Table 1.
Example stimulus materials used in the explicit and implicit language tasks in the present study.
Figure 1.
Illustration of the procedures used to construct brain functional networks.
Raw functional MR images are preprocessed to produce normalized data that are further parcellated by a prior brain atlas into 90 brain regions. Then we averaged the time series over all voxels in each subject for each language task to generate the regional representative time course. The Pearson’s correlations between all possible pairs of 90 time courses for each specific task is computed and averaged for the same task for each subject. A connectivity matrix for a subject is shown for the explicit (SEM) and implicit (FONT) language tasks, respectively. The axial three-dimensional image of the template is shown using MRIcroN software (http://www.sph.sc.edu/comd/rorden/mricron/).
Table 2.
Brain regions used in constructing the human brain functional networks in the present study.
Table 3.
Definitions and descriptions of the global and regional parameters of brain functional networks used in the current study.
Figure 2.
Small-world properties changing with the varied sparsity of the functional networks for both the explicit and implicit language tasks.
Here stands for the normalized clustering coefficient,
for the normalized characteristic path length, and σ for the ratio of
to
. The values of
and
were evaluated on each individual brain network and then averaged over all subjects in the explicit and implicit language tasks, respectively. In a wide range of sparsity (0.10 ≤ sparsity ≤ 0.49), the functional networks for the implicit or explicit language tasks exhibit
>1,
≈1, and σ> 1.1, which indicated prominent small-world properties.
Table 4.
Integrated global parameters mean (SD) of the human brain functional networks and their statistical difference between the explicit and implicit language tasks.
Table 5.
Hub regions of the brain functional networks corresponding to the explicit and implicit language tasks, respectively.
Figure 3.
Brain regions exhibited significant alterations in the integrated betweenness centrality of the functional networks between the explicit and implicit language tasks.
Regions color-coded in cold (warm) represent the increased (decreased) value of integrated betweenness centrality in the implicit language task compared to the explicit language task. Abbreviations: L, left hemisphere; R, right hemisphere.
Table 6.
Brain regions showing significant difference in the mean (SD) integrated betweenness centrality between the brain functional networks corresponding to the explicit and implicit language tasks.