The past decade has seen tremendous advances in characterising functional integration in the brain. Much of this progress is set against the backdrop of a key dialectic between functional and effective connectivity. My talk will focus on the application of dynamic causal modelling to resting state timeseries or endogenous neuronal activity. A special focus will be on advances in network discovery and Bayesian model reduction. I will survey recent (and rapid) developments in modelling distributed neuronal fluctuations (e.g., stochastic, spectral and symmetric DCM for fMRI) – and how this modelling rests upon functional connectivity. I hope to highlight the intimate relationship between functional and effective connectivity and how one informs the other.