Differential Impact of Social Isolation and Space Radiation on Behavior and Motor Learning in Rats.

Future missions to Mars will expose astronauts to several physical and psychological challenges, including exposure to space radiation (SR) and periods of social isolation (SI). Each of these stressors, in addition to mission demands, can affect physical and mental health and potentially negatively impact sleep. The effects of inflight stressors may vary with duration and time course, may be additive or compounding, and may vary with individual differences in stress resilience and vulnerability. Determining how individual differences in resilient and vulnerable phenotypes respond to these mission-related stressors and their interactions with sleep will be crucial for understanding and mitigating factors that can impair performance and damage health. Here, we examined the single and compound effects of ground-based analogs of SI and SR on sensorimotor performance on the balance beam (BB) in rats. We also assessed emotional responses during testing on the BB and assessed whether sensorimotor performance and emotion varied with individual differences in stress resiliency using our established animal model in which stress produces different effects on sleep. Results showed differential motor performance and emotion in the BB task between SI and SR, and these varied based on resilient and vulnerable phenotypes. These findings demonstrate that identifying individual responses to stressors that can impact sensorimotor ability and behavior necessary to perform mission-related tasks will be of particular importance for astronauts and future missions. Should similar effects occur in humans, there may be considerable inter-individual variability in the impact that flight stressors have on the mental health of astronauts and their ability to perform mission-related tasks.