Biology subjects

Hartcher-O'Brien, J.

Publications and source records attributed to Hartcher-O'Brien, J..

4 recordsLinked to original sources

bioRxiv2026

Reduction of Complex Dynamic Touch information to a single stable perceptual feature

Dynamic touch requires the perceptual system to extract stable material properties from complex, evolving signals. We show that the tactile system relies on total spectral energy, the overall vibratory power of contact-induced transients, rather than waveform details or dominant frequency. Using a spectral energy compensation method, we conducted five psychophysical experiments in two degraded feedback scenarios: soft finger interfaces, where fingertip stiffness was reduced by an inflatable silicone bubble, and soft surface interactions, where participants tapped compliant foam surfaces. In both, participants reliably discriminated hardness and identified materials only when natural spectral energy profiles were preserved, independent of signal type. Judgments scaled systematically with energy level, and under conflicting cues, spectral energy dominated over frequency or compliance. These findings establish spectral energy as a governing cue in tactile perception, revealing a simple and robust computation akin to estimating mechanical work. This principle offers a generalizable framework for restoring touch in prosthetics, teleoperation, and immersive virtual environments. TeaserTotal spectral energy - not frequency - is the behaviorally relevant feature driving material perception through dynamic touch.

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

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↗