The influence of ageing on complex brain networks: A graph theoretical analysis

Micheloyannis, Sifis; Vourkas, Michael; Tsirka, Vassiliki; Karakonstantaki, Eleni; Kanatsouli, Kassia; Stam, Cornelis J.

doi:10.1002/hbm.20492

Cited by 134 publications

(102 citation statements)

References 42 publications

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“…The finding that small-worldness and cost efficiency were reduced in seniors is in agreement with previous results for resting state networks (Achard et al, 2007;Micheloyannis et al, 2009). We can thus generalize the result to working memory networks.…”

Section: Matthä Us Et Alsupporting

confidence: 92%

Effects of Age on the Structure of Functional Connectivity Networks During Episodic and Working Memory Demand

et al. 2012

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The aim of the study was to investigate age-related differences in large-scale functional connectivity networks during episodic and working memory challenge. A graph theoretical approach was used providing an exhaustive set of topological measures to quantify age-related differences in the network structure on various scales. In a single session, 10 young (22-30 years) and 10 senior (62-77 years) subjects performed an episodic and a working memory task during functional magnetic resonance imaging. Networks of functional connectivity were constructed by correlating the blood oxygenation level-dependent (BOLD) signal for every pair of voxels. Statistical network parameters yield a global characterization of the network topology, the quantification of the importance of specific regions, and shifts in local connectivity. An age-related increase in the density and size of the networks and loss of small-worldness was observed, related to an expanded distribution of brain activity during both memory demands in seniors, and a more specific and localized activity in young subjects. In addition, we found highly symmetrical neural networks in young subjects accompanied by a strong coupling between parietal and occipital regions. In contrast, seniors showed pronounced left-hemispheric asymmetry with decreased connectivity within occipital areas, but increased connectivity within parietal areas. Moreover, seniors engaged an additional frontal network strongly connected to parietal areas. In contrast to young subjects, seniors showed an almost identical structure of network connectivity during both memory tasks. The chosen network approach is explorative and hypothesis-free. Our results extend seed-based and BOLD-signal intensity focused studies, and support present hypotheses like compensation and dedifferentiation.

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Section: Matthä Us Et Alsupporting

confidence: 92%

Effects of Age on the Structure of Functional Connectivity Networks During Episodic and Working Memory Demand

et al. 2012

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“…In a study of language perception, agerelated declines in global efficiency were found [52] . During mathematical thinking, the α2 band showed a degree of SWN disorganization in adults compared to children, whereas β and γ bands showed lower synchronization and lower SWN organization [53] . Recently published reviews are helpful to understand the normal organization and development [54][55][56][57][58] .…”

Section: Normal Brain Network Organizationmentioning

confidence: 91%

Graph-based network analysis in schizophrenia

Micheloyannis¹

2012

WJP

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Over the last few years, many studies have been published using modern network analysis of the brain. Researchers and practical doctors alike should understand this method and its results on the brain evaluation at rest, during activation and in brain disease. The studies are noninvasive and usually performed with elecroencephalographic, magnetoencephalographic, magnetic resonance imaging and diffusion tensor imaging brain recordings. Different tools for analysis have been developed, although the methods are in their early stages. The results of these analyses are of special value. Studies of these tools in schizophrenia are important because widespread and local network disturbances can be evaluated by assessing integration, segregation and several structural and functional properties. With the help of network analyses, the main findings in schizophrenia are lower optimum network organization, less efficiently wired networks, less local clustering, less hierarchical organization and signs of disconnection. There are only about twenty five relevant papers on the subject today. Only a few years of study of these methods have produced interesting results and it appears promising that the development of these methods will present important knowledge for both the preclinical signs of schizophrenia and the methods' therapeutic effects.

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“…The topological cost efficiency (Latora and Marchiori, 2001) of brain functional networks oscillating at ␤-band frequencies was shown to be more strongly correlated with variability of performance on a working memory task than the cost efficiency of networks operating at other frequencies (Bassett et al, 2009). Working memory task-related changes in synchronization likelihood and smallworldness of MEG networks were most salient in ␤-and ␥-bands (Micheloyannis et al, 2009). Together, it seems that ␤-band synchronization is very likely a key mechanism in the task-related workspace configuration of large-scale brain functional networks.…”

Section: Complex Network and Workpace Theorymentioning

confidence: 95%

Cognitive Effort Drives Workspace Configuration of Human Brain Functional Networks

et al. 2011

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Effortful cognitive performance is theoretically expected to depend on the formation of a global neuronal workspace. We tested specific predictions of workspace theory, using graph theoretical measures of network topology and physical distance of synchronization, in magnetoencephalographic data recorded from healthy adult volunteers (N ϭ 13) during performance of a working memory task at several levels of difficulty. We found that greater cognitive effort caused emergence of a more globally efficient, less clustered, and less modular network configuration, with more long-distance synchronization between brain regions. This pattern of task-related workspace configuration was more salient in the ␤-band (16 -32 Hz) and ␥-band (32-63 Hz) networks, compared with both lower (␣-band; 8 -16 Hz) and higher (high ␥-band; 63-125 Hz) frequency intervals. Workspace configuration of ␤-band networks was also greater in faster performing participants (with correct response latency less than the sample median) compared with slower performing participants. Processes of workspace formation and relaxation in relation to time-varying demands for cognitive effort could be visualized occurring in the course of task trials lasting Ͻ2 s. These experimental results provide support for workspace theory in terms of complex network metrics and directly demonstrate how cognitive effort breaks modularity to make human brain functional networks transiently adopt a more efficient but less economical configuration.

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The influence of ageing on complex brain networks: A graph theoretical analysis

Cited by 134 publications

References 42 publications

Effects of Age on the Structure of Functional Connectivity Networks During Episodic and Working Memory Demand

Effects of Age on the Structure of Functional Connectivity Networks During Episodic and Working Memory Demand

Graph-based network analysis in schizophrenia

Cognitive Effort Drives Workspace Configuration of Human Brain Functional Networks

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