  Spike correlations between neurons are ubiquitous in the cortex, but their
role is at present not understood. Here we describe the firing response of a
leaky integrate-and-fire neuron (LIF) when it receives a temporarily correlated
input generated by presynaptic correlated neuronal populations. Input
correlations are characterized in terms of the firing rates, Fano factors,
correlation coefficients and correlation timescale of the neurons driving the
target neuron. We show that the sum of the presynaptic spike trains cannot be
well described by a Poisson process. Solutions of the output firing rate are
found in the limit of short and long correlation time scales.
