We identify generic sources of complex and irregular spiking in biological
neural networks. For the network description, we operate on a mathematicall
y exact mesoscopic approach. Starting from experimental data, we determine
exact properties of noise-driven, binary neuron interaction and extrapolate
from there to properties of more complex types of interaction. Our approac
h fills a gap between approaches that start from detailed biophysically mot
ivated simulations but fail go make mathematically exact global predictions
, and approaches that are able to make exact statements but only on levels
of description that are remote from biology. As a consequence of the approa
ch, a novel coding scheme emerges, shedding new light on local information
processing in biological neural networks.