Journal
JOURNAL OF NEUROSCIENCE
Volume 35, Issue 46, Pages 15254-15262Publisher
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.2135-15.2015
Keywords
alluvial diagram; default mode network; flexibility; functional connectivity; graph theory; large-scale brain network
Categories
Funding
- Evelyn Trust [RUAG/018]
- Yousef Jameel Academic Program
- National Institute for Health Research (NIHR) Cambridge Biomedical Centre [RCZB/004]
- NIHR Senior Investigator Award [RCZB/014]
- Stephen Erskine Fellowship, Queens' College Cambridge
- National Institute for Health Research [NF-SI-0512-10090] Funding Source: researchfish
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The default mode network (DMN) has been traditionally assumed to hinder behavioral performance in externally focused, goal-directed paradigms and to provide no active contribution tohumancognition. However, recent evidence suggests greater DMN activity in an array of tasks, especially those that involve self-referential and memory-based processing. Although data that robustly demonstrate a comprehensive functional role for DMN remains relatively scarce, the global workspace framework, which implicates the DMN in global information integration for conscious processing, can potentially provide an explanation for the broad range of higher-order paradigms that report DMN involvement. We used graph theoretical measures to assess the contribution of the DMN to global functional connectivity dynamics in 22 healthy volunteers during an fMRI-based n-back working-memory paradigm with parametric increases in difficulty. Our predominant finding is that brain modularity decreases with greater task demands, thus adapting a more global workspace configuration, in direct relation to increases in reaction times to correct responses. Flexible default mode regions dynamically switch community memberships and display significant changes in their nodal participation coefficient and strength, which may reflect the observed whole-brain changes in functional connectivity architecture. These findings have important implications for our understanding of healthy brain function, as they suggest a central role for the DMN in higher cognitive processing.
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