Spiral ganglion cell site of excitation II: Numerical model analysis

An anatomically based model of cochlear neuron electrophysiology has been developed and used to interpret the physiological responses of the auditory neuron to electrical summation and refractory pulse-pair stimuli. For summation pulses, the summation time constant, tau(sum), indicates the ability of the membrane to hold charge after cessation of a pulse. When a spiral ganglion cell with a cell body was simulated, the value of tau(sum) was elevated at the peripheral node adjacent to the cell body. For refraction pulses, the refraction time constant, tau(ref), indicates the duration of the relative refractory period of the membrane. In spiral ganglion cell simulations, tau(ref) was decreased at the peripheral node adjacent to the cell body and slightly elevated at other peripheral nodes. The extent of the cell body influence on tau(sum) and tau(ref) was high localized. Excitation times for the nodes adjacent to the cell body were either simultaneous or near simultaneous resulting in similar response latencies. Results indicate that values of tau(sum) and tau(ref) may be useful for distinguishing central and peripheral excitation sites while latency measures alone are not a good indication of site of excitation.