Overlapping but distinct default network functions revealed by independent component analysis

Default network is a set of tightly synchronized brain regions whose continuous, internal activity is “distracted” by tasks. In spite of its potential confounding effect on functional brain mapping in general, the network is yet to be understood in many aspects. In the present study, we investigated the network behavior during externally- or internally-oriented tasks that are supposed to evoke opposite responses in the network. Independent component analysis revealed several network components with various time courses indicating different functions, but still with significant overlaps. We conclude that the default network as defined using various methods can be different in origin and it is desirable to take overlaps of functions into account.