Abstract
While functional connectivity networks are often extracted from resting-state fMRI scans, they have been shown to be active during task performance as well. However, the effect of an in-scanner task on functional connectivity networks is not completely understood. While there is evidence that task-evoked positive BOLD response can alter functional connectivity networks, particularly in the primary sensorimotor cortices, the effect of task-evoked negative BOLD response on the functional connectivity of the Default mode network (DMN) is somewhat ambiguous. In this study, we aim to investigate whether task performance, which is associated with negative BOLD response in the DMN regions, alters the time-course of functional connectivity in the same regions obtained by independent component analysis (ICA). ICA has been used to effectively extract functional connectivity networks during task performance and resting-state. We first demonstrate that performing a simple visual-motor task alters the temporal time-course of the network extracted from the primary visual cortex. Then we show that despite detecting a robust task-evoked negative BOLD response in the DMN regions, a simple visual-motor task does not alter the functional connectivity of the DMN regions. Our findings suggest that different mechanisms may underlie the relationship between task-related activation/deactivation networks and the overlapping functional connectivity networks in the human large-scale brain networks.
Highlights
Recent advances in the acquisition and analysis of functional magnetic resonance image have made it possible to discover numerous large-scale brain networks based on their spontaneous, but synchronized, low frequency fluctuations at resting-state, as well as during task performance (Biswal et al, 1995; Greicius et al, 2003; Greicius and Menon, 2004; Power et al, 2011; Smith et al, 2013; Cole et al, 2014)
The main goal of this study is to investigate whether or not task-evoked negative blood oxygenation level dependent (BOLD) response alters the temporal characteristics of the tb-Functional connectivity (FC) network when both are extracted from the Default mode network (DMN) regions
We demonstrate here that removing task-related activity from the tb-functional magnetic resonance image (fMRI) data significantly alters the temporal/spatial characteristics of the task-based FC (tb-FC) networks extracted from primary visual cortex, whereas it has no significant effect on the temporal/spatial characteristics of the tb-FC networks extracted from DMN regions, providing evidence that taskevoked negative BOLD response does not alter overlapping FC in DMN regions
Summary
Recent advances in the acquisition and analysis of functional magnetic resonance image (fMRI) have made it possible to discover numerous large-scale brain networks based on their spontaneous, but synchronized, low frequency fluctuations at resting-state, as well as during task performance (Biswal et al, 1995; Greicius et al, 2003; Greicius and Menon, 2004; Power et al, 2011; Smith et al, 2013; Cole et al, 2014). Positive and negative blood oxygenation level dependent (BOLD) signal, which gives rise to Negative BOLD Response in DMN activation/deactivation networks, can only be extracted from task-based fMRI (tb-fMRI) scans, and is often based on the timecourse of the task being performed Both task-evoked BOLD response and FC networks during task and rest have been used to investigate the functional architecture of the human brain (Cole et al, 2014; Krienen et al, 2014; Stern et al, 2014). Gaining a more complete understanding of the accordance and discordance between rs-FC networks and tbFC networks, is crucial toward estimating the true underlying functional architecture of the human brain
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