Published: Feb. 28, 2024 By

Rachael Seidler, professor of applied physiology & kinesiology at the University of Florida will deliver this year’s 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, “Brain and Behavioral Changes with Human Spaceflight: Dysfunction and Adaptive Plasticity,” 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. 

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’s gravity for the microgravity of space. Using advanced MRI techniques—scans of astronaut’s brains before and after missions to the International Space Station—Seidler 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’s 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’re 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.  

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. “I thought this was just a really fascinating way of looking at the maximum capacity for neuroplasticity in the healthy brain,” said Seidler. “Because when you’re in microgravity, you’re exposed to the stimulus 24 hours a day, the whole time you’re there. You can’t even escape it when you’re sleeping.”

For Seidler and colleagues, what began as an inquiry into the effects of space on neuroplasticity has revealed much more. Their recent work, 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’s 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. “We did certainly see evidence for that but we also saw a lot of surprising findings that I tend to describe as physical changes,” said Seidler. 

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. “There 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,” 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—namely ventricular expansion—in 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. 

“It 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,” said Seidler. “So it’s really interesting to see how these systems work and function when there is no gravity and it’s something a person has never experienced before.” With the consequences for long-term brain health still being studied, Seidler’s 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’ age, sex and prior spaceflight experience. Given NASA’s 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.) 

“I think understanding individual differences has big practical implications in terms of how you might design the mission,” said Seidler. “But I also think it’s really interesting scientifically, in terms of what it may mean about our brains and our adaptability.”

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’s ventricles). Seidler’s 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 NeurologyLancet Neurology 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 “Girls with Nerve” camp aimed at cultivating interest in STEM sciences and empowering girls, and underserved minority students in particular, to explore neuroscience.