Can we understand the interspike interval (ISI) statistics of spontaneous neural activity? What is the relation between input and output statistics of a neuron? --> Important for understanding population activity. Most theoretical studies assume that neurons are driven by Poisson spike trains ("white noise" processes, i.e. uncorrelated in time) However, realistic synaptic inputs have temporal structure ("colored noise"), e.g. due to refractoriness, bursting, structured "signals", short-term synaptic plasticity, oscillatory activity, adaptation.