Sound Localization Ability and Glycinergic Innervation of the Superior Olivary Complex Persist after Genetic Deletion of the Medial Nucleus of the Trapezoid Body

Abstract

The medial nucleus of the trapezoid body (MNTB) in the superior olivary complex (SOC) is an inhibitory hub considered critical for binaural sound localization. We show that genetic ablation of MNTB neurons in mice only subtly affects this ability by prolonging the minimum time required to detect shifts in sound location. Furthermore, glycinergic innervation of the SOC is maintained without an MNTB, consistent with the existence of parallel inhibitory inputs. These findings redefine the role of MNTB in sound localization and suggest that the inhibitory network is more complex than previously thought.

Aging effects on the binaural interaction component of the auditory brainstem response in the Mongolian gerbil: Effects of interaural time and level differences

“…Wave 1 is due to the activity in the auditory nerve and therefore represents the peripheral part of the auditory pathway whereas wave 4 is likely to arise in fibers from the SOC (which include the binaural nuclei the LSO and MSO) to LL and represents the central part of the auditory pathway (Boettcher, 2002). Previous studies have related wave 3 to the integrity of the MNTB or its output (Wada and Starr, 1989, 1983, Jalabi et al 2013). …”

“…In all mammals, wave 1 likely represents the auditory nerve activity (Boettcher, 2002). The occurrence of wave 3 correlates with the integrity of the MNTB or its output (Wada and Starr, 1989, 1983; Jalabi et al, 2013) although Boettcher (2002) suggested that it is based on the activity of the cochlear nucleus. Wave 4 in the gerbil and cat and wave 5 in humans are attributed to more central stages of the auditory pathway already representing binaural cues like neurons in the medial superior olive (MSO) and the lateral superior olive (LSO) and fibers from the superior olivary complex (SOC) to the lateral lemniscus (LL; Boettcher, 2002; Riedel and Kollmeier, 2002; Ungan and Yagcioglu 2002; Grothe et al, 2010).…”

Test-Retest Reliability of the Binaural Interaction Component of the Auditory Brainstem Response

“…This is especially true in comparison to Waves I and II, and particularly given the present electrode montage (Figure 1B) which is typically used to record the BIC in animal subjects. Furthermore, Wave III is thought to have its origin in a monaural structure (the medial nucleus of the trapezoid body, MNTB, Tsuchitani 1994; Jalabi et al 2013; Koka & Tollin 2014) and thus does not contribute to the BIC waveform (i.e. it is equal to Wave III calculated from the sum of the two appropriately time-shifted monaural waveforms), in contrast with Wave IV/V (Figure 1).…”

The Physiological Basis and Clinical Use of the Binaural Interaction Component of the Auditory Brainstem Response

“…An all species, wave I is likely to arise in the distal part of the auditory nerve, whereas wave II in humans is due to the activity of the auditory nerve at the auditory nerve-brainstem junction (Boettcher et al 1993; Boettcher 2002). Wave III in humans corresponds to the wave complex II-III complex in gerbils, which originates in the cochlear nucleus, although wave III in guinea pigs (Gardi & Bledsoe 1981), cats (Tsuchitani 1994) and mice (Jalabi et al 2013) has been attributed to the MNTB. Wave IV in humans is generated by the SOC, whereas wave IV in gerbils is comparable to wave V in humans being likely to originate from fibers of the LL (Boettcher 2002).…”