Carbon dioxide is a potent cerebral vasodilator. We have identified a significant source of low-frequency variation in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal at 3 T arising from spontaneous fluctuations in arterial carbon dioxide level in volunteers at rest. Fluctuations in the partial pressure of end-tidal carbon dioxide (Pet(CO(2))) of +/-1.1 mm Hg in the ...

BACKGROUND AND PURPOSE Low-frequency (<0.08 Hz) fluctuations in spontaneous blood oxygen level-dependent (BOLD) signal intensity show synchronization across anatomically interconnected and functionally specific brain regions, suggesting a neural origin of fluctuations. To determine the mechanism by which high-frequency neural activity results in low-frequency BOLD fluctuations, I obtained measu...

The southern oscillation index (SOI) is a characteristic of the El Niño phenomenon. SOI monthly averaged data is analyzed for the time interval 1866-2000. The tail of the cumulative distribution of the fluctuations of SOI signal is studied in order to characterize the amplitude scaling of the fluctuations and the occurrence of extreme events. Large fluctuations are more likely to occur than the...

INTRODUCTION Spontaneous fluctuations in BOLD signal are used for functional connectivity [1]. It has been suggested that these spontaneous fluctuations may influence trial-to-trial variability of the evoked BOLD response [2]. Taken together, these studies suggest that the amplitude of the spontaneous fluctuation has significance for the strength of the functional connectivity (between symmetri...