Abstract
Consistent resting brain activity patterns have been repeatedly demonstrated using measures derived from resting BOLD fMRI data. While those metrics are presumed to reflect underlying spontaneous brain activity (SBA), it is challenging to prove that association because resting BOLD fMRI metrics are purely model-free and scale-free variables. Cerebral blood flow (CBF) is typically closely coupled to brain metabolism and is used as a surrogate marker for quantifying regional brain function, including resting function. Assessing the correlations between resting BOLD fMRI measures and CBF correlation should provide a means of linking of those measures to the underlying SBA, and a means to quantify those scale-free measures. The purpose of this paper was to examine the CBF correlations of 3 widely used neuroimaging-based SBA measures, including seed-region based functional connectivity (FC), regional homogeneity (ReHo), and amplitude of low frequency fluctuation (ALFF). Test-retest data were acquired to check the stability of potential correlations across time. Reproducible posterior cingulate cortex (PCC) FC vs regional CBF correlations were found in much of the default mode network and visual cortex. Dorsal anterior cingulate cortex (ACC) FC vs CBF correlations were consistently found in bilateral prefrontal cortex. Both ReHo and ALFF were found to be reliably correlated with CBF in most of brain cortex. None of the assessed SBA measures was correlated with whole brain mean CBF. These findings suggest that resting BOLD fMRI-derived measures are coupled with regional CBF and are therefore linked to regional SBA.
Highlights
The human brain consumes about 20% of the body’s energy [1] and most of the ‘‘energy budget’’ in the brain is spent on the intrinsic or spontaneous activity supporting communication among neurons and their supporting cells [2]
As shown in the results of group level one sample T test based on the relative Cerebral blood flow (CBF) images (Fig. 1c and 1d), higher than average CBF was found in medial orbitofrontal cortex, frontal cortex (FC), cingulate cortex, insula, middle and superior temporal cortex (TC), putamen, precuneus, bilateral parietal cortex (PC), and visual cortex (VC) in both sessions
This study provides the first evidence that the resting BOLD imaging-based spontaneous brain activity (SBA) measures are related to regional CBF
Summary
The human brain consumes about 20% of the body’s energy [1] and most of the ‘‘energy budget’’ in the brain is spent on the intrinsic or spontaneous activity supporting communication among neurons and their supporting cells [2] This striking neurophysiologic phenomenon motivates the increasing interest in examining spontaneous brain activity (SBA) using BOLD fMRI data acquired at rest. Various data-derived resting brain activity measures have been assumed to reflect underlying SBA including seed-region based functional connectivity (SRFC), regional coherence, and regional low frequency fluctuations [2,3,4,5,6,7,8,9,10,11,12] Evidence demonstrates that such SBA measures, derived from resting functional neuroimaging, can be altered by either functional tasks [8,11,13,14] or brain disorders [15,16,17,18]. Examining that link is important for verifying the physiological significance of these SBA metrics since the metrics themselves are unitless
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