Exaggerated force production in altered Gz-levels during parabolic flight: the role of computational resources allocation.

The purpose of the present experiment was to examine whether the previously observed exaggerated isometric force production in changed-Gz during parabolic flight (Mierau et al. 2008) can be explained by a higher computational demand and, thus, inadequate allocation of the brain's computational resources to the task. Subjects (n = 12) were tested during the micro-Gz, high-Gz and normal-Gz episodes of parabolic flight. They produced isometric forces of different magnitudes and directions, according to visually prescribed vectors with their right, dominant hand and performed a choice reaction-time task with their left hand. Tasks were performed either separately (single-task) or simultaneously (dual-task). Dual-task interference was present for both tasks, indicating that each task was resources-demanding. However, this interference remained unaffected by the Gz-level. It was concluded that exaggerated force production in changed-Gz is probably not related to inadequate allocation of the brain's computational resources to the force production task. Statement of Relevance: The present study shows that deficient motor performance in changed-Gz environments (both micro-Gz and high-Gz) is not necessarily related to inadequate computational resources allocation, as was suggested in some previous studies. This finding is of great relevance not only for fundamental research, but also for the training and safety of humans operating in changed-Gz environments, such as astronauts and jet pilots.