  Synchronized bursts (SBs) with complex structures are common in neuronal
cultures. Although the origin of SBs is still unclear, they have been studied
for their information processing capabilities. Here, we investigate the
properties of these SBs in a culture on multi-electrode array system. We find
that structures of these SBs are related to the different developmental stages
of the cultures. A model based on short term synaptic plasticity, recurrent
connections and astrocytic recycling of neurotransmitters has been developed
successfully to understand these structures. A phase diagram obtained from this
model shows that networks exhibiting SBs are in an oscillatory state due to
large enough positive feedback provided by synaptic facilitation and recurrent
connections. In this model, the structures of the SBs are the results of
intrinsic synaptic interactions; not information stored in the network.
