Structure and function of the bat superior olivary complex

The superior olivary complex (SOC) is a mammalian auditory brainstem struct ure that contains several nuclei. Some of them are part of the ascending sy stem projecting to higher auditory centers, others belong to the descending system projecting to the cochlear nuclei or the cochlea itself. The main n uclei of the ascending system, the lateral and medial superior olive (LSO, MSG), as well as the lateral and medial nuclei of the trapezoid body (LNTB, MNTB), have been traditionally associated with sound localization. Here we review the results of recent studies on the main SOC nuclei in echolocatin g bats. These studies suggest that some SOC structures and functions are hi ghly conserved across mammals (e.g., the LSO, which is associated with inte raural intensity difference processing), while others are phylogenetically highly variable in both form and function (e.g., the MSG, traditionally ass ociated with interaural time difference processing). For the MSG, these var iations indicate that we should broaden our view regarding what functions t he MSO might participate in, since its function in echolocation seems to li e in the context of pattern recognition rather than sound localization. Fur thermore, across bat species, variations in the form and physiology of the MSO can be linked to specific behavioral adaptations associated with differ ent echolocation strategies. Finally, the comparative approach, including a uditory specialists such as bats, helps us to reach a more comprehensive vi ew of the functional anatomy of auditory structures that are still poorly u nderstood, like the nucleus of the central acoustic tract (NCAT). Microsc. Res. Tech. 51:382-402, 2000. (C) 2000 Wiley-Liss, Inc.