Functional connectivity and the sleep-deprived brain.

Resting state functional connectivity (rsFC) evaluated by detecting temporal co-variation of BOLD signals across multiple brain regions undergoes three major changes following sleep deprivation that indicate the occurrence of sleep intrusions; a loss of integration within networks like the default mode network as well as between networks like the salience and dorsal attention systems; a loss of segregation between networks, for example, between the dorsal attention and default mode networks; and an increase in global signal. Changes in vigilance affect rsFC and these likely occur in many scans involving persons with neuropsychiatric conditions. Ensuring "healthy" or "control" participants do not fall asleep in the scanner is increasingly acknowledged as a being important for proper inference in fMRI studies. Dynamic functional connectivity analyses evaluating the relative proportion of time spent in "low" or "high" arousal states during the well-rested state can predict propensity for vigilance decline when sleep deprived.