Axonal pathways to the lateral superior olive labeled with biotinylated dextran amine injections in the dorsal cochlear nucleus of rats

Abstract

The lateral superior olive (LSO) contains cells that are sensitive to intensity differences between the two ears, a feature used by the brain to localize sounds in space. This report describes a source of input to the LSO that complements bushy cell projections from the ventral cochlear nucleus (VCN). Injections of biotinylated dextran amine (BDA) into the dorsal cochlear nucleus (DCN) of the rat label axons and swellings in several brainstem structures, including the ipsilateral LSO. Labeling in the ipsilateral LSO was confined to a thin band that extended throughout the length of the structure such that it resembled an LSO isofrequency lamina. The source of this labeled pathway was not obvious, because DCN neurons do not project to the LSO, and VCN bushy cells were not filled by these injections. Filled neurons in several brainstem structures emerged as possible sources. Three observations suggest that most of the axonal labeling in the LSO derives from a single source. First, the number of labeled VCN planar multipolar cells and the amount of labeling in the LSO were consistent and robust across animals. In contrast, the number of labeled cells in most other structures was small and highly variable. Second, the locations of planar cells and filled axons in the LSO were related topographically to the position of the DCN injection site. Third, labeled terminal arborizations in the LSO arose from collaterals of axons in the trapezoid body (output tract of planar cells). We infer that planar multipolar cells, in addition to bushy cells, are a source of ascending input from the cochlear nucleus to the LSO.

Axonal Patterns and Targets of dA1 Interneurons in the Chick Hindbrain

“…4 E-H ). As PCN neurons, as well as subsets of CN neurons, project to the cerebellum (Mason, 1986;Hatten and Heintz, 1995;Bermingham et al, 2001;Díaz et al, 2003;Doucet and Ryugo, 2003;Cicirata et al, 2005;Dipietrantonio and Dymecki, 2009;Rose et al, 2009a), we then wished to inspect the dA1 axonal routes in detail within the cerebellum. The cerebellum was dissected out from E9.5-E13.5 embryos and stained for the zinc finger transcription factor Zic1, which marks the EGL and IGL, and with the Ca 2ϩ -binding protein Calbindin, which marks the Purkinje layer, to delineate the various cerebellar domains (Baimbridge et al, 1992;Aruga et al, 1994Aruga et al, , 2002Grinberg et al, 2004).…”

Dendritic Ca2+ responses in neonatal lateral superior olive neurons elicited by glycinergic/GABAergic synapses and action potentials

“…The LSO contains binaural neurons which are excited by sound at the ipsilateral ear and inhibited by sound at the contralateral ear (Boudreau and Tsuchitani, 1968;Tollin, 2003). LSO neurons receive their excitatory inputs from glutamatergic bushy and multipolar cells in the ipsilateral cochlear nucleus (CN) (Glendenning et al, 1985;Cant and Casseday, 1986;Thompson and Thompson, 1987;Doucet and Ryugo, 2003). The inhibitory input to the LSO arises from glycinergic neurons in the ipsilateral medial nucleus of the Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication.…”

Cell-Specific Activity-Dependent Fractionation of Layer 2/3→5B Excitatory Signaling in Mouse Auditory Cortex

“…Behavioral studies show that corticocollicular projections mediate learning-induced plasticity (Suga et al, 2002;Bajo et al, 2010). Whereas progress has been made toward characterizing AC¡IC projections at the level of the IC (Doucet et al, 2003;Suga and Ma, 2003;Bajo et al, 2010), the intracortical circuits and cellular mechanisms shaping the activity of corticocollicular neurons remain incompletely understood.…”

“…Corticocollicular neurons in AC are located in L5B (Games and Winer, 1988;Doucet and Ryugo, 2003;Doucet et al, 2003;Slater et al, 2013). L5B also contains another major class of projection neurons, the corticocallosal neurons (Games and Winer, 1988).…”