While a large body of research has documented the effects of microgravity on the cardiovascular system, body fluids, skeletal muscle, and bone metabolism, there is a renewed interest in the understanding how long-term space flight affects cognitive functioning and in particular neuroplasticity. In spite of increasing knowledge on behavioral adaptations during space flight, these studies remain controversial and are not necessarily reliable predictors of changes in brain structure and function. Data from the investigators’ ground-based analog experiments (i.e. bed rest and isolation studies in Antarctica) indicate that the hippocampus will be particularly vulnerable to detrimental effects associated with the various stressors during long-duration space flight. The hippocampus is part of the limbic system and plays important roles in learning and memory formation, and specifically spatial learning and episodic memory. Any malfunction and/or structural changes of the hippocampus could have substantial consequences on learning and memory consolidation as well as general cognitive performance.
In spite of ongoing research projects employing state-of-the-art imaging techniques, none of these experiments focused on the hippocampus. The primary objective of this project was to identify the changes in hippocampal subfield volume. Investigators hypothesize that hippocampal subfield volume will be reduced after 30 days of isolation and confinement in NASA’s Human Exploration Research Analog (HERA) facility. Moreover, investigators expect that these changes correlate with decrements in visuo-spatial navigation and memory. They also expect that these changes can be explained by changes in important neurotrophic key factors. This study aimed to assess the impact of human isolation and confinement on:
The study compared 16 participants living in the HERA facility for 30 days to 16 control subjects, matched for gender, age, and educational level, who continued their normal living conditions. Subjects completed the Cognition Test on their iPads. Cognition is a test battery that consists of 10 different cognitive tests that are administered with the Cognition software. The battery started with a brief questionnaire, followed by administration of the 10 cognitive tests. Subjects were asked to perform the Cognition battery (all 10 tests) three times pre-mission, once weekly in-mission, and three times post-mission. To assess visuo-spatial performance, working memory, and executive function visuospatial ability testing (10 computer-based tasks) were performed four times pre-mission, once weekly in-mission, and twice post-mission. Subjects also completed Visual Analog Scales (VAS) on their iPad. It is a standardized questionnaire of perceived mental and physical exhaustion, fatigue, stress, workload, conflict, depression, anxiety, personality, social desirability, and sleep quality. They performed this three times pre-mission, once weekly in-mission and up to three times post-mission.
The investigators used an innovative, state-of-the art technique for high-resolution hippocampal neuroimaging as well as a unique human 3-D water maze task, which was used as a human analog model for the classical spatial learning task typically employed for laboratory rodents to assess spatial orientation. In addition, biomarkers were obtained from blood and plasma samples to determine key neurotrophic and inflammatory factors related to neuroplasticity. To further elucidate the effects of isolation on neuronal growth investigators assessed hippocampal plasticity in-vitro using an immortalized multipotent, hippocampal progenitor cell line.
NASA does not currently have an agreement to archive the hippocampal plasticity and biomarker data from this International investigation. However, the Co-Investigator, Dr. Mathias Basner, submitted the cognitive and behavioral data from all subjects.