Brain neuronal network is simultaneously modified by input from outer world in activity dependent manner. To analyze electrical response patterns evoked by inputs or mutual electrical interaction between neurons in a circuit, we prepared a dissociated culture of rat hippocampal neurons on a multi-electrodes array (MEA) dish. Cultured rat hippocampal neurons on MEA are suitable for analysing specific property of the network function. Dissociated neurons reorganized a complex networks autonomously on a MEA dish and frequent spontaneous electrical activity was observed. We applied a single stimulus and paired stimuli to the neuronal network in various timing. Recordings of electrical activity were performed before and after the conditioning paired stimulus. Intervals between the peaks of the number of spontaneous activity after a single stimulus were compared among 3 different conditions, before stimulus, after single stimulus and paired stimuli. The mean intervals between the first and second bursting peaks of the activity are 405.5±67.7 ms (mean±SE) before stimulus, 713.7±92.5 ms after single stimulus, 864.8±94.8 ms after paired stimuli (ISI = 1000 ms) . The mean intervals between the peaks of the activity increased after single stimulus and paired stimuli. In the case that the interval of stimuli was 1000 ms, the mean intervals after paired stimuli were increased to approximately 800 - 900 ms. The value was close to the ISI of paired stimuli. The intervals between the peaks in number of spontaneous spikes depended on the ISI of applied paired stimuli, in other words, intervals of spontaneous burst activity were able to be controlled by ISI of applied stimuli. The results suggest that a cultured neuronal network is able to keep memory of stimulus timings.