  Functional brain network has been widely studied to understand the
relationship between brain organization and behavior. In this paper, we aim to
explore the functional connectivity of brain network under a \emph{multi-step}
cognitive task involving with consecutive behaviors, and further understand the
effect of behaviors on the brain organization. The functional brain networks
are constructed base on a high spatial and temporal resolution fMRI dataset and
analyzed via complex network based approach. We find that at voxel level the
functional brain network shows robust small-worldness and scale-free
characteristics, while its assortativity and rich-club organization are
slightly restricted to order of behaviors performed. More interestingly, the
functional connectivity of brain network in activated ROIs strongly correlates
with behaviors and behaves obvious differences restricted to order of behaviors
performed. These empirical results suggest that the brain organization has the
generic properties of small-worldness and scale-free characteristics, and its
diverse function connectivity emerging from activated ROIs is strongly driven
by these behavioral activities via the plasticity of brain.
