Abstract
Studies of brain functional connectivity have provided a better understanding of organization and integration of large-scale brain networks. Functional connectivity using resting-state functional magnetic resonance imaging (fMRI) is typically based upon the correlations of the low-frequency fluctuation of fMRI signals. Reproducible spatial maps in the brain have also been observed using the amplitude of low-frequency fluctuations (ALFF) in resting-state. However, little is known about the influence of the ALFF on the functional connectivity measures. In the present study, we analyzed resting-state fMRI data on 79 healthy old individuals. Spatial independent component analysis and regions of interest (ROIs) based connectivity analysis were performed to obtain measures of functional connectivity. ALFF maps were also calculated. First, voxel-matched inter-subject correlations were computed between back-reconstructed IC and ALFF maps. For all the resting-state networks, there was a consistent correlation between ALFF variability and network strengths (within regions that had high IC strengths). Next, inter-subject variance of correlations across 160 functionally defined ROIs were correlated with the corresponding ALFF variance. The connectivity of several ROIs to other regions were more likely to correlate with its own regional ALFF. These regions were mainly located in the anterior cingulate cortex, medial prefrontal cortex, precuneus, insula, basal ganglia, and thalamus. These associations may suggest a functional significance of functional connectivity modulations. Alternatively, the fluctuation amplitudes may arise from physiological noises, and therefore, need to be controlled when studying resting-state functional connectivity.
Highlights
Studies of brain networks and functional connectivity have provided a better understanding of organization and integration of large-scale brain networks
RELATIONSHIPS BETWEEN NETWORK STRENGTH AND amplitude of low-frequency fluctuations (ALFF) Out of the 20 ICs, 8 ICs were identified which corresponded to the 8 networks described by Cole et al (2010), including the default mode network (DMN), left and right executive, attention, salience, motor, visual, and fronto-parietal opercular networks
For the DMN network, correlations between network strengths and ALFFs were observed in the posterior cingulate cortex/precuneus, medial prefrontal cortex (MPFC), and the right inferior parietal lobule/superior temporal gyrus
Summary
Studies of brain networks and functional connectivity have provided a better understanding of organization and integration of large-scale brain networks. After the initial observation that the motor cortex exhibits highly synchronized intrinsic fluctuations during the absence of specific tasks (Biswal et al, 1995), the restingstate functional connectivity has emerged as a promising approach to investigate the functional integration of the brain. ICA simultaneously investigate multiple networks such as the DMN, salience, left/right executive, attention, motor, and visual networks (Greicius et al, 2004; Beckmann et al, 2005) and several successful applications have been reported in mental diseases (e.g., Greicius et al, 2004; Veer et al, 2010; Westlye et al, 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
