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SUMMARY:Mapping overlapping\, dynamic brain networks from resting-state FM
 RI - Professor Stephen Smith\, Oxford Centre for Functional MRI of the Bra
 in (FMRIB)\, University of Oxford
DTSTART:20120703T100000Z
DTEND:20120703T110000Z
UID:TALK38616@talks.cam.ac.uk
CONTACT:Mikail Rubinov
DESCRIPTION:Resting-state functional magnetic resonance imaging has become
  a powerful tool for the study of functional networks in the brain. Even 
 “at rest\,” the brain's different functional networks spontaneously fl
 uctuate in their activity level\; each network's spatial extent can theref
 ore be mapped by finding temporal correlations between its different subre
 gions. The talk will start with a brief background on the use of resting-s
 tate fluctuations to map functional networks\,\nincluding our previous wor
 k showing correspondence between resting-state networks and networks found
  from explicit task-activation studies. I will then go on to describe our 
 most recent work\, where we reconsider how we should separate distinct net
 works from each other. Current correlation-based approaches measure the av
 erage functional connectivity between regions\, but this average is less m
 eaningful for regions that are part of multiple networks\; one ideally wan
 ts a network model that explicitly allows overlap\, for example\, allowing
  a region's activity pattern to reflect one network's activity some of the
  time\, and another network's activity at other times. However\, even thos
 e approaches that do allow overlap have often maximized mutual spatial ind
 ependence\, which may be suboptimal if distinct networks have significant 
 overlap. In this work\, we identify functionally distinct networks by virt
 ue of their temporal independence\, taking advantage of the additional tem
 poral richness available via improvements in functional magnetic resonance
  imaging sampling rate. We identify multiple “temporal functional modes\
 ,” including several that subdivide the default-mode network (and the re
 gions anticorrelated with it) into several functionally distinct\, spatial
 ly overlapping\, networks\, each with its own pattern of correlations and 
 anticorrelations. These functionally distinct modes of spontaneous brain a
 ctivity are\, in general\, quite different from resting-state networks pre
 viously reported\, and may have greater biological interpretability.
LOCATION:MRC CBU\, Chaucer Road
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