Detecting resting-state brain activity by spontaneous cerebral blood volume fluctuations using whole brain vascular space occupancy imaging

Abstract

Resting-state brain activity has been investigated extensively using BOLD contrast. However, BOLD signal represents the combined effects of multiple physiological processes and its spatial localization is less accurate than that of cerebral blood flow and volume (CBF and CBF, respectively). In this study, we demonstrate that resting-state brain activity can be reliably detected by spontaneous fluctuations of CBV-weighted signal using whole-brain gradient and spin echo (GRASE) based vascular space occupancy (VASO) imaging. Specifically, using independent component analysis, intrinsic brain networks, including default mode, salience, executive control, visual, auditory, and sensorimotor networks were revealed robustly by the VASO technique. We further demonstrate that taskevoked VASO signal aligned well with expected gray matter areas, while blood-oxygenation level dependent (BOLD) signal extended outside of these areas probably due to their different spatial specificity. The improved spatial localization of VASO is consistent with previous studies using animal models. Moreover, we showed that the 3D-GRASE VASO images had reduced susceptibility-induced signal voiding, compared to the BOLD technique. This is attributed to the fact that VASO does not require T 2 * weighting, thus the acquisition can use a shorter TE and can employ spin-echo scheme. Consequently VASO-based functional connectivity signals were well preserved in brain regions that tend to suffer from signal loss and geometric distortion in BOLD, such as orbital prefrontal cortex. Our study suggests that 3D-GRASE VASO imaging, with its improved spatial specificity and less sensitivity to susceptibility artifacts, may have advantages in resting-state fMRI studies.Published by Elsevier Inc.

Functional Connectivity-Based Parcellation of the Thalamus: An Unsupervised Clustering Method and Its Validity Investigation

“…Activity of the thalamic clusters from the K = 7 parcellation showed responses in certain clusters to visuomotor stimulation that are consistent with previous reports of visuomotor task activation (Calhoun et al, 2001;Miao et al, 2014;Witt et al, 2008), providing validity of our thalamic parcellation results. Specifically, Clusters 2, Cluster 3 and Cluster 5 were activated during the visuomotor task.…”

Neuronal and Physiological Correlation to Hemodynamic Resting-State Fluctuations in Health and Disease

“…These findings are in line with resting-state MRI measurements of blood flow and blood volume (Miao et al, 2014;Zhu et al, 2013;Zou et al, 2009), whereby typical low-frequency and connectivity patterns were observed. The findings obtained in this work indicate greater value in blood-oxygenation-based fcMRI compared with CBF-or CBV-sensitive fcMRI for reporting neuronal connectivity.…”

“…Changes in vascular function or oxidative metabolism may occur with or without changes in neural activity. Although some studies have explored physiological correlates of low-frequency fluctuations (De Luca et al, 2006;Miao et al, 2014;Wu et al, 2009;Zou et al, 2009), fundamental gaps remain regarding the relationship between these fluctuations and brain function, including the relative contributions of neuronal and vascular factors to the measured fcMRI time series. A complicating factor is that vascular smooth muscle is known to have slow contractile rhythms, termed vasomotion, around this frequency range (Mayhew et al, 1996).…”

Comparison of BOLD and CBV using 3D EPI and 3D GRASE for cortical layer fMRI at 7T

“…Recently the technique has been used successfully at UHF (38) for laminar specific applications (9, 10). 3D GRASE can also be used as readout sequence in CBV imaging, as used at low resolutions for fMRI at 3T (39–41) and in resting state experiments (42, 43). However, VASO 3D GRASE has not been developed or evaluated for mesoscale high resolution CBV-fMRI.…”