title: Normalization for sparse encoding of odors by a wide-field interneuron.
abstract: Sparse coding presents practical advantages for sensory representations and memory storage. In the insect olfactory system, the representation of general odors is dense in the antennal lobes but sparse in the mushroom bodies, only one synapse downstream. In locusts, this transformation relies on the oscillatory structure of antennal lobe output, feed-forward inhibitory circuits, intrinsic properties of mushroom body neurons, and connectivity between antennal lobe and mushroom bodies. Here we show the existence of a normalizing negative-feedback loop within the mushroom body to maintain sparse output over a wide range of input conditions. This loop consists of an identifiable "giant" nonspiking inhibitory interneuron with ubiquitous connectivity and graded release properties.
authors.affiliation: Division of Biology, Computation and Neural Systems Program, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Papadopoulou
authors.forename: Stijn
authors.initials: S
authors.lastname: Cassenaer
authors.forename: Thomas
authors.initials: T
authors.lastname: Nowotny
authors.forename: Gilles
authors.initials: G
authors.lastname: Laurent
mesh_terms: D000200:Action Potentials; D000818:Animals; D057506:Arthropod Antennae / Q000166:cytology / Q000502:physiology*; D001369:Axons / Q000502:physiology; D003712:Dendrites / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials; D056228:Feedback, Sensory; D005260:Female; D006110:Grasshoppers / Q000166:cytology / Q000502:physiology*; D053444:Inhibitory Postsynaptic Potentials; D007395:Interneurons / Q000502:physiology*; D008297:Male; D024521:Mushroom Bodies / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition; D009812:Odorants; D009833:Olfactory Pathways / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D005680:gamma-Aminobutyric Acid