Relationship Between Evoked and Spontaneous Activity in Cultured Neuronal Circuits

Relationship between evoked activity and spontaneous activity in neuronal circuits is one of the important theme for the improvement of neuroprosthetic apparatus. The spontaneous activity and evoked action potentials are mutually related in the cultured neuronal network autonomously reconstructed on the culture dish, but there is a question whether spontaneous activity and the evoked action potentials constitute one state respectively or the spontaneous activity is only a random background noise. Comparing the frequencies and standard deviations of spontaneous activity with those of evoked activity, we found that the silent and reproducible period lasting for 1 sec immediately after the activity evoked primally. In addition, the repetitive stimuli suppress the spontaneously occurring bursting activity in frequency, even though the inter-stimulus-interval was more than 10 sec. These results suggests that distinct internal state of the neuronal circuit was triggered by an electrical stimulation, and there were state of spontaneous mode and evoked mode in a neuronal circuit.