Descending connections between superior olivary and cochlear nuclear complexes in the cat studied by autoradiographic and horseradish peroxidase methods.

The descending pathways from the superior olivary complex (SO) to the cochlear nuclear complex (CN) were investigated in 58 cats using labelled aminoacid and horseradish peroxidase transport techniques. Descending connections were found coursing bilaterally through the trapezoid body (TB) and ipsilaterally in the intermediate and dorsal acoustic striae. The dorsolateral periolivary nucleus (DLPO) sends fibres through both the intermediate and dorsal striae, which are joined by others from the lateral preolivary nucleus (LPO). Both the latter nucleus and the medial preolivary nucleus (MPO) give rise to a bilateral descending projection which traverses TB. The distribution of these descending pathways within CN is described (although the technique did not permit precise synaptic identification). The possible implications of these pathways for response patterns at the level of CN are discussed.