Biology subjects

Hayward, V.

Publications and source records attributed to Hayward, V..

5 recordsLinked to original sources

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

Cue Integration of Texture and Elasticity Induces Roughness Metamers in Touch

Roughness perception is a fundamental dimension of touch that guides object recognition and manipulation. While perceived roughness is typically attributed to surface texture, realworld materials rarely vary in texture alone-they also differ in material properties such as elasticity. Whether material properties contribute to roughness perception, and how they might interact with surface cues, remains poorly understood. Here, we investigated how texture and elasticity jointly influence perceived roughness by parametrically varying both features within a Bayesian optimization discrimination task. Participants compared pairs of stimuli differing in stochastic surface roughness and material elasticity, under both direct and tool-mediated touch. This approach enabled us to estimate two-dimensional perceptual functions and identify haptic roughness metamers-physically distinct stimuli perceived as equally rough. These perceptual equivalences were mirrored in confidence ratings and varied systematically with the relative stiffness between the stimulus and the probing tool or finger, implicating contact-induced vibrations as a mediating factor. Our findings reveal how texture and elasticity cues jointly constrain roughness perception, demonstrating that perceived roughness emerges from the integration of multiple stimulus dimensions rather than surface properties alone. These findings offer practical implications for the design of haptic interfaces and prosthetics, where equivalent percepts may be achieved through different combinations of material and texture, and contribute to a broader understanding of cue integration in haptic perception. Significance StatementHuman touch perception must contend with ambiguity from varying tools, materials, and contexts. This study reveals that perceived roughness arises not from surface texture alone, but from the integration of texture and material elasticity-two physical cues that can trade off to produce indistinguishable tactile roughness percepts. These "roughness metamers" emerge even when touch is mediated through a probe, underscoring the role of vibratory cues, but their emergence depends on the relative stiffness between probe and surface. This finding expands how we understand roughness perception and has direct implications for the design of artificial limbs, robotic sensing, and haptic interfaces that aim to recreate natural tactile experiences.

neuroscience↗

bioRxiv2024

Haptic perception is contingent to hemispaces, not to hands

AbsractIt is known that human haptic perception is lateralised, for example, object shape is felt differently according to the hand used to explore objects. Here we show that it is not the hand but the hemispace in which the exploring hand is located that determines differences in perception. This finding implies that our lateralised somatosensory processing depends on hand localisation in space rather than on the hand itself.

animal behavior and cognition↗

bioRxiv2021

The dynamics of touch sensing studied in a mass-spring-damper model of the skin

The mammalian skin is a densely innervated soft tissue where embedded neural mechanoreceptors report to the brain the mechanical events arising at its surface. Up to now, models of the transformations of these events into neural signals relied on quasistatic or viscoelastic mechanical models of the skin. Here, we employed a model which, in addition to elasticity and viscosity, accounted for mass to accurately reproduce the propagation of mechanical waves observed in vivo. Skin dynamics converted sensory inputs into rapidly evolving spatiotemporal patterns that magnified the information made available to a population of mechanoreceptors. Accounting for dynamics greatly enhanced the separability of tactile inputs and was efficient for a large range of mechanical parameter values. This advantage vanished when these parameters were set to approximate the quasistatic or viscoelastic cases.

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↗