title: Small-World Characteristics of Cortical Connectivity Changes in Acute Stroke.
abstract: Background After cerebral ischemia, disruption and subsequent reorganization of functional connections occur both locally and remote to the lesion. Recently, complexity of brain connectivity has been described using graph theory, a mathematical approach that depicts important properties of complex systems by quantifying topologies of network representations. Functional and dynamic changes of brain connectivity can be reliably analyzed via electroencephalography (EEG) recordings even when they are not yet reflected in structural changes of connections. Objective We tested whether and how ischemic stroke in the acute stage may determine changes in small-worldness of cortical networks as measured by cortical sources of EEG. Methods Graph characteristics of EEG of 30 consecutive stroke patients in acute stage (no more than 5 days after the event) were examined. Connectivity analysis was performed using eLORETA in both hemispheres. Results Network rearrangements were mainly detected in delta, theta, and alpha bands when patients were compared with healthy subjects. In delta and alpha bands similar findings were observed in both hemispheres regardless of the side of ischemic lesion: bilaterally decreased small-worldness in the delta band and bilaterally increased small-worldness in the alpha2 band. In the theta band, bilaterally decreased small-worldness was observed only in patients with stroke in the left hemisphere. Conclusions After an acute stroke, brain cortex rearranges its network connections diffusely, in a frequency-dependent modality probably in order to face the new anatomical and functional frame.
authors: Catholic University, Rome, Italy pietro.caliandro@policlinicogemelli.it.|Fondazione Don Carlo Gnocchi Onlus, Milan, Italy.
authors: Pietro
authors: P
authors: Caliandro
authors: IRCCS San Raffaele Pisana, Rome, Italy.
authors: Fabrizio
authors: F
authors: Vecchio
authors: IRCCS San Raffaele Pisana, Rome, Italy.
authors: Francesca
authors: F
authors: Miraglia
authors: Catholic University, Rome, Italy.
authors: Giuseppe
authors: G
authors: Reale
authors: Catholic University, Rome, Italy.
authors: Giacomo
authors: G
authors: Della Marca
authors: Sapienza University of Rome, Rome, Italy.
authors: Giuseppe
authors: G
authors: La Torre
authors: Catholic University, Rome, Italy.
authors: Giordano
authors: G
authors: Lacidogna
authors: Catholic University, Rome, Italy.|Fondazione Don Carlo Gnocchi Onlus, Milan, Italy.
authors: Chiara
authors: C
authors: Iacovelli
authors: Catholic University, Rome, Italy.|Fondazione Don Carlo Gnocchi Onlus, Milan, Italy.
authors: Luca
authors: L
authors: Padua
authors: IRCCS Centro Neurolesi Bonino-Pulejo, Messina, Italy.
authors: Placido
authors: P
authors: Bramanti
authors: Catholic University, Rome, Italy.|IRCCS San Raffaele Pisana, Rome, Italy.
authors: Paolo Maria
authors: PM
authors: Rossini
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology; D012720:Severity of Illness Index; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted; D020521:Stroke / Q000503:physiopathology*
keywords: connectivity; cortex; electroencephalography; graph theory; plasticity; stroke