Assessing functional connectivity in the triple resting-state networks
4th November 2021
Hasan Sbaihat, Ravichandran Rajkumar, Shukti Ramkiran, Abed Al-Nasser Assi, N. Jon Shah, Tanja Veselinović, Irene Neuner
It is now widely accepted that individual brain regions do not achieve cognitive tasks by working in isolation, but rather they form networks of several discrete brain regions that are said to be ‘functionally connected’. This functional connectivity can be measured via the statistical analysis of the BOLD (blood oxygen level dependence) signal acquired in functional magnetic resonance imaging (fMRI).
When the cognitive state is not explicit, i.e., when an individual is at rest, the large-scale brain network is a resting-state network, and the examination of regional spontaneous brain activity and functional connectivity during resting-state conditions appears to be a promising approach for understanding how the brain is organised at the systems level.
Due to their involvement in a wide range of cognitive tasks, the default mode network, the salience network, and the central executive network are considered to be the three core resting-state brain networks. Although a great deal is known about the regional spontaneous activity and functional connectivity of these networks, less is known about the dynamics of the task-associated modulation on these parameters and the task-induced interaction between these three networks.
This study investigated the effects of a visual-oddball paradigm on three fMRI measures (amplitude of low-frequency fluctuations for regional spontaneous activity, regional homogeneity for local functional connectivity, and degree centrality for global functional connectivity) in the three core resting-state networks.
The results show that the observed patterns of change differed noticeably between the networks and were tightly associated with the task-related brain activity. Furthermore, the distinct involvement of the networks in the performance of the single subtasks could also be seen. The inter-network analysis showed an increased synchronisation of the central executive network with the default mode network and the salience network immediately after the task, but not between the default mode network and salience network. Higher pre-task inter-network synchronisation between the default mode network and the central executive network was associated with shorter reaction times and thus better performance.
Although further investigations are required to better understand the functional importance and interplay, these results provide additional insights into the dynamics within and between the triple resting-state network.
The images below on the left show fMRI measures (ALFF, ReHo, and DC) from 21 subjects depicted for the whole brain. The difference between the two resting states (R2-R1) for each of the three fMRI measures is shown in the right row (B).
The graph on the right shows the strength of the functional between each pair of networks in the triple network in the pre- and post-task resting state. A significant increase in functional connectivity between the DMN and CEN, and between the CEN and the SN in the post-task resting-state (p < 0.05) can be seen. The bars represent the standard error.
Origional publication