title: Task-dependent reorganization of functional connectivity networks during visual semantic decision making.
abstract: BACKGROUND
  Functional MRI is widely used to study task-related changes in neuronal activity as well as resting-state functional connectivity. In this study, we explore task-related changes in functional connectivity networks using fMRI. Dynamic connectivity may represent a new measure of neural network robustness that would impact both clinical and research efforts. However, prior studies of task-related changes in functional connectivity have shown apparently conflicting results, leading to several competing hypotheses regarding the relationship between task-related and resting-state brain networks.
  
  
  METHODS
  We used a graph theory-based network approach to compare functional connectivity in healthy subjects between the resting state and when performing a clinically used semantic decision task. We analyzed fMRI data from 21 healthy, right-handed subjects.
  
  
  RESULTS
  While three nonoverlapping, highly intraconnected functional modules were observed in the resting state, an additional language-related module emerged during the semantic decision task. Both overall and within-module connectivity were greater in default mode network (DMN) and classical language areas during semantic decision making compared to rest, while between-module connectivity was diffusely greater at rest, revealing a more widely distributed pattern of functional connectivity at rest.
  
  
  CONCLUSIONS
  The results of this study suggest that there are differences in network topology between resting and task states. Specifically, semantic decision making is associated with a reduction in distributed connectivity through hub areas of the DMN as well as an increase in connectivity within both default and language networks.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging Charlestown, Massachusetts ; Massachusetts General Hospital Boston, Massachusetts.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: DeSalvo
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging Charlestown, Massachusetts ; Massachusetts General Hospital Boston, Massachusetts.
authors.forename: Linda
authors.initials: L
authors.lastname: Douw
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging Charlestown, Massachusetts ; Massachusetts General Hospital Boston, Massachusetts.
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Takaya
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging Charlestown, Massachusetts ; Massachusetts General Hospital Boston, Massachusetts.
authors.forename: Hesheng
authors.initials: H
authors.lastname: Liu
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging Charlestown, Massachusetts ; Massachusetts General Hospital Boston, Massachusetts.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Stufflebeam
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D003657:Decision Making / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology; D009483:Neuropsychological Tests; D012146:Rest; D012189:Retrospective Studies; D012660:Semantics; D012815:Signal Processing, Computer-Assisted; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Connectomics; default mode network; functional magnetic resonance imaging; graph theory; language; memory; resting state