@article {69008, title = {Nested neural circuits generate distinct acoustic signals during Drosophila courtship}, journal = {Current Biology}, volume = {34}, year = {2024}, month = {2024 Feb 26}, pages = {808-24}, abstract = {

Many motor control systems generate multiple movements using a common set of muscles. How are premotor circuits able to flexibly generate diverse movement patterns? Here, we characterize the neuronal circuits that drive the distinct courtship songs of\ Drosophila melanogaster. Male flies vibrate their wings towards females to produce two different song modes {\textendash} pulse and sine song {\textendash} which signal species identity and male quality. Using cell-type specific genetic reagents and the connectome, we provide a cellular and synaptic map of the circuits in the male ventral nerve cord that generate these songs and examine how activating or inhibiting each cell type within these circuits affects the song. Our data reveal that the song circuit is organized into two nested feed-forward pathways, with extensive reciprocal and feed-back connections. The larger network produces pulse song, the more complex and ancestral song form. A subset of this network produces sine song, the simpler and more recent form. Such nested organization may be a common feature of motor control circuits in which evolution has layered increasing flexibility on to a basic movement pattern.

}, doi = {10.1016/j.cub.2024.01.015}, url = {https://doi.org/10.1016/j.cub.2024.01.015}, author = {Joshua L. Lillvis and Kaiyu Wang and Hiroshi M. Shiozaki and Min Xu and David L. Stern and Barry J. Dickson} } @article {68974, title = {Combinatorial circuit dynamics orchestrate flexible motor patterns in Drosophila.}, journal = {bioRxiv}, year = {2023}, month = {2023 Sep 07}, abstract = {

Motor systems flexibly implement diverse motor programs to pattern behavioral sequences, yet their neural underpinnings remain unclear. Here, we investigated the neural circuit mechanisms of flexible courtship behavior in\ Drosophila. Courting males alternately produce two types of courtship song. By recording calcium signals in the ventral nerve cord (VNC) in behaving flies, we found that different songs are produced by activating overlapping neural populations with distinct motor functions in a combinatorial manner. Recordings from the brain suggest that song is driven by two descending pathways {\textendash} one defines when to sing and the other specifies what song to sing. Connectomic analysis reveals that these {\textquotedblleft}when{\textquotedblright} and {\textquotedblleft}what{\textquotedblright} descending pathways provide structured input to VNC neurons with different motor functions. These results suggest that dynamic changes in the activation patterns of descending pathways drive different combinations of motor modules, thereby flexibly switching between different motor actions.

}, doi = {10.1101/2022.12.14.520499}, url = {https://doi.org/10.1101/2022.12.14.520499}, author = {Hiroshi M. Shiozaki and Kaiyu Wang and Joshua L. Lillvis and Min Xu and Barry J. Dickson and David L. Stern} } @article {68966, title = {The Neural Basis of Drosophila Courtship Song}, journal = {bioRxiv}, year = {2023}, month = {2023 Sep 01}, abstract = {

Animal sounds are produced by patterned vibrations of specific organs, but the neural circuits that drive these vibrations are not well defined in any animal. Here we provide a functional and synaptic map of most of the neurons in the\ Drosophila\ male ventral nerve cord (the analog of the vertebrate spinal cord) that drive complex, patterned song during courtship. Male\ Drosophila\ vibrate their wings toward females during courtship to produce two distinct song modes {\textendash} pulse and sine song {\textendash} with characteristic features that signal species identity and male quality. We identified song-producing neural circuits by optogenetically activating and inhibiting identified cell types in the ventral nerve cord (VNC) and by tracing their patterns of synaptic connectivity in the male VNC connectome. The core song circuit consists of at least eight cell types organized into overlapping circuits, where all neurons are required for pulse song and a subset are required for sine song. The pulse and sine circuits each include a feed-forward pathway from brain descending neurons to wing motor neurons, with extensive reciprocal and feed-back connections. We also identify specific neurons that shape the individual features of each song mode. These results reveal commonalities amongst diverse animals in the neural mechanisms that generate diverse motor patterns from a single set of muscles.

}, doi = {10.1101/2023.08.30.555537}, url = {https://doi.org/10.1101/2023.08.30.555537}, author = {Joshua L. Lillvis and Kaiyu Wang and Hiroshi M. Shiozaki and Min Xu and David L. Stern and Barry J. Dickson} } @article {68117, title = {An essential experimental control for functional connectivity mapping with optogenetics.}, journal = {bioRxiv}, year = {2022}, month = {2022 May 28}, abstract = {

To establish functional connectivity between two candidate neurons that might form a circuit element, a common approach is to activate an optogenetic tool such as Chrimson in the candidate pre-synaptic neuron and monitor fluorescence of the calcium-sensitive indicator GCaMP in a candidate post-synaptic neuron. While performing such experiments, we found that low levels of leaky Chrimson expression can lead to strong artifactual GCaMP signals in presumptive postsynaptic neurons even when Chrimson is not intentionally expressed in any particular neurons. Withholding all-trans\ retinal, the chromophore required as a co-factor for Chrimson response to light, eliminates GCaMP signal but does not provide an experimental control for leaky Chrimson expression. Leaky Chrimson expression appears to be an inherent feature of current Chrimson transgenes, since artifactual connectivity was detected with Chrimson transgenes integrated into three different genomic locations (two insertions tested in larvae; a third insertion tested in the adult fly). These false-positive signals may complicate the interpretation of functional connectivity experiments. We illustrate how a no-Gal4 negative control improves interpretability of functional connectivity assays. We also propose a simple but effective procedure to identify experimental conditions that minimize potentially incorrect interpretations caused by leaky Chrimson expression.

}, doi = {10.1101/2022.05.26.493610}, url = {https://doi.org/10.1101/2022.05.26.493610}, author = {David Tadres and Hiroshi M. Shiozaki and Ibrahim Tastekin and David L. Stern and Matthieu Louis} } @article {68569, title = {Neural coding of distinct motor patterns during Drosophila courtship song}, journal = {bioRxiv}, year = {2022}, month = {2022 Dec 15}, abstract = {

Animals flexibly switch between different actions by changing neural activity patterns for motor control. Courting\ Drosophila melanogaster\ males produce two different acoustic signals, pulse and sine song, each of which can be promoted by artificial activation of distinct neurons. However, how the activity of these neurons implements flexible song production is unknown. Here, we developed an assay to record neuronal calcium signals in the ventral nerve cord, which contains the song motor circuit, in singing flies. We found that sine-promoting neurons, but not pulse-promoting neurons, show strong activation during sine song. In contrast, both pulse- and sine-promoting neurons are active during pulse song. Furthermore, population calcium imaging in the song circuit suggests that sine song involves activation of a subset of neurons that are also active during pulse song. Thus, differential activation of overlapping, rather than distinct, neural populations underlies flexible motor actions during acoustic communication in\ D. melanogaster.

}, doi = {10.1101/2022.12.14.520499}, url = {https://doi.org/10.1101/2022.12.14.520499}, author = {Hiroshi M. Shiozaki and Kaiyu Wang and Joshua L. Lillvis and Min Xu and Barry J. Dickson and David L. Stern} }