Participants in the study complete timed obstacle courses and tests of their spatial memory and the ability to visualize and manipulate a three-dimensional shape before and after space flight. The tests are conducted aboard the ISS, mid-way through and near the end of a six-month flight.
Structural and functional magnetic resonance imaging (MRI) scans of the brain are conducted before and after aflight.
"We are looking at the volume of different structures in the brain and whether they changed in size or shape during spaceflight," says principal investigator Rachael D. Seidler, director of the University of Michigan's Neuromotor Behaviour Laboratory, in a statement reported by NDTV.
The astronauts experienced changes with balance and perceptual illusions in microgravity.
"On Earth, your vestibular--or balance--system tells you how your head moves relative to gravity, but in space, the gravity reference is gone," says Seidler.
"That causes these perceptual illusions, as well as difficulty coordinating movement of the eyes and head."
Such difficulties could have serious consequences for astronauts, especially when changing between gravitational environments. Astronauts will be required to perform tasks such as using tools and driving a rover. They also must be capable of escape in a landing emergency.
The study results could also reveal whether astronauts return to "normal" post-flight because the brain changes back, or if the brain instead learns to compensate for the changes that took place in space.