Projections from the cochlear nuclear complex to rhombencephalic auditory centers and torus semicircularis in the turtle.

The projections arising from the cochlear nucleus complex in the turtle were investigated using [35S]methionine as a tracer. Commissural connections between the auditory tubercles terminate in both the laminar and the magnocellular nuclei. The cochlear projections to the superior olivary complex, the lateral lemniscus complex and the torus semicircularis were predominantly contralateral. Terminal labeling in the torus semicircularis was found in the peritoral region (TSP) and in the central nucleus (TSC), particularly its caudoventral and rostromedial portions. The caudal dorsolateral portion of TSC, which had previously been shown to receive ascending spinal fibers was not labeled following injections of tracer into the cochlear nuclear complex. Ascending spinal and cochlear projections, however, appeared to overlap in the rostral portions of TSC and in TSP.