Effects of Gap Junctions and Inhibition on the Synchronization Behavior of a Biophysically Detailed Neural Network...

Auditory-nerve fiber (ANF) responses to sound are processed by several distinct neural circuits in the cochlear nucleus (CN). One of the main cochlear nucleus cell types that projects to higher auditory nuclei is bushy cells (BCs), which can be divided into two subtypes, globular and spherical, depending on the shape of their soma and their innervation patterns. Apart from receiving excitatory inputs from ANFs and inhibitory inputs from D-Stellate and tuberculoventral cells, BCs receive excitation via gap junctions (a.k.a. electrical synapses) from neighboring BCs. One of the distinctive features of the BCs is the enhancement of the synchronization behavior in ANFs. For globular BCs, which receive subthreshold inputs from many ANFs, a coincidence-detection mechanism is proposed, whereas for spherical BCs, the mechanism for the synchronization enhancement is still not fully understood.

In this study, fully connected bushy cell network models were created. The effects of gap junctions on the synchronization of the BCs were inspected by connecting the membrane potentials of clusters of five fully connected BCs.

As the strength of the gap junction connections was increased within a given cell network, the synchronization was enhanced. The effects of inhibition on the synchronization were also explored and were found to be non-monotonic.

Synchronization index values of the simulated network models with different gap junction strengths indicated that gap junctions can strongly contribute to the synchronization of models for both globular and spherical BCs.