Biology subjects

Didier, A.

Publications and source records attributed to Didier, A..

8 recordsLinked to original sources

bioRxiv2026

The formation and content of odor memory from childhood

As illustrated by Marcel Prousts madeleine, childhood olfactory autobiographical memory carries a stronger positive emotional valence than memories associated with other senses. However, little is known about its content or the conditions of encoding and maintenance. Here, we asked 647 participants to freely recall and characterize their earliest childhood olfactory memory. We found that this memory is typically encoded around age six, involves pleasant odors embedded within rich multisensory contexts, and retains a strong positive emotional valence despite age-related declines in some experiential qualities. The most frequently reported scenes took place at home, in the presence of the mother, and were predominantly associated with food-related odors, although natural-vegetation odors were also commonly reported. By contrast, the non-olfactory memory is encoded earlier, visually dominated, less multisensory, less pleasant, and more frequently associated with institutional settings and friends. These findings characterize childhood olfactory memory and highlight its distinctive content among autobiographical memories.

neuroscience↗

bioRxiv2026

Biuret inhibits Arabidopsis root growth through an active, reversible, and genetically tractable developmental response

Biuret, a nitrogen-rich by-product of urea and a common contaminant of urea-based fertilisers, has long been considered a passive phytotoxin, affecting plant performances. Yet its effects on root development and the existence of endogenous mechanisms of perception or tolerance remain largely uncharacterised. Here we combined physiological, developmental, genetic and transcriptomic approaches to investigate the response of Arabidopsis thaliana to biuret. Biuret inhibited primary root growth in a dose-dependent manner by reducing meristematic cell division rather than cell elongation, and concomitantly impaired shoot growth by limiting leaf expansion. This root inhibition was reversible upon biuret removal and was accompanied by increased auxin-responsive (DR5) and decreased cytokinin-responsive (TCS) outputs at the root apex, consistent with a regulated remodelling of meristem activity rather than purely cumulative damage. A forward genetic screen identified the biuret-resistant mutant bir29, which sustained root and inflorescence development under inhibitory concentrations. Using {superscript 1}N-labelled biuret, we showed that resistance occurred without any change in biuret influx or accumulation, uncoupling sensitivity from exposure. Whole-genome transcriptomics revealed that bir29 fails to execute the wild-type response, neither repressing the cell-cycle machinery nor deploying the stress-associated programme induced by biuret. Genetic characterisation linked resistance to multiple genomic loci required for full resistance. Together, the results indicate that biuret triggers an active, reversible and genetically tractable developmental response, suggesting that this xenobiotic compound is integrated into endogenous signalling networks. Significance StatementBiuret, a poorly metabolised contaminant of urea fertilisers, is generally regarded as a passive phytotoxin, yet we show that it inhibits Arabidopsis root growth through a reversible and genetically tractable developmental response, accompanied by reorganised auxin and cytokinin signalling, rather than through cumulative chemical injury. The isolation of the resistant mutant bir29 suggests that plants integrate this xenobiotic molecule into endogenous signalling networks, reframing biuret as an informative probe of root developmental regulation.

Plant Biology↗

bioRxiv2026

Engram and neural underpinning dynamics of the long-lasting childhood olfactory memory

Olfactory childhood memories are particularly important for forming ones identity. However, we dont know how they exert their privileged influence and shape brain structure. To address this, we modeled childhood olfactory memory in mice based on a human survey indicating that our earliest olfactory memory arises from repeated positive experiences paired with a pleasant odorant. Accordingly, mice were exposed during childhood to a pleasant odorant in a playful environment. In adulthood, memory recall relied on neonatal-born granule cells in the olfactory bulb, as their optogenetic silencing impaired retrieval, and on increased functional connectivity in the reward system. With age, memory persistence depended on re-exposure to the childhood odorant and was associated with the disengagement of neonatal-born granule cells, alongside with strengthened limbic functional connectivity. Together, these findings identify neonatal neurons as a key substrate for encoding childhood olfactory memory and reveal dynamic reorganization of brain networks supporting its long-term significance.

neuroscience↗

bioRxiv2024

Enhancing Statistical Power While Maintaining Small Sample Sizes in Behavioral Neuroscience Experiments Evaluating Success Rates

Studies with low statistical power reduce the probability of detecting true effects and often lead to overestimated effect sizes, undermining the reproducibility of scientific results. While several free statistical software tools are available for calculating statistical power, they often do not account for the specialized aspects of experimental designs in behavioral studies that evaluate success rates. To address this gap, we developed "SuccessRatePower" a free and user-friendly power calculator based on Monte Carlo simulations that takes into account the particular parameters of these experimental designs. Using "SuccessRatePower", we demonstrated that statistical power can be increased by modifying the experimental protocol in three ways: 1) reducing the probability of succeeding by chance (chance level), 2) increasing the number of trials used to calculate subject success rates, and, in some circumstance, 3) employing statistical analyses suited for discrete values. These adjustments enable even studies with small sample sizes to achieve high statistical power. Finally, we performed an associative behavioral task in mice, confirming the simulated statistical advantages of reducing chance levels and increasing the number of trials in such studies

neuroscience↗

bioRxiv2023

Fecal microbiomics biomarkers for Chronic Wasting Disease

Chronic wasting disease (CWD) is a naturally occurring prion disease in cervids that has been rapidly proliferating in the US. Here we investigated a potential link between CWD infection and gut microbiome by analyzing 50 fecal samples obtained from CWD-positive animals of different sexes from various regions in the US, compared to 50 CWD-negative controls using high throughput sequencing of the 16S ribosomal RNA and targeted metabolomics. Our analysis reveals promising trends in the gut microbiota that could potentially be CWD-dependent, including several bacterial taxa at each rank level, as well as taxa pairs, that can differentiate between CWD-negative and CWD-positive deer. At each rank level, these taxa and taxa pairs could facilitate identification of around 70% of both the CWD-negative and the CWD-positive samples. Our results provide a potential tool for diagnostics and surveillance of CWD in the wild, as well as conceptual advances in our understanding of the disease. ImportanceThis is a comprehensive study that tests the connection between the composition of the gut microbiome in deer in response to Chronic Wasting Disease (CWD). We analyzed 50 fecal samples obtained from CWD-positive animals compared to 50 CWD-negative controls to identify CWD-dependent changes in the gut microbiome, matched with the analysis of fecal metabolites. Our results show promising trends suggesting that fecal microbial composition can directly correspond to CWD disease status. These results point to microbial composition of the feces as a potential tool for diagnostics and surveillance of CWD in the wild, including non-invasive CWD detection in asymptomatic deer and deer habitats, and enable conceptual advances in our understanding of the disease.

microbiology↗

bioRxiv2023

Long-Run Olfactory Enrichment Promotes Non-Olfactory Cognition, Noradrenergic Plasticity And Remodeling Of Brain Functional Connectivity In Aged Mice

Normal brain aging is accompanied by functional and structural changes, leading to cognitive decline. A high level of cognitive stimulation during life is associated with improved cognitive performances in elderly, forming the so-called cognitive reserve whose cellular mechanisms remain largely unknown. Noradrenaline has been proposed as a molecular link between environmental stimulation and the constitution of the cognitive reserve. Taking advantage of the ability of olfactory stimulation to trigger noradrenaline release, we used repeated olfactory enrichment sessions distributed over the mouse lifespan to enable the cognitive reserve buildup. Mice submitted to lifelong olfactory enrichment whether started in early or late adulthood, displayed improved olfactory discrimination at late ages. Interestingly, benefits extended to spatial memory and cognitive flexibility and olfactory and non-olfactory cognitive performances correlated with increased noradrenergic innervation in the olfactory bulb and dorsal hippocampus. Finally, using c-Fos mapping and connectivity analysis, we reported task-specific remodeling of functional neural networks in aged mice with increased network specialization or enlargement in an olfactory discrimination or a spatial memory task respectively. We thus propose long-run olfactory enrichment as a mouse model of the cognitive reserve buildup relying on plasticity of the noradrenergic system and network remodeling to promote better cognitive aging.

neuroscience↗

bioRxiv2021

M-CAMP™: A cloud-based web platform with a novel approach for species-level classification of 16S rRNA microbiome sequences

The M-CAMP (Microbiome Computational Analysis for Multiomic Profiling) Cloud Platform was designed to provide users with an easy-to-use web interface to access best in class microbiome analysis tools. This interface allows bench scientists to conduct bioinformatic analysis on their samples and then download publication-ready graphics and reports. The core pipeline of the platform is the 16S-seq taxonomic classification algorithm which provides species-level classification of Illumina 16s sequencing. This algorithm uses a novel approach combining alignment and kmer based taxonomic classification methodologies to produce a highly accurate and comprehensive profile. Additionally, a comprehensive proprietary database combining reference sequences from multiple sources was curated and contains 18056 unique V3-V4 sequences covering 11527 species. The M-CAMP 16S taxonomic classification algorithm was validated on 52 sequencing samples from both public and in-house standard sample mixtures with known fractions. Compared to current popular public classification algorithms, our classification algorithm provides the most accurate species-level classification of 16S rRNA sequencing data.

bioinformatics↗

bioRxiv2020

Norepinephrine, olfactory bulb and memory stability

Memory stability is essential for animal survival when environment and behavioral state change over short or long time spans. The stability of a memory can be expressed by its duration, its perseverance when conditions change as well as its specificity to the learned stimulus. Using optogenetic and pharmacological manipulations, we show that stability of an odor-reward association can be modulated by noradrenergic inputs to the first olfactory network, the olfactory bulb. We show that while manipulations of noradrenaline during an odor-reward acquisition have no acute effects, they impact learning flexibility as well as the duration and the specificity of the memory. We use a computational approach to propose a proof of concept model showing that a single, simple network effect of noradrenaline on olfactory bulb dynamics can underlie these seemingly different behavioral effects. Our results show how acute changes in network dynamics can have long term effects that extend beyond the network that was manipulated.

neuroscience↗