Alterations in sleep homeostasis, autonomic nervus system and cortical plasticity induced by simulated microgravity.

Background. Sleep problems, such as poor quality sleep, insomnia and hypersomnolence have been observed during space flights. It has recently been hypothesized that sleep promotes plastic changes in the cerebral cortex that benefit cognitive functions and general work efficiency, as such sleep disturbances can have a negative action on these functions.. Aims of the study: 1) to evaluate the effects of simulated microgravity on sleep after bed rest; 2) to assess changes of autonomic neural system (ANS) during the different sleep stages; 3) to investigate whether circadian sleep-wake alterations occurs in microgravity conditions. Methods. The study will consist of different different experimental protocols: 1) polysomnographic studies to assess sleep macro- and microstructure. Spectral analysis of heart rate variability will be performed to assess ANS during the different stages of the sleep-wake cycles. Moreover non-linear algorithms will be used to evaluate the regularity and synchronization of cardiorespiratory coupling; 2) an actigraphic study lasting for the whole duration of the bed rest, and spectral analysis of Holter recordings will be performed to assess circadian alterations of the sleep-wake cycle and ANS; 3) Global and local aspects of cortical sleep homeostasis (slow wave activity) will also be measured.

Keywords:Holter monitoring, circadian variation, microgravity simulation, polysomnography, heart rate variability, sleep, Head-down-bed-rest

Disciplines:Cardiac and vascular medicine