  Spontaneous fluctuations and stimulus response are essential features of
neural functioning but how they are connected is poorly understood. I derive
fluctuation-dissipation relations (FDR) between the spontaneous spike and
voltage correlations and the firing rate susceptibility for i) the leaky
integrate-and-fire (IF) model with white noise; ii) an IF model with arbitrary
voltage dependence, an adaptation current, and correlated noise. The FDRs can
be used to derive correlation statistics or to infer the system's response from
observations of its spontaneous activity.
