Biology subjects

Spriet, C.

Publications and source records attributed to Spriet, C..

9 recordsLinked to original sources

bioRxiv2026

Acceleration of vision changes object representations from infancy to adulthood

While much of the neural and cognitive machinery for visual perception is in place within weeks from birth, we identified and quantified a fundamental difference between infant and adult vision: the temporal rate at which meaningful visual information can be reliably extracted. Using frequency-tagging electroencephalography with rapid serial visual presentation, we found that object categorization at 4 and 9 months is respectively seven times and two to three times slower than in adults. Using quantitative information from infants experiments, we created and presented accelerated visual streams to adults, to match infants perceptual experience. We used deep convolutional neural networks to identify object representations that match those elicited in adults when accelerating the information flow. Results show that acceleration compromises finer-grained object distinction while sparing broad, general object representations. We propose that slow vision is a design feature of early development for preserving and highlighting the most stable and general features of the world.

neuroscience↗

bioRxiv2026

Delayed onset and heterogeneous collective organization characterize twitching motility in Acinetobacter baumannii

Type IV pili (T4P) mediate twitching motility and contribute to surface colonization, biofilm formation, and host interactions in Acinetobacter baumannii. However, the prevalence, dynamics, and diversity of twitching motility across A. baumannii populations remain poorly understood. Here, we compared twitching motility in a collection of 35 A. baumannii strains originating from clinical, environmental, and animal sources, using Pseudomonas aeruginosa PAO1 as a reference. Standardization of assay conditions revealed a strong influence of agar composition on twitching motility, with Eiken agar supporting the most robust surface translocation. Under these conditions, 14 of 35 A. baumannii isolates exhibited detectable twitching motility. Time-lapse microscopy revealed major differences between A. baumannii and P. aeruginosa. Whereas PAO1 initiated twitching within minutes after inoculation and formed characteristic multicellular rafts, motile A. baumannii strains displayed a prolonged non-motile phase before movement initiation and exhibited distinct patterns of collective organization. Two major expansion phenotypes were identified, termed Homogeneous Front (HF) and Raft-Like Front (RLF), together with Early-Onset Motility (EOM) and Delayed-Onset Motility (DOM) subgroups. Quantitative analyses further revealed substantial variation in speed, directional persistence, and migration dynamics among strains. Because a majority of isolates were non-motile, we investigated the contribution of the minor pilin FimT. Although deletion of fimT abolished twitching motility and specific substitutions modulated motility efficiency, sequence variation in FimT alone could not account for the observed phenotypic diversity. Collectively, these findings reveal extensive heterogeneity in T4P-mediated surface motility in A. baumannii and identify delayed twitching activation and distinct collective migration strategies as key features of surface colonization in this species. HighlightsO_LIPopulation analysis reveals extensive twitching diversity in A. baumannii C_LIO_LIDelayed motility onset distinguishes A. baumannii from P. aeruginosa C_LIO_LIHomogeneous and raft-like fronts define distinct migration strategies C_LIO_LIFimT contributes to motility but not all non-motile phenotypes C_LI

microbiology↗

bioRxiv2026

Hard-to-beat animacy perception: EEG evidence of accurate animate-inanimate distinction for ambiguous objects

Human recognition of objects as animate or inanimate is fast and accurate. However, this task may be challenging for objects with animal-like properties (e.g., presence of eyes/face), albeit being inanimate (e.g., a cow-mug). Lookalike objects provide an opportunity to examine how visual perception resolves categorical ambiguities and whether it exhibits an intrinsic bias to see animacy. During electroencephalography (EEG), we presented healthy humans with images of objects at a regular, rapid frequency (6 Hz), where every five exemplars of a standard category (animate or inanimate), an exemplar of the other oddball category was shown (1.2 Hz). In some conditions, oddball-stimuli were replaced by lookalikes. Periodic visual stimulation should give rise to a distinctive EEG response at 6 Hz. Moreover, if the oddball category elicits a different neural response than the standard category, a distinct response should be observed at 1.2 Hz. This categorization response was found for animate-oddballs among inanimate objects, and vice versa. It was also found for lookalike-oddballs presented among animate or inanimate objects, but it was significantly higher in the first case, implying that lookalike objects were perceived as more similar to inanimate than animate objects. The degree of animal resemblance modulated the amplitude of neural response to lookalikes, without however changing the category boundary. These results--also replicated in an artificial model of human vision--demonstrate that animal resemblance of objects is registered in visual perception, but it does not alter the critical ability to distinguish between what is truly alive and what is not.

neuroscience↗

bioRxiv2025

Animate-inanimate object categorization from minimal visual information in the human brain, human behavior, and deep neural networks

The distinction between animate and inanimate things is a main organizing principle of information in perception and cognition. Yet, animacy, as a visual property, has so far eluded operationalization. Which visual features are necessary and sufficient to see animacy? At which level of the visual hierarchy does the animate-inanimate distinction emerge? Here, we show that the animate-inanimate distinction is preserved even among images of objects that are made unrecognizable and only retain low- and mid-level visual features of their natural version. In particular, in three experiments, healthy human adults saw rapid sequences of images (6 Hz) where every five exemplars of a category (i.e., animate), an exemplar of another category (i.e., inanimate) was shown (1.2 Hz). Using frequency-tagging electroencephalography (ftEEG), we found significant neural responses at 1.2 Hz, indicating rapid and automatic detection of the periodic categorical change. Moreover, such effect was found -although increasingly weaker- for impoverished stimulus-sets that retained only certain (high-, mid-or low-level) features of the original colorful images (i.e., grayscale, texform and phase-scrambled images), and even if the images were unrecognizable. Similar effects were found with two Deep Neural networks (DNNs) presented with the same stimulus-sets. In sum, reliable categorization effects for dramatically impoverished and unrecognizable images, in humans EEG and DNN data, demonstrate that animacy representation emerges early in the visual hierarchy and is remarkably resilient to the loss of visual information.

neuroscience↗

bioRxiv2023

Structural basis of the interaction between ESV1 and LESV from Arabidopsis thaliana with starch glucans.

Starch is the major energy storage compound in plants. Whether it is transient or stored, it is accumulated in the form of insoluble, semi-crystalline granules. The structure of these granules is related to the structure of the main component: amylopectin. Amylopectin consists of linear polymers of glucose units linked by -1,4 bonds, forming double helices that combine to form the semi-crystalline lamellae of the granules, and -1,6 branching points that form the amorphous lamellae. This particular structure of amylopectin is linked to the action of isoamylases, which cut the excess of branching points and allow the granules to be structured. For a long time, it was thought that the action of these enzymes was responsible for the structuring of starch granules. Recently, two new proteins, LESV and ESV1, have been characterized and are involved in the phase transition of amylopectin (LESV) or in the maintenance of the granule structure (ESV1). These proteins share a tryptophan-rich domain folded into an antiparallel {beta}-sheet that is particularly well suited to bind amylopectin double helices. In this paper we present the structural study of these interactions using integrative structural biology approaches and show that LESV, in contrast to ESV1 can intervenes during amylopectin biosynthesis.

biophysics↗

bioRxiv2021

Mapping lignification dynamics with a combination of chemistry, data segmentation and ratiometric analysis

This article describes a new methodology for detailed mapping of the lignification capacity of plant cell walls that we have called "REPRISAL" for REPorter Ratiometrics Integrating Segmentation for Analyzing Lignification. REPRISAL consists of the combination of three separate approaches. In the first approach, H*, G* and S* monolignol chemical reporters, corresponding to p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol, are used to label the growing lignin polymer in a fluorescent triple labelling strategy based on the sequential use of 3 main bioorthogonal chemical reactions. In the second step, an automatic parametric and/or artificial intelligence (AI) segmentation algorithm is developed that assigns fluorescent image pixels to 3 distinct cell wall zones corresponding to cell corners (CC), compound middle lamella (CML) and secondary cell walls (SCW). The last step corresponds to the exploitation of a ratiometric approach enabling statistical analyses of differences in monolignol reporter distribution (ratiometric method 1) and proportions (ratiometric method 2) within the different cell wall zones. In order to demonstrate the potential of REPRISAL for investigating lignin formation we firstly describe its use to map developmentally-related changes in the lignification capacity of WT Arabidopsis interfascicular fiber cells. We then show how it can be used to reveal subtle phenotypical differences in lignification by analyzing the Arabidopsis prx64 peroxidase mutant and provide further evidence for the implication of the AtPRX64 protein in floral stem lignification. Finally, we demonstrate the general applicability of REPRISAL by using it to map lignification capacity in poplar, flax and maize.

plant biology↗

bioRxiv2021

Visual object categorization in infancy

Humans make sense of the world by organizing things into categories. When and how does this process begin? We investigated whether real-world object categories that spontaneously emerge in the first months of life match categorical representations of objects in the human visual cortex. Taking infants looking times as a measure of similarity, we defined a representational space where each object was defined in relation to others of the same or different categories. This space was compared with hypothesis-based and fMRI-based models of visual-object categorization in the adults visual cortex. Analyses across different age groups revealed an incremental process with two milestones. Between 4 and 10 months, visual exploration guided by saliency gives way to an organization according to the animate-inanimate distinction. Between 10 and 19 months, a category spurt leads towards a mature organization. We propose that these changes underlie the coupling between seeing and thinking in the developing mind.

neuroscience↗

bioRxiv2020

Malignant assignment of neuronal Na+ leak channel, NALCN: governor of Ca2+ oscillations-encoded invadopodogenesis

Cytosolic Ca2+ oscillations provide signaling input to several effector systems of the cell. These include neuronal development, migration and networking. Although similar signaling events are hijacked by highly aggressive cancer cells, the complexity of the neuron-like remodeling in metastasis remains to be explored. Here, using a variety of in vitro and in vivo techniques we show that strongly metastatic prostate cancer cells acquire specific Na+/Ca2+ signature required for persistent invasion. We identify the neuronal Na+ leak channel, NALCN, at the hot spots of the Ca2+ wave initiation and invadopodia formation. Mechanistically, NALCN associates functionally with plasmalemmal and mitochondrial Na+/Ca2+ exchangers, reactive oxygen species and store-operated channels to generate intracellular Ca2+ oscillations. In turn, this stimulates the activity of protooncogene Src kinase co-localized with NALCN, actin remodeling and secretion of proteolytic enzymes, thus increasing an invasive potential of the cancer cells and metastatic lesions in vivo (accessed in pre-clinical models). Overall, our findings provide new insight into the signaling pathway specific for metastatic cells where NALCN plays the role of the persistent invasion "launcher and controller".

cell biology↗

bioRxiv2018

PII1: a protein involved in starch initiation that determines granule number and size in Arabidopsis chloroplast.

The initiation of starch granule formation is still poorly understood. However, soluble starch synthase 4 (SS4) appears to be a major component of this process since it is required to synthetize the correct number of starch granules in the chloroplasts of Arabidopsis thaliana plants. A yeast-2-hybrid screen allowed the identification of several putative SS4 interacting partners. We identified the product of At4g32190 locus as a chloroplast-targeted PROTEIN INVOLVED IN STARCH INITIATION (named PII1). Arabidopsis mutants devoid of PII1 display an alteration of starch initiation process and accumulate, on average, one starch granule per plastid instead of the 5 to 7 granules found in plastids of wild-type plants. These granules are larger than in wild type and they remain flat and lenticular. pii1 mutants display wild-type growth rates and accumulate standard starch amounts. Moreover, starch characteristics, such as amylopectin chain length distribution, remain unchanged. Our results reveal the involvement of PII1 in starch priming process in Arabidopsis leaves through interaction with SS4.

plant biology↗