Differences in the resting-state fMRI global signal amplitude between the eyes open and eyes closed states are related to changes in EEG vigilance.
In resting-state functional connectivity magnetic resonance imaging (fcMRI) studies, measures of functional connectivity are often calculated after the removal of a global mean signal component. While the application of the global signal regression approach has been shown to reduce the influence of physiological artifacts and enhance the detection of functional networks, there is considerable controversy regarding its use as the method can lead to significant bias in the resultant connectivity measures. In addition, evidence from recent studies suggests that the global signal is linked to neural activity and may carry clinically relevant information. For instance, in a prior study we found that the amplitude of the global signal was negatively correlated with EEG measures of vigilance across subjects and experimental runs. Furthermore, caffeine-related decreases in global signal amplitude were associated with increases in EEG vigilance. In this study, we extend the prior work by examining measures of global signal amplitude and EEG vigilance under eyes-closed (EC) and eyes-open (EO) resting-state conditions. We show that changes (EO minus EC) in the global signal amplitude are negatively correlated with the associated changes in EEG vigilance. The slope of this EO-EC relation is comparable with the slope of the previously reported relation between caffeine-related changes in the global signal amplitude and EEG vigilance. Our findings provide further support for a basic relationship between global signal amplitude and EEG vigilance.
Center for Functional Magnetic Resonance Imaging, University of California San Diego, La Jolla, CA, USA; Department of Radiology, University of California San Diego, La Jolla, CA, USA. Electronic address: cwwong@ieee.org.
Chi Wah
CW
Wong
Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, CA, USA; Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
Pamela N
PN
DeYoung
Center for Functional Magnetic Resonance Imaging, University of California San Diego, La Jolla, CA, USA; Department of Radiology, University of California San Diego, La Jolla, CA, USA; Department of Bioengineering, University of California San Diego, La Jolla, CA, USA. Electronic address: ttliu@ucsd.edu.
Thomas T
TT
Liu
D000328:Adult; D001143:Arousal; D001931:Brain Mapping; D002110:Caffeine / Q000008:administration & dosage; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009799:Ocular Physiological Phenomena; D055815:Young Adult
D002110:Caffeine
Electroencephalography; Eyes-closed; Eyes-open; Global signal; Resting-state fMRI; Vigilance