This study investigates the coupling strength between low-frequency peripheral and cerebral hemodynamics among young, healthy volunteers, with concurrent acquisition of peripheral NIRS, brain fMRI, and EEG across wake and NREM sleep. The results document a strong positive coupling between low-frequency peripheral and cerebral hemodynamics during all stages except deep sleep (NREM3). Collectively, our results demonstrate that systemic physiology remains a dominant source of variability in brain hemodynamics both during resting wakefulness and light NREM sleep. However, deep NREM3 sleep may be an exception to this phenomenon implicative of its noteworthy role in optimal restoration of cerebral vasomotion.
Three one-dimensional (1D) optical transducers are known to be effective in determining the spatial coordinates of a target (marker) with higher speed and accuracy compared to the two-dimensional (2D) optical transducers system. But one disadvantage is that it can only position one marker at a time and couldn't solve the correspondence problem when two or more markers are lighted simultaneously, for which reason this tracking system necessitates a markers controlling system and is inconvenient in some applications. This paper proposes an approach to solve the correspondence problem by adding a fourth linear transducer to the current three ones. The geometric model of this system is presented and the constraint for correspondence is deduced. An analysis of the constraint degeneration is given and simulation experiments are conducted under both ideal and error conditions. Experiments show that this approach enables 1D transducers system to perform both active and passive tracking, and its high tracking accuracy is further improved.
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