Morphology of physiologically characterised ventral cochlear nucleus stellate cells.

Stellate cells within the ventral cochlear nucleus (VCN) are a diverse cell group that have been classified according to their size and morphology. Some of these stellate cell types constitute major projection neurones into the brainstem and directly into the inferior colliculus, while others are implicated in more local processing. It is still not clear whether a specific physiological profile is uniquely associated with each distinct type of stellate cell. To investigate such associations, we have analysed 23 units with a battery of physiological stimuli in vivo and then examined their shape and outputs following juxtacellular labelling with biocytin. Five physiologically identified groups of cells were filled. These formed two major response classes: onset cells and chopper cells. The two classes could be separated purely on morphological grounds. The onset cells had large somata, large symmetrical dendritic trees and profuse axonal branches that were restricted to the cochlear nucleus on one (On-L) or both sides (On-C) of the brainstem. The chopper cells had smaller, asymmetric, dendritic trees, which were either planar or marginal, had smaller somata and an output axon that left via the trapezoid body. We have confirmed profuse projections into the dorsal cochlear nucleus from all onset cells, and more focal projections from some members of all three groups of chopper cells.