Modulation of functional connectivity during the resting state and the motor task

Abstract

Quite a few studies in functional magnetic resonance imaging (fMRI) have tested that, even in a resting state, motor cortices constitute a network. It has never been investigated how the network modulates from the resting state to the motor task state. In this report, by a newly developed approach taking into account n-to-1 connectivity using 1-to-1 connectivity measures instead of conventional pairwise connectivity, we show the existence of a large organized functional connectivity network related to motor function in the resting brain with fMRI. More importantly, we found that such a network can be modulated from a conscious resting state to planning, initiation, coordination, guidance, and termination of voluntary movement state, exhibited by significant changes of functional connectivity of some brain regions in different brain activity. Moreover, a quantitative description of such a functional modulation has also been presented.

Figure 1

Group activation t‐map of the movement task (P < 0.01, uncorrected, clusters with size > 20 voxels). Some brain regions (e.g., the M1, SMA, SCb, PCC, etc.) show task‐related increases or decreases during the task. z‐Axis from Z = −39 to Z = +62 in standard Talairach and Tournoux coordinates. L indicates the left hemisphere of the brain.

Figure 2

The partition of a large activated cluster. In the left of the slice (Z = −39), there is a large cluster, and obviously it includes two different brain regions (i.e., AICb and PICb). We, therefore, partitioned it into two sub‐clusters, and two peak voxels were selected separately within each. The blue arrows show their locations. Similarly, we dealt with other large clusters. L indicates the left hemisphere of the brain. For details, see Methods.

Figure 3

A flow chart involved in the definition of ROIs. A three‐step process was undertaken. First, a random‐effect analysis was performed across subjects on their individual r‐maps to produce a group activation t‐map (A). Then, each peak voxel and its nearest 26 neighbors in the t‐map were defined as a group ROI (B). Finally, subject‐specific ROIs were obtained on the basis of the group ROIs (C). For details, see Methods.

Figure 4

Plot shows Γ (±SD) of each brain region in the resting state across all subjects. Those brain regions with larger Γ are considered to be important nodes in the resting state functional connectivity network.

Figure 5

Ranking of the selected brain regions based on their (±SD). A: Resting state. B: Movement state. C: Difference in between two states. *P < 0.05; **P < 0.01; ***P < 0.001 (paired t‐test).