AGBRESA – Centrifuge rides against changes in astronauts’ vision
Participants in AGBRESA are on a long-duration mission to advance our understanding of the effects of spaceflight on the human body. During the AGBRESA mission, our team, Eric Bershad, Karina Marshall-Goebel and others, seek to understand how long-duration exposure to a six-degree head-down tilt, a spaceflight analogue, affects brain and eye health.
This is a critical aim of the overall AGBRESA mission, since it is known that a significant proportion of astronauts have developed structural changes to their brain and eyes during past missions on the International Space Station. The alterations in the eyes lead to a change in the astronaut’s vision toward far-sightedness (acquired hyperopia). This may potentially affect an astronaut’s ability to perform critical mission tasks. What makes the AGBRESA study so interesting and important is the introduction of artificial gravity using intermittent short-arm centrifugation as a possible way to combat the effects of spaceflight on the human body. This countermeasure may help to restore the body’s fluid distribution to a manner experienced in the upright and sitting position on Earth, thus protecting the astronauts from the adverse effects of headward fluid shifting experienced in microgravity.
Brain and eye structure
In our part of the study, we aim to measure the brain and eye structure and function using a comprehensive suite of tools including MRI, near infrared light, ultrasound, and automated eye movement tracking systems. The most novel part of this study is using a centrifuge to simulate Earth’s gravity. However, in addition to studying the potential benefits, we must also look into the adverse effects. For example, in our study the brain and eye MRI will assess the starting anatomical structure of the brain compartments and eye, as well as the flow of blood and cerebrospinal fluid. Periodic MRI scans will determine whether pathological changes occur due to the head down tilt, and whether the participants who are subjected to artificial gravity centrifugation will be protected against these effects.
Ultrasound and eye movement tracking
On the centrifuge itself, we will instrument the participant with a NIRS device that monitors changes in blood volume in various parts of the body from head to toe, and concurrent measures of the internal jugular vein, blood pressure, and cerebral blood flow using transcranial Doppler ultrasound. In this manner, we will have a whole-body, real-time assessment of the effects of artificial gravity on the brain and body blood flow. This will help confirm whether the artificial gravity is having the expected redistribution effects of fluids from head to feet. Additionally, the iPAS is an eye movement tracking system that will help us determine whether any detrimental effects of the AG on the vestibular system are occurring during the study, and whether participants adapt to the effects. This is important since a future daily centrifuge regimen may have persisting effects on the vestibular system that could affect critical mission tasks.
Daily doses of centrifugation
In this way, we will be able to study the myriad effects of head-down tilt on the brain and eye, and whether the artificial gravity countermeasure is effective for preventing changes to these critical organs, thus optimising brain and eye health. If successful, humans traveling through deep space may require a daily dose of centrifugation to ensure optimal eye and brain performance.
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