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Mechanisms of synaptic interactions in the superior olivary complex of the guinea pig: an in vitro whole brain study

English title Mechanisms of synaptic interactions in the superior olivary complex of the guinea pig: an in vitro whole brain study
Applicant Babalian Alexandre
Number 111925
Funding scheme Project funding
Research institution Division de Physiologie Département de Médecine Université de Fribourg
Institution of higher education University of Fribourg - FR
Main discipline Neurophysiology and Brain Research
Start/End 01.05.2006 - 31.10.2010
Approved amount 246'152.00
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Keywords (5)

synaptic potentials; superior olive; isolated whole brain; binaural interactions; auditory brainstem

Lay Summary (English)

Lay summary
The superior olivary complex (SOC), composed of three main nuclei, the lateral superior olive (LSO), the medial superior olive (MSO), the medial nucleus of the trapezoid body, and a group of 10-15 periolivary nuclei (PON) is generally considered as the first auditory relay receiving strong binaural inputs relevant for directional hearing. SOC neurons most likely encode two major physical cues, the interaural intensity (level) differences (IIDs) and interaural time differences (ITDs), for localizing mainly high-frequency and low-frequency sounds, respectively. It is thought that the LSO is principally involved in processing of IIDs, whereas the main function of the MSO is the detection and processing of ITDs. The mechanisms of synaptic interactions in the SOC that underlie processing of binaural cues were rarely studied in vivo due to difficulties of intracellular recordings from ventrally located SOC nuclei and were mainly addressed in brain slice studies. However, given the complexity of connections in the SOC, the stimulation protocols used in brain slice studies (placing electrodes on the tracts in the regions containing various populations of SOC neurons and axons) could result in influences that do not match the natural order and timing of synaptic events triggered from auditory nerves (AN). Therefore the attempts to characterize bilateral interactions in the SOC may not be accurate using brain slices. We propose to use the advantages of the isolated whole brain (IWB) preparation (preserved brain circuitry combined with in vitro conditions) in order to characterize the mechanisms, sequence and timing of synaptic events taking place in identified neurons of different SOC subdivisions in response to AN activation and to study how these parameters could account for neuronal encoding of IIDs and ITDs. Thus we hope to obtain novel information on functional integration occurring in the SOC that will contribute to better understanding of fundamental mechanisms of hearing.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
66731 Functional integration in the auditory brainstem nuclei: an in vitro whole brain study. 01.05.2002 Project funding