  The dynamical properties of a diluted fully-inhibitory network of
pulse-coupled neurons are investigated. Depending on the coupling strength, two
different phases can be observed. At low coupling the evolution rapidly
converges towards periodic attractors where all neurons fire with the same
rate. At larger couplings, a new phase emerges, where all neurons are mutually
unlocked. The irregular behaviour turns out to be "confined" to an
exponentially long, stationary and linearly stable transient. In this latter
phase we also find an exponentially tailed distribution of the inter-spike
intervals (ISIs). Finally, we show that in the unlocked phase a subset of the
neurons can be eventually synchronized under the action of an external signal,
the remaining part of the neurons acting as a background noise. The dynamics of
these ''background'' neurons is quite peculiar, in that it reveals a broad ISI
distribution with a coefficient of variation that is close to 1.
