stimuli

Glucocorticoid administration has been shown to exert complex effects on cognitive and emotional processing. In the current study we investigated the effects of glucocorticoid administration on attention towards emotional words, using an Affective Go/No-go task on which healthy humans have shown an attentional bias towards positive as compared to negative words. Healthy volunteers received placebo and either low-dose (0.15mg/kg) or high-dose (0.45mg/kg) hydrocortisone intravenously during two separate visits in a double-blind, randomized design. Seventy-five minutes post-infusion, the subjects performed tests of attention (Rapid Visual Information Processing [RVIP]), spatial working memory (Spatial Span) and emotional processing (Affective Go/No-go task [AGNG]). On the attention task, performance was impaired under both hydrocortisone doses relative to placebo, though the effect on error rate was not significant after controlling for age; Spatial Span performance was unaffected by hydrocortisone administration. On the AGNG task, relative to the placebo condition the low-dose hydrocortisone infusion decreased response time to emotional words while high-dose hydrocortisone increased response time. In the females specifically, both high and low dose hydrocortisone administration attenuated the normal attentional bias toward positively valenced words. These data suggest that, in healthy women, the modulation of attention by the emotional salience of stimuli is influenced by glucocorticoid hormone concentrations.

The neurobiology of depression and antidepressant action

We present a comprehensive overview of the neurobiology of unipolar major depression and antidepressant drug action, integrating data from affective neuroscience, neuro- and psychopharmacology, neuroendocrinology, neuroanatomy, and molecular biology. We suggest that the problem of depression comprises three sub-problems: first episodes in people with low vulnerability ('simple' depressions), which are strongly stress-dependent; an increase in vulnerability and autonomy from stress that develops over episodes of depression (kindling); and factors that confer vulnerability to a first episode (a depressive diathesis). We describe key processes in the onset of a 'simple' depression and show that kindling and depressive diatheses reproduce many of the neurobiological features of depression. We also review the neurobiological mechanisms of antidepressant drug action, and show that resistance to antidepressant treatment is associated with genetic and other factors that are largely similar to those implicated in vulnerability to depression. We discuss the implications of these conclusions for the understanding and treatment of depression, and make some strategic recommendations for future research.

Stress modulates the engagement of multiple memory systems in classification learning

Learning and memory are supported by anatomically and functionally distinct systems. Recent research suggests that stress may alter the contributions of multiple memory systems to learning, yet the underlying mechanism in the human brain remains completely unknown. Using event-related functional magnetic resonance imaging, we asked in the present experiment whether stress may modulate the engagement of hippocampus-based "declarative" and striatum-based "procedural" memory systems during classification learning in humans and what brain mechanisms are involved in this effect. We found that stress reduced declarative knowledge about the learning task and changed the used learning strategy from a single-cue-based declarative strategy to a multicue-based procedural strategy, whereas learning performance per se remained unaffected by stress. Neuroimaging revealed that hippocampal activity correlated positively with task performance in the control condition, whereas striatal activity correlated with performance in the stress condition. After stress, hippocampal activity was reduced and even negatively correlated with learning performance. These findings show for the first time that stress alters the engagement of multiple memory systems in the human brain. Stress impaired the hippocampus-dependent system and allowed the striatum to control behavior. The shift toward "procedural" learning after stress appears to rescue task performance, whereas attempts to engage the "declarative" system disrupt performance.

Post-exposure sleep deprivation facilitates correctly timed interactions between glucocorticoid and adrenergic systems, which attenuate traumatic stress responses

Reliable evidence supports the role of sleep in learning and memory processes. In rodents, sleep deprivation (SD) negatively affects consolidation of hippocampus-dependent memories. As memory is integral to post-traumatic stress symptoms, the effects of post-exposure SD on various aspect of the response to stress in a controlled, prospective animal model of post-traumatic stress disorder (PTSD) were evaluated. Rats were deprived of sleep for 6 h throughout the first resting phase after predator scent stress exposure. Behaviors in the elevated plus-maze and acoustic startle response tests were assessed 7 days later, and served for classification into behavioral response groups. Freezing response to a trauma reminder was assessed on day 8. Urine samples were collected daily for corticosterone levels, and heart rate (HR) was also measured. Finally, the impact of manipulating the hypothalamus-pituitary-adrenal axis and adrenergic activity before SD was assessed. Mifepristone (MIFE) and epinephrine (EPI) were administered systemically 10-min post-stress exposure and behavioral responses and response to trauma reminder were measured on days 7-8. Hippocampal expression of glucocorticoid receptors (GRs) and morphological assessment of arborization and dendritic spines were subsequently evaluated. Post-exposure SD effectively ameliorated long-term, stress-induced, PTSD-like behavioral disruptions, reduced trauma reminder freezing responses, and decreased hippocampal expression of GR compared with exposed-untreated controls. Although urine corticosterone levels were significantly elevated 1 h after SD and the HR was attenuated, antagonizing GRs with MIFE or stimulation of adrenergic activity with EPI effectively abolished the effect of SD. MIFE- and EPI-treated animals clearly demonstrated significantly lower total dendritic length, fewer branches and lower spine density along dentate gyrus dendrites with increased levels of GR expression 8 days after exposure, as compared with exposed-SD animals. Intentional prevention of sleep in the early aftermath of stress exposure may well be beneficial in attenuating traumatic stress-related sequelae. Post-exposure SD may disrupt the consolidation of aversive or fearful memories by facilitating correctly timed interactions between glucocorticoid and adrenergic systems.

Critical role of plasma corticosteroid-binding-globulin during stress to promote glucocorticoid delivery to the brain: impact on memory retrieval

We aimed at demonstrating that corticosteroid binding globulin (CBG), a plasma glycoprotein binding glucocorticoids with high affinity in blood, endorses a major role under stress conditions by regulating free glucocorticoid access to the brain and thereby influences glucocorticoid-dependent behaviors. Hence, we compared CBG-deficient mice (Cbg-/-) and their controls (Cbg+/+) in a specific memory task, i.e. the delayed alternation behavior, requiring memory retrieval both under stress and nonstress conditions and previously shown to be dependent on hippocampal glucocorticoid levels. Our results evidence that Cbg-/- mice, unlike controls, remain insensitive to stress applied before memory retrieval. Furthermore, under stress conditions, we observed a blunted surge of corticosterone (CORT) in plasma and no free CORT rise in the hippocampus of Cbg-/-. Moreover, intrahippocampal infusion of CORT through implanted cannulae was used to mimic stress CORT rise before memory retrieval. This infusion of CORT reproduced memory retrieval impairments in Cbg-/- as in Cbg+/+ controls. Finally, we provide evidence that Cbg-/- mice exhibit a normal adrenal response to stress and ACTH. Given that CBG deficiency is known to markedly impact on CORT clearance from plasma, our current article demonstrates that Cbg-/- insensitivity in memory retrieval after stress results from the blunted CORT response due to increased CORT clearance. Overall, our data suggest that the impact of CBG genetic deficiency on various behavioral patterns reported previously stems from a smaller CORT reservoir in blood. Inasmuch as CBG discloses interindividual variations, such a parameter ought to be taken into account when studying stress-induced glucocorticoid action in brain.

Dose-dependent effects of hydrocortisone infusion on autobiographical memory recall

The glucocorticoid hormone cortisol has been shown to impair episodic memory performance. The present study examined the effect of two doses of hydrocortisone (synthetic cortisol) administration on autobiographical memory retrieval. Healthy volunteers (n = 66) were studied on two separate visits, during which they received placebo and either moderate-dose (0.15 mg/kg IV; n = 33) or high-dose (0.45 mg/kg IV; n = 33) hydrocortisone infusion. From 75 to 150 min post-infusion subjects performed an Autobiographical Memory Test and the California Verbal Learning Test (CVLT). The high-dose hydrocortisone administration reduced the percent of specific memories recalled (p = .04), increased the percent of categorical (nonspecific) memories recalled (p < .001), and slowed response times for categorical memories (p < .001), compared with placebo performance. Under moderate-dose hydrocortisone the autobiographical memory performance did not change significantly with respect to percent of specific or categorical memories recalled or reaction times. Performance on the CVLT was not affected by hydrocortisone. These findings suggest that cortisol affects accessibility of autobiographical memories in a dose-dependent manner. Specifically, administration of hydrocortisone at doses analogous to those achieved under severe psychosocial stress impaired the specificity and speed of retrieval of autobiographical memories.

Survival processing in times of stress

Recent studies have found that processing information according to an evolutionary relevant (i.e., survival) scenario improves its subsequent memorability, potentially as a result of fitness advantages gained in the ancestral past. So far, research has not revealed much about any proximate mechanisms that might underlie this so-called survival processing advantage in memory. Intriguingly, research has shown that the memorability of stressful situations is enhanced via the release of stress hormones acting on brain regions involved in memory. Since survival situations habitually involve some degree of stress, in the present study, we investigated whether stress serves as a proximate mechanism to promote survival processing. Participants rated words for their relevance to either a survival or a neutral (moving) scenario after they had been exposed to a psychosocial stressor or a no-stress control condition. Surprise retention tests immediately following the rating task revealed that survival processing and acute stress independently boosted memory performance. These results therefore suggest that stress does not serve as a proximate mechanism of the survival processing advantage in memory.

Impact of stress on resident performance in simulated trauma scenarios

BACKGROUND

Training and practice in medicine are inherently stressful. The effects of stress on performance in clinical situations are poorly understood. The purpose of this study was to examine the stress responses and clinical performance of residents during low and high stress (HS) simulated trauma resuscitations.

METHODS

Thirteen emergency medicine and general surgery residents were evaluated in HS and low stress (LS) trauma resuscitation simulations. Subjective and physiologic (heart rate, salivary cortisol) responses were measured at baseline and in response to the scenarios. Performance was assessed with global rating and checklist scores of technical performance, time to record critical information, and the Anesthesia Non-Technical Skills tool. Post-scenario recall was assessed with the completion of a standardized trauma history form.

RESULTS

Post-scenario subjective stress and cortisol levels were higher in the HS scenario compared with the LS scenario (p < 0.05). Checklist performance scores and post-scenario recall were significantly lower in the HS compared with the LS condition (p < 0.05).

CONCLUSION

In trainees, some aspects of performance and immediate recall appear to be impaired in complex clinical scenarios in which they exhibit elevated subjective and physiologic stress responses. The findings of this study highlight a potential threat to patient safety and demand further investigation. Future studies should strive to further elucidate the effects of stress on specific components of performance and investigate ways to reduce its negative impact.

Effects of acute restraint-induced stress on glucocorticoid receptors and brain-derived neurotrophic factor after mild traumatic brain injury

We have previously reported that experimental mild traumatic brain injury results in increased sensitivity to stressful events during the first post-injury weeks, as determined by analyzing the hypothalamic-pituitary-adrenal (HPA) axis regulation following restraint-induced stress. This is the same time period when rehabilitative exercise has proven to be ineffective after a mild fluid-percussion injury (FPI). Here we evaluated effects of stress on neuroplasticity. Adult male rats underwent either an FPI or sham injury. Additional rats were only exposed to anesthesia. Rats were exposed to 30 min of restraint stress, followed by tail vein blood collection at post-injury days (PID) 1, 7, and 14. The response to dexamethasone (DEX) was also evaluated. Hippocampal tissue was collected 120 min after stress onset. Brain-derived neurotrophic factor (BDNF) along with glucocorticoid (GR) and mineralocorticoid (MR) receptors was determined by Western blot analysis. Results indicated injury-dependent changes in glucocorticoid and mineralocorticoid receptors that were influenced by the presence of dexamethasone. Control and FPI rats responded differentially to DEX in that GR increases after receiving the lower dose of DEX were longer lasting in the FPI group. A suppression of MR was found at PID 1 in vehicle-treated FPI and Sham groups. Decreases in the precursor form of BDNF were observed in different FPI groups at PIDs 7 and 14. These findings suggest that the increased sensitivity to stressful events during the first post-injury weeks, after a mild FPI, has an impact on hippocampal neuroplasticity.

Glucocorticoids interact with the hippocampal endocannabinoid system in impairing retrieval of contextual fear memory

There is extensive evidence that glucocorticoid hormones impair the retrieval of memory of emotionally arousing experiences. Although it is known that glucocorticoid effects on memory retrieval impairment depend on rapid interactions with arousal-induced noradrenergic activity, the exact mechanism underlying this presumably nongenomically mediated glucocorticoid action remains to be elucidated. Here, we show that the hippocampal endocannabinoid system, a rapidly activated retrograde messenger system, is involved in mediating glucocorticoid effects on retrieval of contextual fear memory. Systemic administration of corticosterone (0.3-3 mg/kg) to male Sprague-Dawley rats 1 h before retention testing impaired the retrieval of contextual fear memory without impairing the retrieval of auditory fear memory or directly affecting the expression of freezing behavior. Importantly, a blockade of hippocampal CB1 receptors with AM251 prevented the impairing effect of corticosterone on retrieval of contextual fear memory, whereas the same impairing dose of corticosterone increased hippocampal levels of the endocannabinoid 2-arachidonoylglycerol. We also found that antagonism of hippocampal β-adrenoceptor activity with local infusions of propranolol blocked the memory retrieval impairment induced by the CB receptor agonist WIN55,212-2. Thus, these findings strongly suggest that the endocannabinoid system plays an intermediary role in regulating rapid glucocorticoid effects on noradrenergic activity in impairing memory retrieval of emotionally arousing experiences.

Stress hormones receptors in the amygdala mediate the effects of stress on the consolidation, but not the retrieval, of a non aversive spatial task

This study examined the effects of the arousal level of the rat and exposure to a behavioral stressor on acquisition, consolidation and retrieval of a non-aversive hippocampal-dependent learning paradigm, the object location task. Learning was tested under two arousal conditions: no previous habituation to the experimental context (high novelty stress/arousal level) or extensive prior habituation (reduced novelty stress/arousal level). Results indicated that in the habituated rats, exposure to an out-of-context stressor (i.e, elevated platform stress) impaired consolidation and retrieval, but not acquisition, of the task. Non-habituated animals under both stressed and control conditions did not show retention of the task. In habituated rats, RU-486 (10 ng/side), a glucocorticoid receptor (GR) antagonist, or propranolol (0.75 µg/side), a beta-adrenergic antagonist, injected into the basolateral amygdala (BLA), prevented the impairing effects of the stressor on consolidation, but not on retrieval. The CB1/CB2 receptor agonist WIN55,212-2 (WIN, 5 µg/side) microinjected into the BLA did not prevent the effects of stress on either consolidation or retrieval. Taken together the results suggest that: (i) GR and β-adrenergic receptors in the BLA mediate the impairing effects of stress on the consolidation, but not the retrieval, of a neutral, non-aversive hippocampal-dependent task, (ii) the impairing effects of stress on hippocampal consolidation and retrieval are mediated by different neural mechanisms (i.e., different neurotransmitters or different brain areas), and (iii) the effects of stress on memory depend on the interaction between several main factors such as the stage of memory processing under investigation, the animal's level of arousal and the nature of the task (neutral or aversive).

Psychosocial stress exposure impairs memory retrieval in children

Negative consequences of stress on working memory and delayed memory retrieval have been observed in adult humans. Little is known about the occurrence of similar effects in children. Forty-four German full-term children, aged 8-10 years, were randomly assigned to a stressful (Trier Social Stress Test for Children--TSST-C) or to a non-stressful control condition. Afterwards, delayed memory retrieval was tested using a computerized version of the well-known card game "Memory". It contained positive, neutral and negative stimuli. In addition, working memory of verbal and non-verbal material was assessed. The stressed children showed pronounced cortisol increases accompanied by a decrease in mood. Children exposed to the stressor performed poorer in the delayed memory retrieval test (memory card game). They committed more errors. No differences were found for working memory. The stress-induced memory retrieval impairment mirrors findings in adults. In contrast, the missing working memory effects could suggest developmental differences in stress sensitivity.

Gut memories: towards a cognitive neurobiology of irritable bowel syndrome

The brain and the gut are engaged in continual crosstalk along a number of pathways collectively termed the 'brain-gut axis'. Over recent years it has become increasingly clear that dysregulation of the axis at a number of levels can result in disorders such as irritable bowel syndrome (IBS). With recent advances in neuroimaging technologies, insights into the neurobiology of IBS are beginning to emerge. However the cognitive neurobiology of IBS has remained relatively unexplored to date. In this review we summarise the available data on cognitive function in IBS. Moreover, we specifically address three key pathophysiological factors, namely; stress, immune activation and chronic pain, together with other factors involved in the manifestation of IBS, and explore how each of these components may impact centrally, what neurobiological mechanisms might be involved, and consider the implications for cognitive functioning in IBS. We conclude that each factor addressed could significantly impinge on central nervous system function, supporting the view that future research efforts must be directed towards a detailed assessment of cognitive function in IBS.

Memory modulation

Our memories are not all created equally strong: Some experiences are well remembered while others are remembered poorly, if at all. Research on memory modulation investigates the neurobiological processes and systems that contribute to such differences in the strength of our memories. Extensive evidence from both animal and human research indicates that emotionally significant experiences activate hormonal and brain systems that regulate the consolidation of newly acquired memories. These effects are integrated through noradrenergic activation of the basolateral amygdala that regulates memory consolidation via interactions with many other brain regions involved in consolidating memories of recent experiences. Modulatory systems not only influence neurobiological processes underlying the consolidation of new information, but also affect other mnemonic processes, including memory extinction, memory recall, and working memory. In contrast to their enhancing effects on consolidation, adrenal stress hormones impair memory retrieval and working memory. Such effects, as with memory consolidation, require noradrenergic activation of the basolateral amygdala and interactions with other brain regions.

Opposite Effects of Cortisol on Consolidation of Temporal Sequence Memory during Waking and Sleep

Memory functions involve three stages: encoding, consolidation, and retrieval. Modulating effects of glucocorticoids (GCs) have been consistently observed for declarative memory with GCs enhancing encoding and impairing retrieval, but surprisingly, little is known on how GCs affect memory consolidation. Studies in rats suggest a beneficial effect of GCs that were administered during postlearning wake periods, whereas in humans, cortisol impaired memory consolidation when administered during postlearning sleep. These inconsistent results raise the question whether effects of GCs critically depend on the brain state during consolidation (sleep vs. wake). Here, we compare for the first time directly the effects of cortisol on memory consolidation during postlearning sleep and wakefulness in different measures of declarative memory. Cortisol (13 mg vs. placebo) was intravenously infused during a postlearning nap or a time-matched period of wakefulness after participants had encoded neutral and emotional text material. Memory for the texts was tested (a) by asking for the contents of the texts (“item” memory) and (b) for the temporal order of the contents within the texts (“relational” memory). Neither postlearning infusion of cortisol during sleep nor during wakefulness affected retention of content words of emotional or neutral texts. Critically, however, the retention of temporal order within the texts, known to rely most specifically on the hippocampus proper within the medial-temporal lobe memory system, was distinctly improved by cortisol infusion during the wake phase but impaired by cortisol during sleep. These results point toward fundamentally different mechanisms of hippocampal memory consolidation, depending on the brain state.

Progesterone at encoding predicts subsequent emotional memory

Significant sex differences in the well-documented relationship between stress hormones and memory have emerged in recent studies. The potentiating effects of glucocorticoids on memory vary across the menstrual cycle, suggesting a potential interaction between these stress hormones and endogenously cycling sex hormones. Here, we show that memory for emotional materials changes significantly in accordance with hormonal changes across the menstrual cycle, suggesting that ovarian sex hormones influence the modulation of emotional memories. Sixty healthy, naturally cycling women rated 120 images on arousal and valence. One week later they completed free recall and recognition memory tests. Their menstrual cycle phases were estimated by self-report and confirmed by salivary assay of 17β-estradiol and progesterone. Memory for emotional items only was significantly better in the high hormone (luteal) phase compared with the low hormone (follicular) phase on the free recall test; on both tests memory correlated positively with progesterone collected at the time of encoding. These findings suggest that emotional memory performance changes across the menstrual cycle, and that this change is in part mediated by endogenous progesterone cycling.

Stress and glucocorticoids impair memory retrieval via β2-adrenergic, Gi/o-coupled suppression of cAMP signaling

Acute stress impairs the retrieval of hippocampus-dependent memory, and this effect is mimicked by exogenous administration of stress-responsive glucocorticoid hormones. It has been proposed that glucocorticoids affect memory by promoting the release and/or blocking the reuptake of norepinephrine (NE), a stress-responsive neurotransmitter. It has also been proposed that this enhanced NE signaling impairs memory retrieval by stimulating β(1)-adrenergic receptors and elevating levels of cAMP. In contrast, other evidence indicates that NE, β(1), and cAMP signaling is transiently required for the retrieval of hippocampus-dependent memory. To resolve this discrepancy, wild-type rats and mice with and without gene-targeted mutations were stressed or treated with glucocorticoids and/or adrenergic receptor drugs before testing memory for inhibitory avoidance or fear conditioning. Here we report that glucocorticoids do not require NE to impair retrieval. However, stress- and glucocorticoid-induced impairments of retrieval depend on the activation of β(2) (but not β(1))-adrenergic receptors. Offering an explanation for the opposing functions of these two receptors, the impairing effects of stress, glucocorticoids and β(2) agonists on retrieval are blocked by pertussis toxin, which inactivates signaling by G(i/o)-coupled receptors. In hippocampal slices, β(2) signaling decreases cAMP levels and greatly reduces the increase in cAMP mediated by β(1) signaling. Finally, augmenting cAMP signaling in the hippocampus prevents the impairment of retrieval by systemic β(2) agonists or glucocorticoids. These results demonstrate that the β(2) receptor can be a critical effector of acute stress, and that β(1) and β(2) receptors can have quite distinct roles in CNS signaling and cognition.

Interacting brain systems modulate memory consolidation

Emotional arousal influences the consolidation of long-term memory. This review discusses experimental approaches and relevant findings that provide the foundation for current understanding of coordinated interactions between arousal activated peripheral hormones and the brain processes that modulate memory formation. Rewarding or aversive experiences release the stress hormones epinephrine (adrenalin) and glucocorticoids from the adrenal glands into the bloodstream. The effect of these hormones on memory consolidation depends upon binding of norepinephrine to beta-adrenergic receptors in the basolateral complex of the amygdala (BLA). Much evidence indicates that the stress hormones influence release of norepinephrine in the BLA through peripheral actions on the vagus nerve which stimulates, through polysynaptic connections, cells of the locus coeruleus to release norepinephrine. The BLA influences memory storage by actions on synapses, distributed throughout the brain, that are engaged in sensory and cognitive processing at the time of amygdala activation. The implications of the activation of these stress-activated memory processes are discussed in relation to stress-related memory disorders.

Implications of hypothalamic-pituitary-adrenal axis functioning in posttraumatic stress disorder

BACKGROUND

Cortisol secretions serve as the barometer of the hypothalamic-pituitary-adrenal (HPA) axis, which regulates and controls responses to stress. Studies of cortisol secretions in patients with posttraumatic stress disorder (PTSD) reveal inconsistent results.

PURPOSE

Current research on HPA axis functioning in PTSD is examined to elucidate the neuroendocrine contributions in the disorder, identify current treatment's impact on the HPA axis, and consider implications for nursing care and areas for future research.

FINDINGS

There is evidence for HPA dysregulation in PTSD, which contributes to widespread impairment in functions such as memory and stress reactivity and to physical morbidity via processes such as allostatic load. There is limited, but building, evidence that dehydroepiandrosterone (DHEA), which is released simultaneously with cortisol, may provide anti-glucocorticoid and neuroprotective effects.

CONCLUSION

Current treatments such as selective serotonin reuptake inhibitors and psychotherapy may have a beneficial impact on the HPA axis in PTSD populations. Somatic approaches to treating PTSD have not yet been studied in relation to their impact on HPA axis parameters in PTSD patients. Treatment studies of DHEA or glucocorticoids have not yet used HPA axis endpoints. PTSD treatment studies that include measures of HPA axis target mechanisms and consider HPA axis regulation as an additional treatment outcome are warranted.

Blocking mineralocorticoid receptors prior to retrieval reduces contextual fear memory in mice

Background

Corticosteroid hormones regulate appraisal and consolidation of information via mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) respectively. How activation of these receptors modulates retrieval of fearful information and the subsequent expression of fear is largely unknown. We tested here whether blockade of MRs or GRs during retrieval also affects subsequent expression of fear memory.

Methodology/Principal Findings

Mice were trained in contextual or tone cue fear conditioning paradigms, by pairing mild foot shocks with a particular context or tone respectively. Twenty-four hours after training, context-conditioned animals were re-exposed to the context for 3 or 30 minutes (day 2); tone-conditioned animals were placed in a different context and re-exposed to one or six tones. Twenty-four hours (day 3) and one month later, freezing behavior to the aversive context/tone was scored again. MR or GR blockade was achieved by giving spironolactone or RU486 subcutaneously one hour before retrieval on day 2. Spironolactone administered prior to brief context re-exposure reduced freezing behavior during retrieval and 24 hours later, but not one month later. Administration of spironolactone without retrieval of the context or immediately after retrieval on day 2 did not reduce freezing on day 3. Re-exposure to the context for 30 minutes on day 2 significantly reduced freezing on day 3 and one month later, but freezing was not further reduced by spironolactone. Administration of spironolactone prior to tone-cue re-exposure on day 2 did not affect freezing behavior. Treatment with RU486 prior to re-exposure did not affect context or tone-cue fear memories at any time point.

Conclusions/Significance

We conclude that MR blockade prior to retrieval strongly reduces the expression of contextual fear, implying that MRs, rather than GRs, play an important role in retrieval of emotional information and subsequent fear expression.

Regulation of excitatory synapses and fearful memories by stress hormones

Memories for emotionally arousing and fearful events are generally well retained. From the evolutionary point of view this is a highly adaptive behavioral response aimed to remember relevant information. However, fearful memories can also be inappropriately and vividly (re)expressed, such as in posttraumatic stress disorder. The memory formation of emotionally arousing events is largely modulated by hormones, peptides, and neurotransmitters which are released during and after exposure to these conditions. One of the core reactions in response to a stressful situation is the rapid activation of the autonomic nervous system, which results in the release of norepinephrine in the brain. In addition, stressful events stimulate the hypothalamus-pituitary-adrenal axis which slowly increases the release of glucocorticoid hormones from the adrenal glands. Here we will review how glucocorticoids and norepinephrine regulate the formation of fearful memories in rodents and humans and how these hormones can facilitate the storage of information by regulating excitatory synapses.

Cortisol acutely reduces selective attention for erotic words in healthy young men

Psychological stress prompts activity of the hypothalamic-pituitary-adrenal (HPA) axis resulting in increased release of cortisol. Long-term HPA aberrations have been observed for stress-related affective disorders but research into acute effects of cortisol on affect-regulation has only recently begun. Previous studies reported that exogenous cortisol acutely attenuated automatic attentional processing of task-irrelevant threatening information. This has been taken to suggest that cortisol may have acute anxiolytic properties, possibly through facilitating inhibition of threatening information. However, the role of cortisol in attentional inhibition of non-threatening arousing stimuli remained unclear. Therefore acute effects of 40 mg cortisol on performance of a masked and unmasked emotional Stroop task (EST) were assessed. Results for only the unmasked task demonstrated EST interference (interpreted as increased automatic attention) for erotic stimuli which was abolished by cortisol administration. This implies that effects of cortisol may not be restricted to attenuation of specifically anxiogenic information processing, as previously suggested.

Acute glucocorticoid effects on the multicomponent model of working memory

OBJECTIVE

In comparison with basal physiological levels, acute, high levels of cortisol affect learning and memory. Despite reports of cortisol-induced episodic memory effects, no study has used a comprehensive battery of tests to evaluate glucocorticoid effects on the multicomponent model of working memory. Here, we report the results of a double-blind, placebo-controlled, between-subjects study.

METHODS

Twenty healthy young men were randomly assigned to either acute cortisol (30 mg hydrocortisone) or placebo administration. Participants were subjected to an extensive cognitive test battery that evaluated all systems of the multicomponent model of working memory, including various executive domains (shifting, updating, inhibition, planning and access to long-term memory).

RESULTS

Compared with placebo, hydrocortisone administration increased cortisol blood levels and impaired working memory in storage of multimodal information in the episodic buffer and maintenance/reverberation of information in the phonological loop. Hydrocortisone also decreased performance in planning and inhibition tasks, the latter having been explained by changes in storage of information in working memory.

CONCLUSIONS

Thus, hydrocortisone acutely impairs various components of working memory, including executive functioning. This effect must be considered when administering similar drugs, which are widely used for the treatment of many clinical disorders.

Xamoterol impairs hippocampus-dependent emotional memory retrieval via Gi/o-coupled β2-adrenergic signaling

Xamoterol, a partial β(1)-adrenergic receptor agonist, has been reported to impair the retrieval of hippocampus-dependent spatial reference memory in rats. In contrast, xamoterol restores memory retrieval in gene-targeted mice lacking norepinephrine (NE) and in a transgenic mouse model of Down syndrome in which NE levels are reduced. Restoration of retrieval by xamoterol in these two models complements the observation that NE and β(1) signaling are required for hippocampus-dependent retrieval of contextual and spatial reference memory in wild-type mice and rats. Additional evidence indicates that cAMP-mediated PKA and Epac signaling are required for the retrieval of hippocampus-dependent memory. As a result, we hypothesized that xamoterol has effects in addition to the stimulation of β(1) receptors that, at higher doses, act to counter the effects of β(1) signaling. Here we report that xamoterol-induced disruption of memory retrieval depends on β(2)-adrenergic receptor signaling. Interestingly, the impairment of memory retrieval by xamoterol is blocked by pretreatment with pertussis toxin, an uncoupling agent for G(i/o) signaling, suggesting that β(2) signaling opposes β(1) signaling during memory retrieval at the level of G protein and cAMP signaling. Finally, similar to the time-dependent roles for NE, β(1), and cAMP signaling in hippocampus-dependent memory retrieval, xamoterol only impairs retrieval for several days after training, indicating that its effects are also limited by the age of the memory. We conclude that the disruption of memory retrieval by xamoterol is mediated by G(i/o)-coupled β(2) signaling, which opposes the G(s)-coupled β(1) signaling that is transiently required for hippocampus-dependent emotional memory retrieval.

Relationship of a common polymorphism of the glucocorticoid receptor gene to traumatic memories and posttraumatic stress disorder in patients after intensive care therapy

OBJECTIVE

Glucocorticoids play a major role in the consolidation and retrieval of traumatic information. They act through the glucocorticoid receptor, for which, in humans, several polymorphisms have been described. In particular, the BclI single-nucleotide polymorphism is associated with hypersensitivity to glucocorticoids and with susceptibility to development of major depression. Furthermore, in patients with posttraumatic stress disorder carrying the BclI GG genotype, cortisol levels were lower and showed an inverse relationship to posttraumatic stress disorder symptom intensity. Here, we studied the association of the BclI polymorphism with plasma cortisol levels, traumatic memories, posttraumatic stress disorder symptoms, and health-related quality of life outcomes in 126 patients undergoing cardiac surgery and intensive care unit therapy.

DESIGN

Prospective observational study.

SETTING

Cardiovascular intensive care unit in a university hospital.

PATIENTS

A total of 126 patients undergoing cardiac surgery and intensive care unit treatment.

INTERVENTIONS

No interventions were performed.

MEASUREMENTS AND MAIN RESULTS

Validated questionnaires were used to quantify end points. Measurements were taken 1 day before and 1 wk and 6 months after cardiac surgery. Homozygous carriers of the BclI G allele (n = 21) had significantly lower preoperative plasma cortisol levels and more long-term traumatic memories from intensive care unit therapy at 6 months after cardiac surgery than heterozygous carriers or noncarriers (1.9 ± 1.4 vs. 1.0 ± 1.2, p = .01). Anxiety was significantly more common as a long-term traumatic memory in homozygous BclI G allele carriers than in heterozygous carriers or noncarriers (57% vs. 35%, p = .03). Posttraumatic stress disorder symptom scores were significantly higher at discharge from the intensive care unit in homozygous BclI G allele carriers than in heterozygous carriers or noncarriers. Only heterozygous carriers or BclI G allele noncarriers had a significant gain in health-related quality of life physical function at 6 months after cardiac surgery (p < .01). Baseline values were not statistically different between carriers of the different BclI alleles.

CONCLUSION

Homozygous BclI G allele carriers are at risk for traumatic memories, posttraumatic stress disorder symptoms, and lower health-related quality of life after cardiac surgery and intensive care unit therapy. The BclI single-nucleotide polymorphism may help to identify individuals at need for tailored medical care.

Maternal responsiveness moderates the relationship between allostatic load and working memory

A substantial amount of research has demonstrated the deleterious effects of chronic stress on memory. However, much less is known about protective factors. In the current study we test the role of maternal responsiveness in buffering the effects of childhood allostatic load on subsequent adolescent working memory. Allostatic load is a marker of cumulative stress on the body that is caused by mobilization of multiple physiological systems in response to chronic environmental demands. Results of the study suggest that allostatic load negatively affects working memory, but that this effect is significantly attenuated in children with responsive mothers.

Stress effects on memory: an update and integration

It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in particular catecholamine and glucocorticoid, actions are taken into account. Integrating two popular models, we argue here that rapid catecholamine and non-genomic glucocorticoid actions interact in the basolateral amygdala to shift the organism into a 'memory formation mode' that facilitates the consolidation of stressful experiences into long-term memory. The undisturbed consolidation of these experiences is then promoted by genomic glucocorticoid actions that induce a 'memory storage mode', which suppresses competing cognitive processes and thus reduces interference by unrelated material. Highlighting some current trends in the field, we further argue that stress affects learning and memory processes beyond the basolateral amygdala and hippocampus and that stress may pre-program subsequent memory performance when it is experienced during critical periods of brain development.

Aspects of psychodynamic neuropsychiatry II: psychical locality and biology: toward the neurobiology of psychotherapy

Throughout his career, Freud believed that psychiatry in general and psychoanalysis in particular would one day be rooted in anatomical/biological ground. He felt confidant that such ground would replace the psychological understanding on which he had been forced to base most of his clinical theory and practice. He felt confidant that one day psychotherapy would be more "scientific." This article seeks to demonstrate that this day is arriving. A clinical case is presented where assessment and formulation are largely based on neurobiology, where treatment was conducted less in accord with psychodynamic theory than neurodynamic data of anatomy and biology.

Oral cortisol impairs implicit sequence learning

RATIONALE

Glucocorticoids have been shown to affect declarative memory, an explicit form of memory for facts and events operated by medial temporal lobe structures. Recent neuroimaging data suggest that the medial temporal lobe (including the hippocampus) is also active in implicit sequence learning.

OBJECTIVES

The aim of the present study was to investigate whether implicit sequence learning may also be affected by glucocorticoid administration.

METHODS

Oral cortisol (30 mg) was given to 29 healthy subjects whereas 31 control subjects received placebo. One hour after treatment all volunteers performed five consecutive blocks of a five-choice serial reaction time task by responding to colored lights by pressing buttons of the same color. The subjects responded without knowing to a quasi-randomized stimulus sequence, including higher-order sequential regularities (a combination of two colors that predicted the following target color). The reaction speed of every button-press (100 per block) was determined and difference scores were calculated as a proof of learning.

RESULTS

Both groups showed significant implicit sequence learning throughout the experiment. However, we found an impaired learning performance of the cortisol group compared with the placebo group. Further analysis revealed that a delayed learning in the cortisol group occurred at the very beginning of the task.

CONCLUSIONS

This study is the first human investigation indicating impaired implicit memory function after exogenous administration of the stress hormone cortisol. This effect may depend on hippocampus engagement in implicit sequence learning, but the involvement of other brain structures is also discussed.

Hydrocortisone impairs working memory in healthy humans, but not in patients with major depressive disorder

OBJECTIVE

Several studies have shown that stress or the administration of glucocorticoids can impair hippocampus-based declarative memory retrieval and prefrontal dependent working memory performance in healthy subjects. Major Depressive Disorder (MDD) is often characterized by memory impairment and increased cortisol secretion. Studies indicate that the impairing effects of glucocorticoids on declarative memory performance are missing in patients with MDD. The purpose of our study was to investigate whether the finding of missing effects of acute cortisol administration on memory performance in MDD is also seen when examining prefrontal-based working memory.

METHODS

In a placebo-controlled study, 57 patients with MDD and 56 sex- and age-matched healthy control subjects received either placebo or 10 mg of hydrocortisone orally before memory testing. To test the verbal modality of working memory, the Word Suppression Test was applied with one negative and one neutral test part.

RESULTS

After hydrocortisone intake, healthy subjects showed a significantly poorer working memory performance compared to placebo treatment when negative interference words were administered. In contrast, memory performance of MDD patients was not affected by hydrocortisone treatment.

CONCLUSIONS

The missing effects of glucocorticoid administration on working memory in MDD might be interpreted in the context of reduced central glucocorticoid receptor function.

Acute stress impairs memory retrieval independent of time of day

It is widely recognized that acute stress and associated glucocorticoid stress responses yield memory-enhancing effects when the memory consolidation phase is targeted, while impairing effects are generally found with regard to memory retrieval performance. While some evidence exists that the memory-enhancing effects of consolidation stress are modulated by time of day, no study to date has investigated whether stress-induced retrieval deficits are also prone to such time of day effects. To address this issue, participants (N=76) were exposed to a stressor or control condition before a retrieval test that probed for neutral and negative words learned 24h before. Results show that stress exposure resulted in impaired retrieval of both neutral and negative words, but that time of day did not moderate this effect. This memory-impairing effect was larger for negative than for neutral information, and was significantly associated with stress-induced cortisol responses. The current findings demonstrate the robustness of stress-induced retrieval deficits throughout the day, in particular for emotional memory material, and further underscore the importance of cortisol reactivity in impairing memory retrieval.

Elevated Cortisol at Retrieval Suppresses False Memories in Parallel with Correct Memories

Retrieving a memory is a reconstructive process in which encoded representations can be changed and distorted. This process sometimes leads to the generation of “false memories,” that is, when people remember events that, in fact, never happened. Such false memories typically represent a kind of “gist” being extracted from single encountered events. The stress hormone cortisol is known to substantially impair memory retrieval. Here, in a double-blind, placebo-controlled crossover design, we tested the effect of an intravenous cortisol infusion before retrieval testing on the occurrence of false memories and on recall of correct memories using a modified Deese–Roediger–McDermott paradigm. Subjects studied sets of abstract shapes, with each set being derived from one prototype that was not presented during learning. At retrieval taking place 9 hr after learning, subjects were presented with studied shapes, nonstudied shapes, and the prototypes, and had to indicate whether or not each shape had been presented at learning. Cortisol administration distinctly reduced susceptibility to false memories (i.e., false recognition of prototypes) and, in parallel, impaired retrieval of correct memories (i.e., correct recognition of studied shapes). Response bias as well as confidence ratings and remember/know/guess judgments were not affected. Our results support gist-based theories of false memory generation, assuming a simultaneous storage of the gist and specific details of an event. Cortisol, by a general impairing influence on retrieval operations, decreases, in parallel, retrieval of false (i.e., gist) and correct (i.e., specific) memories for the event.

Glucocorticoids enhance extinction-based psychotherapy

Behavioral exposure therapy of anxiety disorders is believed to rely on fear extinction. Because preclinical studies have shown that glucocorticoids can promote extinction processes, we aimed at investigating whether the administration of these hormones might be useful in enhancing exposure therapy. In a randomized, double-blind, placebo-controlled study, 40 patients with specific phobia for heights were treated with three sessions of exposure therapy using virtual reality exposure to heights. Cortisol (20 mg) or placebo was administered orally 1 h before each of the treatment sessions. Subjects returned for a posttreatment assessment 3-5 d after the last treatment session and for a follow-up assessment after 1 mo. Adding cortisol to exposure therapy resulted in a significantly greater reduction in fear of heights as measured with the acrophobia questionnaire (AQ) both at posttreatment and at follow-up, compared with placebo. Furthermore, subjects receiving cortisol showed a significantly greater reduction in acute anxiety during virtual exposure to a phobic situation at posttreatment and a significantly smaller exposure-induced increase in skin conductance level at follow-up. The present findings indicate that the administration of cortisol can enhance extinction-based psychotherapy.

The hippocampus in major depression: evidence for the convergence of the bench and bedside in psychiatric research?

Major depressive disorder (MDD) has until recently been conceptualized as an episodic disorder associated with 'chemical imbalances' but no permanent brain changes. Evidence has emerged in the past decade that MDD is associated with small hippocampal volumes. This paper reviews the clinical and biological correlates of small hippocampal volumes based on literature searches of PubMed and EMBASE and discusses the ways in which these data force a re-conceptualization of MDD. Preclinical data describe the molecular and cellular effects of chronic stress and antidepressant treatment on the hippocampus, providing plausible mechanisms through which MDD might be associated with small hippocampal volumes. Small hippocampal volumes are associated with poor clinical outcome and may be a mechanism through which MDD appears to be a risk factor for Alzheimer's disease. The pathways through which stress may be linked to MDD, the emergence of chronicity or treatment resistance in MDD and the association between MDD and memory problems may be at least partially understood by dissecting the association with depression and changes in the hippocampus. MDD must be re-conceived as a complex illness, associated with persistent morphological brain changes that are detectable before illness onset and which may be modified by clinical and treatment variables.

Enhanced fear expression in a psychopathological mouse model of trait anxiety: pharmacological interventions

The propensity to develop an anxiety disorder is thought to be determined by genetic and environmental factors. Here we investigated the relationship between a genetic predisposition to trait anxiety and experience-based learned fear in a psychopathological mouse model. Male CD-1 mice selectively bred for either high (HAB), or normal (NAB) anxiety-related behaviour on the elevated plus maze were subjected to classical fear conditioning. During conditioning both mouse lines showed increased fear responses as assessed by freezing behaviour. However, 24 h later, HAB mice displayed more pronounced conditioned responses to both a contextual or cued stimulus when compared with NAB mice. Interestingly, 6 h and already 1 h after fear conditioning, freezing levels were high in HAB mice but not in NAB mice. These results suggest that trait anxiety determines stronger fear memory and/or a weaker ability to inhibit fear responses in the HAB line. The enhanced fear response of HAB mice was attenuated by treatment with either the α(2,3,5)-subunit selective benzodiazepine partial agonist L-838,417, corticosterone or the selective neurokinin-1 receptor antagonist L-822,429. Overall, the HAB mouse line may represent an interesting model (i) for identifying biological factors underlying misguided conditioned fear responses and (ii) for studying novel anxiolytic pharmacotherapies for patients with fear-associated disorders, including post-traumatic stress disorder and phobias.

Effects of acute psychosocial stress on working memory related brain activity in men

Acute psychosocial stress in humans triggers the release of glucocorticoids (GCs) and influences performance in declarative and working memory (WM) tasks. These memory systems rely on the hippocampus and prefrontal cortex (PFC), where GC-binding receptors are present. Previous studies revealed contradictory results regarding effects of acute stress on WM-related brain activity. We combined functional magnetic resonance imaging with a standardized psychosocial stress protocol to investigate the effects of acute mental stress on brain activity during encoding, maintenance, and retrieval of WM. Participants (41 healthy young men) underwent either a stress or a control procedure before performing a WM task. Stress increased salivary cortisol levels and tended to increase WM accuracy. Neurally, stress-induced increases in cortical activity were evident in PFC and posterior parietal cortex (PPC) during WM maintenance. Furthermore, hippocampal activity was modulated by stress during encoding and retrieval with increases in the right anterior hippocampus during WM encoding and decreases in the left posterior hippocampus during retrieval. Our study demonstrates that stress increases activity in PFC and PPC specifically during maintenance of items in WM, whereas effects on hippocampal activity are restricted to encoding and retrieval. The finding that psychosocial stress can increase and decrease activity in two different hippocampal areas may be relevant for understanding the often-reported phase-dependent opposing behavioral effects of stress on long-term memory.

Glucocorticoid augmentation of prolonged exposure therapy: rationale and case report

RATIONALE

Prolonged exposure (PE) therapy has been found to reduce symptoms of posttraumatic stress disorder (PTSD); however, it is difficult for many patients to engage fully in the obligatory retelling of their traumatic experiences. This problem is compounded by the fact that habituation and cognitive restructuring - the main mechanisms through which PE is hypothesized to work - are not instantaneous processes, and often require several weeks before the distress associated with imaginal exposure abates.

CASE REPORTS

Two cases are described that respectively illustrate the use of hydrocortisone and placebo, in combination with PE, for the treatment of combat-related PTSD. Based on known effects of glucocorticoids on learning and memory performance, we hypothesized that augmentation with hydrocortisone would improve the therapeutic effects of PE by hastening "new" learning and facilitating decreases in the emotional impact of fear memories during the course of treatment. The veteran receiving hydrocortisone augmentation of PE displayed an accelerated and ultimately greater decline in PTSD symptoms than the veteran receiving placebo.

CONCLUSIONS

While no general conclusion can be derived from comparison of two patients, the findings are consistent with the rationale for augmentation. These case reports support the potential for an appropriately designed and powered clinical trial to examine the efficacy of glucocorticoids in augmenting the effects of psychotherapy for PTSD.