Research on mental fatigue based on entropy changes in space environment

This paper detects mental fatigue based on entropy changes in imitating space environment. We calculated changes of sample entropy and power spectrum entropy of fNIR (Functional near-infrared spectroscopy) at normal status and fatigue status, the results indicate that the sample entropy and the power spectrum entropy decreases at fatigue status in imitating space environment comparing to normal status. We proposed the mental fatigue detection method based entropy change of fNIR in space environment and the method is verified by daily routine fatigue experiment.The methodology was validated using imitating space task mental fatigue induction model. The mental fatigue detection methodology based on cw-fNIR (continuous wave-fNIR), which adopts integrate entropies as feature parameters other than concentration changes of hemodynamic indexes can overcome the disadvantages of cw-fNIR, improve convenience of measurement and contract measurement period. It can be concluded that mental fatigue can be reliably and noninvasively detected by applying sample entropy and power spectrum entropy of fNIR. Sample entropy reflects complex of a time sequence, it can measure the probability of generating new patterns of a signal. Power spectrum entropy reflects complex of a signal from frequent domain. The decline of integrate entropies shows that brain is inactive. Through the aforementioned applications it is remarked that integrate entropy can be considered as a very promising and useful tool towards the non-invasive understanding of mental fatigue.