Hydrocortisone accelerates the decay of iconic memory traces: on the modulation of executive and stimulus-driven constituents of sensory information maintenance

Writing about a stressful experience can impair visual working memory

Acute stress has been well-established to impair working memory. However, less is known about how writing about an unresolved stressor may influence working memory or working memory processes. We addressed these issues in the present study (N = 282) by randomly assigning participants to write about an unresolved stressful experience (stressful writing condition or the events of the previous day). We then both measured performance on a change detection task and used computational modeling to estimate the processes underlying performance: attention, capacity, and guessing bias. We found that, relative to the control condition, writing about a stressful experience impaired change detection task performance and significantly impaired task attention. These results show that the effects of writing about an unresolved stressor may mimic the effects of acute stress on working memory, rather than conforming to expectations from mood-as-information theory.

Improving iconic memory through contrast detection training with HOA-corrected vision

Iconic memory and short-term memory are not only crucial for perception and cognition, but also of great importance to mental health. Here, we first showed that both types of memory could be improved by improving limiting processes in visual processing through perceptual learning. Normal adults were trained in a contrast detection task for ten days, with their higher-order aberrations (HOA) corrected in real-time. We found that the training improved not only their contrast sensitivity function (CSF), but also their iconic memory and baseline information maintenance for short-term memory, and the relationship between memory and CSF improvements could be well-predicted by an observer model. These results suggest that training the limiting component of a cognitive task with visual perceptual learning could improve visual cognition. They may also provide an empirical foundation for new therapies to treat people with poor sensory memory.

Accelerated forgetting of a trauma-like event in healthy men and women after a single dose of hydrocortisone

Posttraumatic stress disorder (PTSD) is characterised by dysregulated hypothalamic-pituitary-adrenal axis activity and altered glucocorticoid receptor sensitivity. Early treatment with glucocorticoids may reduce PTSD risk, although the effect of such treatment on the aetiologically critical step of traumatic-memory-formation remains unclear. Here we examine the effects of exogenous cortisol (hydrocortisone) in a preclinical model of PTSD, using a factorial (Drug × Sex), randomised-controlled, double-blind design. Healthy men and women (n = 120) were randomised to receive 30 mg oral hydrocortisone or matched placebo immediately after watching a stressful film. Effects on film-related intrusions were assessed acutely in the lab, and ecologically using daily memory diaries for one week. We found that participants receiving hydrocortisone showed a faster reduction in daily intrusion frequency. Voluntary memory was assessed once, at the end of the week, but was unaffected by hydrocortisone. Exploratory analyses indicated sex-dependent associations between intrusions and baseline estradiol and progesterone levels. In men receiving hydrocortisone, higher baseline estradiol levels were associated with fewer intrusions, whereas women exhibited the opposite pattern. By contrast, progesterone levels were positively associated with intrusions only in men treated with hydrocortisone. The findings suggest that hydrocortisone promotes an accelerated degradation of sensory-perceptual representations underlying traumatic intrusive memories. In addition, while sex alone was not an important moderator, the combination of sex and sex-hormone levels (especially estradiol) influenced hydrocortisone's effects on involuntary aversive memories. Future well-powered experimental studies may provide a basis for a precision-psychiatry approach to optimising early post-traumatic glucocorticoid treatments that target intrusive memories, based on individual endocrinological profiles.

Prospective memory under acute stress: The role of (output) monitoring and ongoing-task demands

Prospective memory (PM) refers to the ability to postpone retrieval and execution of intended actions until the appropriate situation (PM cue) has come, while engaging in other ongoing activities or tasks. In everyday live we often perform PM tasks in stressful situations. While it has been shown that acute stress does not impair PM-cue identification and intention retrieval, little is known about acute stress effects on PM performance and memory for having performed an action (output monitoring) under varying ongoing-task demands. Here we investigated this in eighty healthy participants who performed event-based PM tasks during low- and high-demanding ongoing working memory tasks after having undergone either a standardized stress induction (Maastricht Acute Stress Test) or a standardized control protocol. Successful stress induction in the stress group compared to the no-stress group was confirmed by increased salivary cortisol, an indicator of stress-related hypothalamus-pituitaryadrenal axis activity, throughout the event-based PM tasks. Nevertheless, not-only PM-cue identification but also output monitoring remained fully intact after stress induction. The absence of these effects was independent of ongoing-task demands. Nonetheless, we replicated recent findings of a stress-induced reduction in performance cost of monitoring for PM-cue occurrences. Taken together our findings suggest that acute stress alters PM monitoring by enhancing selective attention, decreasing PM response thresholds or by shifting performance towards more automatic processes in PM, while not affecting PM-cue identification and output monitoring.

Glucocorticoid-induced enhancement of extinction-from animal models to clinical trials

Extensive evidence from both animal model and human research indicates that glucocorticoid hormones are crucially involved in modulating memory performance. Glucocorticoids, which are released during stressful or emotionally arousing experiences, enhance the consolidation of new memories, including extinction memory, but reduce the retrieval of previously stored memories. These memory-modulating properties of glucocorticoids have recently received considerable interest for translational purposes because strong aversive memories lie at the core of several fear-related disorders, including post-traumatic stress disorder and phobias. Moreover, exposure-based psychological treatment of these disorders relies on successful fear extinction. In this review, we argue that glucocorticoid-based interventions facilitate fear extinction by reducing the retrieval of aversive memories and enhancing the consolidation of extinction memories. Several clinical trials have already indicated that glucocorticoids might be indeed helpful in the treatment of fear-related disorders.

Single-dose hydrocortisone administration does not enhance motor sequence learning or reward learning in humans

Despite its physiological and clinical relevance, the influence of hydrocortisone on specific kinds of learning remains relatively unexplored. We measured the effect of hydrocortisone on motor sequence and reward learning under non-stress conditions. For the study, 54 healthy young volunteers were randomly assigned to a dose of 20 mg hydrocortisone versus placebo. Participants performed two well-defined learning tasks. Hydrocortisone did not affect motor sequence or reward learning.

NMDA receptor modulation by dextromethorphan and acute stress selectively alters electroencephalographic indicators of partial report processing

Proceeding from a biophysical network model, the present study hypothesized that glutamatergic neurotransmission across the NMDA receptor (NMDAR) plays a key role in visual perception and its modulation by acute stress. To investigate these hypotheses, behavioral and electroencephalographic (EEG) indicators of partial report task processing were assessed in twenty-four healthy young men who randomly received a non-competitive NMDAR antagonist (0.8 mg/kg dextromethorphan, DXM) or a placebo, and concurrently accomplished a stress-induction (MAST) or control protocol in three consecutive sessions. Saliva samples served to quantify cortisol responses to the MAST, whereas a passive auditory oddball paradigm was implemented to verify the impact of DXM on the EEG-derived mismatch negativity component (MMN). DXM administration significantly increased MMN amplitudes but not salivary cortisol concentrations. By contrast, concurrent MAST exposure significantly reduced MMN latencies but also increased cortisol concentrations. With regard to EEG indicators, DXM administration reduced visually "evoked" (30Hz to 50Hz) and "induced" occipital gamma-band activity (70Hz to 100Hz), which was partly compensated by additional MAST exposure. However, neither the interventions nor EEG activity were significantly associated with behavioral partial report sensitivities. In summary, the present data suggest that glutamatergic neurotransmission across the NMDAR is only one among many determinants of intact visual perception. Accordingly, therapeutic doses of DXM and their inhibitory modulation by stress probably yield more pronounced electroencephalographic as compared with behavioural effects.

What you get from what you see: Parametric assessment of visual processing capacity in multiple sclerosis and its relation to cognitive fatigue

Multiple sclerosis (MS(1)) is a diffusely disseminated inflammatory disease affecting widespread cerebral networks. Major cognitive impairments are a reduction of processing capacity and mental fatigue, i.e., an "abnormal sense of tiredness or lack of energy". Here, the present study provides the first assessment of the distinct components of visual processing capacity based on a 'theory of visual attention' (TVA(2)) in MS patients and relates it to measures of subjective as well as (more) objective fatigue. The performance of 36 relapsing-remitting MS patients in a whole report task of brief letter arrays was compared to healthy control subjects matched for gender, age and education. Additionally, the sustained attention test PASAT-3(3) served as a measure of objective fatigue, and the self-report questionnaire MFIS(4) as a measure of subjective fatigue. Results indicate generally diminished processing speed as well as iconic memory buffers, and increased perceptual thresholds in MS patients compared to healthy controls. Block-wise analysis of attentional parameters shows that the processing speed performance of MS patients declines in the second half of the TVA-based test compared to healthy controls and in particular for patients with high versus low objective fatigue. These findings describe which aspects of processing capacity are impaired in MS, and show that fatigue mainly affects speed of processing. Thus, TVA-based assessment provides a novel approach in the determination of cognitive impairments and fatigue in MS. However, further research is required to elucidate the complex relations of processing capacity and cognitive functions in MS.

Hydrocortisone Counteracts Adverse Stress Effects on Dual-Task Performance by Improving Visual Sensory Processes

The impact of acute stress on executive processes is commonly attributed to glucocorticoid-induced disruptions of the pFC. However, the occipital cortex seems to express a higher density of glucocorticoid receptors. Consequently, acute stress effects on executive processes could as well be mediated by glucocorticoid (e.g., cortisol)-induced alterations of visual sensory processes. To investigate this alternative route of stress action by demarcating the effects of acute stress and cortisol on executive from those on visual sensory processes, 40 healthy young men completed a standardized stress induction (i.e., the Trier Social Stress Test) and control protocol in two consecutive sessions. In addition, they received either a placebo or hydrocortisone (0.12-mg/kg bodyweight) pill and processed a dual and a partial report task to assess their executive and visual sensory processing abilities, respectively. Hydrocortisone administration improved both partial report and dual-task performance as indicated by increased response accuracies and/or decreased RTs. Intriguingly, the hydrocortisone-induced increase in dual-task performance was completely mediated by its impact on partial report performance (i.e., visual sensory processes). Moreover, RT measures in both tasks shared approximately 26% of variance, which was only in part attributable to hydrocortisone administration (ΔR² = 8%). By contrast, acute stress selectively impaired dual-task performance (i.e., executive processes), presumably through an alternative route of action. In summary, the present results suggest that cortisol secretion (as mimicked by hydrocortisone administration) may counteract adverse residual stress effects on executive processes by improving visual sensory processes (e.g., the maintenance and amplification of task-relevant sensory information).