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Rocking or Rolling – Perception of Ambiguous Motion after Returning from Space
The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive an accurate representation of spatial orientation. Adaptive changes during spaceflight in how the brain integrates vestibular cues with other sensory information can lead to impaired movement coordination, vertigo, spatial disorientation, and perceptual illusions after return to Earth. The purpose of this study was to compare tilt and translation motion perception in astronauts before and after returning from spaceflight. We hypothesized that these stimuli would be the most ambiguous in the low-frequency range (i.e., at about 0.3 Hz) where the linear acceleration can be interpreted either as a translation or as a tilt relative to gravity. Verbal reports were obtained in eleven astronauts tested using a motion-based tilt-translation device and a variable radius centrifuge before and after flying for two weeks on board the Space Shuttle. Consistent with previous studies, roll tilt perception was overestimated shortly after spaceflight and then recovered with 1-2 days. During dynamic linear acceleration (0.15-0.6 Hz, ±1.7 m/s2) perception of translation was also overestimated immediately after flight. Recovery to baseline was observed after 2 days for lateral translation and 8 days for fore-aft translation. These results suggest that there was a shift in the frequency dynamic of tilt-translation motion perception after adaptation to weightlessness. These results have implications for manual control during landing of a space vehicle after exposure to microgravity, as it will be the case for human asteroid and Mars missions.
Journal Article
Orion by Walt Simonson
\"Walt Simonson's stunning, unmistakable art and storytelling are on full display here in his groundbreaking work ORION. Expanding the beloved universe originally created by Jack Kirby, Simonson's sprawling storylines and dynamic artwork elevate his titular hero, as well as the rest of the Fourth World's indispensible characters, to incredible new heights. Collected here for the first time are all twenty-five issues of Walter Simonson's ORION, as well as never-before reprinted short stories, pinups and sketch material.\"-- Provided by publisher.
BOOK
Brain plasticity and sensorimotor deterioration as a function of 70 days head down tilt bed rest
Adverse effects of spaceflight on sensorimotor function have been linked to altered somatosensory and vestibular inputs in the microgravity environment. Whether these spaceflight sequelae have a central nervous system component is unknown. However, experimental studies have shown spaceflight-induced brain structural changes in rodents' sensorimotor brain regions. Understanding the neural correlates of spaceflight-related motor performance changes is important to ultimately develop tailored countermeasures that ensure mission success and astronauts' health.
Head down-tilt bed rest (HDBR) can serve as a microgravity analog because it mimics body unloading and headward fluid shifts of microgravity. We conducted a 70-day 6° HDBR study with 18 right-handed males to investigate how microgravity affects focal gray matter (GM) brain volume. MRI data were collected at 7 time points before, during and post-HDBR. Standing balance and functional mobility were measured pre and post-HDBR. The same metrics were obtained at 4 time points over ~90 days from 12 control subjects, serving as reference data.
HDBR resulted in widespread increases GM in posterior parietal regions and decreases in frontal areas; recovery was not yet complete by 12 days post-HDBR. Additionally, HDBR led to balance and locomotor performance declines. Increases in a cluster comprising the precuneus, precentral and postcentral gyrus GM correlated with less deterioration or even improvement in standing balance. This association did not survive Bonferroni correction and should therefore be interpreted with caution. No brain or behavior changes were observed in control subjects.
Our results parallel the sensorimotor deficits that astronauts experience post-flight. The widespread GM changes could reflect fluid redistribution. Additionally, the association between focal GM increase and balance changes suggests that HDBR also may result in neuroplastic adaptation. Future studies are warranted to determine causality and underlying mechanisms.
Journal Article
Microfluidic chip-based co-culture system for modeling human joint inflammation in osteoarthritis research
Here we present a microfluidic model that allows for co-culture of human osteoblasts, chondrocytes, fibroblasts, and macrophages of both quiescent (M0) and pro-inflammatory (M1) phenotypes, maintaining initial viability of each cell type at 24 h of co-culture. We established healthy (M0-based) and diseased (M1-based) joint models within this system. An established disease model based on supplementation of IFN-γ and lipopolysaccharide in cell culture media was used to induce an M1 phenotype in macrophages to recapitulate inflammatory conditions found in Osteoarthritis. Cell viability was assessed using NucBlue™ Live and NucGreen™ Dead fluorescent stains, with mean viability of 83.9% ± 14% and 83.3% ± 12% for healthy and diseased models, respectively, compared with 93.3% ± 4% for cell in standard monoculture conditions. Cytotoxicity was assessed via a lactate dehydrogenase (LDH) assay and showed no measurable increase in lactate dehydrogenase release into the culture medium under co-culture conditions, indicating that neither model promotes a loss of cell membrane integrity due to cytotoxic effects. Cellular metabolic activity was assessed using a PrestoBlue™ assay and indicated increased cellular metabolic activity in co-culture, with levels 5.9 ± 3.2 times mean monolayer cell metabolic activity levels in the healthy joint model and 5.3 ± 3.4 times mean monolayer levels in the diseased model. Overall, these findings indicate that the multi-tissue nature of in vivo human joint conditions can be recapitulated by our microfluidic co-culture system at 24 h and thus this model serves as a promising tool for studying the pathophysiology of rheumatic diseases and testing potential therapeutics.
Journal Article
Development of head-trunk coordination measures for assessing sensorimotor function in laboratory and natural settings using wearable sensors
Stabilization of the head in space is important for postural and locomotion control. Disruptions in head-trunk coordination can impair functional performance during aging, pathophysiology, or exposure to altered sensory environment states such as spaceflight. Monitoring head-trunk coordination could aid in understanding the risks associated with sensorimotor impairment. The present study evaluated a custom algorithm developed from parameters of head-trunk coordination obtained from wearable sensors. Task performance of healthy adults during standard laboratory tasks both with and without physical restriction via a neck brace were assessed to develop the algorithm and motion thresholds. The algorithm was applied to 12 blinded 4-hr datasets to evaluate the reliability and sensitivity of the measures for identifying altered head-to-trunk coordination when a neck brace was worn during daily activities in a natural setting. The primary head-to-trunk coordination metrics showing high detection accuracy were the root mean square deviation between the angular velocity signals of the head and trunk, followed by the difference in the magnitude orientation. Additionally, the coherence of angular velocity along the X and Z global axes demonstrated good detection sensitivity. The present work lays the foundation for future applications, particularly in monitoring impaired head-trunk coordination in natural settings to provide valuable insights for rehabilitation.
Journal Article
Ocular Counter Rolling in Astronauts After Short- and Long-Duration Spaceflight
Ocular counter-rolling (OCR) is a reflex generated by the activation of the gravity sensors in the inner ear that stabilizes gaze and posture during head tilt. We compared the OCR measures that were obtained in 6 astronauts before, during, and after a spaceflight lasting 4–6 days with the OCR measures obtained from 6 astronauts before and after a spaceflight lasting 4–9 months. OCR in the short-duration fliers was measured using the afterimage method during head tilt at 15°, 30°, and 45°. OCR in the long-duration fliers was measured using video-oculography during whole body tilt at 25°. A control group of 7 subjects was used to compare OCR measures during head tilt and whole body tilt. No OCR occurred during head tilt in microgravity, and the response returned to normal within 2 hours of return from short-duration spaceflight. However, the amplitude of OCR was reduced for several days after return from long-duration spaceflight. This decrease in amplitude was not accompanied by changes in the asymmetry of OCR between right and left head tilt. These results indicate that the adaptation of otolith-driven reflexes to microgravity is a long-duration process.
Journal Article
Bilateral vestibulopathy affects spatial and temporal perception
This study assessed impairments in spatial and temporal perception in individuals with bilateral vestibulopathy (BVP). A total of 30 BVP subjects and 35 healthy controls (CTL) participated in a series of tests to assess their perception of distance (1–6 meters), angle (90–360 degrees), duration (2–10 seconds), and a combination of distance and angle during a triangle completion task (TCT). When performing distance and angle perception tasks separately, the BVP subjects showed larger errors than the CTL subjects. During the TCT, the BVP subjects walked longer paths and exhibited greater angle deviations compared to the CTL subjects. The angle deviations of the BVP subjects during the TCT were larger than when the angle perception task was performed separately. Moreover, the BVP subjects demonstrated accurate time interval perception, whereas the CTL subjects did not. Although the vestibular system is crucial for balance and spatial awareness, the proprioceptive system, in combination with visual and cognitive strategies, as well as motor efference copies, can help individuals with labyrinthine defects in separately perceiving distances and angles. However, this compensatory approach becomes less effective when these tasks are combined. These findings are relevant for space (planetary) exploration because exposure to microgravity mimics loss of vestibular otolith function.
Journal Article
Impacts of spaceflight experience on human brain structure
Spaceflight induces widespread changes in human brain morphology. It is unclear if these brain changes differ with varying mission duration or spaceflight experience history (i.e., novice or experienced, number of prior missions, time between missions). Here we addressed this issue by quantifying regional voxelwise changes in brain gray matter volume, white matter microstructure, extracellular free water (FW) distribution, and ventricular volume from pre- to post-flight in a sample of 30 astronauts. We found that longer missions were associated with greater expansion of the right lateral and third ventricles, with the majority of expansion occurring during the first 6 months in space then appearing to taper off for longer missions. Longer inter-mission intervals were associated with greater expansion of the ventricles following flight; crew with less than 3 years of time to recover between successive flights showed little to no enlargement of the lateral and third ventricles. These findings demonstrate that ventricle expansion continues with spaceflight with increasing mission duration, and inter-mission intervals less than 3 years may not allow sufficient time for the ventricles to fully recover their compensatory capacity. These findings illustrate some potential plateaus in and boundaries of human brain changes with spaceflight.
Journal Article