Effect of soma polarization on electrical stimulation thresholds of retinal ganglion cells

In models of electrical stimulation of the retina, somata are typically represented either as several compartments or just a single compartment. When stimulated by a subretinal or suprachoroidal prosthesis, the soma polarizes within a microsecond after the application of extracellular field, whereas neurites polarize at a slower rate. We describe an idealized model that compares these two mechanisms conceptually, and a biologically plausible model that places the two mechanisms in the context of a morphologically and biophysically detailed retinal ganglion cell. Two versions of the latter model are compared, which differ only in the number of compartments used to represent the soma. Simulation results show that predicted thresholds may be lower by as much as 70% when using a multicompartment soma rather than a single-compartment one.