Abstract
Measures of resting-state functional magnetic resonance imaging (rsfMRI) activity have been shown to be sensitive to cognitive function and disease state. However, there is growing evidence that variations in vigilance can lead to pronounced and spatially widespread differences in resting-state brain activity. Unless properly accounted for, differences in vigilance can give rise to changes in resting-state activity that can be misinterpreted as primary cognitive or disease-related effects. In this paper, we examine in detail the link between vigilance and rsfMRI measures, such as signal variance and functional connectivity. We consider how state changes due to factors such as caffeine and sleep deprivation affect both vigilance and rsfMRI measures and review emerging approaches and methodological challenges for the estimation and interpretation of vigilance effects.
Highlights
Resting-state fMRI is a widely used method to characterize the functional organization of the brain at rest
Given the link between resting-state functional magnetic resonance imaging (rsfMRI) measures and vigilance and prior findings indicating a decrease in EEG vigilance with schizophrenia (Boutros et al, 2008; Razavi et al, 2013), it is likely that disease-related vigilance effects contributed to the observed differences
There is substantial evidence indicating that vigilance effects play a significant role in resting-state fMRI studies
Summary
Resting-state fMRI (rsfMRI) is a widely used method to characterize the functional organization of the brain at rest. A commonly used rsfMRI measure is the correlation coefficient between the blood oxygenation level dependent (BOLD) time series observed in different brain regions. This measure of functional connectivity (FC) has been shown to be sensitive to cognitive function and disease state (Greicius, 2008; Hampson et al, 2010). Other rsfMRI measures may have diagnostic potential, such as the use of the variance of the rsfMRI global brain signal (defined as the mean of all BOLD signals in the brain) to distinguish schizophrenic patients from healthy controls (Yang et al, 2014) Because they do not require the subject to perform a task, rsfMRI measures are attractive for both research and clinical applications. We will review emerging methods for the estimation of vigilance effects and conclude with a consideration of methodological concerns, potential mechanisms, and future avenues of research
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