title: Default Mode Dynamics for Global Functional Integration.
abstract: 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 to human cognition. 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.
  
  
  CONCLUSIONS
  The default mode network (DMN) has been shown to increase its activity during the absence of external stimulation, and hence was historically assumed to disengage during goal-directed tasks. Recent evidence, however, implicates the DMN in self-referential and memory-based processing. We provide robust evidence for this network's active contribution to working memory by revealing dynamic reconfiguration in its interactions with other networks and offer an explanation within the global workspace theoretical framework. These promising findings may help redefine our understanding of the exact DMN role in human cognition.
authors.affiliation: Division of Anaesthesia and Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, and ddsv2@cam.ac.uk.
authors.forename: Deniz
authors.initials: D
authors.lastname: Vatansever
authors.affiliation: Division of Anaesthesia and Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, and.
authors.forename: David K
authors.identifier: http://orcid.org/0000-0002-3228-9692
authors.initials: DK
authors.lastname: Menon
authors.affiliation: Division of Anaesthesia and Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, and.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Manktelow
authors.affiliation: Department of Psychiatry, School of Clinical Medicine, University of Cambridge, Cambridge CB2 0QQ, United Kingdom.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Sahakian
authors.affiliation: Division of Anaesthesia and Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, and.
authors.forename: Emmanuel A
authors.initials: EA
authors.lastname: Stamatakis
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping; D003071:Cognition / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D008959:Models, Neurological; D009415:Nerve Net / Q000098:blood supply / Q000502:physiology; D009483:Neuropsychological Tests; D017711:Nonlinear Dynamics; D055815:Young Adult
keywords: alluvial diagram; default mode network; flexibility; functional connectivity; graph theory; large-scale brain network