title: Sparse, decorrelated odor coding in the mushroom body enhances learned odor discrimination.
abstract: Sparse coding may be a general strategy of neural systems for augmenting memory capacity. In Drosophila melanogaster, sparse odor coding by the Kenyon cells of the mushroom body is thought to generate a large number of precisely addressable locations for the storage of odor-specific memories. However, it remains untested how sparse coding relates to behavioral performance. Here we demonstrate that sparseness is controlled by a negative feedback circuit between Kenyon cells and the GABAergic anterior paired lateral (APL) neuron. Systematic activation and blockade of each leg of this feedback circuit showed that Kenyon cells activated APL and APL inhibited Kenyon cells. Disrupting the Kenyon cell-APL feedback loop decreased the sparseness of Kenyon cell odor responses, increased inter-odor correlations and prevented flies from learning to discriminate similar, but not dissimilar, odors. These results suggest that feedback inhibition suppresses Kenyon cell activity to maintain sparse, decorrelated odor coding and thus the odor specificity of memories.
authors.affiliation: Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, UK.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Lin
authors.affiliation: Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, UK.
authors.forename: Alexei M
authors.initials: AM
authors.lastname: Bygrave
authors.affiliation: Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, UK.
authors.forename: Alix
authors.initials: A
authors.lastname: de Calignon
authors.affiliation: Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, USA.
authors.forename: Tzumin
authors.initials: T
authors.lastname: Lee
authors.affiliation: Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, UK.
authors.forename: Gero
authors.initials: G
authors.lastname: Miesenböck
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000502:physiology; D025461:Feedback, Physiological / Q000502:physiology; D059330:GABAergic Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D007858:Learning / Q000502:physiology*; D024521:Mushroom Bodies / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009812:Odorants; D055696:Olfactory Perception / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins