Biology subjects

Ruta, V.

Publications and source records attributed to Ruta, V..

11 recordsLinked to original sources

bioRxiv2026

Developing an accessible judgement bias task for non-human primates

Objective and efficient methods for investigating animal's mental states are important for advancing animal welfare research. Behavioural observations and physiological measures provide valuable information but may not fully capture affective states. Judgment Bias Tasks (JBTs) offer a promising method to infer affective states from animals' responses to ambiguous stimuli, as distressed individuals show more pessimistic tendencies. However, the application of JBTs outside research settings may be limited due to time-consuming training and methodological or infrastructural requirements. With the present study, we aimed to test the feasibility of a simple and accessible JBT for non-human primates and to investigate its sensitivity to affective states. Eight brown capuchins (Sapajus apella) and eleven Tonkean macaques (Macaca tonkeana) were tested under positive and negative affective conditions. Individuals were trained to discriminate between never rewarded conditioned stimuli and always rewarded ones. They were then presented with ambiguous probes they had never seen before to analyse their responses to ambiguity. The discrimination training required, on average, about 12 sessions lasting a few minutes each to successfully train every individual animal. Both species significantly discriminated between conditioned stimuli and ambiguous probes. Additionally, macaques showed a greater tendency to interact with the never rewarded condition stimuli and the probes under positive conditions during early sessions. In capuchins, however, the affective conditions presented had no significant effect, although the descriptive analysis tended to show that the latency to investigate the probes was greater in the negative condition. This study also highlights key methodological considerations, such as a decrease in ambiguity across sessions. Overall, the present results suggest that, with a few improvements, this method could be effectively implemented to assess affective states of primates under human care, supporting this tool as a valuable candidate for welfare assessment.

animal behavior and cognition↗

bioRxiv2026

Lipid Activation of a Thalamic GPCR Extends Working Memory Time-scales

Working memory capacity is poorly understood. The ability to control and extend working memory time-scales provides the potential to alleviate cognitive decline in disease and aging. Through an unbiased genetic search, we previously identified a thalamic orphan receptor Gpr12 as a potent enhancer of working memory, however its activation mechanism remains poorly understood. Here, we describe the CryoEM structure of Gpr12, revealing a lipidic regulatory site enabling an activated signaling state. By surveying the native lipidic environment in mouse thalamus we identified a class of 20 carbon:4 double bond fatty acid eicosanoids as potential ligands. Cell-based assays confirmed that the endogenous cannabinoid anandamide (AEA), but not other closely related family members or derivatives, robustly activates Gpr12. In vivo imaging during behavior revealed that Gpr12 activation produces a striking molecular state - the persistent suppression of cAMP in thalamus that tracks the duration of memory maintenance. Notably, genetic or pharmacological manipulations that enhance the AEA-Gpr12 signaling axis are sufficient to prolong cAMP suppression and extend the temporal window of memory maintenance. Furthermore, AEA-mediated cAMP suppressions in thalamus support sustained neural activity in PFC, specifically during memory maintenance. Thus, while cannabinoids often impair memory, here we identify an AEA-Gpr12 signaling axis in thalamus that enhances memory, including in primates. These findings identify a lipidic signaling mechanism in thalamus that is sufficient to control and extend working memory duration.

neuroscience↗

bioRxiv2026

The structural logic of insect olfactory receptor assembly and gating

Insects detect the chemical world using a large family of odorant-gated ion channels, each formed from a variable odorant-binding subunit (OR) and a single conserved co-receptor Orco. This modular organization is thought to allow tuning ORs to diversify their chemical recognition while Orco provides structural stability to the heteromer. Yet Orco can be autonomously activated by synthetic agonists, suggesting that it may contribute to channel gating rather than serving solely as a structural scaffold. Here, we combine cryo-electron microscopy with analyses of receptor stoichiometry and function to define the structural logic underlying Orco-OR assembly and gating. We show that Orco retains the canonical ligand-binding pocket of ORs but is chemically insulated from environmental odorants by a phospholipid that occupies this site. The Orco agonist VUAA4 instead binds a membrane-accessible crevice adjacent to the gate, defining a distinct site of allosteric modulation. We further demonstrate that Orco-OR heteromers can assemble in multiple stoichiometries through shape complementarity within the intracellular anchor domain and resolve structures with both a 3:1 and 2:2 architecture. Receptors constrained to a 2:2 stoichiometry are functional but productive gating requires cooperative engagement of multiple subunits within the heteromer. Comparison with the distinct gating states of a basal homomeric olfactory receptor suggests that existing Orco-OR structures capture nonconductive intermediates within the broader conformational landscape of this receptor family. Together, these findings suggest how Orco can flexibly assemble and function with highly divergent ORs, acting not simply as a structural scaffold but as an integral partner in cooperative channel gating, thereby enabling the extraordinary diversification of insect olfactory receptors.

neuroscience↗

bioRxiv2025

Ecological cues orchestrate concerted courtship in a Drosophila host specialist

Mating decisions are often attributed to the sensory signaling between prospective sexual partners. Yet these interactions are also shaped by the broader environmental context in which they unfold, to appropriately align sexual arousal with reproductive opportunities. Here we show that in the host specialist Drosophila erecta mating is strictly contingent on the ecological and social environment generated as flies densely aggregate in groups on a food patch. We find that food volatiles directly promote male sexual arousal, triggering individuals to sample and pursue potential mates, giving rise to dynamic interactions across the group. The ensuing visual motion transforms each males visual field, which in turn further amplifies his arousal, generating a multisensory feedback loop that coordinately promotes courtship across individuals. D. erectas strict dependence on environmental cues appears latent in related species, such as D. melanogaster, where food odor can promote arousal but is dispensable for vigorous courtship. Comparative circuit analyses reveal that species-specific thresholds for sexual arousal reflect variation in how olfactory input modulates conserved nodes controlling courtship drive, rendering food volatiles a strict sensory gate only in D. erecta. Together, our findings highlight how ecological cues not directly tied to sexual signaling can profoundly influence reproductive behavior and reorganize the social landscape to ensure mating occurs in contexts where reproductive opportunities are abundant.

neuroscience↗

bioRxiv2025

Strain variation identifies a neural substrate for behavioral evolution in Drosophila

Sexual selection acts on heritable differences within species, driving the parallel diversification of signal production in one sex and behavioral responses in the other. This coevolution implies that sensory preferences are themselves variable traits, yet the neural basis of such variation remains unclear. Here, we identify striking strain-specific differences in Drosophila melanogaster male mate preferences that arise from differential sensitivity to heterospecific female pheromones. We map this variation to an ascending inhibitory pathway targeting a central circuit node known to dynamically pattern courtship. Inhibitory circuits thus emerge as a key locus for shaping mate discrimination via transient suppression of a males pursuit. Our findings highlight how variation within sensory circuitry serves as a substrate for selection, fueling the evolution of reproductive barriers between species.

neuroscience↗

bioRxiv2025

A vector-based strategy for olfactory navigation in Drosophila

Odors serve as essential cues for navigation. Although tracking an odor plume has been modeled as a reflexive process, it remains unclear whether animals can use memories of their past odor encounters to infer the spatial structure of their chemical environment or their location within it. Here we developed a virtual-reality olfactory paradigm that allows head-fixed Drosophila to navigate structured chemical landscapes, offering insight into how memory mechanisms shape their navigational strategies. We found that flies track an appetitive odor corridor by following its boundary, alternating between rapid counterturns to exit the plume and directed returns to its edge. Using a combination of behavioral modeling, functional calcium imaging, and neural perturbations, we demonstrate that this edge-tracking strategy relies on vector-based computations within the Drosophila central complex in which flies store and dynamically update memories of the direction to return them to the plumes boundary. Consistent with this, we find that FC2 neurons within the fan-shaped body, which encode a flys navigational goal, signal the direction back to the odor boundary when flies are outside the plume. Together, our studies suggest that flies leverage the plumes boundary as a dynamic landmark to guide their navigation, analogous to the memory-based strategies other insects use for long-distance migration or homing to their nests. Plume tracking thus uses components of a conserved navigational toolkit, enabling flies to use memory mechanisms to navigate through a complex shifting chemical landscape.

neuroscience↗

bioRxiv2024

Social state gates vision using three circuit mechanisms in Drosophila

Animals are often bombarded with visual information and must prioritize specific visual features based on their current needs. The neuronal circuits that detect and relay visual features have been well-studied. Yet, much less is known about how an animal adjusts its visual attention as its goals or environmental conditions change. During social behaviors, flies need to focus on nearby flies. Here, we study how the flow of visual information is altered when female Drosophila enter an aggressive state. From the connectome, we identified three state-dependent circuit motifs poised to selectively amplify the response of an aggressive female to fly-sized visual objects: convergence of excitatory inputs from neurons conveying select visual features and internal state; dendritic disinhibition of select visual feature detectors; and a switch that toggles between two visual feature detectors. Using cell-type-specific genetic tools, together with behavioral and neurophysiological analyses, we show that each of these circuit motifs function during female aggression. We reveal that features of this same switch operate in males during courtship pursuit, suggesting that disparate social behaviors may share circuit mechanisms. Our work provides a compelling example of using the connectome to infer circuit mechanisms that underlie dynamic processing of sensory signals.

neuroscience↗

bioRxiv2023

Male-male interactions shape mate selection in Drosophila

Males of many species have evolved behavioral traits to both attract females and repel rivals. Here, we explore mate selection in Drosophila from both the male and female perspective to shed light on how these key components of sexual selection -- female choice and male-male competition -- work in concert to guide reproductive strategies. We find that male flies fend off competing suitors by interleaving their courtship of a female with aggressive wing flicks, which both repel competitors and generate a song that obscures the females auditory perception of other potential mates. Two higher-order circuit nodes - P1a and pC1x neurons - are coordinately recruited to allow males to flexibly interleave these agonistic actions with courtship displays, assuring they persistently pursue females until their rival falters. Together, our results suggest that female mating decisions are shaped by male-male interactions, underscoring how a males ability to subvert his rivals is central to his reproductive success.

neuroscience↗

bioRxiv2023

A modular circuit architecture coordinates the diversification of courtship strategies in Drosophila

Identifying a mate is a central imperative for males of most species but poses the challenge of distinguishing a suitable partner from an array of potential male competitors or females of related species. Mate recognition systems are thus subject to strong selective pressures, driving the rapid coevolution of female sensory cues and male sensory preferences. Here we leverage the rapid evolution of female pheromones across the Drosophila genus to gain insight into how males coordinately adapt their detection and interpretation of these chemical cues to hone their mating strategies. While in some Drosophila species females produce unique pheromones that act to attract and arouse their conspecific males, the pheromones of most species are sexually monomorphic such that females possess no distinguishing chemosensory signatures that males can use for mate recognition. By comparing several close and distantly-related Drosophila species, we reveal that D. yakuba males have evolved the distinct ability to use a sexually-monomorphic pheromone, 7-tricosene (7-T), as an excitatory cue to promote courtship, a sensory innovation that enables D. yakuba males to court in the dark thereby expanding their reproductive opportunities. To gain insight into the neural adaptations that enable 7-T to act as an excitatory cue, we compared the functional properties of two key nodes within the pheromone circuits of D. yakuba and a subset of its closest relatives. We show that the instructive role of 7-T in D. yakuba arises from concurrent peripheral and central circuit changes: a distinct subpopulation of sensory neurons has acquired sensitivity to 7-T which in turn selectively signals to a distinct subset of P1 neurons in the central brain that trigger courtship behaviors. Such a modular circuit organization, in which different sensory inputs can independently couple to multiple parallel courtship control nodes, may facilitate the evolution of mate recognition systems by allowing males to take advantage of novel sensory modalities to become aroused. Together, our findings suggest how peripheral and central circuit adaptations can be flexibly linked to underlie the rapid evolution of mate recognition and courtship strategies across species.

neuroscience↗

bioRxiv2021

The structural basis of odorant recognition in insect olfactory receptors

Olfactory systems must detect and discriminate an enormous diversity of chemicals in the environment. To contend with this challenge, diverse species have converged on a common strategy in which odorant identity is encoded through the combinatorial activation of large families of olfactory receptors (ORs), thus allowing a finite number of receptors to detect an almost infinite chemical world. Although most individual ORs are sensitive to a variety of odorants, the structural basis for such flexible chemical recognition remains unknown. Here, we combine cryo-electron microscopy with functional studies of receptor tuning to gain insight into the structural and mechanistic basis of promiscuous odorant recognition. We show that OR5 from the jumping bristletail, Machilis hrabei, assembles as a homo-tetrameric odorant-gated ion channel with broad chemical tuning. We elucidated the structure of OR5 in multiple gating states, alone and in complex with two of its agonists--the odorant eugenol and the insect repellent DEET. Both ligands bind to a common binding site located in the transmembrane region of each subunit, composed of a simple geometric arrangement of aromatic and hydrophobic residues. We reveal that binding is mediated by hydrophobic, non-directional interactions with residues distributed throughout the binding pocket, enabling the flexible recognition of structurally distinct odorants. Mutation of individual residues lining the binding pocket predictably altered OR5s sensitivity to eugenol and DEET and broadly reconfigured the receptors tuning, supporting a model in which diverse odorants share the same structural determinants for binding. Together, these studies provide structural insight into odorant detection, shedding light onto the molecular recognition mechanisms that ultimately endow the olfactory system with its immense discriminatory capacity.

neuroscience↗

bioRxiv2020

An arousal gated visual circuit controls pursuit during Drosophila courtship

Long-lasting internal states, like hunger, aggression, and sexual arousal, pattern ongoing behavior by defining how the sensory world is translated to specific actions that subserve the needs of an animal. Yet how enduring internal states shape sensory processing or behavior has remained unclear. In Drosophila, male flies will perform a lengthy and elaborate courtship ritual, triggered by activation of sexually-dimorphic P1 neurons, in which they faithfully follow and sing to a female. Here, by recording from males as they actively court a fictive female in a virtual environment, we gain insight into how the salience of female visual cues is transformed by a males internal arousal state to give rise to persistent courtship pursuit. We reveal that the gain of LCt0a visual projection neurons is strongly increased during courtship, enhancing their sensitivity to moving targets. A simple network model based on the LCt0a circuit accurately predicts a males tracking of a female over hundreds of seconds, underscoring that LCt0a visual signals, once released by P1-mediated arousal, become coupled to motor pathways to deterministically control his visual pursuit. Furthermore, we find that P1 neuron activity correlates with fluctuations in the intensity of a males pursuit, and that their acute activation is sufficient to boost the gain of the LCt0 pathways. Together, these results reveal how alterations in a males internal arousal state can dynamically modulate the propagation of visual signals through a high-fidelity visuomotor circuit to guide his moment-to-moment performance of courtship.

neuroscience↗