Neuropsychological and emotional changes during simulated microgravity: effects of triiodothyronine alendronate, and testosterone

Long-term spaceflight composite stress induces depression and cognitive impairment in astronauts-insights from neuroplasticity

The environment on the space station is quite unique compared to Earth, which is a composite of multiple stressors, such as microgravity, isolation, confinement, noise, circadian rhythm disturbance, and so on. During prolonged space missions, astronauts have to stay in such extreme environments for long periods, which could induce adverse effects on both their physical and mental health. In some circumstances, this kind of long-term spaceflight composite stress (LSCS) could also induce depression and cognitive impairment in various ways, including dysregulating the neuroplasticity of the brains of astronauts, which should be attached to great importance. Here, we have comprehensively reviewed the impact of individual and combined stressors on depression and cognitive function during long-term spaceflight, explained the underlying mechanisms of those effects from the perspective of neuroplasticity, and current countermeasures for mitigating these challenges. This review provides insights into LSCS and potential neuroplasticity mechanisms, current with potentially great impact for understanding and mitigating the mental health risks and traumas of career astronauts and space tourists.

Physiologic dysfunction scores and cognitive function test performance in U.S. adults

OBJECTIVE

To investigate the relationship between a measure of cumulative physiologic dysfunction and specific domains of cognitive function.

METHODS

We examined a summary score measuring physiologic dysfunction, a multisystem measure of the body's ability to effectively adapt to physical and psychological demands, in relation to cognitive function deficits in a population of 4511 adults aged 20 to 59 who participated in the Third National Health and Nutrition Examination Survey (1988-1994). Measures of cognitive function comprised three domains: working memory, visuomotor speed, and perceptual-motor speed. "Physiologic dysfunction" scores summarizing measures of cardiovascular, immunologic, kidney, and liver functions were explored. We used multiple linear regression models to estimate associations between cognitive function measures and physiologic dysfunction scores, adjusting for socioeconomic factors, test conditions, and self-reported health factors.

RESULTS

We noted a dose-response relationship between physiologic dysfunction and working memory (coefficient = 0.207, 95% confidence interval = 0.066-0.348, p < .0001), which persisted after adjustment for all covariates (p = .03). We did not observe any significant relationships between dysfunction scores and visuomotor (p = .37) or perceptual-motor ability (p = .33).

CONCLUSIONS

Our findings suggest that multisystem physiologic dysfunction is associated with working memory. Future longitudinal studies are needed to clarify the underlying mechanisms and explore the persistency of this association into later life. We suggest that such studies should incorporate physiologic data, neuroendocrine parameters, and a wide range of specific cognitive domains.

Physical inactivity and cognitive functioning: results from bed rest studies

In addition to multiple health benefits, participation in physical activity can enhance cognitive functioning. Less clear is how reducing physical activity levels affects cognition, an issue potentially addressed by bed rest studies having included cognitive tests. Detailed and reviewed here are 17 such studies, featuring 251 subjects, bed rest for 7-70 days, and tests of cognition ranging from reaction time to executive functions. The reported effects of bed rest on cognitive performance vary considerably, from a generally expected worsening to an improvement. Practice effects could be implicated in the performance improvements, and reports of worsening are often of limited interpretability or the results were not replicated. Any cognitive effects of bed rest thus remain to be established. Detrimental effects could influence the in-progress plans for human spaceflights to Mars (simulated by bed rest), and have implications for medical conditions promoting inactivity and lifestyles that are largely sedentary.