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Increased segregation of brain networks in focal epilepsy: An fMRI graph theory finding.

Pedersen M, Omidvarnia AH, Walz JM, Jackson GD - Neuroimage Clin (2015)

Bottom Line: Graph theory represents a powerful quantitative framework for investigation of brain networks.We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures.It remains possible that this may be part of the epileptogenic process or an effect of medications.

View Article: PubMed Central - PubMed

Affiliation: The Florey Institute of Neuroscience and Mental Health, Austin Campus, Melbourne, VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia.

ABSTRACT
Focal epilepsy is conceived of as activating local areas of the brain as well as engaging regional brain networks. Graph theory represents a powerful quantitative framework for investigation of brain networks. Here we investigate whether functional network changes are present in extratemporal focal epilepsy. Task-free functional magnetic resonance imaging data from 15 subjects with extratemporal epilepsy and 26 age and gender matched healthy controls were used for analysis. Local network properties were calculated using local efficiency, clustering coefficient and modularity metrics. Global network properties were assessed with global efficiency and betweenness centrality metrics. Cost-efficiency of the networks at both local and global levels was evaluated by estimating the physical distance between functionally connected nodes, in addition to the overall numbers of connections in the network. Clustering coefficient, local efficiency and modularity were significantly higher in individuals with focal epilepsy than healthy control subjects, while global efficiency and betweenness centrality were not significantly different between the two groups. Local network properties were also highly efficient, at low cost, in focal epilepsy subjects compared to healthy controls. Our results show that functional networks in focal epilepsy are altered in a way that the nodes of the network are more isolated. We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures. It remains possible that this may be part of the epileptogenic process or an effect of medications.

No MeSH data available.


Related in: MedlinePlus

Local and global network cost-efficiency: A)CEloc. B)CEglob.
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f0020: Local and global network cost-efficiency: A)CEloc. B)CEglob.

Mentions: CEloc was significantly higher in focal epilepsy compared to controls in 10 of the 26 network density thresholds computed after FDR correction (median effect size = 0.84, CI 95% of 0.12–1.32— Fig.4A). CEglob was not statistically different between groups (median effect size = −0.63, CI 95% of 0.09 to −1.82— Fig.4B).


Increased segregation of brain networks in focal epilepsy: An fMRI graph theory finding.

Pedersen M, Omidvarnia AH, Walz JM, Jackson GD - Neuroimage Clin (2015)

Local and global network cost-efficiency: A)CEloc. B)CEglob.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477107&req=5

f0020: Local and global network cost-efficiency: A)CEloc. B)CEglob.
Mentions: CEloc was significantly higher in focal epilepsy compared to controls in 10 of the 26 network density thresholds computed after FDR correction (median effect size = 0.84, CI 95% of 0.12–1.32— Fig.4A). CEglob was not statistically different between groups (median effect size = −0.63, CI 95% of 0.09 to −1.82— Fig.4B).

Bottom Line: Graph theory represents a powerful quantitative framework for investigation of brain networks.We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures.It remains possible that this may be part of the epileptogenic process or an effect of medications.

View Article: PubMed Central - PubMed

Affiliation: The Florey Institute of Neuroscience and Mental Health, Austin Campus, Melbourne, VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia.

ABSTRACT
Focal epilepsy is conceived of as activating local areas of the brain as well as engaging regional brain networks. Graph theory represents a powerful quantitative framework for investigation of brain networks. Here we investigate whether functional network changes are present in extratemporal focal epilepsy. Task-free functional magnetic resonance imaging data from 15 subjects with extratemporal epilepsy and 26 age and gender matched healthy controls were used for analysis. Local network properties were calculated using local efficiency, clustering coefficient and modularity metrics. Global network properties were assessed with global efficiency and betweenness centrality metrics. Cost-efficiency of the networks at both local and global levels was evaluated by estimating the physical distance between functionally connected nodes, in addition to the overall numbers of connections in the network. Clustering coefficient, local efficiency and modularity were significantly higher in individuals with focal epilepsy than healthy control subjects, while global efficiency and betweenness centrality were not significantly different between the two groups. Local network properties were also highly efficient, at low cost, in focal epilepsy subjects compared to healthy controls. Our results show that functional networks in focal epilepsy are altered in a way that the nodes of the network are more isolated. We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures. It remains possible that this may be part of the epileptogenic process or an effect of medications.

No MeSH data available.


Related in: MedlinePlus