Abstract
The rat hippocampal dissociated culture system is effective as the minimum system possessing the principle bases of brain information processing. Rat hippocampal neuronal cells were cultured on a dish with 64 planer microelectrodes and they recomposed a complex network. In this research, we analyzed stability of neuronal electrical activity pattern evoked by input stimulation in a reconstructed network on a culture dish. In this system, spontaneous activity without any inputs is observed approximately 10 days in vitro. We calculated distances between each spike pattern after electrical stimulation and the template generated from spike patterns, averaged along time axis or along trial axis. The difference between activity pattern within 5 ms-width-time-window and averaged spike pattern template began to reduce immediately after the input and gradually recovered to the stable level. In addition, evoked spike patterns were reproducible, and it tended that spatiotemporal pattern of the electrical activity periodically changed in the domain of being considered to be spontaneous activity. These results suggest that the internal states of the neural network being applied inputs was changed. It is considered that the network activity sustained the internal state of the neuronal network by reflexive and reverberative re-entry of the activity for several seconds and the state corresponding to the short-term memory was formed.
