Rachael Seidler, professor of applied physiology & kinesiology at the University of Florida will deliver this year鈥檚 Rose M. Litman Memorial Lecture in Science.
Seidler studies the interaction between the brain and movement, and neural changes related to age, disease and spaceflight. Her groundbreaking research on astronauts is advancing understanding of the hazards to the human body posed by space travel.
Space travel has never been more popular and, in her April 4 talk, 鈥淏rain and Behavioral Changes with Human Spaceflight: Dysfunction and Adaptive Plasticity,鈥� Seidler will discuss her recent findings of the effects of microgravity and how it may affect everyone from space tourists to astronauts on a lengthy future mission to Mars.听
During the time Seidler has been working with astronauts, including a decade-long, NASA-funded spaceflight study, her research has shed light on what happens to the human body when it swaps Earth鈥檚 gravity for the microgravity of space. Using advanced MRI techniques鈥攕cans of astronaut鈥檚 brains before and after missions to the International Space Station鈥擲eidler and her team have investigated shifts in brain function and structure and what those may mean for balance, mobility and cognition.
Why study astronauts? For decades, Seidler has been interested in neuroplasticity, or the brain鈥檚 ability to form new and rearrange old connections, structures and functions in response to experience or injury. She wanted to answer questions like, where does the brain store motor memories and what does it look like when we鈥檙e learning new skills? It was a rich path of inquiry but also limited by study subjects who were either recovering (from a stroke or traumatic brain injury, for example) or healthy individuals who could only be studied for a limited time.听听
Compared to the average mortal, astronauts are in a league of their own. They are generally excellent physical specimens but, when on a mission, are subject continuously to adverse conditions. 鈥淚 thought this was just a really fascinating way of looking at the maximum capacity for neuroplasticity in the healthy brain,鈥� said Seidler. 鈥淏ecause when you鈥檙e in microgravity, you鈥檙e exposed to the stimulus 24 hours a day, the whole time you鈥檙e there. You can鈥檛 even escape it when you鈥檙e sleeping.鈥�
For Seidler and colleagues, what began as an inquiry into the effects of space on neuroplasticity has revealed much more. Their , published in June 2023 in Scientific Reports, has shown both adaptive, neuroplastic changes as well as dysfunctional effects. Seidler gives the example of the human ear鈥檚 tubular system which helps orientation and balance. Absent gravity, the brain ignores the haywire signals coming from that system and astronauts learn to rely on the input from other senses. 鈥淲e did certainly see evidence for that but we also saw a lot of surprising findings that I tend to describe as physical changes,鈥� said Seidler.听
Gravitational shifts
While studying 30 astronauts, both female and male, Seidler and colleagues observed that microgravity exposure has mechanical effects on the nervous and circulatory systems. 鈥淭here are a lot of structural changes that seem to come from the physics of the environment rather than neuroplastic changes that might occur with experience and practice and training. And that part was somewhat unexpected to us,鈥� she said.
The team observed that, lacking gravity, fluids in the body shift toward the head. In her lecture, Seidler will detail the mechanisms, impacts and timeline of that response鈥攏amely ventricular expansion鈥攊n which cerebral spinal fluid moves upwards and forces the brain to sit higher in the skull. Age-related ventricular expansion due to natural brain atrophy is associated with cognitive decline on Earth, but the implications of that condition for astronauts both in space and when they return home are still largely unknown and more long-term follow-up is needed.听
鈥淚t turns out that there are a lot of things about human physiology that have adapted to either leverage gravity or have adapted to counteract the effects of gravity,鈥� said Seidler. 鈥淪o it鈥檚 really interesting to see how these systems work and function when there is no gravity and it鈥檚 something a person has never experienced before.鈥� With the consequences for long-term brain health still being studied, Seidler鈥檚 lab has recently been awarded a 10-year grant from NASA to investigate brain recovery up to five years postflight.
In her talk, Seidler will also touch on large individual differences in the changes that occur, related to the space travelers鈥� age, sex and prior spaceflight experience. Given NASA鈥檚 plan to send a manned mission to Mars in the 2030s, Seidler said scientists need to work efficiently to protect astronauts from space risks to the human body. (She is also involved in a NASA project aimed at mitigating Mars mission health hazards.)听
鈥淚 think understanding individual differences has big practical implications in terms of how you might design the mission,鈥� said Seidler. 鈥淏ut I also think it鈥檚 really interesting scientifically, in terms of what it may mean about our brains and our adaptability.鈥�
Earthy impacts of interstellar breakthroughs
By observing astronauts, scientists can also learn a lot about supporting human health on Earth. For example, understanding physical responses to microgravity may help treat similar conditions that occur every day on our planet (such as hydrocephalus, a neurological condition caused by a buildup of cerebrospinal fluid in the brain鈥檚 ventricles). Seidler鈥檚 work also extends to age-related mobility issues and, with a $5.6 million National Institutes of Health (NIH) grant, her research explores how the brain compensates for declines, in an effort to prevent falls in older adults.
Seidler has authored roughly 175 papers in journals such as Science, JAMA Neurology,听Lancet Neurology听and more, and her research has been cited more than 17,000 times. Throughout her academic career, she has secured millions of dollars in research grants from renowned institutions like NASA, NIH, National Science Foundation and the Translational Research Institute for Space Health.
Seidler is fiercely committed to mentorship and to inspiring the next generation of diverse female scientists. Each summer, her lab runs a week-long 鈥淕irls with Nerve鈥� camp aimed at cultivating interest in STEM sciences and empowering girls, and underserved minority students in particular, to explore neuroscience.听
Professor Rachael D. Seidler, University of Florida