title: Impairment of functional integration of the default mode network correlates with cognitive outcome at three months after stroke.
abstract: Resting-state studies conducted with stroke patients are scarce. The study of brain activity and connectivity at rest provides a unique opportunity for the investigation of brain rewiring after stroke and plasticity changes. This study sought to identify dynamic changes in the functional organization of the default mode network (DMN) of stroke patients at three months after stroke. Eleven patients (eight male and three female; age range: 48-72) with right cortical and subcortical ischemic infarctions and 17 controls (eleven males and six females; age range: 57-69) were assessed by neurological and neuropsychological examinations and scanned with resting-state functional magnetic ressonance imaging. First, we explored group differences in functional activity within the DMN by means of probabilistic independent component analysis followed by a dual regression approach. Second, we estimated functional connectivity between 11 DMN nodes both locally by means of seed-based connectivity analysis, as well as globally by means of graph-computation analysis. We found that patients had greater DMN activity in the left precuneus and the left anterior cingulate gyrus when compared with healthy controls (P < 0.05 family-wise error corrected). Seed-based connectivity analysis showed that stroke patients had significant impairment (P = 0.014; threshold = 2.00) in the connectivity between the following five DMN nodes: left superior frontal gyrus (lSFG) and posterior cingulate cortex (t = 2.01); left parahippocampal gyrus and right superior frontal gyrus (t = 2.11); left parahippocampal gyrus and lSFG (t = 2.39); right parietal and lSFG (t = 2.29). Finally, mean path length obtained from graph-computation analysis showed positive correlations with semantic fluency test (r(s)  = 0.454; P = 0.023), phonetic fluency test (r(s)  = 0.523; P = 0.007) and the mini mental state examination (r(s)  = 0.528; P = 0.007). In conclusion, the ability to regulate activity of the DMN appears to be a central part of normal brain function in stroke patients. Our study expands the understanding of the changes occurring in the brain after stroke providing a new avenue for investigating lesion-induced network plasticity.
authors.affiliation: Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Barcelona, Spain; Group of Computational Intelligence, Department of CCIA, University of the Basque Country UPV/EHU, San Sebastian, Spain.
authors.forename: Rosalia
authors.initials: R
authors.lastname: Dacosta-Aguayo
authors.forename: Manuel
authors.initials: M
authors.lastname: Graña
authors.forename: Yasser
authors.initials: Y
authors.lastname: Iturria-Medina
authors.forename: Marina
authors.initials: M
authors.lastname: Fernández-Andújar
authors.forename: Elena
authors.initials: E
authors.lastname: López-Cancio
authors.forename: Cynthia
authors.initials: C
authors.lastname: Cáceres
authors.forename: Núria
authors.initials: N
authors.lastname: Bargalló
authors.forename: Maite
authors.initials: M
authors.lastname: Barrios
authors.forename: Immaculada
authors.initials: I
authors.lastname: Clemente
authors.forename: Pera
authors.initials: P
authors.lastname: Toran
authors.forename: Rosa
authors.initials: R
authors.lastname: Forés
authors.forename: Antoni
authors.initials: A
authors.lastname: Dávalos
authors.forename: Tibor
authors.initials: T
authors.lastname: Auer
authors.forename: Maria
authors.initials: M
authors.lastname: Mataró
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000503:physiopathology*; D002545:Brain Ischemia / Q000503:physiopathology* / Q000523:psychology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology; D009483:Neuropsychological Tests; D012146:Rest; D012815:Signal Processing, Computer-Assisted; D020521:Stroke / Q000503:physiopathology* / Q000523:psychology*
keywords: default mode network; graph-computation analysis; probabilistic independent component analysis; seed-based connectivity analysis