Modulation of brain resting-state networks by sad mood induction

Background: There is growing interest in the nature of slow variations of the blood oxygen level-dependent (BOLD) signal observed in functional MRI resting-state studies. In humans. these slow BOLD variations are thought to reflect an underlying or intrinsic form of brain functional connectivity in discrete neuroanatomical systems. While these resting-state networks maybe relatively enduring phenomena, other evidence suggest that dynamic changes in their functional connectivity may also emerge depending on the brain state subjects during scanning. Methodology/Principle Findings: In this study, we examined healthy subjects (n-24) with a mood induction paradigm during two continuous fMRI recording to assess the effects of a change in self-generated mood state (neutral to sad) on the networks that were common to both experimental states, each showing dominant signal fluctuation in the very low frequency domain ( 0.04 Hz). Between the two states, we observed apparent increases and decreases in the overall functional connectivity of these networks. Primary findings included increased connectivity strength of a paralimbic networks involving the dorsal anterior cingulate and anterior insula cortices with sunjects increasing sadness and decreased functional connectivity of the default mode network. Conclusions/Significance: These findings support recent studies that suggest the functional connectivity of certain resting-state networks may in part, reflect a dynamic image of the current brain state. In our study, this was linked to changes in subjective mood