Dynamics of binaural processing in the mammalian sound localization pathway – The role of GABAB receptors

The initial binaural processing in the superior olive represents the fastest computation known in the entire mammalian brain. Although the binaural system has to perform under very different and often highly dynamic acoustic conditions, the integration of binaural information in the superior olivary complex (SOC) has not been considered to be adaptive or dynamic itself. Recent evidence, however, shows that the initial processing of interaural level and interaural time differences relies on well-adjusted interactions of both the excitatory and the inhibitory projections, respectively. Under static conditions, these inputs seem to be tightly balanced, but may also require dynamic adjustment for proper function when the acoustic environment changes. GABAB receptors are at least one mechanism rendering the system more dynamic than considered so far. A comprehensive description of how binaural processing in the SOC is dynamically regulated by GABAB receptors in adults and in early development is important for understanding how spatial auditory processing changes with acoustic context.

► Initial binaural processing in the mammalian auditory brainstem is dynamic.
► Synaptic strength in olivary nuclei is controlled via pre-synaptic GABAB receptors.
► GABAB mediated suppression controls the balance of excitation and inhibition.
► Lateral superior olivary neurons control their inputs via dendritic release of GABA.
► The source of GABA in the medial superior olive is still unclear.