The neuronal architecture of the mushroom body provides a logic for associative learning

Abstract

We identified the neurons comprising the Drosophila mushroom body (MB), an associative center in invertebrate brains, and provide a comprehensive map describing their potential connections. Each of the 21 MB output neuron (MBON) types elaborates segregated dendritic arbors along the parallel axons of ∼2000 Kenyon cells, forming 15 compartments that collectively tile the MB lobes. MBON axons project to five discrete neuropils outside of the MB and three MBON types form a feedforward network in the lobes. Each of the 20 dopaminergic neuron (DAN) types projects axons to one, or at most two, of the MBON compartments. Convergence of DAN axons on compartmentalized Kenyon cell–MBON synapses creates a highly ordered unit that can support learning to impose valence on sensory representations. The elucidation of the complement of neurons of the MB provides a comprehensive anatomical substrate from which one can infer a functional logic of associative olfactory learning and memory.DOI: http://dx.doi.org/10.7554/eLife.04577.001

Optimized tools for multicolor stochastic labeling reveal diverse stereotyped cell arrangements in the fly visual system

“…We have used those lines here and they have also been used in other brain regions (35,36). However, the MCFO reagents can also be readily incorporated into more complex genetic schemes.…”

What the fly’s nose tells the fly’s brain

“…In the earlier sections, I assumed three things: (i) all Kenyon cells have six claws, (ii) all Kenyon cells are interchangeable and sample all glomeruli with the same probability, and (iii) all synapses made by projection neurons onto Kenyon cells have the same strength. In fact, the number of Kenyon cell claws ranges from around 1 to 11 (16), three classes of Kenyon cells with different properties and different targets for their axons are known (14,30), and the synaptic strength varies considerably from one synapse to the next (28), whereas I used the mean value. Relaxing these simplifying assumptions changes my results quantitatively, but does not alter the main conclusions.…”

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