Astronauts will spend prolonged periods in an isolated, confined, and extreme (ICE) spaceflight environment on long-duration space exploration missions. Continuous confinement in close quarters with a few crewmembers will require high levels of crew cohesion to promote mission success and crewmember wellbeing. In the past, the most common measure of crew cohesion were surveys, which tend to have high participant bias. More recently, researchers have analyzed video recordings that provide detailed proximity information but are time consuming to score and prone to interobserver bias. Here, we measured crewmember proximity as a surrogate measure of crew cohesion with proximity sensors worn by crewmembers during two Antarctic 10-14 months winter-over missions (N = 13 in 2015 and N = 12 in 2016). These sensors recorded instances of crewmembers being close in distance to each other, allowing for the identification of trends in crewmember interactions and crewmember withdrawal. We demonstrate that proximity is an unobtrusive, objective, and easy to obtain surrogate measure for crew cohesion that reveals systematic changes with time in mission. This includes a decrease in crew cohesion resulting from more time spent alone as each mission progressed, and higher average crew cohesion scores in Year 1 than in Year 2. Findings from this study could be used to monitor sudden or gradual withdrawal from other crewmembers and provide insights unobtrusively on crew cohesion without compromising crew autonomy.

Astronauts face significant stress in space, and understanding its neurobiological basis is key to assessing risk and resilience. Analogue environments, like the Antarctic Concordia Station, replicate isolated, confined, and extreme (ICE) conditions. This study assessed brain structure changes in 25 crewmembers who spent 12 months at Concordia, with MRI scans conducted before, immediately after, and five months post-mission. The study included 25 controls scanned over a similar interval and 4 "flying phantom" individuals who were scanned at all sites. Gray matter in the temporal and parietal lobes, hippocampus, pallidum, and thalamus as well as global white matter decreased during the mission in crewmembers, with all but the thalamus returning to baseline after five months. Brain ventricle volume increased, and better sleep correlated with less brain volume loss, highlighting its potentially protective role. These findings emphasize the importance of understanding mechanisms driving brain changes, particularly with growing interest in extended space missions in ICE environments.

Monkeys sometimes accurately predict their memory accuracy, a form of metamemory. The memory signals that support this ability may differ between memory systems and depend on when memory judgments are made. Working memory requires active maintenance through the delay interval. Familiarity allows recognition without active maintenance and is triggered by representation of memoranda at test. We measured metamemory prospectively, during delay intervals, and concurrently, at the time of tests, while six male rhesus monkeys performed tasks that favored working memory or familiarity. Metamemory was accurate at both times in both tasks, and highest for concurrent judgments in the familiarity task.

Category learning is often tested with similar images that have no significance outside of the experiment for the subjects. By contrast, in nature animals often need to generalize a behavioral response like “eat” across visually distinct stimuli, such as spiders and seeds. Forming functional categories like “food” and “predator” may require conceptual rather than purely perceptual generalization. We trained free-range chickens to classify images assigned to one of four categories based on putative functional significance: inanimate objects, predators, food, and non-competing vertebrates. Images were visually diverse within each category, discouraging classification by perceptual similarity alone. In Experiment 1, chickens classified 80 images into four categories. Chickens then generalized to 80 new exemplars in each of three successive generalization tests. In Experiment 2, chickens saw new types of images to test whether their generalization was perceptual or functional. For example, chickens saw images of skunks for the predator category after training with images of hawks and snakes. Chickens used the “predator” response with these new images for both predators and non-threatening vertebrates, but not for objects or food, and did not successfully generalize any category other than predator. In Experiment 3, chickens categorized fractals as “food,” and three of four chickens categorized a range of vertebrates they had not previously encountered as “predators,” suggesting that chickens did not see the images as representing real world objects and animals. These results highlight constraints on the use of computer-generated images to assess categorization of natural stimuli in chickens.

There is substantial evidence of group-specific behaviors in wild animals that are thought to be socially transmitted. Yet experimental studies with monkeys have reported conflicting evidence on the extent to which monkeys learn by observing their conspecifics. In this study, we tested the feasibility of using pre-recorded video demonstrations to investigate social learning from conspecifics in rhesus monkeys. With training, monkeys gradually learned to respond correctly following videos of a demonstrator, however, follow-up experiments revealed that this was not due to learning from the demonstrator monkey. In generalization tests with videos that were horizontally reversed, monkeys continued responding to the location they had associated with each video, rather than matching the new choice location shown in the mirrored video. When the task was changed to make location irrelevant, such that monkeys could choose correctly only by selecting the same image selected by the demonstrator in the video, observer monkeys did not exceed chance in 12,000 training trials. Because monkeys readily learn to follow nonsocial visual cues presented on a monitor to guide image choice, their inability to learn from a demonstrator here indicates substantial limitations in the capacity for social learning from videos. Furthermore, these findings encourage deeper consideration of what monkeys perceive when presented with video stimuli on computer screens.

Background: Sustained high levels of astronaut cognitive performance are a prerequisite for mission success. A neuropsychological battery of 10 brief cognitive tests (Cognition) covering a range of cognitive domains was specifically developed for high performing astronauts to objectively assess cognitive performance. Extended mission durations require repeated cognitive testing and thus high acceptability of the Cognition software to the astronaut population. The aim of this qualitative study was to evaluate acceptability of Cognition to astronauts and astronaut surrogate populations. Methods: Cognition was administered repeatedly to N = 87 subjects (mean age +/- SD 35.1 +/- 8.7 years, 52.8% male) on a laptop or iPad across five individual studies on the International Space Station or in space analog environments on Earth. Following completion of each study, participants were interviewed regarding their experience using Cognition in a semi-structured debrief. Participant comments were analyzed using a qualitative conventional content analysis approach. Results: The majority of participants' comments (86.1%) were coded as positive or neutral in valence, with most positive comments relating to software usability, engagement, and overall design. Among the 10 Cognition tests, subjects liked the Visual Object Learning Test most (28 likes, 32.2% of participants), while the Emotion Recognition Test was liked least (44 dislikes, 50.6% of participants). Some subjects (36.8%) were frustrated with the level of difficulty of some of the 10 Cognition tests, especially during early administrations, which was by design to avoid ceiling effects in repeated administrations of high-performers. Technical difficulties were rare (20.7% of participants), and most often observed in environments with restricted internet access. Most participants (82.3% of those who commented) liked the feedback provided by Cognition after each test, which includes a graph showing performance history. Conclusion: Cognition was found to be acceptable to astronaut and astronaut-surrogate populations across a variety of settings and mission durations. Participant feedback provided was used to further improve Cognition and increase its acceptability during sustained space missions.

Chronic sleep loss is associated with escalating declines in vigilant attention across days of sleep restriction. However, studies exceeding 2 weeks of chronic sleep loss are scarce, and the cognitive performance outcomes assessed are limited. We assessed the effects of 6 weeks of chronic sleep restriction on a range of cognitive domains in 15 high-performing individuals (38.5 ± 8.2 years, 6 women) confined to small space in groups of 4. Sleep opportunities were limited to 5 h on weekdays and 8 h on weekends. Individual sleep-wake patterns were recorded with actigraphy. Neurobehavioral performance was assessed in evenings with Cognition, a computerized battery of ten tests assessing a range of cognitive domains. There were some small to moderate effects of increasing sleep debt relative to pre-mission baseline, with decreases in accuracy across cognitive domains (standardized β = -0.121, p = 0.001), specifically on tests of spatial orientation (β = -0.289, p = 0.011) and vigilant attention (β = -0.688, p < 0.001), which were not restored by two nights of weekend recovery sleep. Cognitive and subjective decrements occurred despite occasional daytime napping in breach of study protocol, evening testing around the circadian peak, and access to caffeine before 14:00. Sensorimotor speed, spatial learning and memory, working memory, abstraction and mental flexibility, emotion identification, abstract reasoning, cognitive throughput, and risk decision making were not significantly affected by sleep debt. Taken together with modest lower subjective ratings of happiness and healthiness, these findings underline the importance of sufficient sleep, on both an acute and chronic basis, for performance in selected cognitive domains and subjective wellbeing in operationally relevant environments.

NEW AND NOTEWORTHY This study investigated the effects of prolonged head-down tilt bed rest with and without elevated (3.73 mmHg) levels of ambient CO2 on cognitive performance across a range of cognitive domains and is one of the few studies investigating combined effects of environmental stressors prevalent in spaceflight. The study showed moderate declines in cognitive speed induced by head-down tilt bed rest and suggests that exposure to elevated levels of ambient CO2 did not modify this effect.

STUDY OBJECTIVES:The psychomotor vigilance test (PVT) is frequently used to measure behavioral alertness in sleep research on various software and hardware platforms. In contrast to many other cognitive tests, PVT response time (RT) shifts of a few milliseconds can be meaningful. It is, therefore, important to use calibrated systems, but calibration standards are currently missing. This study investigated the influence of system latency bias and its variability on two frequently used PVT performance metrics, attentional lapses (RTs ≥500 ms) and response speed, in sleep-deprived and alert participants. METHODS:PVT data from one acute total (N = 31 participants) and one chronic partial (N = 43 participants) sleep deprivation protocol were the basis for simulations in which response bias (±15 ms) and its variability (0-50 ms) were systematically varied and transgressions of predefined thresholds (i.e. ±1 for lapses, ±0.1/s for response speed) recorded. RESULTS:Both increasing bias and its variability caused deviations from true scores that were higher for the number of lapses in sleep-deprived participants and for response speed in alert participants. Threshold transgressions were typically rare (i.e. <5%) if system latency bias was less than ±5 ms and its standard deviation was ≤10 ms. CONCLUSIONS:A bias of ±5 ms with a standard deviation of ≤10 ms could be considered maximally allowable margins for calibrating PVT systems for timing accuracy. Future studies should report the average system latency and its standard deviation in addition to adhering to published standards for administering and analyzing the PVT.

Maintaining optimal cognitive performance in astronauts during spaceflight is critical to crewmember safety and mission success. To investigate the combined effects of confinement, isolation, and sleep deprivation on cognitive performance during spaceflight, we administered the computerized neurobehavioral test battery “Cognition” to crew members of simulated spaceflight missions as part of NASA’s ground-based Human Exploration Research Analog project. Cognition was administered to N = 32 astronaut-like subjects in four 1-week missions (campaign 1) and four 2 weeks missions (campaign 2), with four crewmembers per mission. In both campaigns, subjects performed significantly faster on Cognition tasks across time in mission without sacrificing accuracy, which is indicative of a learning effect. On an alertness and affect survey, subjects self-reported significant improvement in several affective domains with time in mission. During the sleep restriction challenge, subjects in campaign 1 were significantly less accurate on a facial emotion identification task during a night of partial sleep restriction. Subjects in campaign 2 were significantly slower and less accurate on psychomotor vigilance, and slower on cognitive throughput and motor praxis tasks during a night of total sleep deprivation. On the survey, subjects reported significantly worsening mood during the sleep loss challenge on several affective domains. These findings suggest that confinement and relative isolation of up to 2 weeks in this environment do not induce a significant negative impact on cognitive performance in any of the domains examined by Cognition, although the concurrent practice effect may have masked some of the mission’s effects. Conversely, a night of total sleep deprivation significantly decreased psychomotor vigilance and cognitive throughput performance in astronaut-like subjects. This underscores the importance of using cognitive tests designed specifically for the astronaut population, and that survey a range of cognitive domains to detect the differential effects of the wide range of stressors common to the spaceflight environment.

INTRODUCTION: Environmental and operational stressors commonly encountered in spaceflight can affect astronaut cognitive performance. It is currently unclear how performance decrements on test batteries that assess individual cognitive domains translate to complex operational performance.METHODS:N 30 healthy adults (mean SD age 33.5 7.1 yr, range 2548 yr; 16 men) with demographic characteristics similar to astronauts performed all 10 tests of the Cognition test battery as well as a simulated 6 degrees-of-freedom (6df) spacecraft docking task 15 times. Performance on 60 Cognition outcome variables was rank-correlated with 6df docking performance individually as well as in models containing up to 12 predictors after accounting for sex, age, and study design effects.RESULTS: Average response time on the Digit Symbol Substitution Test (DSST)a measure of processing speed requiring complex scanning, visual tracking, and working memorywas the best individual predictor of 6df docking performance (unadjusted r 0.550; semipartial cross-validated R² 0.244). Furthermore, higher levels of spatial orientation efficiency and vigilant attention, lower levels of impulsivity, and faster response speed were associated with higher 6df performance, while sensorimotor speed, memory, and risk decision making were less relevant. After semipartial cross-validation, a model with three Cognition outcomes (DSST average response time, Abstract Matching accuracy, and conservative response bias on the Fractal 2-Back test) explained 30% of the variance in 6df performance.CONCLUSIONS: This study demonstrates direct links between performance on tests designed to assess specific cognitive domains and complex operational docking performance.Basner M, Moore TM, Hermosillo E, Nasrini J, Dinges DF, Gur RC, Johannes B. Cognition test battery performance is associated with simulated 6df spacecraft docking performance. Aerosp Med Hum Perform. 2020; 91(11):861867.

ABSTRACT Introduction Practice effects associated with the repeated administration of cognitive tests often confound true therapeutic or experimental effects. Alternate test forms help reduce practice effects, but generating stimulus sets with identical properties can be difficult. The main objective of this study was to disentangle practice and stimulus set effects for Cognition, a battery of 10 brief cognitive tests specifically designed for high-performing populations with 15 unique versions for repeated testing. A secondary objective was to investigate the effects of test-retest interval on practice effects. Methods The 15 versions of Cognition were administered in three groups of 15–16 subjects (total N = 46, mean±SD age 32.5 ± 7.2 years, range 25–54 years, 23 male) in a randomized but balanced fashion with administration intervals of ≥10 days, ≤5 days, or 4 times per day. Mixed effect models were used to investigate linear and logarithmic trends across repeated administrations in key speed and accuracy outcomes, whether these trends differed significantly between administration interval groups, and whether stimulus sets differed significantly in difficulty. Results Protracted, non-linear practice effects well beyond the second administration were observed for most of the 10 Cognition tests both in accuracy and speed, but test-retest administration interval significantly affected practice effects only for 3 out of the 10 tests and only in the speed domain. Stimulus set effects were observed for the 6 Cognition tests that use unique sets of stimuli. Factors were established that allow for correcting for both practice and stimulus set effects. Conclusions Practice effects are pronounced and probably under-appreciated in cognitive testing. The correction factors established in this study are a unique feature of the Cognition battery that can help avoid masking practice effects, address noise generated by differences in stimulus set difficulty, and facilitate interpretation of results from studies with repeated assessments.

BACKGROUND: Cognition is a neurocognitive test battery created at the University of Pennsylvania and adapted by the National Aeronautics and Space Administration (NASA). It comprises 10 neurocognitive tests that examine multiple domains, and has been validated in a normative sample of STEM-educated adults and compared to NASA's WinSCAT battery.METHODS: The purpose of this study was to follow the original sample to assess Cognition and WinSCAT's test-retest reliability and age, sex, and test-retest interval effects on performance.RESULTS: Performance on both Cognition and WinSCAT decreased with age but improved with repeated administration due to practice effects, and men had higher scores than women on tasks that required vigilant attention, spatial reasoning, and risk-taking behaviors. Assessment of test-retest reliability showed intraclass coefficients for efficiency ranging from 0.417 to 0.810, reflecting the broad nature of constructs assessed by Cognition.DISCUSSION: Results largely matched predictions, with some counter-intuitive results for test-retest reliability interval.Lee G, Moore TM, Basner M, Nasrini J, Roalf DR, Ruparel K, Port AM, Dinges DF, Gur RC. Age, sex, and repeated measures effects on NASA's "Cognition" Test Battery in STEM educated adults. Aerosp Med Hum Perform. 2020; 91(1):18-25.

Background: Microgravity-induced fluid shifts and the resulting changes in cerebral hemodynamics may be linked to cognitive performance alterations in spaceflight. Head-down tilt (HDT) bed rest serves as a well-validated spaceflight analog for microgravity-induced cephalic fluid shifts. This study examined the effects of short-term (t < 4 h) changes in body position (supine or -12 degrees HDT) relative to a 45 degrees upright position on cognitive performance. Methods: In this within-subject cross-over study, ten male subjects without significant medical comorbidities (mean +/- standard deviation [SD] age: 34 years +/- 3, weight: 81 kg +/- 11, height: 1.77 m +/- 0.06, body mass index: 26 kg/m(2) +/- 3) performed the Cognition test battery on an iPad at baseline (45 degrees upright), after 1, 2, 3, and 4 h in the -12 degrees HDT or supine position, and after 30-minute recovery in 45 degrees upright position. The order of conditions ( -12 degrees HDT or supine) was randomized, with > 1 week washout between test days. Results: Mixed model analyses of z-transformed Cognition test scores indicate a small (0.21-0.25 SD) decrease in accuracy that did not survive adjustment for multiple testing and no change in speed (0.00-0.12 SD) across cognitive domains in the supine and -12 degrees HDT position relative to upright. A true decrease in speed may have been masked by practice effects, as speed was found to increase by 0.06 SD per test bout in condition (95% confidence interval 0.03; 0.10). Performance differences between -12 degrees HDT and supine positions across cognitive domains were less than small ( < 0.2 SD) according to conventional standards. Discussion: This study on short-term positional changes on cognitive performance suggests that performing Cognition in the supine or -12 degrees HDT position on a tablet is associated with small decreases in accuracy and, if practice effects are taken into account, potentially also speed, but with no relevant differences between positions. These findings help interpret bed rest studies that use the new -12 degrees HDT paradigm.

Acute exposure to carbon dioxide (CO 2 ) concentrations below those found on the International Space Station are reported to deteriorate complex decision-making. Effective decision-making is critical to human spaceflight, especially during an emergency response. Therefore, effects of acutely elevated CO 2 on decision-making competency and various cognitive domains were assessed in astronaut-like subjects by the Strategic Management Simulation (SMS) and Cognition test batteries. The double-blind cross-over study included 22 participants at the Johnson Space Center randomly assigned to one of four groups. Each group was exposed to a different sequence of four concentrations of CO 2 (600, 1200, 2500, 5000 ppm). Subjects performed Cognition before entering the chamber, 15 min and 2.5 h after entering the chamber, and 15 min after exiting the chamber. The SMS was administered 30 min after subjects entered the chamber. There were no clear dose–response patterns for performance on either SMS or Cognition . Performance on most SMS measures and aggregate speed, accuracy, and efficiency scores across Cognition tests were lower at 1200 ppm than at baseline (600 ppm); however, at higher CO 2 concentrations performance was similar to or exceeded baseline for most measures. These outcomes, which conflict with those of other studies, likely indicate differing characteristics of the various subject populations and differences in the aggregation of unrecognized stressors, in addition to CO 2 , are responsible for disparate outcomes among studies. Studies with longer exposure durations are needed to verify that cognitive impairment does not develop over time in crew-like subjects.

To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intima-media thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress-related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight.

Microgravity and elevated levels of CO2 are two common environmental stressors in spaceflight that may affect cognitive performance of astronauts. In this randomized, double-blind, crossover trial (SPACECOT), 6 healthy males (mean ± SD age: 41 ± 5 yr) were exposed to 0.04% (ambient air) and 0.5% CO2 concentrations during 26.5-h periods of -12° head-down tilt (HDT) bed rest with a 1-wk washout period between exposures. Subjects performed the 10 tests of the Cognition Test Battery before and on average 0.1, 5.2, and 21.0 h after the initiation of HDT bed rest. HDT in ambient air induced a change in response strategy, with increased response speed (+0.19 SD; P = 0.0254) at the expense of accuracy (-0.19 SD; P = 0.2867), resulting in comparable cognitive efficiency. The observed effects were small and statistically significant for cognitive speed only. However, even small declines in accuracy can potentially cause errors during mission-critical tasks in spaceflight. Unexpectedly, exposure to 0.5% CO2 reversed the response strategy changes observed under HDT in ambient air. This was possibly related to hypercapnia-induced cerebrovascular reactivity that favors cortical regions in general and the frontal cortex in particular, or to the CNS arousing properties of mildly to moderately increased CO2 levels. There were no statistically significant time-in-CO2 effects for any cognitive outcome. The small sample size and the small effect sizes are major limitations of this study and its findings. The results should not be generalized beyond the group of investigated subjects until they are confirmed by adequately powered follow-up studies. NEW & NOTEWORTHY Simulating microgravity with exposure to 21 h of -12° head-down tilt bed rest caused a change in response strategy on a range of cognitive tests, with a statistically significant increase in response speed at the expense of accuracy. Cognitive efficiency was not affected. The observed speed-accuracy tradeoff was small but may nevertheless be important for mission-critical tasks in spaceflight. Importantly, the change in response strategy was reversed by increasing CO2 concentrations to 0.5%.

Study Objectives The Psychomotor Vigilance Test (PVT) is reported to be free of practice effects that can otherwise confound the effects of sleep loss and circadian misalignment on performance. This differentiates the PVT from more complex cognitive tests. To the best of our knowledge, no study has systematically investigated practice effects on the PVT across multiple outcome domains, depending on administration interval, and in ecologically more valid settings. Methods We administered a validated 3-minute PVT (PVT-B) 16 times in 45 participants (23 male, mean ± SD age 32.6 ± 7.3 years, range 25-54 years) with administration intervals of ≥10 days, ≤5 days, or 4 times per day. We investigated linear and logarithmic trends across repeated administrations in 10 PVT-B outcome variables. Results The fastest 10% of response times (RT; plin = .0002), minimum RT (plog = .0010), and the slowest 10% of reciprocal RT (plog = .0124) increased while false starts (plog = 0.0050) decreased with repeated administration, collectively decreasing RT variability (plog = .0010) across administrations. However, the observed absolute changes were small (e.g., -0.03 false starts per administration, linear fit) and are probably irrelevant in practice. Test administration interval did not modify the effects of repeated administration on PVT-B performance (all p > .13 for interaction). Importantly, mean and median RT, response speed, and lapses, which are among the most frequently used PVT outcomes, did not change systematically with repeated administration. Conclusions PVT-B showed stable performance across repeated administrations. Combined with its high sensitivity, this corroborates the status of the PVT as the de facto gold standard measure of the neurobehavioral effects of sleep loss and circadian misalignment.

Across two studies, we explored cultural differences in children’s imitation and transmission of inefficient actions. Chinese American and Caucasian American preschoolers (N = 115) viewed either one or three models using two inefficient tools to perform two different tasks. In the video, when the model(s) performed the task, only the inefficient tool was available; thus, their choice to use that tool could be considered rational. Next, children were invited to complete the task with either the inefficient tool or an efficient alternative. Whereas the two cultural groups imitated a single model at similar rates, Chinese American children imitated significantly more than Caucasian American children after viewing a consensus. Similar results were found when exploring differences in information transmission. The Chinese American children were significantly more likely than their Caucasian American peers to instruct using an inefficient tool when they had initially viewed a consensus demonstrate it. We discuss these findings with respect to differences in children’s use of social versus task-specific cues for learning and teaching.