Parallel Processing of Appetitive Short- and Long-Term Memories In Drosophila

SummaryIt is broadly accepted that long-term memory (LTM) is formed sequentially after learning and short-term memory (STM) formation, but the nature of the relationship between early and late memory traces remains heavily debated [1–5]. To shed light on this issue, we used an olfactory appetitive conditioning in Drosophila, wherein starved flies learned to associate an odor with the presence of sugar [6]. We took advantage of the fact that both STM and LTM are generated after a unique conditioning cycle [7, 8] to demonstrate that appetitive LTM is able to form independently of STM. More specifically, we show that (1) STM retrieval involves output from γ neurons of the mushroom body (MB), i.e., the olfactory memory center [9, 10], whereas LTM retrieval involves output from αβ MB neurons; (2) STM information is not transferred from γ neurons to αβ neurons for LTM formation; and (3) the adenylyl cyclase RUT, which is thought to operate as a coincidence detector between the olfactory stimulus and the sugar stimulus [11–14], is required independently in γ neurons to form appetitive STM and in αβ neurons to form LTM. Taken together, these results demonstrate that appetitive short- and long-term memories are formed and processed in parallel

Two Independent Mushroom Body Output Circuits Retrieve the Six Discrete Components of Drosophila Aversive Memory

SummaryUnderstanding how the various memory components are encoded and how they interact to guide behavior requires knowledge of the underlying neural circuits. Currently, aversive olfactory memory in Drosophila is behaviorally subdivided into four discrete phases. Among these, short- and long-term memories rely, respectively, on the γ and α/β Kenyon cells (KCs), two distinct subsets of the ∼2,000 neurons in the mushroom body (MB). Whereas V2 efferent neurons retrieve memory from α/β KCs, the neurons that retrieve short-term memory are unknown. We identified a specific pair of MB efferent neurons, named M6, that retrieve memory from γ KCs. Moreover, our network analysis revealed that six discrete memory phases actually exist, three of which have been conflated in the past. At each time point, two distinct memory components separately recruit either V2 or M6 output pathways. Memory retrieval thus features a dramatic convergence from KCs to MB efferent neurons

Temperature measurement of sub-micrometric ICs by scanning thermal microscopy

Surface temperature measurements were performed with a Scanning Thermal Microscope mounted with a thermoresistive wire probe of micrometrSurface temperature measurements were performed with a Scanning Thermal Microscope mounted with a thermoresistive wire probe of micrometric size. A CMOS device was designed with arrays of resistive lines 0.35µm in width. The array periods are 0.8 µm and 10µm to study the spatial resolution of the SThM. Integrated Circuits with passivation layers of micrometric and nanometric thicknesses were tested. To enhance signal-to-noise ratio, the resistive lines were heated with an AC current. The passivation layer of nanometric thickness allows us to distinguish the lines when the array period is 10μm. The results raise the difficulties of the SThM measurement due to the design and the topography of ICs on one hand and the size of the thermal probe on the other hand.ic size. A CMOS device was designed with arrays of resistive lines 0.35µm in width. The array periods are 0.8 µm and 10µm to study the spatial resolution of the SThM. Integrated Circuits with passivation layers of micrometric and nanometric thicknesses were tested. To enhance signal-to-noise ratio, the resistive lines were heated with an AC current. The passivation layer of nanometric thickness allows us to distinguish the lines when the array period is 10μm. The results raise the difficulties of the SThM measurement due to the design and the topography of ICs on one hand and the size of the thermal probe on the other hand

Learning From Aggressive Interactions: What Can Drosophila Melanogaster Teach Us?

International audienc

Learning From Aggressive Interactions: What Can Drosophila Melanogaster Teach Us?

International audienc

Learning from fights: consequences of agonistic encounters in male Drosophila melanogaster

International audienc

Learning From Aggressive Interactions: What Can Drosophila Melanogaster Teach Us?

International audienc

Analyse fonctionnelle de circuits neuronaux impliqués dans la dynamique des mémoires olfactives chez Drosophila melanogaster

Les Drosophiles à jeûn peuvent être conditionnées dans le but d associer une odeur avec du sucre. Un cycle de conditionnement appétitif induit la formation de mémoire à court terme (MCT) et de mémoire à long terme (MLT). Ainsi, nous avons montré que les MCT et MLT sont formées indépendamment l une de l autre et impliquent des structures neuronales distinctes au sein des Corps Pédonculés (CPs), le centre de la mémoire olfactive. Nous avons proposé un nouveau modèle de la dynamique des phases de mémoire appétitive où la formation des MCT et MLT s effectue de manière parallèle. Suite à cette étude, nous avons identifié deux paires de neurones extrinsèques aux CPs impliqués dans la restitution de l information appétitive à long terme. Enfin, nous nous sommes intéressés aux mécanismes moléculaires et aux réseaux neuronaux impliqués dans la consolidation de la mémoire aversive. Chez la Drosophile, l appariement d une odeur à des chocs électriques deux formes de mémoires consolidées, la mémoire résistante à l anesthésie (MRA) et la MLT (dépendante de la synthèse protéique de novo). Nous avons montré que 3 paires de neurones dopaminergiques aux CPs jouent un rôle d interrupteur contrôlant une bascule entre la MRA et la MLT. Ainsi, bloquer ces trois paires de neurones dopaminergiques durant la période de consolidation induit une augmentation de la MRA et une inhibition de la MLT, alors qu activer ces neurones après conditionnement entraîne une inhibition de la MRA, et favorise la mise en place de la MLT. En conclusion, nous avons caractérisé fonctionnellement des ensembles neuronaux discrets jouant un rôle dans différentes étapes de l'apprentissage et de la mémorisation olfactifsWhen we present an odor associated with sugar to starved flies, they will be attracted by this odor. One cycle of conditioning induces both Short-Term Memory (STM) and Long-Term Memory (LTM). It is accepted that STM and LTM formation is a sequential process but the link between these two memories remains unknown. We adressed this question and clearly demonstrated that STM and LTM can be formed independently and that they involved different neural structures within the Mushroom Bodies (MB), a memory center. We proposed a new model of dynamic of appetitive memory phases where STM and LTM are formed in a parallel way. Then, using the genetically expressed thermosensible toxine allowing a transiently inactivation of neurotransmission, we identified one type of MB efferent neurons involved in appetitive LTM retrieval. Additionally, we were interested to the molecular mechanisms and the neuronal circuits involved in aversive consolidated memories. Pairing an odor with electric shocs induces aversive memory. In drosophila, there are two forms of consolidated memories, the Anesthesia-Resistant Memory (ARM) and LTM (dependent on de novo protein synthesis). We show that three pairs of oscillatory dopaminergic neurons play a essential role of gating between ARM and LTM formation. So, blocking the neurotransmission of these neurons during the consolidation phase leads to a increase of ARM and inhibition of LTM whereas, artificial activation of these neurons after conditioning leads to an inhibition of ARM and favors the implementation LTM. In conclusion, we characterized functionally a restricted population of neurons playing a role in various stage of learning and memory processPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Strategy changes in subsequent fights as consequences of winning and losing in fruit fly fights

In competition for food, territory and mates, male fruit flies (Drosophila melanogaster) engage in agonistic encounters with conspecifics. The fighting strategies used to obtain these resources are influenced by previous and present experience, environmental cues, and the internal state of the animal including hormonal and genetic influences. Animals that experience prior defeats show submissive behavior and are more likely to lose 2nd contests, while animals that win 1st fights are more aggressive and have a higher probability of winning 2nd contests. In a recent report, we examined these loser and winner effects in greater detail and demonstrated that both winners and losers show short-term memory of the results of previous bouts while only losers demonstrate a longer-term memory that requires protein synthesis. The recent findings also suggested that an individual recognition mechanism likely exists that can serve important roles in evaluating the fighting ability of opponents and influencing future fighting strategy. In this article, we follow up on these results by asking how previous defeated and victorious flies change their fighting strategies in the presence of 2nd losing and winning flies, by searching for evidence of territory marking, and discussing the existing literature in light of our findings