Regulations of spontaneous rhythmic activity and preserved stimulus dependent patterns by spike timing dependent synaptic plasticity (STDP) were investigated in the hippocampal CA3 network model. With the presence of STDP, the rhythmic activity such as the theta rhythm might modify recurrent connections in the hippocampal CA3. In this study, we applied STDP to a hippocampal CA3 network model that causes spontaneous rhythmic activity. As a result, some local regions appeared in the network by themselves, from which the spontaneous rhythmic activity propagated toward surrounding area (source of propagation). We found that the frequency of the spontaneous rhythmic activity converged into one specific frequency depending on the shape of the STDP modification function. We also found that burst stimulation with sufficiently high frequency of bursts could produce a source of propagation at the stimulus site. The period of time for which the source of propagation was preserved after the termination of the stimulation depended on the shape of the STDP modification function.