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/_c). Furthermore, t_c is found to scale with the cell plating density ρ as t_c ∼ ρ^-β with β ≃ 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.