Biology subjects

Auvray, M.

Publications and source records attributed to Auvray, M..

6 recordsLinked to original sources

bioRxiv2025

Pleasant touch mediated by Aβ-afferents remains primarily dependent on tactile velocity

Pleasantness of touch is classically attributed to C-tactile (CT) afferents, based on multiple evidence showing identical inverted-U curves as a function of velocities for pleasantness and CT activity. Recent research suggests that pleasant touch is not solely mediated by CT activation, pointing to a potential contribution of A{beta}-afferents and cognitive processes, potentially through the mechanism of velocity inference. To investigate the contributions of A{beta}-afferents, our study compared the illusion of vibrotactile apparent motion, which recruits almost exclusively A{beta}-afferents, and brush stroking, which additionally recruits CT afferents. A first experiment investigated the impact of stroke contrast on the pleasantness of 3 cm/s strokes by mingling them with pleasant (1 and 10 cm/s) or less pleasant (0.5 and 30 cm/s) ones. A second experiment in virtual reality probed velocity inference from visual cue by testing how congruence between visual and tactile velocity affects perceived pleasantness. The results showed that the pleasantness of strokes targeting A{beta}-afferents also follows an inverted U-curve and that 3 cm/s reference strokes remained unaffected by the speed of mixed strokes regardless of the condition. Even though differences in incongruence were not clearly perceived, discrepant visual velocities influenced the pleasantness of vibrotactile 1 cm/s strokes, for which the pleasantness ratings followed the visual rather than the tactile velocity. Overall, vibrotactile pleasantness can be mediated by A{beta}-afferents, but most probably through velocity inference since only vibrotactile strokes were prone to visual illusion. Because not clearly detected, visual inferences could have played a stronger role through larger speed discrepancies.

neuroscience↗

bioRxiv2025

Inside Out: Functional Flexibility in Assigning the Body's inside-outside

Tactile surface perception is often assumed to reflect a fixed boundary between body and world, with the skin providing a stable oriented surface that separates inside from outside. We show that this assumption fails in functionally specific ways. Using moving tactile stimuli on the hand, participants perceived stimulus direction on the fingertips as reversed when hand posture changed - reporting motion as if it originated from the opposite side of the skin, while responses on the palm were less consistent and less sensitive to posture. Congenitally blind participants exhibited stable, individualized surface assignments on the fingertips, demonstrating that vision is not required to construct oriented tactile surfaces. However, visual experience modulated posture effects: sighted individuals showed posture-dependent, skin-orientation assignments driven by motion direction, whereas congenitally blind individuals showed posture-invariant assignments determined by functional use. These findings indicate that tactile surface perception is not globally fixed but dynamically inferred according to functional demands; rather than enforcing a purely geometric body-world boundary, the brain flexibly assigns where the surface is and which side we occupy.

neuroscience↗

bioRxiv2025

Biocompatible sulfonium-based covalent probes for endogenous tubulin fluorescence nanoscopy in live and fixed cells

Fluorescent probes enable the visualization of dynamic cellular processes with high precision, particularly when coupled with super-resolution imaging techniques that surpass the diffraction limit. Traditional methods include fluorescent protein fusion (e.g., GFP) or organic fluorophores linked to ligands targeting the protein of interest. However, these approaches often introduce functional disruptions or ligand-associated biological effects. Herein, we address these challenges by developing covalent fluorescent probes for endogenous tubulin, a critical cytoskeletal protein involved in processes such as cell movement, division, and biomolecule trafficking. Using well-known tubulin binder cabazitaxel and cell permeable fluorophore silicon-rhodamine--as a basis, we introduce a novel biocompatible cleavable linker containing a sulfonium center. This allowed the construction of the optimized probe, 6-SiR-o-C9-CTX, demonstrating excellent cell permeability, fluorogenic properties, and the ability to covalently label tubulin across various human cell lines. Importantly, the targeting moiety could be washed out while preserving tubulin staining, ensuring minimal disruption of tubulin function. This labeling technique is compatible with STED nanoscopy in both live and fixed cells, offering a powerful high-resolution imaging tool.

biochemistry↗

bioRxiv2023

Tactile Sensitivity to the Frequency Spectrum of Complex Vibrotactile Signals

Haptic interactions with objects induce complex vibrotactile signals that are central to tactile perception. Despite the broad literature on vibrotactile perception, there is surprisingly little knowledge of the sensory processing of complex tactile signals made of multiple frequencies. To fill this gap, the study reported here investigated the impact of the constitutive pure tones of a complex vibrotactile signal on its perception. Participants completed a 3-AFC task, in which they were asked to identify an odd signal among two complex references. The odd signal was created by removing one pure tone from the reference, which varied in spectral composition, harmonicity, and inter-frequency intervals. Each reference signal was made of either two, three, or four pure tones. The results revealed that the removed pure tones value as well as the inter-frequency interval play a significant role on participants performance whereas changes in harmonicity, complexity have little impact. In addition, the results showed that the smaller the ratio between the removed frequency and the lowest one of the reference signals, the better the participants capacity to identify the one with a missing tone. Overall, the detection of a missing tone in a complex signal predominantly depends on the tones frequency value of the removed signal suggesting a tactile sensitivity to the frequency spectrum of complex vibrotactile signals. NEW & NOTEWORTHYThis research reports an investigation of the respective roles of frequency range, harmonicity, and complexity on human perception of vibrotactile signals. The results revealed that only pure tones that are close to the lower end of the frequency spectrum are noticed when they are missing. This finding sheds new light on the mechanisms of frequency selectivity in touch.

neuroscience↗

bioRxiv2021

Visualizing sounds: training-induced plasticity with a visual-to-auditory conversion device

Sensory substitution devices aim at restoring visual functions by converting visual information into auditory or tactile stimuli. Although these devices show promises in the range of behavioral abilities they allow, the processes underlying their use remains underspecified. In particular, while an initial debate focused on the visual versus auditory or tactile nature of sensory substitution, since over a decade, the idea that it reflects a mixture of both has emerged. In order to investigate behaviorally the extent to which visual and auditory processes are involved, participants completed a Stroop-like crossmodal interference paradigm before and after being trained with a conversion device which translates visual images into sounds. In addition, participants auditory abilities and their phenomenologies were measured. Our study revealed that, after training, when asked to identify sounds, processes shared with vision were involved, as participants performance in sound identification was influenced by the simultaneously presented visual distractors. In addition, participants performance during training and their associated phenomenology depended on their auditory abilities, revealing that processing finds its roots in the input sensory modality. Our results pave the way for improving the design and learning of these devices by taking into account inter-individual differences in auditory and visual perceptual strategies. HighlightsO_LITrained people spontaneously use processes shared with vision when hearing sounds from the device C_LIO_LIProcesses with conversion devices find roots both in vision and audition C_LIO_LITraining with a visual-to-auditory conversion device induces perceptual plasticity C_LI

neuroscience↗

bioRxiv2020

Harnessing Tactile Waves to Measure Skin-to-Skin Interactions

Skin-to-skin touch is an essential form of tactile interaction, yet, there is no known method to quantify how we touch our own skin or someone elses skin. Skin-to-skin touch is particularly challenging to measure objectively since interposing an instrumented sheet, no matter how thin and flexible, between the interacting skins is not an option. To fill this gap, we explored a technique that takes advantage of the propagation of vibrations from the locus of touch to pick up a signal remotely that contains information about skin-to-skin tactile interactions. These "tactile waves" were measured by an accelerometer sensor placed on the touching finger. Tactile tonicity and speed had a direct influence on measured signal power when the target of touch was the self or another person. The measurements were insensitive to changes in the location of the sensor relative to the target. Our study suggests that this method has potential for probing behaviour during skin-to-skin tactile interactions and could be a valuable technique to study social touch, self-touch, and motor-control. The method is non-invasive, easy to commission, inexpensive, and robust.

neuroscience↗