Biology subjects

Glasauer, S.

Publications and source records attributed to Glasauer, S..

11 recordsLinked to original sources

bioRxiv2026

Functional maturation in abducens motoneurons populations during angular VOR larval development

Extraocular motoneurons are the final neuronal relay implicated in gaze motor control and are known to be subdivided in functional subgroups, differently implicated in ocular motion dynamics. However, the maturation of these functional populations of extraocular motoneurons, in relation with the development of gaze-stabilizing reflexes remains largely unexplored. In amphibian tadpoles, the angular vestibulo-ocular reflex (VOR) appears later than other visuo-vestibular ocular reflexes and matures until the metamorphosis climax. Two types of Abducens motoneurons have been described to participate to the angular VOR in larval frog: spontaneous motor units, exhibiting a robust resting activity and silent motor units recruited only during head motion. The aim of this study was to investigate the maturation of these two types of Abducens motor units in relation with the development of the angular VOR by evaluating their discharge dynamic in response to head rotation in semi-intact preparations of larval Xenopus laevis. During larval life, the discharge modulation during sinusoidal head rotations increases significantly for silent units only, demonstrating a better sensitivity of this Abducens motoneuron sub-population to horizontal semicircular canal activation. In addition, this functional maturation was accompanied by an increase of the myelination in the lateral rectus motor nerve, promoting a faster conductivity in late larval stages than in early one. These findings showed that the development of the angular VOR is supported by a selective maturation of extraocular motoneurons subpopulations, specifically implicated in the improvement of the ocular kinematic during the reflex.

neuroscience↗

bioRxiv2026

Mineral dust stimulates microbial exoenzyme activity and enhances carbon mineralization capabilities in nutrient-poor peat soil

Nutrient limitation is an important control on heterotrophic microbial activity that helps to stabilize the massive stocks of organic carbon held in ombrotrophic peatlands. Minerals contained in atmospheric dusts are critical nutrient sources for peatlands, yet the role of dust in supporting the below-ground microbial processes that underpin primary productivity is largely unknown. We investigated how mineral dust generated from mining waste rock (<20 {micro}m) influences element bioavailability and subsurface microbial functioning using flow-through soil mesocosms. The bioavailability of base cations (Ca, Mg, K), transition metals (Fe, Al, Ni, Cu), Al, and P was tracked over two months at three soil depths (0-6, 6-12, and 12-18 cm) using an extended sequential extraction method. We also analyzed microbial community composition (16S rRNA and ITS amplicon sequencing) and mineralization capacity (exoenzyme assays and carbon substrate incubations). After two months, the concentration of metals in the peat increased substantially after dust application, but the mobility and bioavailability varied by element. Responses of microbial communities to dust application were highly dependent on depth from the surface. Carbon substrate incubations revealed enhanced mineralization capabilities in soil from the surface zone (0-6 cm), but a relatively low stimulation of exoenzymes. Soil pH and phosphorus mobility were also impacted near the site of dust application, while acid phosphatase activity was lower throughout the column. In the middle zone (6-12 cm), the activities of {beta}-glucosidase, {beta}-xylosidase, and NAGase were higher with dust exposure. Measured microbial activity mostly remained unchanged in the lowest depth (12-18 cm). We observed increases in the relative abundances of putative saprotrophic fungi throughout the mesocosm profile. Results from this experiment show that the deposition and weathering of mineral dust can induce a complex set of changes to the capacity and nature of microbial carbon mineralization within a shallow layer of peat.

ecology↗

bioRxiv2025

Explaining attractive and repulsive biases in the subjective visual vertical

Perception of gravity can be assessed by measuring the subjective visual vertical (SVV), the visually indicated spatial direction that appears earth-vertical to an observer. When the SVV is measured in darkness while the observer is roll-tilted, it shows substantial biases. At tilts larger than 45{degrees}, the bias is attractive, that is, the visual indicator appears vertical when rotated toward the observer. At smaller tilts, however, a repulsive bias is observed. The attractive bias has been explained within the Bayesian framework as the effect of a prior for upright posture. The repulsive bias has so far been considered anti-Bayesian, suboptimal, or as the result of uncompensated ocular counterroll. Here we show that both biases can be explained within a purely Bayesian model. More specifically, the repulsive bias at small roll-tilts is a consequence of the known tilt-dependent variability of the SVV, which is hypothesized to reflect different levels of sensory noise of the otolith organs. We thus provide a solution to a century-old question of why there is a repulsive bias in vertical perception.

neuroscience↗

bioRxiv2025

Neural correlates of perceptual biases in duration perception

How we perceive a current event depends not only on its immediate context, but also on how our internal expectations are shaped by prior experience. In time perception, these expectations manifest as systematic biases, namely sequential dependence, where the current percept is influenced by the previous stimulus, and central tendency, the overestimation of short durations and underestimation of long ones. Both perceptual biases, corresponding to individual beliefs about stimulus generation, can vary substantially between participants. However, the neural correlates of these individual beliefs and their effects are unknown. Here, we investigate how these biases and their individual variations are reflected in neural responses in a duration reproduction task. Our EEG results show that in the frontocentral region, the Contingent Negative Variation (CNV) while experiencing the current stimulus depends on the previous stimulus regardless of whether sequential dependence is high or low. In contrast, in the right parietal region, CNV significantly correlated with the amount of sequential dependence. Central tendency was associated with frontocentral CNV amplitude and post-stimulus P2 components. A Bayesian model of time perception reproduced the observed neural dynamics, suggesting that internal estimates and expectations of stimulus offset are reflected in EEG responses. Our results demonstrate that both forms of perceptual bias, sequential dependence and central tendency, are reflected in neural activity while experiencing the ongoing stimulus, suggesting that both biases directly affect the measurement of time. New and NoteworthyIndividuals differ in how they perceive magnitudes, exhibiting systematic biases, sequential dependence and central tendency, which reflect internal expectations about stimulus generation. Using EEG, we show that both behavioral biases are reflected in neural dynamics during stimulus encoding, which can be reproduced by a Bayesian model. The correspondence between perceptual biases and patterns of brain activity indicates that perceptual history and expectations directly influence how the brain measures and represents time.

neuroscience↗

bioRxiv2023

Neural Mechanisms of Sequential Dependence in Time Perception: The Impact of Prior Task and Memory Processing

Our perception and decision-making are susceptible to prior context. Such sequential dependence has been extensively studied in the visual domain, but less is known about its impact on time perception. Moreover, there are ongoing debates about whether these sequential biases occur at the perceptual stage or during subsequent post-perceptual processing. Using functional Magnetic Resonance Imaging (fMRI), we investigated neural mechanisms underlying temporal sequential dependence and the role of action in time judgments across trials. Participants performed a timing task where they had to remember the duration of green coherent motion and were cued to either actively reproduce its duration or simply view it passively. We found that sequential biases in time perception were only evident when the preceding task involved active duration reproduction. Merely encoding a prior duration without reproduction failed to induce such biases. Neurally, we observed activation in networks associated with timing, such as striato-thalamo-cortical circuits, and performance monitoring networks, particularly when a "Response" trial was anticipated. Importantly, the hippocampus showed sensitivity to these sequential biases, and its activation negatively correlated with the individuals sequential bias following active reproduction trials. These findings highlight the significant role of memory networks in shaping time-related sequential biases at the post-perceptual stages. Significance StatementOur study explores the neural mechanisms of sequential dependence in time perception and reveals that active reproduction of time duration in the previous trial can bias subsequent estimates, resulting in a sequential dependence effect. In contrast, passive viewing of a stimulus without reproducing its duration does not produce this effect. At the neural level, we observed increased activity in memory regions like the hippocampus when sequential biases were reduced. Furthermore, we found a negative correlation between hippocampal activation and sequential bias following active reproduction trials, suggesting that the involvement of memory networks mediates how we are influenced by past experiences when judging time.

neuroscience↗

bioRxiv2022

nl-DDM: a non-linear drift-diffusion model accounting for the dynamics of single-trial perceptual decisions

The Drift-Diffusion Model (DDM) is widely accepted for two-alternative forced-choice decision paradigms thanks to its simple formalism and close fit to behavioral and neurophysiological data. However, this formalism presents strong limitations in capturing inter-trial dynamics at the single-trial level and endogenous influences. We propose a novel model, the non-linear Drift-Diffusion Model (nl-DDM), that addresses these issues by allowing the existence of several trajectories to the decision boundary. We show that the non-linear model performs better than the drift-diffusion model for an equivalent complexity. To give better intuition on the meaning of nl-DDM parameters, we compare the DDM and the nl-DDM through correlation analysis. This paper provides evidence of the functioning of our model as an extension of the DDM. Moreover, we show that the nl-DDM captures time effects better than the DDM. Our model paves the way toward more accurately analyzing across-trial variability for perceptual decisions and accounts for peri-stimulus influences.

neuroscience↗

bioRxiv2022

Duration reproduction under memory pressure: Modeling the roles of visual memory load in duration encoding and reproduction

Duration estimates are often biased by the sampled statistical context, yielding the classical central-tendency effect, i.e., short durations are over- and long duration underestimated. Most studies of the central-tendency bias have primarily focused on the integration of the sensory measure and the prior information, without considering any cognitive limits. Here, we investigated the impact of cognitive (visual working-memory) load on duration estimation in the duration encoding and reproduction stages. In four experiments, observers had to perform a dual, attention-sharing task: reproducing a given duration (primary) and memorizing a variable set of color patches (secondary). We found an increase in memory load (i.e., set size) during the duration-encoding stage to increase the central-tendency bias, while shortening the reproduced duration in general; in contrast, increasing the load during the reproduction stage prolonged the reproduced duration, without influencing the central tendency. By integrating an attentional-sharing account into a hierarchical Bayesian model, we were able to predict both the general over- and underestimation and the central-tendency effects observed in all four experiments. The model suggests that memory pressure during the encoding stage increases the sensory noise, which elevates the central-tendency effect. In contrast, memory pressure during the reproduction stage only influences the monitoring of elapsed time, leading to a general duration over-reproduction without impacting the central tendency.

neuroscience↗

bioRxiv2021

Self-organized morphogenesis of a human neural tube in vitro by geometric constraints

Understanding how human embryos develop their shape is a fundamental question in physics of life with strong medical implications. However, it is challenging to study the dynamics of organ formation in humans. Animals differ from humans in key aspects, and in particular in the development of the nervous system. Conventional organoids are quantitatively unreproducible and exhibit highly variable morphology. Here we present a morphologically reproducible and scalable approach for studying human organogenesis in a dish, which is compatible with live imaging. We achieve this by precisely controlling cell fate pattern formation in 2D stem cell sheets, while allowing for self-organization of tissue shape in 3D. Upon triggering neural pattern formation, the initially flat stem cell sheet undergoes folding morphogenesis and self-organizes into a millimeter long anatomically accurate model of the neural tube, covered by epidermis. We find that neural and epidermal human tissues are necessary and sufficient for folding morphogenesis in the absence of mesoderm activity. Furthermore, we find that molecular inhibition of tissue contractility leads to defects similar to neural tube closure defects, consistent with in vivo studies. Finally, we discover that neural tube shape, including the number and location of hinge points, depends on neural tissue size. This suggests that neural tube morphology along the anterior posterior axis depends on neural plate geometry in addition to molecular gradients. Our approach provides a new path to study human organ morphogenesis in health and disease.

developmental biology↗

bioRxiv2021

Individual believes about temporal continuity explain perceptual biases

Perception of magnitudes such as duration or distance is often found to be systematically biased. The biases, which result from incorporating prior knowledge in the perceptual process, can vary considerably between individuals. The variations are commonly attributed to differences in sensory precision and reliance on priors. However, another factor not considered so far is the implicit belief about how successive sensory stimuli are generated: independently from each other or with certain temporal continuity. The main types of explanatory models proposed so far - static or iterative - mirror this distinction but cannot adequately explain individual biases. Here we propose a new unifying model that explains individual variation as combination of sensory precision and beliefs about temporal continuity and predicts the experimentally found changes in biases when altering temporal continuity. Thus, according to the model, individual differences in perception depend on beliefs about how stimuli are generated in the world.

neuroscience↗

bioRxiv2019

Head motion predictability explains activity-dependent suppression of vestibular balance control

Vestibular balance control is dynamically weighted during locomotion. This might result from a selective suppression of vestibular inputs in favor of a feed-forward balance regulation based on locomotor efference copies. The feasibility of such a feed-forward mechanism should however critically depend on the predictability of head movements (PHM) during locomotion. To test this, we studied in healthy subjects the differential impact of a stochastic vestibular stimulation (SVS) on body sway (center-of-pressure, COP) during standing and walking at different speeds using time-frequency analyses and compared it to activity-dependent changes in PHM. SVS-COP coupling decreased from standing to walking and further dropped with faster locomotion. Correspondingly, PHM increased with faster locomotion. Furthermore, SVS-COP coupling depended on the gait-cycle-phase with peaks corresponding to periods of least PHM. These findings support the assumption that during stereotyped human self-motion, locomotor efference copies selectively replace vestibular cues, similar to what was previously observed in animal models.

physiology↗

bioRxiv2018

150 years of research on Vierordt’s law - Fechner’s fault?

150 years ago, the physiologist Karl Vierordt discovered one type of systematic errors in time perception - an overestimation of long durations and underestimation of short durations, now known as Vierordt's law. Here we review the original study in its historical context and ask whether Vierordt's law is a result of an unnatural experimental randomization protocol. Using iterative Bayesian updating, we simulated the original results with astonishing accuracy. To validate whether the experimental protocol matters, we compared duration reproduction from two sequences with the same sampled distribution and found that trial-wise variation determines the reproduction error. We conclude that Vierordt's law is caused by an unnatural yet widely used experimental protocol.

neuroscience↗