Assessment of Mental Stress During 240-Days Isolation and Confined Environment using EEG Signals

Detecting the influence of psychological stress is particularly important in prolonged space missions in confined environment. In this study, we proposed utilizing electroencephalography (EEG), alpha amylase and behavioral measures to assess the level of mental stress during a period of 240 days of isolation and confinement. We quantified the levels of mental stress using the reaction time (RT) to stimuli, accuracy of target detection, and the functional connectivity network of the brain's electrical beta EEG signals estimated by Phase Locking Values (PLV). Our results showed that, the alpha amylase level has increased by 62% from the beginning of the mission to the end of the 240-days mission. This indicates that isolation and confinement contributes to elevation of mental stress. The functional connectivity network showed a significant decrease in the information flow in the frontal regions across all subjects with statistical significance of $\mathbf{p} < \boldsymbol{0.05}$. Meanwhile, the behavioral data showed no differences from the beginning to the end of the 240-days mission, which could be due to the short data recording time of 10 minutes during each experiment time. The overall results suggested that the frontal beta EEG connectivity can be used as a potential biomarker for detecting elevated stress in isolation and confined environment.