title: Differences in synaptic and intrinsic properties result in topographic heterogeneity of temporal processing of neurons within the inferior colliculus.
abstract: The identification and characterization of organization principals is essential for the understanding of neural function of brain areas. The inferior colliculus (IC) represents a midbrain nexus involved in numerous aspects of auditory processing. Likewise, neurons throughout the IC are tuned to a diverse range of specific stimulus features. Yet beyond a topographic arrangement of the cochlea-inherited frequency tuning, the functional organization of the IC is not well understood. Particularly, a common principle that links the diverse tuning characteristics is unknown. Here we used in vitro patch clamp recordings combined with laser-uncaging, and in vivo single cell recordings to study the spatial and functional organization principles of the central IC. We identified a topographic bias of ascending synaptic input timing that is balanced between inhibition and excitation and co-varies with in vivo first-spike latency. This bias was paralleled post-synaptically by differences in biophysical membrane properties and firing patterns, with integrating neurons predominantly found in the dorso-medial part, and coincidence-detector neurons biased to the ventro-lateral IC. Importantly, these cellular and network features translated into distinct temporal processing capabilities irrespectively of the neurons' characteristic frequency. Our data therefore imply that heterogeneity of synaptic inputs, intrinsic properties and temporal processing are functional principles that underlie the spatial organization of the central IC.
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Lina
authors.initials: L
authors.lastname: Yassin
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Pecka
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Kajopoulos
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Gleiss
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany; Bernstein Center for Computational Neuroscience Munich, Großhaderner Straße 2, D-82152 Martinsried, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Leibold
authors.affiliation: Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University München, Großhaderner Straße 2, D-82152 Martinsried, Germany. Electronic address: felix.felmy@TiHo-Hannover.de.
authors.forename: Felix
authors.initials: F
authors.lastname: Felmy
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D004594:Electrophysiology; D005260:Female; D005849:Gerbillinae / Q000502:physiology; D007245:Inferior Colliculi / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D013997:Time Factors
keywords: Auditory midbrain; Balanced excitation and inhibition; Functional mapping; Intrinsic connectivity; Synaptic integration; Topography