Connectivity induced synchronization in cortical neuronal networks

Synchronization of cortical neural cultures is studied as a function of the effective network connectivity in the phenomenon of synchronized firing(SF). The synchronized bursting frequency (during SF) of the network is found to be much slower than the characteristic time scale of a neuron and increases with the network connectivity. The synchronized bursting frequency f is characterized by a critical age (t(c)) as: f = f(c) + f(o) log(t/t(c)). Furthermore, t(c) is found to scale with the cell plating density rho as t(c) similar to rho(-beta) with beta similar or equal to 0.44 +/- 0.08. Although some aspects of the observed SF is similar to the array enhanced synchronization, detailed comparison of measured spike statistics from synchronized and non-synchronized cultures suggests that the nature of synchronization during SF is different from that of the array-enhanced synchronization. In particular, electrophysiological measurements using double patch technique revel that even though the bursting frequencies are synchronized, the intra-burst spikes are not.