Connectomic features underlying diverse synaptic connection strengths and subcellular computation

Liu, Tony X; Davoudian, Pasha A; Lizbinski, Kristyn M.; Jeanne, James M.

doi:10.1016/j.cub.2021.11.056

Cited by 27 publications

(31 citation statements)

References 84 publications

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“…MIPergic LNs generally display glomerulus-specific odor-evoked responses. Synapse counts have been shown to strongly predict functional output strength in neu- rons within other systems, including other Drosophila AL neurons 28,[69][70][71][72][73][74] . Our connectomic analyses intraglomerular putMIP LN arbors generally receive mostly excitatory input within a given glomerulus (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Regardless, the amount of excitatory input generally dominates (~1.2-2.5x more) (Figure 3B), which suggests MIPergic LNs may be broadly activated. Synapse counts have been shown to strongly predict functional output strength in neurons within other systems, including other Drosophila AL neurons 26,[65][66][67][68][69][70] . Hence, we hypothesized MIPergic LNs would be broadly activated by diverse odors, as intraglomerular putMIP LN arbors generally receive mostly excitatory input within a given glomerulus (Figure 3B), However, in vivo MIPergic LN odor-evoked responses to a panel of chemically diverse odors revealed that most odors drive intraglomerular inhibitory responses in MIPergic LN neurites, regardless of behavioral valence (Figure 3C-3E).…”

Section: Mipergic Lns Provide and Receive Broad Input Andmentioning

confidence: 99%

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Heterogeneous Receptor Expression Underlies Non-uniform Peptidergic Modulation of Olfaction inDrosophila

Sizemore

Jonaitis

Dacks

2022

Preprint

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Sensory systems are dynamically adjusted according to the animal’s ongoing needs by neuromodulators, such as neuropeptides. Despite their prevalence across all nervous systems1,2, how peptidergic neurons and the neuropeptide they release act to adjust sensory processing remains poorly understood. Here, we reveal that a heterogeneous ensemble of local interneurons (LNs) release the neuropeptide myoinhibitory peptide (MIP) within the Drosophila primary olfactory center (the antennal lobe, AL). We find MIPergic LNs form reciprocal connections with many AL principal neurons, but only a subset express the inhibitory MIP receptor (sex peptide receptor, SPR). We find both the MIPergic LNs and several of the SPR-expressing neurons are activated by the food-related odor apple cider vinegar (ACV), therefore suggesting MIP plays a role in adjusting ACV responses within the AL. We demonstrate that MIP can simultaneously decrease olfactory input to some glomeruli, while indirectly increasing olfactory input to others. As those glomeruli boosted by MIP – as well as MIP itself – are necessary and sufficient to initiate an attractive behavioral response to ACV3,4, the neural substrates identified here may represent a key circuit element for the animal’s switch in behavioral responses.

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Section: Resultsmentioning

confidence: 99%

Section: Mipergic Lns Provide and Receive Broad Input Andmentioning

confidence: 99%

Heterogeneous Receptor Expression Underlies Non-uniform Peptidergic Modulation of Olfaction inDrosophila

Sizemore

Jonaitis

Dacks

2022

Preprint

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“…A strong OSNs>uPN synaptic connection will drive non-linear signal amplification, which improves signal detection at low odor concentrations (Ng et al, 2002;Bhandawat et al, 2007;Kazama and Wilson, 2008;Masse et al, 2009). Increasing the number of synapses of this type could have the potential to improve this amplification effect, as shown by artificial increase of synaptic sites in the AL (Acebes and Ferrus, 2001) and in lateral horn dendrites (Liu et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

“…This could be important in a large compartmentalized dendrite that receives inhomogeneous excitation by several OSNs at distinct dendritic sites, in order to enhance synchronized depolarization events along the dendrite, supporting signal integration (Graubard et al, 1980;Tran-Van-Minh et al, 2015). Clustered autapses could mediate local signal input amplification for distinct dendritic subunits (Kumar et al, 2018;Liu et al, 2022). Autaptic contacts, finally, could be able to shift the uPN membrane depolarization towards the spiking threshold, and enhance the firing probability during activation.…”

Section: Discussionmentioning

confidence: 99%

The unique synaptic circuitry of specialized olfactory glomeruli inDrosophila melanogaster

Gruber

Cantera

Pleijzier

et al. 2022

Preprint

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To manage the great complexity of detecting and identifying olfactory cues, the insect olfactory system has evolved two main strategies: combinatorial coding and specialized, narrowly tuned olfactory pathways. In combinatorial coding, odorants are encoded by activation of multiple, broadly tuned olfactory sensory neurons that innervate distinct sets of glomeruli. In specialized olfactory pathways, information regarding a single or a few odorants is processed in a discrete, narrowly tuned circuit within a dedicated glomerulus. Here, we compared the narrowly tuned glomerulus DA2 with the broadly tuned glomerulus DL5 at the ultrastructural level, by using volume based focused ion beam scanning electron microscopy. We provide a detailed analysis of neuronal innervation, synaptic composition as well as a circuit diagram of the major glomerular cell types: olfactory sensory neurons (OSNs), uniglomerular projection neurons (uPNs) and multiglomerular neurons (MGNs). By comparing our data with a previously mapped narrowly tuned glomerulus (VA1v), we disclose putative generic features of narrowly tuned glomerular circuits: a high density of neuronal fibers and synapses, a low degree of sensory lateralization, strong axo-axonic connections between OSNs as well as dendro-dendritic connections between uPNs, and a low degree of presynaptic inhibition at the OSN axons. We also show a unique property of the large uPN dendrite in DL5, which forms substantial amount of autapses.

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“…[ 198 , 199 ]). More generally, study of PN-to-lateral horn neuron neurotransmission has been a useful model to assess the functional significance of anatomical features revealed by the connectome, including synapse density and distance from the soma [ 200 ]; these insights should be pertinent throughout the nervous system.…”

Section: Functionmentioning

confidence: 99%

Drosophila olfaction: past, present and future

Benton

2022

Proc. R. Soc. B.

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Among the many wonders of nature, the sense of smell of the fly Drosophila melanogaster might seem, at first glance, of esoteric interest. Nevertheless, for over a century, the ‘nose’ of this insect has been an extraordinary system to explore questions in animal behaviour, ecology and evolution, neuroscience, physiology and molecular genetics. The insights gained are relevant for our understanding of the sensory biology of vertebrates, including humans, and other insect species, encompassing those detrimental to human health. Here, I present an overview of our current knowledge of D. melanogaster olfaction, from molecules to behaviours, with an emphasis on the historical motivations of studies and illustration of how technical innovations have enabled advances. I also highlight some of the pressing and long-term questions.

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Connectomic features underlying diverse synaptic connection strengths and subcellular computation

Cited by 27 publications

References 84 publications

Heterogeneous Receptor Expression Underlies Non-uniform Peptidergic Modulation of Olfaction inDrosophila

Heterogeneous Receptor Expression Underlies Non-uniform Peptidergic Modulation of Olfaction inDrosophila

The unique synaptic circuitry of specialized olfactory glomeruli inDrosophila melanogaster

Drosophila olfaction: past, present and future

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