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1.
Curr Biol ; 34(3): R91-R94, 2024 02 05.
Artículo en Inglés | MEDLINE | ID: mdl-38320480

RESUMEN

In the absence of directional cues, most foraging animals explore space by turning and zigzagging in search of sensory information. Recent progress in the identification of the neural correlates of turns in flies offers exciting new perspectives on the evolution of neural circuits controlling fundamental aspects of orientation responses.


Asunto(s)
Drosophila melanogaster , Drosophila , Animales , Drosophila/fisiología , Drosophila melanogaster/fisiología , Vuelo Animal/fisiología
2.
Artículo en Inglés | MEDLINE | ID: mdl-37258056

RESUMEN

In a closed-loop experimental paradigm, an animal experiences a modulation of its sensory input as a function of its own behavior. Tools enabling closed-loop experiments are crucial for delineating causal relationships between the activity of genetically labeled neurons and specific behavioral responses. We have recently developed an experimental platform known as "Raspberry Pi Virtual Reality" (PiVR) that is used to perform closed-loop optogenetic stimulation of neurons in unrestrained animals. PiVR is a system that operates at high temporal resolution (>30-Hz) and with low latencies. Larvae of the fruit fly Drosophila melanogaster are ideal to study the role of individual neurons in modulating behavior to aid the understanding of the neural pathways underlying various guided behaviors. Here, we introduce larval chemotaxis as an example of a navigational behavior in which an animal seeks to locate a target-in this case, the attractive source of an odor-by tracking a concentration gradient. The methodologies that we describe here combine the use of PiVR with the study of larval chemotaxis in real and virtual odor gradients, but these can also be readily adapted to other sensory modalities.

3.
Artículo en Inglés | MEDLINE | ID: mdl-37258057

RESUMEN

Here, we present a detailed protocol for the study of the orientation behavior of larvae of the fruit fly Drosophila melanogaster in response to both real and virtual odors (chemotaxis). An element common to the study of navigation directed by all sensory modalities is the need to correlate changes in behavioral states (e.g., crawling and turning) with temporal changes in the stimulus preceding these events. It has been shown recently that virtual odor landscapes, with any arbitrary geometry, can be created by combining a platform known as "Raspberry Pi virtual reality" (PiVR) with optogenetics. This methodology offers a technical foundation with which to characterize how the larval nervous system responds to stimulation by real and virtual odors. Furthermore, the experimental steps presented and discussed herein highlight important considerations that are needed to ensure experimental reproducibility. Finally, we believe that this framework can be easily adapted and generalized to allow investigators to study other sensory modalities in the Drosophila larva and in other animals.

4.
Sci Adv ; 8(50): eade7209, 2022 Dec 16.
Artículo en Inglés | MEDLINE | ID: mdl-36525486

RESUMEN

Upon strong and prolonged excitation, neurons can undergo a silent state called depolarization block that is often associated with disorders such as epileptic seizures. Here, we show that neurons in the peripheral olfactory system undergo depolarization block as part of their normal physiological function. Typically, olfactory sensory neurons enter depolarization block at odor concentrations three orders of magnitude above their detection threshold, thereby defining receptive fields over concentration bands. The silencing of high-affinity olfactory sensory neurons produces sparser peripheral odor representations at high-odor concentrations, which might facilitate perceptual discrimination. Using a conductance-based model of the olfactory transduction cascade paired with spike generation, we provide numerical and experimental evidence that depolarization block arises from the slow inactivation of sodium channels-a process that could affect a variety of sensory neurons. The existence of ethologically relevant depolarization block in olfactory sensory neurons creates an additional dimension that expands the peripheral encoding of odors.

5.
Curr Biol ; 32(1): R39-R42, 2022 01 10.
Artículo en Inglés | MEDLINE | ID: mdl-35015994

RESUMEN

Nervous systems continuously receive environmental signals with distinct behavioral meanings. To process ambiguous sensory inputs, neural circuits rely on hubs with compartmentalized synaptic structures. A new study has revealed how, in Drosophila larvae, this architecture with the local release of neuropeptides enables the control of flexible and context-dependent behavioral outcomes.


Asunto(s)
Drosophila , Neuropéptidos , Animales , Drosophila/fisiología , Larva/fisiología , Sistema Nervioso
6.
PLoS Biol ; 18(7): e3000712, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32663220

RESUMEN

Tools enabling closed-loop experiments are crucial to delineate causal relationships between the activity of genetically labeled neurons and specific behaviors. We developed the Raspberry Pi Virtual Reality (PiVR) system to conduct closed-loop optogenetic stimulation of neural functions in unrestrained animals. PiVR is an experimental platform that operates at high temporal resolution (70 Hz) with low latencies (<30 milliseconds), while being affordable (

Asunto(s)
Conducta Animal/fisiología , Drosophila melanogaster/fisiología , Optogenética , Corteza Sensoriomotora/fisiología , Realidad Virtual , Animales , Quimiotaxis , Larva/fisiología , Luz , Locomoción , Masculino , Neuronas/fisiología , Odorantes , Sensación/fisiología , Programas Informáticos , Gusto/fisiología , Pez Cebra
7.
Curr Opin Neurobiol ; 64: 1-9, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-31837503

RESUMEN

The neural logic underlying the conversion of non-stationary (dynamic) olfactory inputs into odor-search behaviors has been difficult to crack due to the distributed nature of the olfactory code - food odors typically co-activate multiple olfactory sensory neurons. In the Drosophila larva, the activity of a single olfactory sensory neuron is sufficient to direct accurate reorientation maneuvers in odor gradients (chemotaxis). In this reduced sensory system, a descending pathway essential for larval chemotaxis has been delineated from the peripheral olfactory system down to the premotor system. Here, I review how anatomical and functional inspections of this pathway have advanced our understanding of the neural mechanisms that convert behaviorally relevant sensory signals into orientation responses.


Asunto(s)
Neuronas Receptoras Olfatorias , Olfato , Animales , Encéfalo , Drosophila , Odorantes , Vías Olfatorias
8.
Neuron ; 101(5): 768-770, 2019 03 06.
Artículo en Inglés | MEDLINE | ID: mdl-30844394

RESUMEN

Odorant molecules are detected through the combinatorial activation of ensembles of olfactory sensory neurons. By capitalizing on the numerical simplicity of the Drosophila larval brain, Si et al. (2019) uncover principles constraining the representation of the quality and intensity of olfactory stimuli.


Asunto(s)
Neuronas Receptoras Olfatorias , Animales , Encéfalo , Drosophila , Larva , Odorantes
9.
Elife ; 72018 11 22.
Artículo en Inglés | MEDLINE | ID: mdl-30465650

RESUMEN

Sensory navigation results from coordinated transitions between distinct behavioral programs. During chemotaxis in the Drosophila melanogaster larva, the detection of positive odor gradients extends runs while negative gradients promote stops and turns. This algorithm represents a foundation for the control of sensory navigation across phyla. In the present work, we identified an olfactory descending neuron, PDM-DN, which plays a pivotal role in the organization of stops and turns in response to the detection of graded changes in odor concentrations. Artificial activation of this descending neuron induces deterministic stops followed by the initiation of turning maneuvers through head casts. Using electron microscopy, we reconstructed the main pathway that connects the PDM-DN neuron to the peripheral olfactory system and to the pre-motor circuit responsible for the actuation of forward peristalsis. Our results set the stage for a detailed mechanistic analysis of the sensorimotor conversion of graded olfactory inputs into action selection to perform goal-oriented navigation.


Asunto(s)
Conducta Animal , Quimiotaxis , Drosophila melanogaster/citología , Corteza Sensoriomotora/fisiología , Animales , Bioensayo , Pruebas Genéticas , Larva/citología , Locomoción/fisiología , Actividad Motora/fisiología , Neuronas Motoras/fisiología , Neuronas Receptoras Olfatorias/fisiología , Neuronas Receptoras Olfatorias/ultraestructura , Optogenética , Peristaltismo , Fenotipo , Olfato/fisiología
10.
J Neurosci ; 38(44): 9383-9389, 2018 10 31.
Artículo en Inglés | MEDLINE | ID: mdl-30381430

RESUMEN

Localizing the sources of stimuli is essential. Most organisms cannot eat, mate, or escape without knowing where the relevant stimuli originate. For many, if not most, animals, olfaction plays an essential role in search. While microorganismal chemotaxis is relatively well understood, in larger animals the algorithms and mechanisms of olfactory search remain mysterious. In this symposium, we will present recent advances in our understanding of olfactory search in flies and rodents. Despite their different sizes and behaviors, both species must solve similar problems, including meeting the challenges of turbulent airflow, sampling the environment to optimize olfactory information, and incorporating odor information into broader navigational systems.


Asunto(s)
Algoritmos , Ambiente , Odorantes , Olfato/fisiología , Animales , Humanos , Memoria/fisiología , Especificidad de la Especie
11.
Elife ; 72018 06 26.
Artículo en Inglés | MEDLINE | ID: mdl-29943732

RESUMEN

The neurons that connect the brain and ventral nerve cord in fruit flies have been mapped in unprecedented detail.


Asunto(s)
Drosophila , Optogenética , Animales , Encéfalo , Proteínas de Drosophila/genética , Neuronas
12.
Elife ; 62017 09 05.
Artículo en Inglés | MEDLINE | ID: mdl-28871963

RESUMEN

Animals explore their environment to encounter suitable food resources. Despite its vital importance, this behavior puts individuals at risk by consuming limited internal energy during locomotion. We have developed a novel assay to investigate how food-search behavior is organized in Drosophila melanogaster larvae dwelling in hydrogels mimicking their natural habitat. We define three main behavioral modes: resting at the gel's surface, digging while feeding near the surface, and apneic dives. In unstimulated conditions, larvae spend most of their time digging. By contrast, deep and long exploratory dives are promoted by olfactory stimulations. Hypoxia and chemical repellents impair diving. We report remarkable differences in the dig-and-dive behavior of D. melanogaster and the fruit-pest D. suzukii. The present paradigm offers an opportunity to study how sensory and physiological cues are integrated to balance the limitations of dwelling in imperfect environmental conditions and the risks associated with searching for potentially more favorable conditions.


Asunto(s)
Conducta Animal , Drosophila melanogaster/fisiología , Conducta Alimentaria , Respiración , Sensación/fisiología , Animales , Conducta Exploratoria , Dureza , Hidrogel de Polietilenoglicol-Dimetacrilato , Larva , Odorantes , Olfato/fisiología , Especificidad de la Especie
13.
Curr Biol ; 27(18): R1010-R1012, 2017 09 25.
Artículo en Inglés | MEDLINE | ID: mdl-28950082

RESUMEN

Insects are capable of spectacular achievements through collective behavior, but examples of such behavior in fruit flies are rare. New research indicates that Drosophila larvae engage in coordinated digging to feed collectively.


Asunto(s)
Conducta Cooperativa , Drosophila , Animales , Drosophila melanogaster , Relaciones Interpersonales , Larva
14.
J Exp Biol ; 220(Pt 13): 2452-2475, 2017 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-28679796

RESUMEN

Mapping brain function to brain structure is a fundamental task for neuroscience. For such an endeavour, the Drosophila larva is simple enough to be tractable, yet complex enough to be interesting. It features about 10,000 neurons and is capable of various taxes, kineses and Pavlovian conditioning. All its neurons are currently being mapped into a light-microscopical atlas, and Gal4 strains are being generated to experimentally access neurons one at a time. In addition, an electron microscopic reconstruction of its nervous system seems within reach. Notably, this electron microscope-based connectome is being drafted for a stage 1 larva - because stage 1 larvae are much smaller than stage 3 larvae. However, most behaviour analyses have been performed for stage 3 larvae because their larger size makes them easier to handle and observe. It is therefore warranted to either redo the electron microscopic reconstruction for a stage 3 larva or to survey the behavioural faculties of stage 1 larvae. We provide the latter. In a community-based approach we called the Ol1mpiad, we probed stage 1 Drosophila larvae for free locomotion, feeding, responsiveness to substrate vibration, gentle and nociceptive touch, burrowing, olfactory preference and thermotaxis, light avoidance, gustatory choice of various tastants plus odour-taste associative learning, as well as light/dark-electric shock associative learning. Quantitatively, stage 1 larvae show lower scores in most tasks, arguably because of their smaller size and lower speed. Qualitatively, however, stage 1 larvae perform strikingly similar to stage 3 larvae in almost all cases. These results bolster confidence in mapping brain structure and behaviour across developmental stages.


Asunto(s)
Conducta Animal , Drosophila melanogaster/fisiología , Animales , Encéfalo/citología , Encéfalo/fisiología , Drosophila melanogaster/crecimiento & desarrollo , Larva/crecimiento & desarrollo , Larva/fisiología
15.
Front Behav Neurosci ; 11: 45, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28469564

RESUMEN

Larval Drosophila offer a study case for behavioral neurogenetics that is simple enough to be experimentally tractable, yet complex enough to be worth the effort. We provide a detailed, hands-on manual for Pavlovian odor-reward learning in these animals. Given the versatility of Drosophila for genetic analyses, combined with the evolutionarily shared genetic heritage with humans, the paradigm has utility not only in behavioral neurogenetics and experimental psychology, but for translational biomedicine as well. Together with the upcoming total synaptic connectome of the Drosophila nervous system and the possibilities of single-cell-specific transgene expression, it offers enticing opportunities for research. Indeed, the paradigm has already been adopted by a number of labs and is robust enough to be used for teaching in classroom settings. This has given rise to a demand for a detailed, hands-on manual directed at newcomers and/or at laboratory novices, and this is what we here provide. The paradigm and the present manual have a unique set of features: The paradigm is cheap, easy, and robust;The manual is detailed enough for newcomers or laboratory novices;It briefly covers the essential scientific context;It includes sheets for scoring, data analysis, and display;It is multilingual: in addition to an English version we provide German, French, Japanese, Spanish and Italian language versions as well.The present manual can thus foster science education at an earlier age and enable research by a broader community than has been the case to date.

16.
Elife ; 52016 05 13.
Artículo en Inglés | MEDLINE | ID: mdl-27177418

RESUMEN

The sense of smell enables animals to react to long-distance cues according to learned and innate valences. Here, we have mapped with electron microscopy the complete wiring diagram of the Drosophila larval antennal lobe, an olfactory neuropil similar to the vertebrate olfactory bulb. We found a canonical circuit with uniglomerular projection neurons (uPNs) relaying gain-controlled ORN activity to the mushroom body and the lateral horn. A second, parallel circuit with multiglomerular projection neurons (mPNs) and hierarchically connected local neurons (LNs) selectively integrates multiple ORN signals already at the first synapse. LN-LN synaptic connections putatively implement a bistable gain control mechanism that either computes odor saliency through panglomerular inhibition, or allows some glomeruli to respond to faint aversive odors in the presence of strong appetitive odors. This complete wiring diagram will support experimental and theoretical studies towards bridging the gap between circuits and behavior.


Asunto(s)
Drosophila/ultraestructura , Animales , Microscopía Electrónica , Vías Nerviosas/ultraestructura , Neuronas/ultraestructura , Corteza Olfatoria/ultraestructura
17.
PLoS Comput Biol ; 11(11): e1004606, 2015 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-26600460

RESUMEN

Detailed observations of larval Drosophila chemotaxis have characterised the relationship between the odour gradient and the runs, head casts and turns made by the animal. We use a computational model to test whether hypothesised sensorimotor control mechanisms are sufficient to account for larval behaviour. The model combines three mechanisms based on simple transformations of the recent history of odour intensity at the head location. The first is an increased probability of terminating runs in response to gradually decreasing concentration, the second an increased probability of terminating head casts in response to rapidly increasing concentration, and the third a biasing of run directions up concentration gradients through modulation of small head casts. We show that this model can be tuned to produce behavioural statistics comparable to those reported for the larva, and that this tuning results in similar chemotaxis performance to the larva. We demonstrate that each mechanism can enable odour approach but the combination of mechanisms is most effective, and investigate how these low-level control mechanisms relate to behavioural measures such as the preference indices used to investigate larval learning behaviour in group assays.


Asunto(s)
Conducta Animal/fisiología , Quimiotaxis/fisiología , Drosophila/fisiología , Larva/fisiología , Modelos Biológicos , Animales , Biología Computacional , Olfato/fisiología
18.
Elife ; 42015 Jun 16.
Artículo en Inglés | MEDLINE | ID: mdl-26077825

RESUMEN

Behavioral strategies employed for chemotaxis have been described across phyla, but the sensorimotor basis of this phenomenon has seldom been studied in naturalistic contexts. Here, we examine how signals experienced during free olfactory behaviors are processed by first-order olfactory sensory neurons (OSNs) of the Drosophila larva. We find that OSNs can act as differentiators that transiently normalize stimulus intensity-a property potentially derived from a combination of integral feedback and feed-forward regulation of olfactory transduction. In olfactory virtual reality experiments, we report that high activity levels of the OSN suppress turning, whereas low activity levels facilitate turning. Using a generalized linear model, we explain how peripheral encoding of olfactory stimuli modulates the probability of switching from a run to a turn. Our work clarifies the link between computations carried out at the sensory periphery and action selection underlying navigation in odor gradients.


Asunto(s)
Quimiotaxis/fisiología , Drosophila/fisiología , Neuronas Receptoras Olfatorias/fisiología , Orientación/fisiología , Células Receptoras Sensoriales/fisiología , Olfato/fisiología , Potenciales de Acción/fisiología , Algoritmos , Animales , Difusión , Larva/fisiología , Modelos Teóricos , Actividad Motora/fisiología , Odorantes
19.
Curr Biol ; 25(11): 1448-60, 2015 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-25959970

RESUMEN

Chemotaxis is a powerful paradigm to investigate how nervous systems represent and integrate changes in sensory signals to direct navigational decisions. In the Drosophila melanogaster larva, chemotaxis mainly consists of an alternation of distinct behavioral modes: runs and directed turns. During locomotion, turns are triggered by the integration of temporal changes in the intensity of the stimulus. Upon completion of a turning maneuver, the direction of motion is typically realigned toward the odor gradient. While the anatomy of the peripheral olfactory circuits and the locomotor system of the larva are reasonably well documented, the neural circuits connecting the sensory neurons to the motor neurons remain unknown. We combined a loss-of-function behavioral screen with optogenetics-based clonal gain-of-function manipulations to identify neurons that are necessary and sufficient for the initiation of reorientation maneuvers in odor gradients. Our results indicate that a small subset of neurons residing in the subesophageal zone controls the rate of transition from runs to turns-a premotor function compatible with previous observations made in other invertebrates. After having shown that this function pertains to the processing of inputs from different sensory modalities (olfaction, vision, thermosensation), we conclude that the subesophageal zone operates as a general premotor center that regulates the selection of different behavioral programs based on the integration of sensory stimuli. The present analysis paves the way for a systematic investigation of the neural computations underlying action selection in a miniature brain amenable to genetic manipulations.


Asunto(s)
Drosophila/fisiología , Retroalimentación Sensorial , Neuronas/fisiología , Orientación/fisiología , Animales , Femenino , Larva/fisiología , Masculino , Fenotipo
20.
Learn Mem ; 22(5): 267-77, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25887280

RESUMEN

How do animals adaptively integrate innate with learned behavioral tendencies? We tackle this question using chemotaxis as a paradigm. Chemotaxis in the Drosophila larva largely results from a sequence of runs and oriented turns. Thus, the larvae minimally need to determine (i) how fast to run, (ii) when to initiate a turn, and (iii) where to direct a turn. We first report how odor-source intensities modulate these decisions to bring about higher levels of chemotactic performance for higher odor-source intensities during innate chemotaxis. We then examine whether the same modulations are responsible for alterations of chemotactic performance by learned odor "valence" (understood throughout as level of attractiveness). We find that run speed (i) is neither modulated by the innate nor by the learned valence of an odor. Turn rate (ii), however, is modulated by both: the higher the innate or learned valence of the odor, the less often larvae turn whenever heading toward the odor source, and the more often they turn when heading away. Likewise, turning direction (iii) is modulated concordantly by innate and learned valence: turning is biased more strongly toward the odor source when either innate or learned valence is high. Using numerical simulations, we show that a modulation of both turn rate and of turning direction is sufficient to account for the empirically found differences in preference scores across experimental conditions. Our results suggest that innate and learned valence organize adaptive olfactory search behavior by their summed effects on turn rate and turning direction, but not on run speed. This work should aid studies into the neural mechanisms by which memory impacts specific aspects of behavior.


Asunto(s)
Quimiotaxis/fisiología , Memoria/fisiología , Odorantes , Recompensa , Olfato/fisiología , Animales , Conducta Animal/fisiología , Drosophila , Larva
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