Simulation studies of vestibular macular afferent-discharge patterns usinga new, quasi-3-D finite volume method

A quasi-three-dimensional finite-volume numerical simulator was developed t o study passive voltage spread in vestibular macular afferents. The method, borrowed from computational fluid dynamics, discretizes events transpiring in small volumes over time. The afferent simulated had three calyces with processes. The number of processes and synapses, and direction and timing o f synapse activation, were varied. Simultaneous synapse activation resulted in shortest latency, while directional activation (proximal to distal and distal to proximal) yielded most regular discharges. Color-coded visualizat ions showed that the simulator discretized events and demonstrated that dis charge produced a distal spread of voltage from the spike initiator into th e ending. The simulations indicate that directional input, morphology, and timing of synapse activation can affect discharge properties, as must also distal spread of voltage from the spike initiator. The finite volume method has generality and can be applied to more complex neurons to explore discr ete synaptic effects in four dimensions.