Graph properties of synchronized cortical networks during visual working memory maintenance

Palva, S. , Monto, S. and Palva, J. M. (2010) Graph properties of synchronized cortical networks during visual working memory maintenance. NeuroImage, 49(4), pp. 3257-3268. (doi: 10.1016/j.neuroimage.2009.11.031) (PMID:19932756)

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Oscillatory synchronization facilitates communication in neuronal networks and is intimately associated with human cognition. Neuronal activity in the human brain can be non-invasively imaged with magneto- (MEG) and electroencephalography (EEG), but the large-scale structure of synchronized cortical networks supporting cognitive processing has remained uncharacterized. We combined simultaneous MEG and EEG (MEEG) recordings with minimum-norm-estimate-based inverse modeling to investigate the structure of oscillatory phase synchronized networks that were active during visual working memory (VWM) maintenance. Inter-areal phase-synchrony was quantified as a function of time and frequency by single-trial phase-difference estimates of cortical patches covering the entire cortical surfaces. The resulting networks were characterized with a number of network metrics that were then compared between delta/theta- (3–6 Hz), alpha- (7–13 Hz), beta- (16–25 Hz), and gamma- (30–80 Hz) frequency bands. We found several salient differences between frequency bands. Alpha- and beta-band networks were more clustered and small-world like but had smaller global efficiency than the networks in the delta/theta and gamma bands. Alpha- and beta-band networks also had truncated-power-law degree distributions and high k-core numbers. The data converge on showing that during the VWM-retention period, human cortical alpha- and beta-band networks have a memory-load dependent, scale-free small-world structure with densely connected core-like structures. These data further show that synchronized dynamic networks underlying a specific cognitive state can exhibit distinct frequency-dependent network structures that could support distinct functional roles.

Item Type:Articles
Additional Information:This study was supported by the Academy of Finland, by the Helsinki University Research Funds and by the Wihuri foundation.
Glasgow Author(s) Enlighten ID:Palva, Professor Satu and Palva, Professor Matias
Authors: Palva, S., Monto, S., and Palva, J. M.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:NeuroImage
ISSN (Online):1095-9572
Published Online:22 November 2009

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