Neural correlates of cognitive task performance during orthostatic challenge

More than 80% of astronauts that fly long duration missions suffer from postflight orthostatic intolerance. Additionally, astronauts experience high levels of workload resulting in fatigue, which can affect performance. However, the effects of concurrent orthostatic challenge and fatigue on performance have not been adequately investigated. The purpose of this study was to determine neural correlates of cognitive stressors during orthostatic challenge and the influence of fatigue on those neural correlates. Sixteen healthy participants performed 1) a compensatory tracking task, and 2) a serial-n mental arithmetic task, in the absence and presence of a prior 1-hour fatiguing exercise, on separate days under orthostatic challenge (lower body negative pressure). Study variables included task performance and prefrontal cortex oxygenation using near infrared spectroscopy. Results indicated that in general, orthostatic challenge decreased cerebral oxygenation. Introduction of the cognitive tasks during orthostatic challenge improved cerebral blood flow, however, oxygenation decreased significantly with the cognitive tasks under the fatigue conditions, particularly during the tracking task. While there was little evidence to suggest any cognitive performance decrements due to fatigue, the results revealed cognitive-stressor specific differences in neural activation related to fatigue that may be useful in the development of countermeasures for orthostatic intolerance.

Neural correlates of cognitive task performance during orthostatic challenge Conference Paper