heterogeneous population of cells, this nucleus projects to many auditory nuclei, and forms the medial olivocochlear bundle (MOC) which innervates cochlear outer hair cells. These cells contain electromotile fibers, and act as mechanical amplifiers/attenuators within the cochlea. The nucleus projects to both IC, with no cells projecting bilaterally. Lateral nucleus of the trapezoid body (LNTB) Located ventral to the LSO AVCN spherical bushy cells project collaterals bilaterally, and globular bushy cells project collaterals ipsilaterally to LNTB neurons. Cells are immunoreactive for glycine, and are retrogradely labeled following injection of tritiated glycine into the LSO The nucleus projects to both IC, with few cells projecting bilaterally, as well as the ipsilateral LSO. Large multipolar cells project to the cochlear nucleus, but not the IC, in both cat and guinea pig. Inputs are often via end-bulbs of Held, producing very fast signal transduction. Superior periolivary nucleus (SPON) (dorsomedial periolivary nucleus (DMPO)) Located directly dorsal to the MNTB In rats, SPON is a homogeneous GABAergic nucleus. These tonotopically organized neurons receive excitatory inputs from octopus and multipolar cells in the contralateral ventral cochlear nucleus, a glycinergic (inhibitory) input from the ipsilateral MNTB, an unknown GABAergic (inhibitory) input, and project to the ipsilateral ICC. Most neurons respond only at the offset of a stimulus, can phase lock to AM stimuli up to 200 Hz, and may form the basis for ICC duration selectivity. Notably, SPON neurons do not receive descending inputs from the IC, and it does not project to the cochlea or cochlear nucleus as many periolivary nuclei do. In contrast, glycinergic projections to ipsilateral ICC are observed in guinea pigs and chinchillas, suggesting a species-related neurotransmitter difference. In guinea pigs, round to oval multipolar cells project to both IC, with many cells projecting bilaterally. The more elongated cells that project to the cochlear nucleus to not project to the ICC. There appear to be to populations of cells, one that projects ipsilaterally, and one that projects bilaterally. The majority of information had come from rodent SPON, due to the nucleus' prominent size in these species, with very few studies have been done in cat DMPO, none of which were extensive. Dorsal periolivary nucleus (DPO) Located dorsal and medial to the LSO Contains both EE (excited by both ears) and E0 (excited by the contralateral ear only) units. Neurons are tonotopically organized, and high frequency. May belong to a single nucleus along with