  We study how threshold model neurons transfer temporal and interneuronal
input correlations to correlations of spikes. We find that the low common input
regime is governed by firing rate dependent spike correlations which are
sensitive to the detailed structure of input correlation functions. In the high
common input regime the spike correlations are insensitive to the firing rate
and exhibit a universal peak shape independent of input correlations. Rate
heterogeneous pairs driven by common inputs in general exhibit asymmetric spike
correlations. All predictions are confirmed in in vitro experiments with
cortical neurons driven by synthesized fluctuating input currents.
