Synchronization in Networks of Excitatory and Inhibitory Neurons with Sparse, Random Connectivity

Christoph Börgers, Nancy Kopell
2003 Neural Computation  
In model networks of E-cells and I-cells (excitatory and inhibitory neurons), synchronous rhythmic spiking often comes about from the interplay between the two cell groups: the E-cells synchronize the I-cells and vice versa. Under ideal conditions -homogeneity in relevant network parameters, and all-to-all connectivity for instance -this mechanism can yield perfect synchronization. What happens under less ideal conditions? We find that approximate, imperfect synchronization is possible even
more » ... s possible even with very sparse, random connectivity. The crucial quantity is the expected number of inputs per cell. As long as it is large enough (more precisely, as long as the variance of the total number of synaptic inputs per cell is small enough), tight synchronization is possible. The desynchronizing effect of random connectivity can be reduced by strengthening the E I synapses. More surprisingly, it cannot be reduced by strengthening the I E synapses. However, the decay time constant of inhibition plays an important role: Faster decay yields tighter synchrony. In particular, in models in which the inhibitory synapses are assumed to be instantaneous, the effects of sparse, random connectivity cannot be seen.
doi:10.1162/089976603321192059 pmid:12620157 fatcat:nxfcfjk4gvhylot32kw7gceomy