The wiring diagram of a glomerular olfactory system

Berck, Matthew E.; Khandelwal, Avinash; Claus, Lindsey; Hernandez-Nuñez, Luis; Si, Guangwei; Tabone, Christopher J.; Li, Feng; Truman, James W.; Fetter, Richard D.; Louis, Matthieu; Samuel, Aravinthan D. T.; Cardona, Albert

doi:10.7554/elife.14859

Cited by 195 publications

(290 citation statements)

References 80 publications

(162 reference statements)

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“…The intrinsic MB neurons, the Kenyon cells (KCs), integrate in their dendrites inputs from combinations of projection neurons (PNs) that encode various stimuli, predominantly olfactory in both adult 1,4–6 and larva 12,14 , but also thermal, gustatory, and visual in adult 5,6,15 and larva (reported here for the first time, to our knowledge). Previous analyses in adults 16,17 and larvae 14 suggest that the connectivity between olfactory PNs and KCs is random, but they do not eliminate the possibility of some degree of bilateral symmetry, which requires access to the full PN-to-KC wiring diagram in both hemispheres.…”

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confidence: 90%

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

Eichler

Litwin-Kumar

et al. 2017

Nature

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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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confidence: 90%

“…1b). Their smaller neurons enable fast electron microscopy imaging of the entire nervous system and reconstruction of complete circuits 11,12 .…”

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confidence: 99%

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

Eichler

Litwin-Kumar

et al. 2017

Nature

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480

726

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“…Nevertheless, this threshold could still depend on global variables. Experimental data [12, 13, 34, 41–45] and modeling of the local neurons [15, 22] suggest that the total excitation of all glomeruli inhibits all projection neurons. To capture this we postulate that the threshold γ is a function of the total excitation, where we for simplicity consider a linear dependence, Here, α is a parameter that controls the inhibition strength.…”

Section: Simple Model Of the Olfactory Systemmentioning

confidence: 99%

Normalized Neural Representations of Complex Odors

Zwicker

2016

PLoS ONE

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The olfactory system removes correlations in natural odors using a network of inhibitory neurons in the olfactory bulb. It has been proposed that this network integrates the response from all olfactory receptors and inhibits them equally. However, how such global inhibition influences the neural representations of odors is unclear. Here, we study a simple statistical model of the processing in the olfactory bulb, which leads to concentration-invariant, sparse representations of the odor composition. We show that the inhibition strength can be tuned to obtain sparse representations that are still useful to discriminate odors that vary in relative concentration, size, and composition. The model reveals two generic consequences of global inhibition: (i) odors with many molecular species are more difficult to discriminate and (ii) receptor arrays with heterogeneous sensitivities perform badly. Comparing these predictions to experiments will help us to understand the role of global inhibition in shaping normalized odor representations in the olfactory bulb.

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“…While large-scale connectomic analyses in vertebrates remain challenging, generation of high-resolution connectomes has recently become feasible in Drosophila (Ohyama et al, 2015; Berck et al, 2016; Fushiki et al, 2016; Schneider-Mizell et al, 2016). We took advantage of this and performed an integrated analysis of synaptic and G-protein-coupled receptor (GPCR)-mediated connectivity of hugin neurons in the CNS of Drosophila .…”

Section: Introductionmentioning

confidence: 99%

Synaptic transmission parallels neuromodulation in a central food-intake circuit

Schlegel

Texada

Miroschnikow

et al. 2016

eLife

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NeuromedinU is a potent regulator of food intake and activity in mammals. In Drosophila, neurons producing the homologous neuropeptide hugin regulate feeding and locomotion in a similar manner. Here, we use EM-based reconstruction to generate the entire connectome of hugin-producing neurons in the Drosophila larval CNS. We demonstrate that hugin neurons use synaptic transmission in addition to peptidergic neuromodulation and identify acetylcholine as a key transmitter. Hugin neuropeptide and acetylcholine are both necessary for the regulatory effect on feeding. We further show that subtypes of hugin neurons connect chemosensory to endocrine system by combinations of synaptic and peptide-receptor connections. Targets include endocrine neurons producing DH44, a CRH-like peptide, and insulin-like peptides. Homologs of these peptides are likewise downstream of neuromedinU, revealing striking parallels in flies and mammals. We propose that hugin neurons are part of an ancient physiological control system that has been conserved at functional and molecular level.DOI: http://dx.doi.org/10.7554/eLife.16799.001

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The wiring diagram of a glomerular olfactory system

Cited by 195 publications

References 80 publications

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

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

Normalized Neural Representations of Complex Odors

Synaptic transmission parallels neuromodulation in a central food-intake circuit

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