Limits...
The lesioned brain: still a small-world?

Douw L, van Dellen E, Baayen JC, Klein M, Velis DN, Alpherts WC, Heimans JJ, Reijneveld JC, Stam CJ - Front Hum Neurosci (2010)

Bottom Line: We use the IAP as a reversible model for the effect of lesions on brain network topology.Network topology changed significantly after amobarbital injection: clustering decreased in all frequency bands, while path length decreased in the theta and lower alpha band, indicating a shift toward a more random network topology.Likewise, the edge weight correlation decreased after injection of amobarbital in the theta and beta bands.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, VU University Medical Center Amsterdam, Netherlands.

ABSTRACT
The intra-arterial amobarbital procedure (IAP or Wada test) is used to determine language lateralization and contralateral memory functioning in patients eligible for neurosurgery because of pharmaco-resistant epilepsy. During unilateral sedation, functioning of the contralateral hemisphere is assessed by means of neuropsychological tests. We use the IAP as a reversible model for the effect of lesions on brain network topology. Three artifact-free epochs (4096 samples) were selected from each electroencephalogram record before and after amobarbital injection. Functional connectivity was assessed by means of the synchronization likelihood. The resulting functional connectivity matrices were constructed for all six epochs per patient in four frequency bands, and weighted network analysis was performed. The clustering coefficient, average path length, small-world index, and edge weight correlation were calculated. Recordings of 33 patients were available. Network topology changed significantly after amobarbital injection: clustering decreased in all frequency bands, while path length decreased in the theta and lower alpha band, indicating a shift toward a more random network topology. Likewise, the edge weight correlation decreased after injection of amobarbital in the theta and beta bands. Network characteristics after injection of amobarbital were correlated with memory score: higher theta band small-world index and increased upper alpha path length were related to better memory score. The whole-brain network topology in patients eligible for epilepsy surgery becomes more random and less optimally organized after selective sedation of one hemisphere, as has been reported in studies with brain tumor patients. Furthermore, memory functioning after injection seems related to network topology, indicating that functional performance is related to topological network properties of the brain.

No MeSH data available.


Related in: MedlinePlus

Mean changes in network features after injection of sodium amobarbital. *p < 0.05 (corrected for multiple comparisons). (A) Cw/Cws = normalized clustering coefficient, Lw/Lws = normalized average path length, S = small-world index. (B) Wr = edge weight correlation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2991225&req=5

Figure 1: Mean changes in network features after injection of sodium amobarbital. *p < 0.05 (corrected for multiple comparisons). (A) Cw/Cws = normalized clustering coefficient, Lw/Lws = normalized average path length, S = small-world index. (B) Wr = edge weight correlation.

Mentions: Neural network characteristics after injection of amobarbital were compared to the resting-state before injection by means of Wilcoxon signed rank tests (see Table 1). Results for clustering coefficient, path length, and small-world index are shown in Figure 1A, while changes in edge weight correlation are depicted in Figure 1B.


The lesioned brain: still a small-world?

Douw L, van Dellen E, Baayen JC, Klein M, Velis DN, Alpherts WC, Heimans JJ, Reijneveld JC, Stam CJ - Front Hum Neurosci (2010)

Mean changes in network features after injection of sodium amobarbital. *p < 0.05 (corrected for multiple comparisons). (A) Cw/Cws = normalized clustering coefficient, Lw/Lws = normalized average path length, S = small-world index. (B) Wr = edge weight correlation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2991225&req=5

Figure 1: Mean changes in network features after injection of sodium amobarbital. *p < 0.05 (corrected for multiple comparisons). (A) Cw/Cws = normalized clustering coefficient, Lw/Lws = normalized average path length, S = small-world index. (B) Wr = edge weight correlation.
Mentions: Neural network characteristics after injection of amobarbital were compared to the resting-state before injection by means of Wilcoxon signed rank tests (see Table 1). Results for clustering coefficient, path length, and small-world index are shown in Figure 1A, while changes in edge weight correlation are depicted in Figure 1B.

Bottom Line: We use the IAP as a reversible model for the effect of lesions on brain network topology.Network topology changed significantly after amobarbital injection: clustering decreased in all frequency bands, while path length decreased in the theta and lower alpha band, indicating a shift toward a more random network topology.Likewise, the edge weight correlation decreased after injection of amobarbital in the theta and beta bands.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, VU University Medical Center Amsterdam, Netherlands.

ABSTRACT
The intra-arterial amobarbital procedure (IAP or Wada test) is used to determine language lateralization and contralateral memory functioning in patients eligible for neurosurgery because of pharmaco-resistant epilepsy. During unilateral sedation, functioning of the contralateral hemisphere is assessed by means of neuropsychological tests. We use the IAP as a reversible model for the effect of lesions on brain network topology. Three artifact-free epochs (4096 samples) were selected from each electroencephalogram record before and after amobarbital injection. Functional connectivity was assessed by means of the synchronization likelihood. The resulting functional connectivity matrices were constructed for all six epochs per patient in four frequency bands, and weighted network analysis was performed. The clustering coefficient, average path length, small-world index, and edge weight correlation were calculated. Recordings of 33 patients were available. Network topology changed significantly after amobarbital injection: clustering decreased in all frequency bands, while path length decreased in the theta and lower alpha band, indicating a shift toward a more random network topology. Likewise, the edge weight correlation decreased after injection of amobarbital in the theta and beta bands. Network characteristics after injection of amobarbital were correlated with memory score: higher theta band small-world index and increased upper alpha path length were related to better memory score. The whole-brain network topology in patients eligible for epilepsy surgery becomes more random and less optimally organized after selective sedation of one hemisphere, as has been reported in studies with brain tumor patients. Furthermore, memory functioning after injection seems related to network topology, indicating that functional performance is related to topological network properties of the brain.

No MeSH data available.


Related in: MedlinePlus