Small neurons in the vestibular nerve root project to the marginal shell of the anteroventral cochlear nucleus in the cat.

We injected biotinylated dextran amine (BDA) into marginal shell regions of the anteroventral cochlear nucleus (AVCN) of the cat. These injections led to retrograde labeling of cells including small cells (median some area = 111 micron2, equivalent diameter = 11.9 microns) in the vestibular nerve root (VNR), just ventral to an anterior part of the AVCN. This is an unexpected new finding. The cells were scattered among BDA-labeled fibers and were oriented parallel to the course of the VNR fibers. We suggest that the small neurons of the VNR might serve as second-order vestibular neurons conveying information from vestibular end organs to the cochlear nucleus (CN) and/or act as interneurons between the olivocochlear fibers in the VNR and the CN.