Recurrent Interneuron Connectivity does not Support Synchrony in a Biophysical Dentate Gyrus Model

Synchronous activity of neuronal networks is found in many brain areas and correlates with cognition and behavior. Gamma synchrony is particularly strong in the dentate gyrus, which is thought to process contextual information in the hippocampus. Several network mechanisms for synchrony generation have been proposed and studied computationally. One such mechanism relies solely on recurrent inhibitory interneuron connectivity, but it requires a large enough number of synapses. Here, we incorporate connectivity data of the dentate gyrus into a biophysical computational model to test its ability to generate synchronous activity. We find that recurrent interneuron connectivity is insufficient to induce a synchronous network state. This applies to an interneuron ring network and the broader dentate gyrus circuitry. In the asynchronous state, recurrent interneuron connectivity can have small synchronizing effects but can also desynchronize the network for specific types of synaptic input. Our results show that synchronizing mechanisms relying solely on interneurons are unlikely to be biologically plausible in the dentate gyrus.