The complete connectome of a learning and memory centre in an insect brain

By K. Eichler, Feng Li, Ashok Litwin-Kumar, Youngser Park, Ingrid V. Andrade, Casey M. Schneider-Mizell, T. Saumweber, Annina Huser, Claire Eschbach, B. Gerber and 7 more. 2017

479 citations recorded by the source corpus.

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.

Subfields: Cellular and Molecular Neuroscience, Ecology, Genetics

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Citations in the corpus

Weight Agnostic Neural Networks (2019, background): “While it is a challenge to map out the human connectome [102], with our 90 billion neurons and 150 trillion synapses, the connectome of simple organisms such as roundworms [112, 114] has been constructed, and recent works [20, 105] mapped out the entire brain of a small fruit ﬂy.”
Re-evaluating circuit mechanisms underlying pattern separation (2019, neutral): “This includes mixing of glomeruli with different odour tuning (Gruntman and Turner, 2013) or sensory modalities (Yagi et al., 2016; Eichler et al., 2017).”
A connectome of the Drosophila central complex reveals network motifs suitable for flexible navigation and context-dependent action selection (2020, background): “In contrast to many previous EM-based circuit reconstruction efforts, which have relied on sparse, manual tracing of neurons (Eichler et al., 2017; Helmstaedter et al., 2013; Turner-Evans et al., 2020; Zheng et al., 2018), the hemibrain connectome was generated using a combination of automatic,…”
Modelling learning and memory in Drosophila to understand Intellectual Disabilities. (2020, unknown): “Many comprehensive studies have helped to reveal the complete architecture of the olfactory circuits both in larval and adult fly stages (Strausfeld and Li, 1999; Strausfeld, 2002; Davis, 2004, 2005; Tanaka et al., 2008; Aso et al., 2014a; Eichler et al., 2017; Takemura et al., 2017; Dolan et al., 2”
A Complete Electron Microscopy Volume of the Brain of Adult Drosophila melanogaster (2017, methodology): “The Drosophila MB has ~2,000 intrinsic neurons on each side of the brain called Kenyon cells (KCs).”