Context-dependent memory under stressful conditions: the case of skydiving

Context reinstatement requires a schema relevant virtual environment to benefit object recall

How does our environment impact what we will later remember? Early work in real-world environments suggested that having matching encoding/retrieval contexts improves memory. However, some laboratory-based studies have not replicated this advantageous context-dependent memory effect. Using virtual reality methods, we find support for context-dependent memory effects and examine an influence of memory schema and dynamic environments. Participants (N = 240) remembered more objects when in the same virtual environment (context) as during encoding. This traded-off with falsely "recognizing" more similar lures. Experimentally manipulating the virtual objects and environments revealed that a congruent object/environment schema aids recall (but not recognition), though a dynamic background does not. These findings further our understanding of when and how context affects our memory through a naturalistic approach to studying such effects.

Neuropsychological correlates of evocative multimodal speech: The combined roles of fearful prosody, visuospatial attention, cortisol response, and anxiety

Past research reveals left-hemisphere dominance for linguistic processing and right-hemisphere dominance for emotional prosody processing during auditory language comprehension, a pattern also found in visuospatial attention studies where listeners are presented with a view of the talker's face. Is this lateralization pattern for visuospatial attention and language processing upheld when listeners are experiencing a stress response? To investigate this question, participants completed the Trier Social Stress Test (TSST) between administrations of a visuospatial attention and language comprehension dual-task paradigm. Subjective anxiety, cardiovascular, and saliva cortisol measures were taken before and after the TSST. Higher language comprehension scores in the post-TSST neutral prosody condition were associated with lower cortisol responses, differences in blood pressure, and less subjective anxiety. In this challenging task, visuospatial attention was most focused at the mouth region, both prior to and after stress induction. Greater visuospatial attention on the left side of the face image, compared to the right side, indicated greater right hemisphere activation. In the Fear, but not the Neutral, prosody condition, greater cortisol response was associated with greater visuospatial attention to the left side of the face image. Results are placed into theoretical context, and can be applied to situations where stressed listeners must interpret emotionally evocative language.

Cognitive reappraisal in an unpredictable world: Prior context matters

Cognitive reappraisal is a higher order emotion regulation strategy, the effects of which can be measured using the late positive potential (LPP), an event-related potential that is larger for emotional versus neutral stimuli. Whereas the lab provides a relatively predictable and calm environment in which to engage in reappraisal, outside of the lab, individuals may need to enact reappraisal in unpredictable and anxiety-provoking environments. In prior work, unpredictable auditory tones have been shown to increase threat-processing and induce anxiety. Here, forty-seven participants performed a reappraisal task while being exposed in a blockwise fashion to a "Random Tone" sequence or silence ("No Tone"), to determine the effects of an unpredictable auditory stimulus on the reappraisal of negative pictures. In addition, exploratory analyses assessed whether starting block (i.e., beginning the task in a Random Tone versus No Tone block) would moderate effects. Results showed that during an early time window, reappraisal LPPs were smallest for participants who started in a No Tone block and who performed reappraisal in a No Tone block. Therefore, reappraisal may be optimally performed when conditions are predictable/calm, by participants whose initial learning context was also predictable/calm. In addition, larger LPPs for negative versus neutral images were only observed throughout the later portion of picture presentation for participants who began in a Random Tone block, suggesting that unpredictability may increase sustained attention towards aversive stimuli. The results fit within a growing body of work aimed at understanding contextual and individual differences in emotion regulation.

Memory-Related Encoding-Specificity Paradigm: Experimental Application to the Exercise Domain

The Encoding-Specificity Paradigm indicates that memory recall will be superior when contextual factors are congruent between memory encoding and memory retrieval. However, unlike other contextual conditions (e.g., verbal context, mental operations, global feature context, mood dependency, and physical operations), this paradigm has nearly been ignored in the exercise domain. Thus, the purpose of this study was to examine the Encoding-Specificity Paradigm in the context of exercise and rest conditions. 24 young adults (age: M = 21 years) completed a within-subject, counterbalanced experiment involving four laboratory visits, including 1) R-R (rest-rest) condition, 2) R-E (rest-exercise) condition, 3) E-R (exercise-rest) condition, or 4) E-E (exercise-exercise) condition. The exercise bout included a 15-minute moderate-intensity walk on a treadmill. Memory recall was assessed via a 15 word-list task. Memory recall was greater for R-R (8.71 ± 3.1) versus R-E (7.46 ± 2.8), and similarly, for E-E (8.63 ± 2.7) versus E-R (8.21 ± 2.7). The mean word recall for the congruent and incongruent conditions, respectively, was 8.67 (2.4) and 7.83 (2.4). There was a statistically significant condition effect (F = 5.02; P = .03; partial η² = .18). This experiment provides direct support for the Encoding-Specificity Paradigm in the exercise domain.

Memory, stress, and the hippocampal hypothesis: Firefighters' recollections of the fireground

Nadel, Jacobs, and colleagues have postulated that human memory under conditions of extremely high stress is "special." In particular, episodic memories are thought to be susceptible to impairment, and possibly fragmentation, attributable to hormonally based dysfunction occurring selectively in the hippocampal system. While memory for highly salient and self-relevant events should be better than the memory for less central events, an overall nonmonotonic decrease in spatio/temporal episodic memory as stress approaches traumatic levels is posited. Testing human memory at extremely high levels of stress, however, is difficult and reports are rare. Firefighting is the most stressful civilian occupation in our society. In the present study, we asked New York City firefighters to recall everything that they could upon returning from fires they had just fought. Communications during all fires were recorded, allowing verification of actual events. Our results confirmed that recall was, indeed, impaired with increasing stress. A nonmonotonic relation was observed consistent with the posited inverted u-shaped memory-stress function. Central details about emergency situations were better recalled than were more schematic events, but both kinds of events showed the memory decrement with high stress. There was no evidence of fragmentation. Self-relevant events were recalled nearly five times better than events that were not self-relevant. These results provide confirmation that memories encoded under conditions of extremely high stress are, indeed, special and are impaired in a manner that is consistent with the Nadel/Jacobs hippocampal hypothesis.

Association of physical activity on changes in cognitive function: Boston Puerto Rican Health Study

OBJECTIVE

To evaluate the association of habitual physical activity engagement on changes in cognitive function among Puerto Rican adults.

METHODS

Longitudinal data (2-year follow-up) from the Boston Puerto Rican Health Study were analyzed (n = 862; mean age = 56.5 year). A daily energy expenditure score was calculated using the number of hours over a 24-h period engaged in various activities, including sleeping, light activity, and moderate-to-vigorous exercise. Energy expenditure estimates were weighted based on the rate of oxygen consumption associated with each activity. Seven cognitive function outcomes were evaluated, including an assessment of general cognitive function, episodic memory, attention and working memory, cognitive flexibility, response inhibition, processing speed, and visuo-spatial organization. From these, overall executive function and memory capacity were derived using principal components analysis.

RESULTS

Physical activity was not associated with changes in overall executive function. However, compared to those with low baseline physical activity, those with moderate physical activity had 48% reduced odds of having ≥1 standard deviation decline in memory function (OR = 0.52; 95% CI: 0.32, 0.84; p = 0.008) in 2 years.

CONCLUSION

Among Puerto Rican adults, physical activity may help attenuate memory decline.

Reinstating verbal memories with virtual contexts: Myth or reality?

When learning new information, contextual information about the encoding situation is stored in addition to the focal memory content. Later, these strings of extra information can help retrieve the learned content as demonstrated by experiments where contextual cues from an encoding situation facilitate remembering and improve memory performance when reinstated during retrieval. This context-dependent memory effect has been investigated over the course of several decades and has been demonstrated with many different types of contexts. Based on this, the widely held belief is that context-dependent memory is a strong and robust effect, with transferable substance for everyday learning and potential clinical applications. Here we report the results of a multi-study design investigating the influence of reinstated visual contexts on memory performance. Data from 120 participants were included in three studies comprising a variety of visual cues. We show convincingly that even rich, salient and fully surrounding visual contexts provided by virtual reality are not sufficient to induce effects of context-dependency in a free recall memory task. We also investigated contextual modulation of oscillatory brain activity in order to test the effect of reinstated neural contexts, which failed to evoke a robust effect when re-tested in an internal conceptual replication study. Moreover, a Bayesian sequential statistical analysis revealed moderate to strong evidence against the hypothesis that reinstatement of visual contexts benefits free recall memory tasks indicating that effects are small and may not be suitable for transfer into everyday learning.

The effects of acute stress on episodic memory: A meta-analysis and integrative review

A growing body of research has indicated that acute stress can critically impact memory. However, there are a number of inconsistencies in the literature, and important questions remain regarding the conditions under which stress effects emerge as well as basic questions about how stress impacts different phases of memory. In this meta-analysis, we examined 113 independent studies in humans with 6,216 participants that explored effects of stress on encoding, postencoding, retrieval, or postreactivation phases of episodic memory. The results indicated that when stress occurred prior to or during encoding it impaired memory, unless both the delay between the stressor and encoding was very short and the study materials were directly related to the stressor, in which case stress improved encoding. In contrast, postencoding stress improved memory unless the stressor occurred in a different physical context than the study materials. When stress occurred just prior to or during retrieval, memory was impaired, and these effects were larger for emotionally valenced materials than neutral materials. Although stress consistently increased cortisol, the magnitude of the cortisol response was not related to the effects of stress on memory. Nonetheless, the effects of stress on memory were generally reduced in magnitude for women taking hormonal contraceptives. These analyses indicate that stress disrupts some episodic memory processes while enhancing others, and that the effects of stress are modulated by a number of critical factors. These results provide important constraints on current theories of stress and memory, and point to new questions for future research. (PsycINFO Database Record

[Human factors in medicine]

The concept of human factors is commonly used in the context of patient safety and medical errors, all too often ambiguously. In actual fact, the term comprises a wide range of meanings from human-machine interfaces through human performance and limitations up to the point of working process design; however, human factors prevail as a substantial cause of error in complex systems. This article presents the full range of the term human factors from the (emergency) medical perspective. Based on the so-called Swiss cheese model by Reason, we explain the different types of error, what promotes their emergence and on which level of the model error prevention can be initiated.

Concussion reporting behaviours of community college student-athletes and limits of transferring concussion knowledge during the stress of competition

Concussion education for student-athletes is mandated by several states and is becoming an integral component of concussion management programmes; however, little is known about student-athlete concussion knowledge and self-reporting of suspected concussion. This study explored to what extent collegiate student-athletes are knowledgeable on the topic of concussion, the relationship between having concussion knowledge and reporting behaviours, and factors contributing to not reporting when education has been provided.

Glucose changes and working memory in individuals with type 1 diabetes during air pressure changes simulating skydiving

BACKGROUND

Several countries restrict individuals with type 1 diabetes mellitus (T1DM) from skydiving because of concerns over possible alterations in consciousness. To our knowledge, glucose levels and working memory in individuals with T1DM during skydiving have not been assessed earlier. The objective of this study was to investigate changes in glucose levels and working memory in selected subjects with T1DM compared with control subjects without diabetes mellitus (DM) during ambient air pressure changes as those anticipated during standard skydiving.

SUBJECTS AND METHODS

Six subjects with T1DM and six controls were included. Using a hypobaric chamber, the ambient air pressure was changed to simulate a standard skydive from 4,000 m (13,000 feet) above mean sea level. The procedure was repeated six times to mimic a day of skydiving activity with a median of 8.7 h/day (5(th), 95(th) percentile: 8.1, 9.8 h). All subjects carried a continuous glucose monitor (CGM). Capillary glucose tests were taken in order to calibrate the CGM. Hemoglobin oxygen saturation, heart rate, and working memory, evaluated through digit span, were monitored regularly.

RESULTS

No subject experienced documented symptomatic hypoglycemia with impaired working memory during the simulations. One asymptomatic hypoglycemia episode with a plasma glucose level of <3.9 mmol/L was recorded in a subject with T1DM, with a corresponding CGM trend indicating declining glucose levels. Interstitial glucose levels of <3.9 mmol/L were recorded by CGM in three of the controls during the simulations. There were no significant differences in hemoglobin oxygen saturation, heart rate, or working memory between the T1DM patients and the controls.

CONCLUSIONS

This study of interstitial glucose levels and working memory could not show the activity-specific risk factor (i.e., repetitive rapid-onset hypobaric hypoxia exposures) to be a greater safety concern for selected subjects with T1DM compared with subjects without DM during a simulated day of skydiving. Further studies are needed to clarify the suitability of subjects with T1DM to participate in this air sport.

A survey of anesthesiologists' knowledge of American Heart Association Pediatric Advanced Life Support Resuscitation Guidelines

AIM OF STUDY

Determine anesthesiologists' knowledge of the 2005 American Heart Association (AHA) Pediatric Advanced Life Support (PALS) recommendations.

METHODS

After obtaining institutional review board approval, a survey was sent in February 2007 to members of the Society for Pediatric Anesthesia via a web-based survey tool, and re-sent to nonresponders five times over the following 7 months.

RESULTS

Overall response rate was 51% (389/768 members). Eighty-five percent of respondents had pediatric anesthesia fellowships, 71% provided anesthesia primarily to children, 71% had been in practice >10 years, 29% had PALS or APLS training during the previous year, and 37% had a patient requiring chest compressions in the previous year. Overall, 89% of respondents knew the correct initial dose of epinephrine (adrenaline) for asystole, 44% knew subsequent management for asystole if initial epinephrine dose was ineffective, 49% knew defibrillation sequence to treat pulseless ventricular tachycardia (VT), and 73% knew the medication sequence to treat pulseless VT. Only those respondents who reported to be in practice for >10 years scored significantly (p<0.0001) better on all resuscitation treatment questions. Respondents who had PALS or APLS training in the previous year or previous 2 years scored significantly better on the defibrillation sequence for pulseless VT (p=0.001 and p=0.045, respectively), and the medication sequence for pulseless VT (p=0.0005 and p=0.011, respectively) when compared with those who had no previous training.

CONCLUSION

Deficiencies exist in the knowledge of current AHA PALS guidelines among anesthesiologists. Formal resuscitation training programs should be considered in ongoing continuing medical education.

Pre-training administration of tianeptine, but not propranolol, protects hippocampus-dependent memory from being impaired by predator stress

Extensive research has shown that the antidepressant tianeptine blocks the adverse effects of chronic stress on hippocampal functioning. The current series of experiments extended this area of investigation by examining the influence of tianeptine on acute stress-induced impairments of spatial (hippocampus-dependent) memory. Tianeptine (10 mg/kg, ip) administered to adult male rats before, but not after, water maze training blocked the amnestic effects of predator stress (occurring between training and retrieval) on memory. The protective effects of tianeptine on memory occurred in rats which had extensive pre-stress training, as well as in rats which had only a single day of training. Tianeptine blocked stress effects on memory without altering the stress-induced increase in corticosterone levels. Propranolol, a beta-adrenergic receptor antagonist (5 and 10 mg/kg, ip), in contrast, did not block stress-induced amnesia. These findings indicate that treatment with tianeptine, unlike propanolol, provides an effective means with which to block the adverse effects of stress on cognitive functions of the hippocampus.

The effect of arousal on memory for emotionally-relevant information: A study of skydivers

The aim of the present study was to test memory for information under conditions of extreme arousal in an analogue design to mimic hyperarousal during trauma exposure. Prior to their skydive, 70 novice skydivers were administered measures of fear, heart rate, and anxiety sensitivity. Half the participants learnt a list of words that varied in both relevance to their skydive and valence (irrelevant/relevant, negative/neutral) on the plane (skydivers), and remaining participants learnt an identical list of words on the ground (delayed controls). Following the skydive, participants completed free recall and recognition tasks; heart rate, dissociation, and subjective arousal were also measured. Consistent with an attentional narrowing hypothesis, skydivers recalled comparable a comparable number of relevant words as delayed controls, but significantly less irrelevant words. In terms of recognition performance, skydivers displayed better recognition of relevant words but poorer recognition of irrelevant words than delayed controls. Valence of words did not alter the pattern of results. The implications of the findings are discussed in the context of understanding memory processes under conditions of high threat.

Prevalence of sensory and cognitive disabilities and falls, and their relationships: a community-based study

This study assessed the prevalence of sensory and cognitive disabilities and falls for various age groups, sexes, and socio-occupational categories, and their associations in the Lorraine population. The sample included 6,159 subjects, aged 15 years or more, randomly selected from the Lorraine population. They filled in a mailed questionnaire including socio-demographic characteristics, job, falls with physical injuries at the time of the survey, and sensory and cognitive disabilities. Data analysis was made via the adjusted odds ratios. The prevalences of sensory and cognitive disabilities were 3.0 and 4.7%, respectively, that of falls with physical injuries 2.4%: 1.2% for falls on the same level and 1.2% for falls to a lower level. Subjects aged over 70 were markedly affected, but the other age groups had relatively high prevalences as well; the workmen had the highest prevalence, followed by the foremen, farmers, craftsmen and tradesmen, and employees. A twofold risk independently of age, sex and job was found for the subjects with sensory or cognitive disabilities for all falls combined. These findings show the high prevalences of sensory and cognitive disabilities and falls with physical injuries, and their strong associations in the general population. Preventive measures are needed to detect and follow up the persons with these disabilities, limit their risk of falls and reduce occupational hazards.