Abstract
The Default Mode Network (DMN) is a brain system that mediates internal modes of cognitive activity, showing higher neural activation when one is at rest. Nowadays, there is a lot of interest in assessing functional interactions between its key regions, but in the majority of studies only association of Blood-oxygen-level dependent (BOLD) activation patterns is measured, so it is impossible to identify causal influences. There are some studies of causal interactions (i.e., effective connectivity), however often with inconsistent results. The aim of the current work is to find a stable pattern of connectivity between four DMN key regions: the medial prefrontal cortex (mPFC), the posterior cingulate cortex (PCC), left and right intraparietal cortex (LIPC and RIPC). For this purpose functional magnetic resonance imaging (fMRI) data from 30 healthy subjects (1000 time points from each one) was acquired and spectral dynamic causal modeling (DCM) on a resting-state fMRI data was performed. The endogenous brain fluctuations were explicitly modeled by Discrete Cosine Set at the low frequency band of 0.0078–0.1 Hz. The best model at the group level is the one where connections from both bilateral IPC to mPFC and PCC are significant and symmetrical in strength (p < 0.05). Connections between mPFC and PCC are bidirectional, significant in the group and weaker than connections originating from bilateral IPC. In general, all connections from LIPC/RIPC to other DMN regions are much stronger. One can assume that these regions have a driving role within the DMN. Our results replicate some data from earlier works on effective connectivity within the DMN as well as provide new insights on internal DMN relationships and brain’s functioning at resting state.
Highlights
One of the exiting discoveries in modern cognitive neuroscience, which was anticipated by the founding fathers of electrophysiology, is that our brain is never at rest
The results of Bayesian Model Averaging (BMA) and classical t-test are shown in the tables below
Li et al (2012) using stochastic dynamic causal modeling (DCM) showed an influence from posterior cingulate cortex (PCC) to medial prefrontal cortex (mPFC)
Summary
One of the exiting discoveries in modern cognitive neuroscience, which was anticipated by the founding fathers of electrophysiology, is that our brain is never at rest. During wakeful periods when we are trying not to do anything, global metabolism does not decrease in the brain, and some of its distinct areas are still active These areas constitute networks of the resting state conditions or RSNs. during overall deliberate inactivity and inattention to the external world, small but consistent increases in activity occur in a specific set of regions called the ‘‘Default Mode Network’’ or DMN. During overall deliberate inactivity and inattention to the external world, small but consistent increases in activity occur in a specific set of regions called the ‘‘Default Mode Network’’ or DMN It is a core part of a number of RSNs which were intensively investigated in the past couples of decades. It is believed that DMN, which was one of the first discovered, is closely related to the function of consciousness
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