Biology subjects

Adibi, M.

Publications and source records attributed to Adibi, M..

8 recordsLinked to original sources

bioRxiv2026

Differential modulation of temporal precision and perceived timing by tactile spatial and temporal context

Perception of sensory events depends not only on the stimulus itself but also on the surrounding spatial and temporal context. While contextual interactions have been extensively studied in vision, less is known about how tactile spatial and temporal context shape temporal representation of tactile landmarks embedded within continuous tactile signals. we investigated how neighbouring tactile stimuli influence the temporal precision and perceived timing of a target tactile landmark using an auditory-referenced temporal order judgement task. The number, location, and relative timing of task-irrelevant vibrotactile flankers were manipulated independently. Increasing the number of flankers reduced temporal precision, with comparable effects for adjacent and contralateral stimulation, indicating that temporal precision is limited by contextual interactions beyond local spatial proximity. In contrast, the relative timing of the flankers did not alter temporal sensitivity but systematically shifted perceived target timing. Flankers preceding the target shifted the perceived timing of the target earlier, whereas lagging flankers shifted it to the opposite direction. When one flanker preceded and the other followed the target the direction of the resulting spatiotemporal sequence across the fingers determined the direction of the perceptual bias. These findings reveal two distinct forms of contextual modulation in tactile temporal perception. Spatial context degrades temporal precision, whereas temporal context shifts perceived event timing. These findings demonstrate that spatial and temporal context shape distinct temporal aspects of tactile representations, extending contextual interference from feature identity and localisation to temporal precision and perceived timing.

neuroscience↗

bioRxiv2026

Perceptual, metacognitive, and computational signatures of temporal landmark uncertainty in tactile motion perception

Motion perception depends on estimating the relative timing of sensory events under internal uncertainty. Although perceptual uncertainty is commonly represented by a single internal noise parameter, its structure, sources, and temporal organisation remain poorly understood. Here, I investigated the computational structure of internal uncertainty in phase-based tactile motion perception using continuous amplitude-modulated vibrations delivered simultaneously to two fingertips. Motion discrimination accuracy, response latency, confidence, and confidence entropy exhibited systematic phase-dependent changes, revealing distinct behavioural signatures of temporal uncertainty. Computational analyses demonstrated that tactile motion perception is not explained by a single source of landmark timing uncertainty. Instead, behavioural performance was best accounted for by two additive uncertainty components: an amplitude-dependent component associated with extracting temporal landmarks from the vibration envelope, and an amplitude-independent component shared across stimulus conditions. This dual uncertainty framework consistently explained the frequency dependence of motion perception, the reduced uncertainty observed for sharper vibration envelopes, and the previously reported enhancement of motion perception with exponential compared with sinusoidal modulation. An independent temporal order judgement experiment further validated the uncertainty parameter inferred from motion discrimination, demonstrating that sharpening temporal landmarks reduced timing uncertainty by 35%. Finally, manipulating the initial stimulus state showed that perceptual choices followed the temporal sequence and correspondence of landmark events rather than the initial evolution of the vibration envelopes, providing independent support for landmark-based computations. these findings demonstrate that tactile motion perception is governed by multiple computational sources of landmark timing uncertainty and establish phase-based tactile motion as a tractable paradigm for independently measuring, manipulating, and modelling the computational structure of perceptual uncertainty underlying sensory decisions.

neuroscience↗

bioRxiv2026

Temporal Phase Differences Encode Tactile Motion from Static Vibrotactile Inputs

Motion perception in touch is traditionally attributed to spatially sequential stimulation or skin deformation caused by moving objects. Here, we demonstrate that directional tactile motion can instead be inferred purely from temporal phase differences between two spatially static vibrotactile inputs. Using psychophysical experiments in human participants (n = 56), we show that continuous vibrations delivered to separate fingertips, when offset in phase, evoke a robust and directionally consistent motion percept despite the absence of physical movement. Discrimination performance depended systematically on the temporal phase relationship between stimuli, following a sinusoidal relationship, consistent with a phase-based motion inference mechanism. Vibration amplitude had little influence on perceptual accuracy once stimuli exceeded detection threshold, although higher amplitudes modestly reduced response times. In contrast, envelope dynamics and spatial configuration significantly modulated performance: vibrations with exponential amplitude envelopes - reflecting the natural propagation of mechanical energy through a medium - enhanced phase sensitivity and sped responses, and bimanual stimulation across the two hands im-proved both accuracy and response time. These findings identify temporal phase integration as a fundamental mechanism for tactile motion perception, analogous to timing-based computations in auditory localisation and visual motion detection. Phase-coded vibrotactile stimulation therefore offers a minimal and efficient strategy for conveying directional motion in haptic interfaces without requiring spatial arrays or moving actuators.

neuroscience↗

bioRxiv2023

Growth and tension in explosive fruit

Exploding seed pods of the common weed Cardamine hirsuta have the remarkable ability to launch seeds far from the plant. The energy for this explosion comes from tension that builds up in the fruit valves. Above a critical threshold, the fruit fractures along its dehiscence zone and the two valves coil explosively, ejecting the seeds. Tension is commonly generated as seed pods dry, causing fruit tissues to deform. However, this does not happen in C. hirsuta. Instead, tension is produced by active contraction of growing exocarp cells in the outer layer of the fruit valves. Exactly how growth leads to contraction in these cells is unknown. Here we show that microtubule dynamics in the exocarp cell cortex control the specific orientation of cellulose microfibrils in the cell wall, and the consequent cellular growth pattern, which together drive contraction. We used mechanical modeling and simulations to show how tension emerges through the general process of plant cell growth, due to the highly anisotropic orientation of load-bearing cellulose microfibrils and their effect on cell shape. By explicitly defining the cell wall as multi-layered in our model, we discovered that a cross-lamellate pattern of cellulose microfibrils further enhances the developing tension in growing cells. Therefore, the interplay of cell wall properties with turgor-driven growth enables the fruit exocarp layer to develop sufficient tension to explode.

plant biology↗

bioRxiv2022

A continuous vibration-based virtual tactile motion across fingertips

Motion perception is a fundamental function of the tactile system, essential for object exploration and manipulation. While human studies have largely focused on discrete or pulsed stimuli with staggered onsets, many natural tactile signals are continuous and rhythmically patterned. Here, we investigate whether phase differences between simultaneously presented, continuous amplitude-modulated vibrations can induce the perception of motion across fingertips. Participants reliably perceived motion direction at modulation frequencies up to 1Hz, with discrimination performance systematically dependent on the phase lag between vibrations. Critically, trial-level confidence reports revealed the lowest certainty for anti-phase (180{degrees}) conditions, consistent with stimulus ambiguity as predicted by the mathematical framework. I propose two candidate computational mechanisms for tactile motion processing. The first is a conventional cross-correlation computation over the envelopes; The second is a probabilistic model based on the uncertain detection of temporal reference points (e.g., envelope peaks) within threshold-defined windows. This model, despite having only a single parameter (uncertainty width determined by an amplitude discrimination threshold), accounts for both the nonlinear shape and asymmetries of observed psychometric functions. These results demonstrate that the human tactile system can extract directional information from distributed phase-coded signals in the absence of spatial displacement, revealing a motion perception mechanism that parallels arthropod systems yet potentially arises from distinct perceptual constraints.

neuroscience↗

bioRxiv2021

MorphoGraphX 2.0: Providing context for biological image analysis with positional information

Positional information is a central concept in developmental biology. In developing organs, positional information can be idealized as a local coordinate system that arises from morphogen gradients controlled by organizers at key locations. This offers a plausible mechanism for the integration of the molecular networks operating in individual cells into the spatially-coordinated multicellular responses necessary for the organization of emergent forms. Understanding how positional cues guide morphogenesis requires the quantification of gene expression and growth dynamics in the context of their underlying coordinate systems. Here we present recent advances in the MorphoGraphX software (Barbier de Reuille et al. eLife 2015;4:e05864) that implement a generalized framework to annotate developing organs with local coordinate systems. These coordinate systems introduce an organ-centric spatial context to microscopy data, allowing gene expression and growth to be quantified and compared in the context of the positional information thought to control them.

developmental biology↗

bioRxiv2021

INDEHISCENT regulates explosive seed dispersal

How traits evolve to produce novelty or stasis is an open question in biology. We investigate this question in Cardamine hirsuta, a relative of Arabidopsis thaliana that employs explosive fracture to disperse its seeds. This trait evolved through key morphomechanical innovations that distinguish the otherwise very similar, dehiscent fruit of these two species. Using CRISPR/Cas9, we show that dehiscence zone formation is absolutely required for explosive fracture in C. hirsuta, and is controlled by the bHLH transcription factor INDEHISCENT (IND). Using mutant screens, we identified the MADS-box transcription factor FRUITFULL (FUL) as a negative regulator of IND in C. hirsuta. Although FUL function is conserved in C. hirsuta, the consequences of IND mis-expression differ in ful mutants of C. hirsuta versus A. thaliana. In ful mutants of both species, valve tissue is replaced by dehiscence zone tissue, which comprises two distinct cell types: lignified layer and separation layer cells. While A. thaliana ful mutants develop stunted fruit with ectopic lignified layer cells, C. hirsuta ful mutants have elongated fruit with ectopic separation layer cells. We show that IND dose determines the proportion of these two cell types in ectopic dehiscence zones. We also show that the extent of ectopic lignification caused by IND mis-expression determines fruit length. Our findings indicate developmental system drift in the conserved gene network patterning dehiscent fruit in two related Brassicaceae species.

plant biology↗

bioRxiv2018

A SOSEKI-based coordinate system interprets global polarity cues in Arabidopsis

Multicellular development requires coordinated cell polarization relative to body axes, and translation to oriented cell division. In plants, it is unknown how cell polarities are connected to organismal axes and translated to division. Here, we identify Arabidopsis SOSEKI (SOK) proteins that integrate apical-basal and radial organismal axes to localize to polar cell edges. Localization does not depend on tissue context, requires cell wall integrity and is defined by a transferrable, protein-specific motif. SOK proteins structurally resemble the DIX oligomerization domain in the animal Dishevelled polarity regulator. The DIX-like domain self-interacts and is required for edge localization and for influencing division orientation. Our work identifies a plant compass, interpreted by SOK proteins. Furthermore, despite fundamental differences, polarity in plants and animals converge upon the same protein domain.

plant biology↗