Abstract

Associating stimuli with positive or negative reinforcement is essential for survival, but a complete wiring diagram of a higher-order circuit supporting associative memory has not been previously available. Here we reconstruct one such circuit at synaptic resolution, the Drosophila larval mushroom body. We find that most Kenyon cells integrate random combinations of inputs but that a subset receives stereotyped inputs from single projection neurons. This organization maximizes performance of a model output neuron on a stimulus discrimination task. We also report a novel canonical circuit in each mushroom body compartment with previously unidentified connections: reciprocal Kenyon cell to modulatory neuron connections, modulatory neuron to output neuron connections, and a surprisingly high number of recurrent connections between Kenyon cells. Stereotyped connections found between output neurons could enhance the selection of learned behaviours. The complete circuit map of the mushroom body should guide future functional studies of this learning and memory centre.

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Acknowledgements

We thank A. Khandelwal, J. Lovick, J. Valdes-Aleman, I. Larderet, V. Hartenstein, A. Fushiki, B. Afonso, P. Schlegel and M. Berck for reconstructing 31% of arbor cable and 19% of synapses. We thank R. Axel, G. M. Rubin and Y. Aso for their comments on the manuscript. A.L.-K. was supported by National Institutes of Health grant number F32DC014387. A.L.-K. and L.F.A. were supported by the Simons Collaboration on the Global Brain. L.F.A. was also supported by the Gatsby, Mathers, and Kavli Foundations. C.E.P. and Y.P. were supported by the Defense Advanced Research Projects Agency XDATA program (Air Force Research Laboratory contract FA8750-12-2-0303) and National Science Foundation BRAIN EAGER award DBI-1451081. K.E. and A.S.T. thank the Deutsche Forschungsgemeinschaft, TH1584/1-1, TH1584/3-1; the Swiss National Science Foundation, 31003A_132812/1; the Baden Württemberg Stiftung; Zukunftskolleg of the University of Konstanz; and Deutscher Akademischer Austauschdienst. B.G. and T.S. thank the Deutsche Forschungsgemeinschaft, CRC 779, GE 1091/4-1; the European Commission, FP7-ICT MINIMAL. We thank the Fly EM Project Team at Howard Hughes Medical Institute (HHMI) Janelia for the gift of the electron microscopy volume, the Janelia Visiting Scientist program, the HHMI visa office, and HHMI Janelia for funding.

Author information

Author notes

    • Andreas S. Thum

    Present address: Department of Genetics, University of Leipzig, Talstrasse 33, 04103 Leipzig, Germany.

    • Katharina Eichler
    • , Feng Li
    •  & Ashok Litwin-Kumar

    These authors contributed equally to this work.

    • L. F. Abbott
    • , Andreas S. Thum
    • , Marta Zlatic
    •  & Albert Cardona

    These authors jointly supervised this work.

Affiliations

  1. Howard Hughes Medical Institute Janelia Research Campus, 19700 Helix Drive, Ashburn, Virginia 20147, USA

    • Katharina Eichler
    • , Feng Li
    • , Ingrid Andrade
    • , Casey M. Schneider-Mizell
    • , Claire Eschbach
    • , Richard D. Fetter
    • , James W. Truman
    • , Marta Zlatic
    •  & Albert Cardona
  2. Department of Biology, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany

    • Katharina Eichler
    • , Annina Huser
    •  & Andreas S. Thum
  3. Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, 3227 Broadway, New York, New York 10027, USA

    • Ashok Litwin-Kumar
    •  & L. F. Abbott
  4. Department of Applied Mathematics and Statistics, Whiting School of Engineering, Johns Hopkins University, 100 Whitehead Hall, 3400 North Charles Street, Baltimore, Maryland 21218, USA

    • Youngser Park
    •  & Carey E. Priebe
  5. Abteilung Genetik von Lernen und Gedächtnis, Leibniz Institut für Neurobiologie, 39118 Magdeburg, Germany

    • Timo Saumweber
    •  & Bertram Gerber
  6. Otto von Guericke Universität Magdeburg, Institut für Biologie, Verhaltensgenetik, Universitätsplatz 2, D-39106 Magdeburg, Germany

    • Bertram Gerber
  7. Otto-von-Guericke University Magdeburg, Center for Behavioral Brain Sciences, Universitätsplatz 2, D-39106 Magdeburg, Germany

    • Bertram Gerber
  8. Department of Physiology and Cellular Biophysics, Columbia University, Russ Berrie Pavilion, 1150 St Nicholas Avenue, New York, New York 10032, USA

    • L. F. Abbott
  9. Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK

    • Marta Zlatic
  10. Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK

    • Albert Cardona

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Contributions

K.E., F.L., A.L.-K., B.G., L.F.A., A.S.T., M.Z. and A.C. conceived the project, analysed the data, and wrote the manuscript. K.E., F.L., I.A., C.S.-M., T.S., A.S.T. and A.C. reconstructed neurons. K.E. performed learning experiments. A.L.-K. built the models. J.W.T. contributed GAL4 lines and their imagery. R.D.F. generated electron microscopy image data. A.L.-K., C.S.-M., Y.P. and C.E.P. analysed connectivity patterns. F.L. and A.H. performed immunostainings. C.E. generated functional data.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to L. F. Abbott or Andreas S. Thum or Marta Zlatic or Albert Cardona.

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Extended data

Supplementary information

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  1. 1.

    Supplementary Information

    This file contains Supplementary Tables 2-7, Atlas Figures 1-2 and Supplementary References.

  2. 2.

    Reporting Summary

Zip files

  1. 1.

    Supplementary Table 1

    This file contains the Connectivity matrix of the entire MB network. Neurons in rows are presynaptic to neurons in columns. PN-PN connections are almost all dendro-dendritic and occur within the antennal lobe.

  2. 2.

    Supplementary Data

    This file contains anatomical reconstruction data.

  3. 3.

    Supplementary Data

    This file contains source data for the Main and Extended Data Figures.

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DOI

https://doi.org/10.1038/nature23455

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