Modulatory influences on time-coding neurons in the ventral cochlear nucleus

• Published in: Hearing research 2019-12, Vol.384, p.107824-107824, Article 107824
• Main Author: Kuenzel, Thomas
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation; Animals; Auditory Pathways - physiology; Cochlear Nucleus - cytology; Cochlear Nucleus - physiology; Humans; Neural Inhibition; Neurons - physiology; Periodicity; Sound Localization; Synaptic Transmission; Time Perception
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2019.107824

Bushy cells of the ventral cochlear nucleus are time-coding neurons. They receive axosomatic synaptic terminals from the auditory nerve, the so-called endbulb of Held synapses and project to sound localization centers in the superior olivary complex. Bushy cells are specialized to maintain and even improve the temporal code contained in the auditory nerve activity. In the present review an overview is given of the dynamic features and convergent inputs that modulate the response of bushy cells to auditory stimuli. The biophysics and synaptic specializations and dynamics of these neurons were studied extensively. These studies will be reviewed briefly in the initial part of this paper. In addition to auditory nerve input, powerful but slow inhibitory inputs act on bushy cells. Studies on these inhibitory inputs to bushy cells are discussed as part of this review. Furthermore, evidence for four classes of additional or secondary inputs that also impinge on the bushy cells will be reviewed: 1) small auditory nerve boutons, 2) commissural connections that are either inhibitory or excitatory, 3) multimodal inputs from somatosensory nuclei and 4) descending modulatory axons employing monoaminergic transmitters all interact with the main auditory nerve input in the bushy cells. The present article aims at reviewing how complex the influences on neuronal processing are, already in this early stage of the auditory pathway. It is concluded that the various modulatory influences help to better adapt bushy cell coding functions to dynamics of the sensory world. •Bushy cells of the ventral cochlear nucleus are specialized for microsecond precision and provide input to binaural sound localization brain centers.•Bushy cells are contacted by powerful axosomatic auditory nerve terminals, the endbulbs of Held, which dominate the information processing of this cell type. However, smaller auditory nerve contacts of unknown function also target the dendrite of bushy cells.•Bushy cells receive strong inhibitory inputs from sources in the ventral and dorsal cochlear nucleus which provide inhibition of matched and also wider frequency tuning compared to the excitatory input. Inhibitory signalling is surprisingly slow in this cell type.•Bushy cells receive a number of secondary small inputs from the contralateral cochlear nucleus (inhibitory and excitatory) and somatosensory brain areas. The function of these inputs in hearing is not well understood.•The neurons of the ventral coc