An understanding of associative learning is facilitated if it can be analyzed in a simple animal like the fruit fly Drosophila. Here, we introduce the first visual associative learning paradigm for larval Drosophila; this is remarkable as larvae have an order of magnitude fewer neurons than adult flies. Larvae were subjected to either of two reciprocal training regimes: Light+/Dark- or Light-/Dark+. Subsequently, all larvae were individually tested for their preference between Light versus Dark. The difference between training regimes was therefore exclusively which visual situation was associated with which reinforcer; differences observed during the test thus reflected exclusively associative learning. For positive reinforcement (+) we used fructose (FRU), and for negative reinforcement (-) either quinine or sodium chloride (QUI, NaCl). Under these conditions, associative learning could be reproducibly observed in both wild-type strains tested. We then compared the effectiveness of training using differential conditioning, with both positive and negative reinforcement, to that using only positive or only negative reinforcement. We found that FRU only, but neither QUI nor NaCl, was in itself effective as a reinforcer. This is the first demonstration of appetitive learning in larval Drosophila. It is now possible to investigate the behavioral and neuronal organization of appetitive visual learning in this simple and genetically easy-to-manipulate experimental system.
Importance In patients with acute coronary syndrome (ACS) undergoing invasive treatment, ticagrelor and prasugrel are guideline-recommended P2Y12 receptor inhibitors. The ISAR-REACT5 randomized clinical trial demonstrated superiority for prasugrel, although concerns were raised about the generalizability of some underpowered subgroup analyses. Objectives To emulate a randomized clinical trial evaluating the safety and effectiveness of ticagrelor vs prasugrel under the conditions of routine care in individuals with ACS planned to undergo an invasive treatment strategy. Design, Setting, and Participants This new-user cohort study included secondary data from a German statutory health insurance claims database between January 2012 and December 2021, using 1:1 propensity score nearest-neighbor matching to emulate ISAR-REACT5. Individuals with ACS receiving either ticagrelor or prasugrel treatment after hospital discharge were followed up for 1 year. Eligibility criteria closely emulated those of ISAR-REACT5 and included age of 18 years or older and cardiovascular risk factors. Data were analyzed from May 2023 to May 2024. Exposure Outpatient prescription of ticagrelor or prasugrel. Main Outcomes and Measures The primary end point was the composite of all-cause mortality, myocardial infarction (MI), or stroke within 1 year of outpatient treatment initiation. Secondary end points included individual components of the primary end point and stent thrombosis. The safety end point was major bleeding. A Cox proportional hazards regression model was fitted to the overall cohort. Results Of 17 642 propensity score–matched individuals (mean [SD] age, 63.1 [10.9] years; 73.9% male), 8821 received ticagrelor and 8821 received prasugrel. Agreement was met in 11 of 12 predefined agreement metrics when comparing the results with ISAR-REACT5. The primary composite end point of all-cause mortality, MI, or stroke occurred in 815 individuals (9.2%) receiving ticagrelor and 663 (7.5%) receiving prasugrel (hazard ratio [HR], 1.24; 95% CI, 1.12-1.37). Myocardial infarction (HR, 1.20; 95% CI, 1.06-1.36) and stroke (HR, 1.33; 95% CI, 1.02-1.74) each occurred significantly more often in the ticagrelor group. Analysis of all-cause mortality (HR, 1.27; 95% CI, 0.99-1.64), stent thrombosis (HR, 1.11; 95% CI, 0.89-1.30), and major bleeding (HR, 1.12; 95% CI, 0.96-1.32) revealed no significant differences between treatment groups. Subgroup analysis showed that prasugrel was associated with the primary composite end point in fewer individuals with ST-segment elevation MI (338 of 4941 [6.8%] vs 451 of 4852 [9.3%]). Conclusions and Relevance This cohort study found that prasugrel was associated with lower rates of all-cause mortality, MI, or stroke compared with ticagrelor in individuals with ACS undergoing an invasive treatment strategy in routine care, particularly in individuals with ST-segment elevation MI. The findings suggest that carefully designed database studies can complement and extend findings from randomized clinical trials, informing guidelines and clinical decision-making.
To detail the rationale, design, and future perspective of implementing whole-body magnetic resonance (MR) imaging in the German National Cohort, a large multicentric population-based study.All institutional review boards approved the study, and informed consent is obtained before study enrollment. Participants are enrolled from a random sample of the general population at five dedicated imaging sites among 18 recruitment centers. MR imaging facilities are equipped with identical 3.0-T imager technology and use uniform MR protocols. Imager-specific hardware and software settings remained constant over the study period. On-site and centralized measures of image quality enable monitoring of completeness of the acquisitions and quality of each of the MR sequences. Certified radiologists read all MR imaging studies for presence of incidental findings according to predefined algorithms.Over a 4-year period, six participants per day are examined at each center, totaling a final imaging cohort of approximately 30 000 participants. The MR imaging protocol is identical for each site and comprises a set of 12 native series to cover neurologic, cardiovascular, thoracoabdominal, and musculoskeletal imaging phenotypes totaling approximately 1 hour of imaging time. A dedicated analysis platform as part of a central imaging core incorporates a thin client-based integrative and modular data handling platform to enable multicentric off-site image reading for incidental findings. Scientific analysis will be pursued on a per-project hypothesis-driven basis.Population-based whole-body MR imaging as part of the German National Cohort will serve to compile a comprehensive image repository, will provide insight into physiologic variants and subclinical disease burden, and has the potential to enable identification of novel imaging biomarkers of risk.
Animals must be able to find and evaluate food to ensure survival. The ability to associate a cue with the presence of food is advantageous because it allows an animal to quickly identify a situation associated with a good, bad, or even harmful food. Identifying genes underlying these natural learned responses is essential to understanding this ability. Here, we investigate whether natural variation in the foraging ( for ) gene in Drosophila melanogaster larvae is important in mediating associations between either an odor or a light stimulus and food reward. We found that for influences olfactory conditioning and that the mushroom bodies play a role in this for- mediated olfactory learning. Genotypes associated with high activity of the product of for , cGMP-dependent protein kinase (PKG), showed greater memory acquisition and retention compared with genotypes associated with low activity of PKG when trained with three conditioning trials. Interestingly, increasing the number of training trials resulted in decreased memory retention only in genotypes associated with high PKG activity. The difference in the dynamics of memory acquisition and retention between variants of for suggests that the ability to learn and retain an association may be linked to the foraging strategies of the two variants.
Why does Pavlov's dog salivate? In response to the tone, or in expectation of food? While in vertebrates behaviour can be driven by expected outcomes, it is unknown whether this is true for non-vertebrates as well. We find that, in the Drosophila larva, odour memories are expressed behaviourally only if animals can expect a positive outcome from doing so. The expected outcome of tracking down an odour is determined by comparing the value of the current situation with the value of the memory for that odour. Memory is expressed behaviourally only if the expected outcome is positive. This uncovers a hitherto unrecognized evaluative processing step between an activated memory trace and behaviour control, and argues that learned behaviour reflects the pursuit of its expected outcome. Shown in a system with a simple brain, an apparently cognitive process like representing the expected outcome of behaviour seems to be a basic feature of behaviour control.
