Monitoring Effective Connectivity in the Preterm Brain: A Graph Approach to Study Maturation

Table 3

The main integration and spectral features in three discrete time points. The table shows the indices for both sleep states (QS = quiet sleep, NQS = nonquiet sleep) and they were computed on the Granger causality connectivity graph. The results are reported as median (IQR), where IQR stands for InterQuartile Range. The symbol stands for the Pearson correlation coefficient, while represents a significant correlation with . The values or mean the reported results are multiplied by a factor or .

Network indices: Granger causality
Median (IQR), PMA weeks	≤31		≥37	(%)
Clustering coefficient
QS	.024 (.006)	.019 (.006)	.015 (.002)
NQS	.024 (.007)	.019 (.005)	.016 (.002)
Path length
QS	3.77 (.20)	3.95 (.25)	4.17 (.13)
NQS	3.75 (.33)	3.95 (.27)	4.10 (.14)
Spectral radius
QS	.18 (.06)	.15 (.04)	.10 (.02)
NQS	.18 (.05)	.14 (.03)	.10 (.01)
Spectral gap
QS	.14 (.06)	.13 (.04)	.09 (.02)
NQS	.15 (.05)	.11 (.03)	.11 (.01)
Network indices: Granger causality, CCA
Median (IQR), PMA weeks	≤31		≥37	(%)
Clustering coefficient
QS ()	12.87 (4.8)	9.34 (3.2)	7.39 (1.2)
NQS ()	12.29 (3.4)	9.08 (2.1)	8.51 (1.2)
Path length
QS	4.36 (.37)	4.69 (.33)	4.92 (.16)
NQS	4.41 (.28)	4.71 (.21)	4.77 (.14)
Spectral radius
QS ()	9.52 (3.5)	6.79 (2.6)	5.28 (.8)
NQS ()	8.98 (2.5)	6.50 (1.5)	6.05 (.9)
Spectral gap
QS ()	7.28 (2.4)	5.87 (2.3)	4.91 (1.1)
NQS ()	6.91 (3.0)	6.07 (1.0)	5.35 (1.4)