title: Analysis of signal processing in vestibular circuits with a novel light-emitting diodes-based fluorescence microscope.
abstract: Optical visualization of neural network activity is limited by imaging system-dependent technical tradeoffs. To overcome these constraints, we have developed a powerful low-cost and flexible imaging system with high spectral variability and unique spatio-temporal precision for simultaneous optical recording and manipulation of neural activity of large cell groups. The system comprises eight high-power light-emitting diodes, a camera with a large metal-oxide-semiconductor sensor and a high numerical aperture water-dipping objective. It allows fast and precise control of excitation and simultaneous low noise imaging at high resolution. Adjustable apertures generated two independent areas of variable size and position for simultaneous optical activation and image capture. The experimental applicability of this system was explored in semi-isolated preparations of larval axolotl (Ambystoma mexicanum) with intact inner ear organs and central nervous circuits. Cyclic galvanic stimulation of semicircular canals together with glutamate- and γ-aminobutyric acid (GABA)-uncaging caused a corresponding modulation of Ca(2+) transients in central vestibular neurons. These experiments revealed specific cellular properties as well as synaptic interactions between excitatory and inhibitory inputs, responsible for spatio-temporal-specific sensory signal processing. Location-specific GABA-uncaging revealed a potent inhibitory shunt of vestibular nerve afferent input in the predominating population of tonic vestibular neurons, indicating a considerable impact of local and commissural inhibitory circuits on the processing of head/body motion-related signals. The discovery of these previously unknown properties of vestibular computations demonstrates the merits of our novel microscope system for experimental applications in the field of neurobiology.
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Direnberger
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.|Graduate School of Systemic Neurosciences, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany.
authors.forename: Roberto
authors.initials: R
authors.lastname: Banchi
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Brosel
authors.affiliation: Department Biology I, BioImaging Center, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Seebacher
authors.affiliation: Department Biology I, BioImaging Center, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Laimgruber
authors.affiliation: Department Biology I, BioImaging Center, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Uhl
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.|Department Biology I, BioImaging Center, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Felmy
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Straka
authors.affiliation: Department Biology II, Division of Neurobiology, Ludwig-Maximilians University Munich, Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Kunz
mesh_terms: D000558:Ambystoma mexicanum; D000818:Animals; D020013:Calcium Signaling; D004558:Electric Stimulation; D005971:Glutamates / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008027:Light; D008856:Microscopy, Fluorescence / Q000295:instrumentation* / Q000379:methods*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010648:Phenylacetates / Q000494:pharmacology; D012665:Semicircular Canals / Q000187:drug effects / Q000502:physiology*; D014725:Vestibular Nerve / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C440256:4-methoxy-7-nitroindolinyl-glutamate; D005971:Glutamates; D007211:Indoles; D010648:Phenylacetates; C109231:alpha-carboxy-2-nitrobenzyl gamma-aminobutyrate; D005680:gamma-Aminobutyric Acid
keywords: Ambystoma mexicanum; axolotl; calcium imaging; galvanic stimulation; photo-uncaging; semicircular canal