The temporal resolution of binaural integration in the lateral superior olive and its implications for the electrical restoration of spatial hearing

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The precise temporal integration of synaptic inputs represents one of the fundamental principles of sensory processing in neuronal circuits. Particularly, in the auditory system, neurons in the brainstem detect differences in the arrival time between excitatory and inhibitory inputs on the scale of only microseconds to allow for the accurate localization of a sound source. This ability is essential both for human communication (e.g. attending to a conversation in a noisy environment such as a party) as well as navigation (e.g. crossing a busy road). Whereas we routinely perform these tasks in everyday life, the underlying neuronal mechanisms, particularly the temporal limits of this binaural integration and the role of inhibitory inputs, are still not fully understood. Yet a comprehensive knowledge about these aspects of auditory processing is highly desirable , both for the basic understanding of fast neuronal integration mechanisms and from a clinical perspective, as the restoration of sound localization remains one of the central obstacles of cochlear implants (CIs). Taking advantage of our rich expertise on mammalian auditory brainstem physiology and its phylogeny, we aim to investigate the role of inhibition in neuronal sound location processing, particularly the bounds of temporal precision of inhibition. Utilizing a conceptually novel approach, we will perform in vivo electrophysiological recordings in Mongolian Gerbils (Meriones unguiculatus) to characterize the functional resolution of synaptic inputs both in binaural integration neurons as well as their monaural input nuclei. In parallel to acoustic (i.e. naturalistic) stimulation, we will obtain a complementary data set employing electrical stimulation of the cochleae. This will not only allow us to assess the temporal resolution of binaural integration involving synaptic inhibition, but also to identify basic principles of fast information processing during electrical stimulation, which ultimately will contribute towards the physiological restoration of sound localization in CI users.