Robustness and Variability of Pathways in the Spontaneous Synchronous Bursting of Clusterized Cortical Neuronal Networks In vitro

We experimentally demonstrate the observation of several pathways with a few tens of ms inter-cluster delay but negligible intra-cluster delay, in the spontaneous synchronous burstings (SSBs) of clusterized cortical neuronal networks in vitro through epifluorescence microscopy of Ca 2+ indicator. Nearby clusters sharing the similar relative firing timings in different SSB events form a group. Switching among different SSB pathways initiated by different master groups is found. Under chemical tuning such as decreasing the mutual coupling by increasing [Mg 2+ ] or lowering the effective firing threshold by increasing [K + ], the firing sequence of each pathway remains robust, but the occurrence probability and the temporal persistence of each pathway, and the inter-cluster delay times in the firing sequences can be varied.