Leaving Earth’s gravity may impair sensorimotor coordination in astronauts. Some of the alterations are incapacitating during flight and upon landing. Developing countermeasures for sensorimotor deconditioning in space is crucial for future missions. There are also benefits to people on Earth because patients with brain injury or disease experience many of the same coordination challenges that astronauts experience.

Mental imagery represents a potential countermeasure for sensorimotor and cognitive dysfunctions due to spaceflight. It might help training people to deal with conditions unique to spaceflight. Thus, dynamic interactions with the inertial motion of weightless objects are only experienced in weightlessness, but can be simulated on Earth using mental imagery. Such training might overcome the problem of calibrating fine-grained hand forces and estimating the spatio-temporal parameters of the resulting object motion.

We asked a group of astronauts to grasp an imaginary ball, to throw it against the ceiling or the front-wall, and to catch it after the bounce, during preflight, inflight and postflight experiments. They had to vary the throwing speed across trials and to imagine that the ball moved under Earth gravity or weightlessness. We found that they were able to reproduce qualitative differences between inertial and gravitational motion already on ground, and further adapted their behavior during spaceflight. Thus, they adjusted the throwing speed and the catching time, equivalent to the duration of virtual ball motion, as a function of the imaginary 0g condition versus the imaginary 1g condition. Arm kinematics of the frontal throws further revealed a differential processing of imagined gravity level in terms of the spatial features of the arm and virtual ball trajectories.

We suggest that protocols of this kind may facilitate sensorimotor adaptation and help tuning vestibular plasticity in-flight, since mental imagery of gravitational motion is known to engage the vestibular cortex. The results from this study will not only provide more information that can be used to keep astronauts healthy, but could also lead to new rehabilitation strategies to help people with brain injuries. In fact, mental imagery represents a powerful tool to rehabilitate sensorimotor coordination in disabled patients.

Learn more about our research in the complete article found here:

https://www.nature.com/articles/s41526-021-00179-z

doi: https://doi.org/10.1038/s41526-021-00179-z

Poster image:

Left: Picture of astronaut Garrett Reisman on the ISS, performing the protocol of throwing the imaginary ball to the ceiling and catching it on the rebound. Written informed consent for the publication of the picture was obtained from Garrett Reisman. Image courtesy of NASA (fig 1 of the article)

Right: Results for three different experiments (left to right, imaginary 0 g and 1 g) performed pre-flight (blue), in-flight (red), and post-flight (green) by astronaut S11 (fig 5 of the article)