The effects of transient abolishment of electrical activity on dynamics in a dissociated neuronal network

The higher-order functions of brain depend on neuronal network electrical activity with complex spatiotemporal patterns. The background activity, such as spontaneous electrical activity observed in a dissociated culture of rat hippocampal neurons, is considered to be a fundamental component of internal state of the living neuronal network. The spontaneous activity has dynamic and complicated spatiotemporal activity patterns, thus it is uncertain that transiently discontinued activity pattern recovers to the same activity state. We elucidated the stability of the internal state of network activity after a transient abolishment of neuronal electrical activity. As a result, spontaneous activity pattern became to be bursting and intermittent pattern after the transient block of electrical activity. In addition, spontaneous neuronal activity increased in frequency. These modified patterns lasted for hours then gradually returned to the initial state. These results suggest that steady state of spontaneous activity is a result of complex equilibrium of interactions between neurons. Thus, it is required to consider the influence of the inhibition itself when the neural activity is stopped by pharmacological manipulations.