The effects of a spaceflight analog with elevated CO2 on sensorimotor adaptation.

Aboard the International Space Station (ISS), astronauts must adapt to altered vestibular and somatosensory inputs due to microgravity. Sensorimotor adaptation on Earth is often studied with a task that introduces visuomotor conflict. Retention of the adaptation process, known as savings, can be measured when subjects are exposed to the same adaptive task multiple times. It is unclear how adaptation demands found on the ISS might interfere with the ability to adapt to other sensory conflict at the same time. In the present study, we investigated the impact of 30 days Head-Down tilt Bed Rest combined with elevated carbon dioxide (HDBR+CO2) as a spaceflight analog on sensorimotor adaptation. Eleven subjects used a joystick to move a cursor to targets presented on a computer screen under veridical cursor feedback and 45o-rotated feedback. During this NASA campaign, five individuals presented with optic disk edema, a sign of Spaceflight Associated Neuro-ocular Syndrome (SANS). Thus, we also performed post-hoc exploratory analyses between subgroups who did and did not show signs of SANS. HDBR+CO2 had some impact on sensorimotor adaptation, with a lack of savings across the whole group. SANS individuals showed larger, more persistent after effects, suggesting a shift from relying on cognitive to more implicit processing of adaptive behaviors. Overall, these findings suggest that HDBR+CO2 alters the way in which individuals engage in sensorimotor processing. These findings have important implications for missions and mission training, which require individuals to adapt to altered sensory inputs over long periods in space.