Cross-Correlation Analysis and Phase-Locking in a Model of the Ventral Cochlear Nucleus Stellate Cell

Abstract

There is now considerable evidence that stellate cells in the anteroventral cochlear nucleus (AVCN) receive auditory-nerve inputs on or near their cell bodies (Cant,’ 81, Liberman,’ 92, Ryugo, this volume). Furthermore, auditory-nerve fibers (ANFs) from all spontaneous rate (SR) groups appear to project to AVCN stellate cells (Ryugo, this volume), although it is not known whether a single stellate cell receives inputs from more than one SR group. This morphological evidence raises a number of issues with regard to our understanding of the physiological properties of stellate cells. For example, results of cross-correlation analysis of spike trains from simultaneously recorded ANFs and AVCN chopper units, which are recorded from stellate cells (Roullier and Ryugo,’ 84, Smith and Rhode,’ 89), are consistent with the hypothesis that there are monosynaptic excitatory connections between high SR ANFs and stellate cells, whereas no such evidence exists for connections between low SR ANFs and stellate cells (Young and Sachs,’ 88). Another issue involves phase-locking in chopper units. It is well known that phase-locking in choppers is degraded with respect to that in ANFs at frequencies above about 500 Hz (Blackburn and Sachs,’ 89, Bourk,’ 76, Rhode and Smith,’ 86). It has been suggested that this reduction in phase-locking results from low-pass filtering of AN inputs by the dendritic tree of the stellate cell (White, et al.,’ 90, Young, et al.,’ 88b). The evidence for ANF synapses on and near the soma of these cells raises the question of whether dendritic filtering is sufficient to produce the observed reductions. In this chapter we will examine both of these issues in terms of a simulation model for the stellate cell (Banks and Sachs,’ 91).